Covalent organic framework

Covalent organic frameworks (COFs) are a class of materials that form two- or three- dimensional structures through reactions between organic precursors resulting in strong, covalent bonds to afford porous, stable, and crystalline materials. COFs emerged as a field from the overarching domain of organic materials as researchers optimized both synthetic control and precursor selection. These improvements to coordination chemistry enabled non-porous and amorphous organic materials such as organic polymers to advance into the construction of porous, crystalline materials with rigid structures that granted exceptional material stability in a wide range of solvents and conditions. Through the development of reticular chemistry, precise synthetic control was achieved and resulted in ordered, nano-porous structures with highly preferential structural orientation and properties which could be synergistically enhanced and amplified. With judicious selection of COF secondary building units (SBUs), or precursors, the final structure could be predetermined, and modified with exceptional control enabling fine-tuning of emergent properties. This level of control facilitates the COF material to be designed, synthesized, and utilized in various applications, many times with metrics on scale or surpassing that of the current state-of-the-art approaches.
History.
While at University of Michigan, Omar M. Yaghi (currently at UCBerkeley) and Adrien P Cote published the first paper of COFs in 2005, reporting a series of 2D COFs. They reported the design and successful synthesis of COFs by condensation reactions of phenyl diboronic acid (C6H4[B(OH)2]2) and hexahydroxytriphenylene (C18H6(OH)6). Powder X-ray diffraction studies of the highly crystalline products having empirical formulas (C3H2BO)6·(C9H12)1 (COF-1) and C9H4BO2 (COF-5) revealed 2-dimensional expanded porous graphitic layers that have either staggered conformation (COF-1) or eclipsed conformation (COF-5). Their crystal structures are entirely held by strong bonds between B, C, and O atoms to form rigid porous architectures with pore sizes ranging from 7 to 27 Angstroms. COF-1 and COF-5 exhibit high thermal stability (to temperatures up to 500 to 600 C), permanent porosity, and high surface areas (711 and 1590 square meters per gram, respectively).
The synthesis of 3D COFs has been hindered by longstanding practical and conceptual challenges until it was first achieved in 2007 by Omar M. Yaghi and colleagues. Unlike 0D and 1D systems, which are soluble, the insolubility of 2D and 3D structures precludes the use of stepwise synthesis, making their isolation in crystalline form very difficult. This first challenge, however, was overcome by judiciously choosing building blocks and using reversible condensation reactions to crystallize COFs.
Structure.
Porous crystalline solids consists of secondary building units (SBUs) which assemble to form a periodic and porous framework. An almost infinite numbers of frameworks can be formed through various SBU combinations leading to unique material properties for applications in separations, storage, and heterogeneous catalysis.
Types of porous crystalline solids include zeolites, metal-organic frameworks (MOFs), and covalent organic frameworks (COFs). Zeolites are microporous, aluminosilicate minerals commonly used as commercial adsorbents. MOFs are a class of porous polymeric material, consisting of metal ions linked together by organic bridging ligands and are a new development on the interface between molecular coordination chemistry and materials science.
COFs are another class of porous polymeric materials, consisting of porous, crystalline, covalent bonds that usually have rigid structures, exceptional thermal stabilities (to temperatures up to 600 °C), are stable in water and low densities. They exhibit permanent porosity with specific surface areas surpassing those of well-known zeolites and porous silicates.
Secondary Building Units.
The term ‘secondary building unit’ has been used for some time to describe conceptual fragments which can be compared as bricks used to build a house of zeolites; in the context of this page it refers to the geometry of the units defined by the points of extension.
Reticular Synthesis.
Reticular synthesis enables facile bottom-up synthesis of the framework materials to introduce precise perturbations in chemical composition, resulting in the highly controlled tunability of framework properties. Through a bottom-up approach, a material is built from atomic or molecular components synthetically as opposed to a top-down approach, which forms a material from the bulk through approaches such as exfoliation, lithography, or other varieties of post-synthetic modification. The bottom-up approach is especially advantageous with respect to materials such as COFs because the synthetic methods are designed to directly result in an extended, highly crosslinked framework that can be tuned with exceptional control at the nanoscale level. Geometrical and dimensional principles govern the framework’s resulting topology as the SBUs combine to form predetermined structures. This level of synthetic control has also been termed "molecular engineering", abiding by the concept termed by Arthur R. von Hippel in 1956.
It has been established in the literature that, when integrated into an isoreticular framework, such as a COF, properties from monomeric compounds can be synergistically enhanced and amplified. COF materials possess the unique ability for bottom-up reticular synthesis to afford robust, tunable frameworks that synergistically enhance the properties of the precursors, which, in turn, offers many advantages in terms of improved performance in different applications. As a result, the COF material is highly modular and tuned efficiently by varying the SBUs’ identity, length, and functionality depending on the desired property change on the framework scale. Ergo, there exists the ability to introduce diverse functionality directly into the framework scaffold to allow for a variety of functions which would be cumbersome, if not impossible, to achieve through a top-down method. such as lithographic approaches or chemical-based nanofabrication. Through reticular synthesis, it is possible to molecularly engineer modular, framework materials with highly porous scaffolds that exhibit unique electronic, optical, and magnetic properties while simultaneously integrating desired functionality into the COF skeleton.
Reticular synthesis is different from retrosynthesis of organic compounds, because the structural integrity and rigidity of the building blocks in reticular synthesis remain unaltered throughout the construction process—an important aspect that could help to fully realize the benefits of design in crystalline solid-state frameworks. Similarly, reticular synthesis should be distinguished from supramolecular assembly, because in the former, building blocks are linked by strong bonds throughout the crystal.
Synthetic Chemistry.
Reticular synthesis was used by Yaghi and coworkers in 2005 to construct the first two COFs reported in the literature: COF-1, using a dehydration reaction of benzenediboronic acid (BDBA), and COF-5, via a condensation reaction between hexahydroxytriphenylene (HHTP) and BDBA. These framework scaffolds were interconnected through the formation of boroxine and boronate linkages, respectively, using solvothermal synthetic methods.
COF Linkages.
Since Yaghi and coworkers’ seminal work in 2005, COF synthesis has expanded to include a wide range of organic connectivity such as boron-, nitrogen-, other atom-containing linkages. The linkages in the figures shown are not comprehensive as other COF linkages exist in the literature, especially for the formation of 3D COFs.
Boron condensation.
The most popular COF synthesis route is a boron condensation reaction which is a molecular dehydration reaction between boronic acids. In case of COF-1, three boronic acid molecules converge to form a planar six-membered B3O3 (boroxine) ring with the elimination of three water molecules.
Triazine based trimerization.
Another class of high performance polymer frameworks with regular porosity and high surface area is based on triazine materials which can be achieved by dynamic trimerization reaction of simple, cheap, and abundant aromatic nitriles in ionothermal conditions (molten zinc chloride at high temperature (400 °C)). CTF-1 is a good example of this chemistry.
Imine condensation.
The imine condensation reaction which eliminates water (exemplified by reacting aniline with benzaldehyde using an acid catalyst) can be used as a synthetic route to reach a new class of COFs. The 3D COF called COF-300 and the 2D COF named TpOMe-DAQ are good examples of this chemistry. When 1,3,5-triformylphloroglucinol (TFP) is used as one of the SBUs, two complementary tautomerizations occur (an enol to keto and an imine to enamine) which result in a β-ketoenamine moiety as depicted in the DAAQ-TFP framework. Both DAAQ-TFP and TpOMe-DAQ COFs are stable in acidic aqueous conditions and contain the redox active linker 2,6-diaminoanthroquinone which enables these materials to reversibly store and release electrons within a characteristic potential window. Consequently, both of these COFs have been investigated as electrode materials for potential use in supercapacitors.
Solvothermal Synthesis.
The solvothermal approach is the most common used in the literature but typically requires long reaction times due to the insolubility of the organic SBUs in nonorganic media and the time necessary to reach thermodynamic COF products.
Templated Synthesis.
Morphological control on the nanoscale is still limited as COFs lack synthetic control in higher dimensions due to the lack of dynamic chemistry during synthesis. To date, researchers have attempted to establish better control through different synthetic methods such as solvothermal synthesis, interface-assisted synthesis, solid templation as well as seeded growth. First on of the precursors are deposited onto the solid support followed by the introduction of the second precursor in vapor form. This results in the deposition of the COF as a thin film on the solid support.
Properties.
Porosity.
A defining advantage of COFs is the exceptional porosity that results from the substitution of analogous SBUs of varying sizes. Pore sizes range from 7-23 Å and feature a diverse range of shapes and dimensionalities that remain stable during the evacuation of solvent. The rigid scaffold of the COF structure enables the material to be evacuated of solvent and retain its structure, resulting in high surface areas as seen by the Brunauer–Emmett–Teller analysis. This high surface area to volume ratio and incredible stability enables the COF structure to serve as exceptional materials for gas storage and separation.
Crystallinity.
There are several COF single crystals synthesized to date. There are a variety of techniques employed to improve crystallinity of COFs. The use of modulators, monofunctional version of precursors, serve to slow the COF formation to allow for more favorable balance between kinetic and thermodynamic control, hereby enabling crystalline growth. This was employed by Yaghi and coworkers for 3D imine-based COFs (COF-300, COF 303, LZU-79, and LZU-111). However, the vast majority of COFs are not able to crystallize into single crystals but instead are insoluble powders. The improvement of crystallinity of these polycrystalline materials can be improved through tuning the reversibility of the linkage formation to allow for corrective particle growth and self-healing of defects that arise during COF formation.
Conductivity.
Integration of SBUs into a covalent framework results in the synergistic emergence of conductivities much greater than the monomeric values. The nature of the SBUs can improve conductivity. Through the use of highly conjugated linkers throughout the COF scaffold, the material can be engineered to be fully conjugated, enabling high charge carrier density as well as through- and in-plane charge transport.  For instance, Mirica and coworkers synthesized a COF material (NiPc-Pyr COF) from nickel phthalocyanine (NiPc) and pyrene organic linkers that had a conductivity of 2.51 x 10−3 S/m, which was several orders of magnitude larger than the undoped molecular NiPc, 10−11 S/m. A similar COF structure made by Jiang and coworkers, CoPc-Pyr COF, exhibited a conductivity of 3.69 x 10−3 S/m. In both previously mentioned COFs, the 2D lattice allows for full π-conjugation in the x and y directions as well as π-conduction along the z axis due to the fully conjugated, aromatic scaffold and π-π stacking, respectively. Emergent electrical conductivity in COF structures is especially important for applications such as catalysis and energy storage where quick and efficient charge transport is required for optimal performance.
Characterization.
There exists a wide range of characterization methods for COF materials. There are several COF single crystals synthesized to date. For these highly crystalline materials, X-ray diffraction (XRD) is a powerful tool capable of determining COF crystal structure. The majority of COF materials suffer from decreased crystallinity so powder X-ray diffraction (PXRD) is used. In conjunction with simulated powder packing models, PXRD can determine COF crystal structure.
In order to verify and analyze COF linkage formation, various techniques can be employed such as infrared (IR) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. Precursor and COF IR spectra enables comparison between vibrational peaks to ascertain that certain key bonds present in the COF linkages appear and that peaks of precursor functional groups disappear. In addition, solid-state NMR enables probing of linkage formation as well and is well suited for large, insoluble materials like COFs. Gas adsorption-desorption studies quantify the porosity of the material via calculation of the Brunauer–Emmett–Teller (BET) surface area and pore diameter from gas adsorption isotherms. Electron imagine techniques such as scanning electron microscope (SEM), and transmission electron microscopy (TEM) can resolve surface structure and morphology, and microstructural information, respectively. Scanning tunneling microscope (STM) and atomic force microscopy (AFM) have also been used to characterize COF microstructural information as well. Additionally, methods like X-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICP-MS), and combustion analysis can be used to identify elemental composition and ratios.
Applications.
Gas Storage and Separation.
Due to the exceptional porosity of COFs, they have been used extensively in the storage and separation of gases such as hydrogen, methane, etc.
Hydrogen Storage.
Omar M. Yaghi and William A. Goddard III reported COFs as exceptional hydrogen storage materials. They predicted the highest excess H2 uptakes at 77 K are 10.0 wt % at 80 bar for COF-105, and 10.0 wt % at 100 bar for COF-108, which have higher surface area and free volume, by grand canonical Monte Carlo (GCMC) simulations as a function of temperature and pressure. This is the highest value reported for associative H2 storage of any material. Thus 3-D COFs are most promising new candidates in the quest for practical H2 storage materials. In 2012, the lab of William A. Goddard III reported the uptake for COF102, COF103, and COF202 at 298 K and they also proposed new strategies to obtain higher interaction with H2. Such strategy consist on metalating the COF with alkaline metals such as Li. These complexes composed of Li, Na and K with benzene ligands (such as 1,3,5-benzenetribenzoate, the ligand used in MOF-177) have been synthesized by Krieck et al. and Goddard showed that the THF is important of their stability. If the metalation with alkaline is performed in the COFs, Goddard et al. calculated that some COFs can reach 2010 DOE gravimetric target in delivery units at 298 K of 4.5 wt %: COF102-Li (5.16 wt %), COF103-Li (4.75 wt %), COF102-Na (4.75 wt %) and COF103-Na (4.72 wt %). COFs also perform better in delivery units than MOFs because the best volumetric performance is for COF102-Na (24.9), COF102-Li (23.8), COF103-Na (22.8), and COF103-Li (21.7), all using delivery g H2/L units for 1–100 bar. These are the highest gravimetric molecular hydrogen uptakes for a porous material under these thermodynamic conditions.
Methane Storage.
Omar M. Yaghi and William A. Goddard III also reported COFs as exceptional methane storage materials. The best COF in terms of total volume of CH4 per unit volume COF absorbent is COF-1, which can store 195 v/v at 298 K and 30 bar, exceeding the U.S. Department of Energy target for CH4 storage of 180 v/v at 298 K and 35 bar. The best COFs on a delivery amount basis (volume adsorbed from 5 to 100 bar) are COF-102 and COF-103 with values of 230 and 234 v(STP: 298 K, 1.01 bar)/v, respectively, making these promising materials for practical methane storage. More recently, new COFs with better delivery amount have been designed in the lab of William A. Goddard III, and they have been shown to be stable and overcome the DOE target in delivery basis. COF-103-Eth-trans and COF-102-Ant, are found to exceed the DOE target of 180 v(STP)/v at 35 bar for methane storage. They reported that using thin vinyl bridging groups aid performance by minimizing the interaction methane-COF at low pressure.
Gas Separation.
In addition to storage, COF materials are exceptional at gas separation. For instance, COFs like imine-linked COF LZU1 and azine-linked COF ACOF-1 were used as a bilayer membrane for the selective separation of the following mixtures: H2/CO2, H2/N2, and H2/CH4. The COFs outperformed molecular sieves due to the inherent thermal and operational stability of the structures. It has also been shown that COFs inherently act as adsorbents, adhering to the gaseous molecules to enable storage and separation.
Optical properties.
A highly ordered π-conjugation TP-COF, consisting of pyrene and triphenylene functionalities alternately linked in a mesoporous hexagonal skeleton, is highly luminescent, harvests a wide wavelength range of photons, and allows energy transfer and migration. Furthermore, TP-COF is electrically conductive and capable of repetitive on–off current switching at room temperature.
Porosity/surface-area effects.
Most studies to date have focused on the development of synthetic methodologies with the aim of maximizing pore size and surface area for gas storage. That means the functions of COFs have not yet been well explored, but COFs can be used as catalysts, or for gas separation, etc.
Carbon capture.
In 2015 the use of highly porous, catalyst-decorated COFs for converting carbon dioxide into carbon monoxide was reported.
Sensing.
Due to defining molecule-framework interactions, COFs can be used as chemical sensors in a wide range of environments and applications. Properties of the COF change when their functionalities interact with various analytes enabling the materials to serve as devices in various conditions: as chemiresistive sensors, as well as electrochemical sensors for small molecules.
Catalysis.
Due to the ability to introduce diverse functionality into COFs’ structure, catalytic sites can be fine-tuned in conjunction with other advantageous properties like conductivity and stability to afford efficient and selective catalysts. COFs have been used as heterogeneous catalysts in organic, electrochemical, as well as photochemical reactions.
Electrocatalysis.
COFs have been studied as non-metallic electrocatalyst for energy-related catalysis, including carbon dioxide electro-reduction and water splitting reaction. However, such researches are still in the very earlier stage. Most of the efforts have been focusing on solving the key issues, such as conductivity, stability in electrochemical processes.
Energy Storage.
A few COFs possess the stability and conductivity necessary to perform well in energy storage applications like lithium-ion batteries, and various different metal-ion batteries and cathodes.


Unseptquadium


Lomitapide

Lomitapide , sold under the brand name Juxtapid in the US and as Lojuxta in the EU) is a medication used as a lipid-lowering agent for the treatment of familial hypercholesterolemia, developed by Aegerion Pharmaceuticals.
It has been tested in clinical trials as single treatment and in combinations with atorvastatin, ezetimibe and fenofibrate.
The US Food and Drug Administration (FDA) approved lomitapide on 21 December 2012, as an orphan drug to reduce LDL cholesterol, total cholesterol, apolipoprotein B, and non-high-density lipoprotein (non-HDL) cholesterol in patients with homozygous familial hypercholesterolemia (HoFH).
On 31 May 2013 the European Committee for Medicinal Products for Human Use (CHMP) adopted a positive opinion with a unanimous vote recommending a marketing authorization for lomitapide. On 31 July 2013 the European Commission approved lomitapide as an adjunct to a low-fat diet and other lipid-lowering medicinal products with or without low density lipoprotein (LDL) apheresis in adult patients with HoFH.
Mechanism of action.
Lomitapide inhibits the microsomal triglyceride transfer protein (MTP or MTTP) which is necessary for very low-density lipoprotein (VLDL) assembly and secretion in the liver.
On 24 December 2012, drug manufacturer Aegerion announced they had been approved by the FDA to as "an adjunct to a low-fat diet and other lipid-lowering treatments...in patients with homozygous familial hypercholesterolemia (HoFH)."
Side effects.
In a Phase III study, lomitapide led to elevated aminotransferase levels and fat accumulation in the liver.


Manganese(II) acetate

Manganese(II) acetate are chemical compounds with the formula where n = 0, 2, 4. These materials are white or pale pink solids. Some of these compounds are used as a catalyst and as fertilizer.
Preparation.
Manganese(II) acetate can be formed by treating either manganese(II,III) oxide or manganese(II) carbonate with acetic acid:
Structure.
The anhydrous material and dihydrate are coordination polymers. The dihydrate has been characterized by X-ray crystallography. Each Mn(II) center is surrounded by six oxygen centers provided by aquo ligands and acetates.


Struvite

Struvite (magnesium ammonium phosphate) is a phosphate mineral with formula: NH4MgPO4·6H2O. Struvite crystallizes in the orthorhombic system as white to yellowish or brownish-white pyramidal crystals or in platey mica-like forms. It is a soft mineral with Mohs hardness of 1.5 to 2 and has a low specific gravity of 1.7. It is sparingly soluble in neutral and alkaline conditions, but readily soluble in acid.
Struvite urinary stones and crystals form readily in the urine of animals and humans that are infected with ammonia-producing organisms. They are potentiated by alkaline urine and high magnesium excretion (high magnesium/plant-based diets). They also are potentiated by a specific urinary protein in domestic cats.
Name.
Struvite was first described in 1845 by the German chemist (1811–1883), who found crystals of struvite in what he surmised had once been a medieval midden in Hamburg, Germany; he named the new mineral after the geographer and geologist (1772–1851) of Hamburg.
Occurrence.
Struvite is occasionally found in canned seafood, where its appearance is that of small glass slivers, objectionable to consumers for aesthetic reasons but of no health consequence. A simple test can differentiate struvite from glass.
Use of struvite as an agricultural fertilizer was in fact first described in 1857.
Struvite kidney stones.
Struvite precipitates in alkaline urine, forming kidney stones. Struvite is the most common mineral found in urinary tract stones in dogs, and is found also in urinary tract stones of cats and humans. Struvite stones are potentiated by bacterial infection that hydrolyzes urea to ammonium and raises urine pH to neutral or alkaline values. Urea-splitting organisms include "Proteus", "Xanthomonas", "Pseudomonas", "Klebsiella", "Staphylococcus", and "Mycoplasma".
Even in the absence of infection, accumulation of struvite crystals in the urinary bladder is a problem frequently seen in housecats, with symptoms including difficulty urinating (which may be mistaken for constipation) or blood in the urine (hematuria). The protein cauxin, a protein excreted in large amounts in cat urine that acts to produce a feline pheromone, has recently been found to cause nucleation of struvite crystals in a model system containing the ions necessary to form struvite. This may explain some of the excess struvite production in domestic cats. In the past, surgery has been required to remove struvite uroliths in cats; today, special acidifying low magnesium diets may be used to dissolve sterile struvite stones.
Upper urinary tract stones that involve the renal pelvis and extend into at least 2 calyces are classified as staghorn calculi. Although all types of urinary stones can potentially form staghorn calculi, approximately 75% are composed of a struvite-carbonate-apatite matrix.
Struvite enteroliths.
Struvite is a common mineral found in enteroliths (intestinal concretions) in horses.
Wastewater treatment.
Struvite can be a problem in sewage and waste water treatment, particularly after anaerobic digesters release ammonium and phosphate from waste material. Struvite can form a scale on lines and belts, in centrifuges and pumps, clog system pipes and other equipment including the anaerobic digester itself. Struvite, also referred to as MAP, forms when there is a mole to mole to mole ratio (1:1:1) of magnesium, ammonia and phosphate in the wastewater. The magnesium can be found in soil, seawater as well as drinking water. Ammonia is broken down from the urea in wastewater, and phosphate, which is found through food, soaps and detergents. These elements in place, struvite is more likely to form in a high pH environment, where there is higher conductivity, lower temperatures, and higher concentrations of magnesium, ammonia and phosphate. Recovery of phosphorus from wastestreams as struvite and recycling those nutrients into agriculture as fertilizer appears promising, particularly in agricultural manure and municipal waste water treatment plants.
Having struvite scale in a wastewater treatment system can lead to great inefficiency within the plant or operation due to clogging of the pipes, pumps and equipment. There have been a few options to solve this issue, including replacing the pipes, or using a hydro-jetter or a mechanical grinder to clear them. But many lines can be underground and either of these options implies considerable downtime and labor. Chemical cleaning is now predominately used to clear systems of struvite. Chemical cleaning products have been developed to remove and prevent struvite with minimal downtime. Even a chemical-free, electric method of removing and preventing struvite has been developed and tested successfully at wastewater treatment plants in the USA. The electronic sine wave it produces is sent through the water in the pipe and is therefore effective on underground piping as well.
Uses.
There is considerable interest in the utility of urine-derived struvite as a fertilizer in austere situations.


(2,4,6-Trimethylphenyl)gold

(2,4,6-Trimethylphenyl)gold is a member of a special group of compounds where an aryl carbon atom acts as a bridge between two gold atoms. This compound is formed in a reaction between Au(CO)Cl and the Grignard reagent mesitylmagnesium bromide. It crystallizes as a cyclical pentamer.


Methylammonium chloride

Methylammonium chloride in an organic halide with a formula of CH3NH3Cl. It is an ammonium salt composed of methylamine and hydrogen chloride. The primary application for the methylammonium halides is as a component of perovskite (structure) crystalline solar cells. Methylammonium iodide is the most commonly used, whereas using the chloride instead of, or as minor substituent to, the iodide provides the ability to tune the absorption, conductivity, and apparent bandgap.


Hemihydrate

A hemihydrate, or semihydrate, is a hydrate whose solid contains one molecule of water of crystallization per two molecules, or per two unit cells. An example of this is <chem>CaSO4*1/2H2O</chem> which is the hemihydrate of <chem>CaSO4</chem>.


N-Phenacylthiazolium bromide

"N"-Phenacylthiazolium bromide (PTB) is a cross-link breaker that in one study has been shown to prevent vascular advanced glycation end-product accumulation in diabetic rats.


Zirconyl chloride

Zirconyl chloride is the inorganic compound with the formula of [Zr4(OH)8(H2O)16]Cl8(H2O)12, more commonly written ZrOCl2·8H2O, and referred to as zirconyl chloride octahydrate. It is a white solid and is the most common water-soluble derivative of zirconium. A compound with the formula ZrOCl2 has not been characterized.
Production and structure.
The salt is produced by hydrolysis of zirconium tetrachloride or treating zirconium oxide with hydrochloric acid. It adopts a tetrameric structure, consisting of the cation [Zr4(OH)8]8+. features four pairs of hydroxide bridging ligands linking four Zr4+ centers. The chloride anions are not ligands, consistent with the high oxophilicity of Zr(IV). The salt crystallizes as tetragonal crystals.


Titanium(III) phosphide

Titanium(III) phosphide (TiP) is an inorganic chemical compound of titanium and phosphorus. Normally encountered as a grey powder, it is a metallic conductor with a high melting point. It is not attacked by common acids or water. Its physical properties stand in contrast to the group 1 and group 2 phosphides that contain the P3− anion (such as Na3P), which are not metallic and are readily hydrolysed. Titanium phosphide is classified as a "metal-rich phosphide", where extra valence electrons from the metal are delocalised.
Titanium phosphide can be prepared by the reaction of TiCl4 and PH3.
There are other titanium phosphide phases, including Ti3P, Ti2P, Ti7P4, Ti5P3, and Ti4P3.
Titanium phosphide should not be confused with titanium phosphate or titanium isopropoxide, both of which are sometimes known by the acronym TIP.


Sborgite

Sborgite is a sodium borate mineral with formula Na[B5O6(OH)4]·3H2O. The formula can be written as the oxide formulation, Na2O.5B2O3.10H2O. Sometimes called sodium pentaborate pentahydrate it contains the pentaborate anion, (B5O6(OH)4)−.
Sborgite is colorless with monoclinic crystals. It was named for Umberto Sborgi, (1883–1955), Professor of Chemistry, University of Milan, Italy. Sborgite occurs in Tuscany, Italy and the Furnace Creek district, Death Valley, California, US.


Calcium dobesilate

Calcium dobesilate is a vasoprotective. It is the calcium salt of dobesilic acid.
It is a synthetic molecule with the ability to reduce capillary permeability in the body. In Switzerland the drug is sold by the pharmaceutical company OM Pharma under the trade name of Doxium® in capsules containing 500 mg of active ingredient.
Chemistry.
The compound appears as a white hygroscopic powder . Very soluble in water and easily soluble in alcohol, it is practically insoluble in dichloromethane and poorly soluble in isopropyl alcohol. At the concentration of 10% the aqueous solution has a pH of between 4.5 and 6.0.
Pharmacodynamics.
The molecule has the property of optimizing the microcirculatory function. In fact, it reduces capillary permeability both by stabilizing the basement membrane for an action on the collagen chains that constitute it, and by interacting with different biochemical mediators that favor endothelial permeability itself. In this way it favors a reduction in blood hyperviscosity and also performs an anti- platelet aggregation action.
Pharmacokinetics.
Calcium dobesilate after oral administration is well absorbed from the gastrointestinal tract . Maximum plasma concentrations (C max ) of 6-8 µg / ml are reached approximately six hours after oral administration of 500 mg, which are generally maintained for over 12 hours. In the body the drug is poorly metabolized (less than 10%) and its binding with plasma proteins is rather low. Elimination occurs mainly through excretion from the renal excretion.
Clinical uses.
Calcium dobesilate is indicated in states of fragility and altered capillary permeability, e.g. diabetic retinopathy, chronic venous disease and hemorrhoidal disease. In combination with lidocaine or with lidocaine and dexamethasone, the drug enters the composition of preparations for the therapy of hemorrhoidal disease. In association with potassium hydrodex-sulfate enters the composition of adjuvant gels in the treatment of varicose veins. The efficacy of calcium dobesilate has been described in patients with microangiopathies such as diabetic retinopathy and diabetic nephropathy.
Side effects.
During treatment, gastrointestinal disorders can be observed: dyspepsia, nausea, vomiting, diarrhea . These disorders generally regress with the simple decrease in the dose taken, or with the temporary suspension of the treatment. Other adverse events related to hypersensitivity reactions have also been reported : among these skin rashes, skin rash, fever, arthralgia (joint pain). Rare cases of agranulocytosis have also been reported in medical literature. The rarity of the latter adverse effect led several authors to conclude that perhaps there could have been methodological errors in risk assessments.
Contraindications.
The drug is contraindicated in subjects with known hypersensitivity to the active ingredient or to any of the inactive ingredients contained in the pharmaceutical formulation.
It is also contraindicated in women who are pregnant and breastfeeding.
Therapeutic doses.
Calcium dobesilate is administered orally at a daily dose of 0.5-2 g (equivalent to 1-4 tablets). It can also be administered rectally in the case of hemorrhoidal disease.


Carlfriesite

Carlfriesite is a rare tellurium mineral with the formula CaTe4+2Te6+O8, or more simplified: CaTe3O8. It has a Moh's hardness of 3.5 and it occurs in various shades of yellow, ranging from bright yellow to a light buttery color. It was named after Carl Fries Jr. (1910–1965) from the U.S. Geological Survey and the Geological Institute of the National University, Mexico City, Mexico. It was previously thought to have the formula H4Ca(TeO3)3, but this was proven to be incorrect. It has no uses beyond being a collector's item.
Occurrence.
Carlfriesite is often found in cavities in hydrothermal gold-tellurium deposits. It is found associated with cerussite, chlorargyrite, argentian gold, cesbronite, calcite, dickite, baryte, bornite, galena, hessite and tlapallite. It was first identified in the Bambollita (La Oriental), Moctezuma, Municipio de Moctezuma, Sonora, Mexico. It is also found in another nearby mine, namely the Moctezuma mine.
Synthesis.
Carlfriesite was found to be synthesizable by heating a mixture of CaO, Te(OH)6 and TeO2 to 150-240°C with water at the vapor pressure of the system. The resulting material was very fine-grained and colorless, consisting of aggregates of tiny carlfriesite plates. The material mostly consisted of carlfriesite, but also contained 10-15% paratellurite, as determined by X-ray diffraction.


Hydrogen economy

The hydrogen economy is an envisioned future in which hydrogen is used as a fuel for heat and hydrogen vehicles, for energy storage, and for long distance transport of energy. In order to phase out fossil fuels and limit global warming, hydrogen can be created from water using intermittent renewal sources such as wind and solar, and its combustion only releases water vapor to the atmosphere.
Hydrogen is a powerful fuel, and a frequent component in rocket fuel, but numerous technical challenges prevent the creation of a large-scale hydrogen economy. These include the difficulty of developing long-term storage, pipelines and engine equipment; a relative lack of off-the-shelf engine technology that can currently run safely on hydrogen; safety concerns due to the high reactivity of hydrogen fuel with environmental oxygen in the air; the expense of producing it by electrolysis; and a lack of efficient photochemical water splitting technology. Hydrogen can also be the fuel in a fuel cell, which produces electricity with high efficiency in a process which is the reverse of the electrolysis of water. The hydrogen economy is nevertheless slowly developing as a small part of the low-carbon economy.
, hydrogen is mainly used as an industrial feedstock, primarily for the production of ammonia and methanol, and in petroleum refining. Although initially hydrogen gas was thought not to occur naturally in convenient reservoirs, it is now demonstrated that this is not the case; a hydrogen system is currently being exploited in the region of Bourakebougou, Mali, producing electricity for the surrounding villages. More discoveries of naturally occurring hydrogen in continental, on-shore geological environments have been made in recent years and open the way to the novel field of natural or native hydrogen, supporting energy transition efforts. , almost all (95%) of the world's 70 million tons of hydrogen consumed yearly in industrial processing are produced by steam methane reforming (SMR) that also releases the greenhouse gas carbon dioxide.
A possible less-polluting alternative is the newer technology methane pyrolysis, though SMR with carbon capture also has much reduced carbon emissions.
Small amounts of hydrogen (5%) are produced by the dedicated production of hydrogen from water, usually as a byproduct of the process of generating chlorine from seawater. there is not enough cheap clean electricity (renewable and nuclear) for this hydrogen to become a significant part of the low-carbon economy, and carbon dioxide is a by-product of the SMR process, but it can be captured and stored.
Rationale.
In the current hydrocarbon economy, heating is fueled primarily by natural gas and transportation by petroleum. Burning of hydrocarbon fuels emits carbon dioxide and other pollutants. The demand for energy is increasing, particularly in China, India, and other developing countries. Hydrogen can be an environmentally cleaner source of energy to end-users, without release of pollutants such as particulates or carbon dioxide.
Hydrogen has a high energy density by weight but has a low energy density by volume. Even when highly compressed, stored in solids, or liquified, the energy density by volume is only 1/4 that of gasoline, although the energy density by weight is approximately three times that of gasoline or natural gas. Hydrogen can help to decarbonize long-haul transport, chemicals, and iron and steel and has the potential to transport renewable energy long distance and store it long term, for example from wind power or solar electricity.
History.
The term "hydrogen economy" was coined by John Bockris during a talk he gave in 1970 at General Motors (GM) Technical Center. The concept was proposed earlier by geneticist J.B.S. Haldane.
A hydrogen economy was proposed by the University of Michigan to solve some of the negative effects of using hydrocarbon fuels where the carbon is released to the atmosphere (as carbon dioxide, carbon monoxide, unburnt hydrocarbons, etc.). Modern interest in the hydrogen economy can generally be traced to a 1970 technical report by Lawrence W. Jones of the University of Michigan.
A spike in attention for the concept during the 2000s was repeatedly described as hype by some critics and proponents of alternative technologies. İnterest in the energy carrier resurged in the 2010s, notably by the forming of the Hydrogen Council in 2017. Several manufacturers released hydrogen fuel cell cars commercially, with manufacturers such as Toyota and industry groups in China planning to increase numbers of the cars into the hundreds of thousands over the next decade.
Current hydrogen market.
Hydrogen production is a large and growing industry: with about 70 million tonnes of dedicated production per year, larger than the primary energy supply of Germany.
 fertiliser production and oil refining are the main uses. About half is used in the Haber process to produce ammonia (NH3), which is then used directly or indirectly as fertilizer. Because both the world population and the intensive agriculture used to support it are growing, ammonia demand is growing. Ammonia can be used as a safer and easier indirect method of transporting hydrogen. Transported ammonia can be then converted back to hydrogen at the bowser by a membrane technology.
The other half of current hydrogen production is used to convert heavy petroleum sources into lighter fractions suitable for use as fuels. This latter process is known as hydrocracking. Hydrocracking represents an even larger growth area, since rising oil prices encourage oil companies to extract poorer source material, such as oil sands and oil shale. The scale economies inherent in large-scale oil refining and fertilizer manufacture make possible on-site production and "captive" use. Smaller quantities of "merchant" hydrogen are manufactured and delivered to end users as well.
 almost all hydrogen production is from fossil fuels, and emits 830 million tonnes of carbon dioxide per year. The distribution of production reflects the effects of thermodynamic constraints on economic choices: of the four methods for obtaining hydrogen, partial combustion of natural gas in a NGCC (natural gas combined cycle) power plant offers the most efficient chemical pathway and the greatest off-take of usable heat energy.
The large market and sharply rising prices in fossil fuels have also stimulated great interest in alternate, cheaper means of hydrogen production. As of 2002, most hydrogen is produced on site and the cost is approximately $0.70/kg and, if not produced on site, the cost of liquid hydrogen is about $2.20/kg to $3.08/kg.
Production, storage, infrastructure.
, hydrogen is mainly produced (>90%) from fossil sources.
Color codes.
Hydrogen is often referred to by various colors to indicate its origin. As shown below, some production sources have more than one label with the more common listed first. Although the usage of color codes is not standardized, neither is it ambiguous.
Methods of production.
Molecular hydrogen was discovered in the Kola Superdeep Borehole. It is unclear how much molecular hydrogen is available in natural reservoirs, but at least one company specializes in drilling wells to extract hydrogen. Most hydrogen in the lithosphere is bonded to oxygen in water. Manufacturing elemental hydrogen requires the consumption of a hydrogen carrier such as a fossil fuel or water. The former carrier consumes the fossil resource and in the steam methane reforming (SMR) process produces greenhouse gas carbon dioxide. However in the newer methane pyrolysis process no greenhouse gas carbon dioxide is produced. These processes typically require no further energy input beyond the fossil fuel.
Decomposing water, the latter carrier, requires electrical or heat input, generated from some primary energy source (fossil fuel, nuclear power or a renewable energy). Hydrogen can also be produced by refining the effluent from geothermal sources in the lithosphere. Hydrogen produced by zero emission energy sources such as electrolysis of water using wind power, solar power, nuclear power, hydro power, wave power or tidal power is referred to as green hydrogen. Hydrogen produced from coal may be referred to as brown hydrogen, and when fossil fuel derived, is generally referred to as grey hydrogen. When derived from natural gas, if by non-polluting methane pyrolysis, it is referred to as turquoise hydrogen, if the carbon dioxide is captured, it is referred to as blue hydrogen.
Current production methods.
Steam reforming – gray or blue.
Hydrogen is industrially produced from steam reforming (SMR), which uses natural gas. The energy content of the produced hydrogen is less than the energy content of the original fuel, some of it being lost as excess heat during production. Steam reforming emits carbon dioxide, a greenhouse gas.
Methane pyrolysis – turquoise.
Pyrolysis of methane (natural gas) with a one-step process bubbling methane through a molten metal catalyst is a "no greenhouse gas" approach to produce hydrogen that was perfected in 2017 and now being tested at scale. The process is conducted at high temperatures (1340 K, 1065 °C or 1950 °F).
The industrial quality solid carbon may be sold as manufacturing feedstock or landfilled (no pollution).
Electrolysis of water – green or purple.
Hydrogen can be made via high pressure electrolysis, low pressure electrolysis of water, or a range of other emerging electrochemical processes such as high temperature electrolysis or carbon assisted electrolysis. However, current best processes for water electrolysis have an effective electrical efficiency of 70-80%, so that producing 1 kg of hydrogen (which has a specific energy of 143 MJ/kg or about 40 kWh/kg) requires 50–55 kWh of electricity.
In parts of the world, steam methane reforming is between $1–3/kg on average excluding hydrogen gas pressurization cost. This makes production of hydrogen via electrolysis cost competitive in many regions already, as outlined by Nel Hydrogen and others, including an article by the IEA examining the conditions which could lead to a competitive advantage for electrolysis.
A small part (2% in 2019) is produced by electrolysis using electricity and water, consuming approximately 50 to 55 kilowatt-hours of electricity per kilogram of hydrogen produced.
Kværner process.
The Kværner process or Kvaerner carbon black and hydrogen process (CB&H) is a method, developed in the 1980s by a Norwegian company of the same name, for the production of hydrogen from hydrocarbons (CnHm), such as methane, natural gas and biogas.
Of the available energy of the feed, approximately 48% is contained in the hydrogen, 40% is contained in activated carbon and 10% in superheated steam.
Experimental production methods.
Biological production.
Fermentative hydrogen production is the fermentative conversion of organic substrate to biohydrogen manifested by a diverse group of bacteria using multi enzyme systems involving three steps similar to anaerobic conversion. Dark fermentation reactions do not require light energy, so they are capable of constantly producing hydrogen from organic compounds throughout the day and night. Photofermentation differs from dark fermentation because it only proceeds in the presence of light. For example, photo-fermentation with "Rhodobacter sphaeroides" SH2C can be employed to convert small molecular fatty acids into hydrogen. Electrohydrogenesis is used in microbial fuel cells where hydrogen is produced from organic matter (e.g. from sewage, or solid matter) while 0.2 - 0.8 V is applied.
Biological hydrogen can be produced in an algae bioreactor. In the late 1990s it was discovered that if the algae is deprived of sulfur it will switch from the production of oxygen, i.e. normal photosynthesis, to the production of hydrogen.
Biological hydrogen can be produced in bioreactors that use feedstocks other than algae, the most common feedstock being waste streams. The process involves bacteria feeding on hydrocarbons and excreting hydrogen and CO2. The CO2 can be sequestered successfully by several methods, leaving hydrogen gas. In 2006-2007, NanoLogix first demonstrated a prototype hydrogen bioreactor using waste as a feedstock at Welch's grape juice factory in North East, Pennsylvania (U.S.).
Biocatalysed electrolysis.
Besides regular electrolysis, electrolysis using microbes is another possibility. With biocatalysed electrolysis, hydrogen is generated after running through the microbial fuel cell and a variety of aquatic plants can be used. These include reed sweetgrass, cordgrass, rice, tomatoes, lupines, and algae
High-pressure electrolysis.
High pressure electrolysis is the electrolysis of water by decomposition of water (H2O) into oxygen (O2) and hydrogen gas (H2) by means of an electric current being passed through the water. The difference with a standard electrolyzer is the compressed hydrogen output around 120-200 bar (1740-2900 psi, 12–20 MPa). By pressurising the hydrogen in the electrolyser, through a process known as chemical compression, the need for an external hydrogen compressor is eliminated, the average energy consumption for internal compression is around 3%.
European largest (1 400 000 kg/a, High-pressure Electrolysis of water, alkaline technology) hydrogen production plant is operating at Kokkola, Finland.
High-temperature electrolysis.
Hydrogen can be generated from energy supplied in the form of heat and electricity through high-temperature electrolysis (HTE). Because some of the energy in HTE is supplied in the form of heat, less of the energy must be converted twice (from heat to electricity, and then to chemical form), and so potentially far less energy is required per kilogram of hydrogen produced.
While nuclear-generated electricity could be used for electrolysis, nuclear heat can be directly applied to split hydrogen from water. High temperature (950–1000 °C) gas cooled nuclear reactors have the potential to split hydrogen from water by thermochemical means using nuclear heat. Research into high-temperature nuclear reactors may eventually lead to a hydrogen supply that is cost-competitive with natural gas steam reforming. General Atomics predicts that hydrogen produced in a High Temperature Gas Cooled Reactor (HTGR) would cost $1.53/kg. In 2003, steam reforming of natural gas yielded hydrogen at $1.40/kg. In 2005 natural gas prices, hydrogen costs $2.70/kg.
High-temperature electrolysis has been demonstrated in a laboratory, at 108 MJ (thermal) per kilogram of hydrogen produced, but not at a commercial scale. In addition, this is lower-quality "commercial" grade Hydrogen, unsuitable for use in fuel cells.
Photoelectrochemical water splitting.
Using electricity produced by photovoltaic systems offers the cleanest way to produce hydrogen. Water is broken into hydrogen and oxygen by electrolysis – a photoelectrochemical cell (PEC) process which is also named artificial photosynthesis. William Ayers at Energy Conversion Devices demonstrated and patented the first multijunction high efficiency photoelectrochemical system for direct splitting of water in 1983. This group demonstrated direct water splitting now referred to as an "artificial leaf" or "wireless solar water splitting" with a low cost thin film amorphous silicon multijunction sheet immersed directly in water. Hydrogen evolved on the front amorphous silicon surface decorated with various catalysts while oxygen evolved off the back metal substrate. A Nafion membrane above the multijunction cell provided a path for ion transport. Their patent also lists a variety of other semiconductor multijunction materials for the direct water splitting in addition to amorphous silicon and silicon germanium alloys. Research continues towards developing high-efficiency multi-junction cell technology at universities and the photovoltaic industry. If this process is assisted by photocatalysts suspended directly in water instead of using photovoltaic and an electrolytic system, the reaction is in just one step, which can improve efficiency.
Photoelectrocatalytic production.
A method studied by Thomas Nann and his team at the University of East Anglia consists of a gold electrode covered in layers of indium phosphide (InP) nanoparticles. They introduced an iron-sulfur complex into the layered arrangement, which when submerged in water and irradiated with light under a small electric current, produced hydrogen with an efficiency of 60%.
In 2015, it was reported that Panasonic Corp. has developed a photocatalyst based on niobium nitride that can absorb 57% of sunlight to support the decomposition of water to produce hydrogen gas. The company plans to achieve commercial application "as early as possible", not before 2020.
Concentrating solar thermal.
Very high temperatures are required to dissociate water into hydrogen and oxygen. A catalyst is required to make the process operate at feasible temperatures. Heating the water can be achieved through the use of water concentrating solar power. Hydrosol-2 is a 100-kilowatt pilot plant at the Plataforma Solar de Almería in Spain which uses sunlight to obtain the required 800 to 1,200 °C to heat water. Hydrosol II has been in operation since 2008. The design of this 100-kilowatt pilot plant is based on a modular concept. As a result, it may be possible that this technology could be readily scaled up to the megawatt range by multiplying the available reactor units and by connecting the plant to heliostat fields (fields of sun-tracking mirrors) of a suitable size.
Thermochemical production.
There are more than 352 thermochemical cycles which can be used for water splitting, around a dozen of these cycles such as the iron oxide cycle, cerium(IV) oxide-cerium(III) oxide cycle, zinc zinc-oxide cycle, sulfur-iodine cycle, copper-chlorine cycle and hybrid sulfur cycle, aluminum aluminum-oxide cycle, are under research and in testing phase to produce hydrogen and oxygen from water and heat without using electricity. These processes can be more efficient than high-temperature electrolysis, typical in the range from 35% - 49% LHV efficiency. Thermochemical production of hydrogen using chemical energy from coal or natural gas is generally not considered, because the direct chemical path is more efficient.
None of the thermochemical hydrogen production processes have been demonstrated at production levels, although several have been demonstrated in laboratories.
Microwaving plastics.
A 97% recovery of hydrogen has been achieved through microwaving plastics for a few seconds that have been ground and mixed with iron oxide and aluminium oxide.
Hydrogen as a byproduct of other chemical processes.
The industrial production of chlorine and caustic soda by electrolysis generates a sizable amount of Hydrogen as a byproduct. In the port of Antwerp a 1MW demonstration fuel cell power plant is powered by such byproduct. This unit has been operational since late 2011. The excess hydrogen is often managed with a hydrogen pinch analysis.
Gas generated from coke ovens in steel production is similar to Syngas with 60% hydrogen by volume. The hydrogen can be extracted from the coke oven gas economically.
Storage.
Although molecular hydrogen has very high energy density on a mass basis, partly because of its low molecular weight, as a gas at ambient conditions it has very low energy density by volume. If it is to be used as fuel stored on board the vehicle, pure hydrogen gas must be stored in an energy-dense form to provide sufficient driving range.
Pressurized hydrogen gas.
Increasing gas pressure improves the energy density by volume making for smaller container tanks. The standard material for holding pressurised hydrogen in tube trailers is steel (there is no hydrogen embrittlement problem with hydrogen gas). Tanks made of carbon and glass fibres reinforcing plastic as fitted in Toyota Marai and Kenworth trucks are required to meet safety standards. Few materials are suitable for tanks as hydrogen being a small molecule tends to diffuse through many polymeric materials. The most common on board hydrogen storage in today's 2020 vehicles is hydrogen at pressure 700bar = 70MPa. The energy cost of compressing hydrogen to this pressure is significant.
Pressurized gas pipelines are always made of steel and operate at much lower pressures than tube trailers.
Liquid hydrogen.
Alternatively, higher volumetric energy density liquid hydrogen or slush hydrogen may be used. However, liquid hydrogen is cryogenic and boils at 20.268 K (–252.882 °C or –423.188 °F). Cryogenic storage cuts weight but requires large liquification energies. The liquefaction process, involving pressurizing and cooling steps, is energy intensive. The liquefied hydrogen has lower energy density by volume than gasoline by approximately a factor of four, because of the low density of liquid hydrogen – there is actually more hydrogen in a litre of gasoline (116 grams) than there is in a litre of pure liquid hydrogen (71 grams). Liquid hydrogen storage tanks must also be well insulated to minimize boil off.
Japan has a liquid hydrogen (LH2) storage facility at a terminal in Kobe, and are expected to receive the first shipment of liquid hydrogen via LH2 carrier in 2020. Hydrogen is liquified by reducing its temperature to -253 °C, similar to liquified natural gas (LNG) which is stored at -162 °C. A potential efficiency loss of 12.79% can be achieved, or 4.26kWh/kg out of 33.3kWh/kg.
Storage as hydride.
Distinct from storing molecular hydrogen, hydrogen can be stored as a chemical hydride or in some other hydrogen-containing compound. Hydrogen gas is reacted with some other materials to produce the hydrogen storage material, which can be transported relatively easily. At the point of use the hydrogen storage material can be made to decompose, yielding hydrogen gas. As well as the mass and volume density problems associated with molecular hydrogen storage, current barriers to practical storage schemes stem from the high pressure and temperature conditions needed for hydride formation and hydrogen release. For many potential systems hydriding and dehydriding kinetics and heat management are also issues that need to be overcome. A French company McPhy Energy is developing the first industrial product, based on Magnesium Hydrate, already sold to some major clients such as Iwatani and ENEL. Emergent hydride hydrogen storage technologies have achieved a compressed volume of less than 1/500.
Adsorption.
A third approach is to adsorb molecular hydrogen on the surface of a solid storage material. Unlike in the hydrides mentioned above, the hydrogen does not dissociate/recombine upon charging/discharging the storage system, and hence does not suffer from the kinetic limitations of many hydride storage systems. Hydrogen densities similar to liquefied hydrogen can be achieved with appropriate adsorbent materials. Some suggested adsorbents include activated carbon, nanostructured carbons (including CNTs), MOFs, and hydrogen clathrate hydrate.
Underground hydrogen storage.
Underground hydrogen storage is the practice of hydrogen storage in caverns, salt domes and depleted oil and gas fields. Large quantities of gaseous hydrogen have been stored in caverns by ICI for many years without any difficulties. The storage of large quantities of liquid hydrogen underground can function as grid energy storage. The round-trip efficiency is approximately 40% (vs. 75-80% for pumped-hydro (PHES)), and the cost is slightly higher than pumped hydro. Another study referenced by a European staff working paper found that for large scale storage, the cheapest option is hydrogen at €140/MWh for 2,000 hours of storage using an electrolyser, salt cavern storage and combined-cycle power plant. The European project Hyunder indicated in 2013 that for the storage of wind and solar energy an additional 85 caverns are required as it cannot be covered by PHES and CAES systems. A German case study on storage of hydrogen in salt caverns found that if the German power surplus (7% of total variable renewable generation by 2025 and 20% by 2050) would be converted to hydrogen and stored underground, these quantities would require some 15 caverns of 500,000 cubic metres each by 2025 and some 60 caverns by 2050 – corresponding to approximately one third of the number of gas caverns currently operated in Germany. In the US, Sandia Labs are conducting research into the storage of hydrogen in depleted oil and gas fields, which could easily absorb large amounts of renewably produced hydrogen as there are some 2.7 million depleted wells in existence.
Power to gas.
Power to gas is a technology which converts electrical power to a gas fuel. There are 2 methods, the first is to use the electricity for water splitting and inject the resulting hydrogen into the natural gas grid. The second (less efficient) method is used to convert carbon dioxide and water to methane, (see natural gas) using electrolysis and the Sabatier reaction. The excess power or off peak power generated by wind generators or solar arrays is then used for load balancing in the energy grid. Using the existing natural gas system for hydrogen Fuel cell maker Hydrogenics and natural gas distributor Enbridge have teamed up to develop such a power to gas system in Canada.
Pipeline storage.
A natural gas network may be used for the storage of hydrogen. Before switching to natural gas, the UK and German gas networks were operated using towngas, which for the most part consisted of hydrogen. The storage capacity of the German natural gas network is more than 200,000 GWh which is enough for several months of energy requirement. By comparison, the capacity of all German pumped storage power plants amounts to only about 40 GW·h. Similarly UK pumped storage is far less than the gas network. The transport of energy through a gas network is done with much less loss (<0.1%) than in a power network (8%). The use of the existing natural gas pipelines for hydrogen was studied by NaturalHy. Ad van Wijk, a professor at Future Energy Systems TU Delft, also discusses the possibility of producing electricity in areas or countries with much sunlight (Sahara, Chile, Mexico, Namibia, Australia, New Zealand, ...) and transporting it (via ship, pipeline, ...) to the Netherlands. This being economically seen, still cheaper than producing it locally in the Netherlands. He also mentions that the energy transport capacity of gas lines are far higher than that of electricity lines coming into private houses (in the Netherlands) -30 kW vs 3 kW-.
Infrastructure.
The hydrogen infrastructure would consist mainly of industrial hydrogen pipeline transport and hydrogen-equipped filling stations like those found on a hydrogen highway. Hydrogen stations which were not situated near a hydrogen pipeline would get supply via hydrogen tanks, compressed hydrogen tube trailers, liquid hydrogen trailers, liquid hydrogen tank trucks or dedicated onsite production.
Over 700 miles of hydrogen pipeline currently exist in the United States. Although expensive, pipelines are the cheapest way to move hydrogen over long distances. Hydrogen gas piping is routine in large oil-refineries, because hydrogen is used to hydrocrack fuels from crude oil.
Hydrogen piping can in theory be avoided in distributed systems of hydrogen production, where hydrogen is routinely made on site using medium or small-sized generators which would produce enough hydrogen for personal use or perhaps a neighborhood. In the end, a combination of options for hydrogen gas distribution may succeed.
Hydrogen embrittlement is not a problem for hydrogen gas pipelines. Hydrogen embrittlement only happens with 'diffusible' hydrogen, i.e. atoms or ions. Hydrogen gas, however, is molecular (H2), and there is a very significant energy barrier to splitting it into atoms.
The IEA recommends existing industrial ports be used for production and existing natural gas pipelines for transport: also international co-operation and shipping.
South Korea and Japan, which as of 2019 lack international electrical interconnectors, are investing in the hydrogen economy. In March 2020, a production facility was opened in Namie, Fukushima Prefecture, claimed to be the world's largest.
A key tradeoff: centralized vs. distributed production.
In a future full hydrogen economy, primary energy sources and feedstock would be used to produce hydrogen gas as stored energy for use in various sectors of the economy. Producing hydrogen from primary energy sources other than coal and oil would result in lower production of the greenhouse gases characteristic of the combustion of coal and oil fossil energy resources. The importance of non-polluting methane pyrolysis of natural gas is becoming a recognized method for using current natural gas infrastructure investment to produce hydrogen and no greenhouse gas.
One key feature of a hydrogen economy would be that in mobile applications (primarily vehicular transport) energy generation and use could be decoupled. The primary energy source would need no longer travel with the vehicle, as it currently does with hydrocarbon fuels. Instead of tailpipes creating dispersed emissions, the energy (and pollution) could be generated from point sources such as large-scale, centralized facilities with improved efficiency. This would allow the possibility of technologies such as carbon sequestration, which are otherwise impossible for mobile applications. Alternatively, distributed energy generation schemes (such as small scale renewable energy sources) could be used, possibly associated with hydrogen stations.
Aside from the energy generation, hydrogen production could be centralized, distributed or a mixture of both. While generating hydrogen at centralized primary energy plants promises higher hydrogen production efficiency, difficulties in high-volume, long range hydrogen transportation (due to factors such as hydrogen damage and the ease of hydrogen diffusion through solid materials) makes electrical energy distribution attractive within a hydrogen economy. In such a scenario, small regional plants or even local filling stations could generate hydrogen using energy provided through the electrical distribution grid or methane pyrolysis of natural gas. While hydrogen generation efficiency is likely to be lower than for centralized hydrogen generation, losses in hydrogen transport could make such a scheme more efficient in terms of the primary energy used per kilogram of hydrogen delivered to the end user.
The proper balance between hydrogen distribution, long-distance electrical distribution and destination converted pyrolysis of natural gas is one of the primary questions that arises about the hydrogen economy.
Again the dilemmas of production sources and transportation of hydrogen can now be overcome using on site (home, business, or fuel station) generation of hydrogen from off grid renewable sources..
Distributed electrolysis.
Distributed electrolysis would bypass the problems of distributing hydrogen by distributing electricity instead. It would use existing electrical networks to transport electricity to small, on-site electrolysers located at filling stations. However, accounting for the energy used to produce the electricity and transmission losses would reduce the overall efficiency.
Uses.
For heating and cooking instead of natural gas.
Hydrogen can replace some or all of the natural gas in gas grids. the maximum in a grid is 20%.
Fuel cells as alternative to internal combustion and electric batteries.
One of the main offerings of a hydrogen economy is that the fuel can replace the fossil fuel burned in internal combustion engines and turbines as the primary way to convert chemical energy into kinetic or electrical energy, thereby eliminating greenhouse gas emissions and pollution from that engine. Ad van Wijk, a professor at Future Energy Systems TU Delft also mentions that hydrogen is better for larger vehicles - such as trucks, buses and ships - than electric batteries. This because a 1 kg battery, , can store 0.1 kWh of energy whereas 1 kg of hydrogen has a usable capacity of 33 kWh.
Although hydrogen can be used in conventional internal combustion engines, fuel cells, being electrochemical, have a theoretical efficiency advantage over heat engines. Fuel cells are more expensive to produce than common internal combustion engines.
Some types of fuel cells work with hydrocarbon fuels, while all can be operated on pure hydrogen. In the event that fuel cells become price-competitive with internal combustion engines and turbines, large gas-fired power plants could adopt this technology.
Hydrogen gas must be distinguished as "technical-grade" (five nines pure, 99.999%) produced by methane pyrolysis or electrolysis, which is suitable for applications such as fuel cells, and "commercial-grade", which has carbon- and sulfur-containing impurities, but which can be produced by the slightly cheaper steam-reformation process that releases carbon dioxide greenhouse gas. Fuel cells require high-purity hydrogen because the impurities would quickly degrade the life of the fuel cell stack.
Much of the interest in the hydrogen economy concept is focused on the use of fuel cells to power hydrogen vehicles, particularly large trucks. Hydrogen fuel cells suffer from a low power-to-weight ratio. Fuel cells are more efficient than internal combustion engines. If a practical method of hydrogen storage is introduced, and fuel cells become cheaper, they can be economically viable to power hybrid fuel cell/battery vehicles, or purely fuel cell-driven ones. The combination of the fuel cell and electric motor is 2-3 times more efficient than an internal-combustion engine. Capital costs of fuel cells have reduced significantly over recent years, with a modeled cost of $50/kW cited by the Department of Energy.
A 2019 video by "Real Engineering" noted that using hydrogen as a fuel for cars, as a practical matter, does not help to reduce carbon emissions from transportation. The 95% of hydrogen still produced from fossil fuels releases carbon dioxide, and producing hydrogen from water is an energy-consuming process. Storing hydrogen requires more energy either to cool it down to the liquid state or to put it into tanks under high pressure, and delivering the hydrogen to fueling stations requires more energy and may release more carbon. The hydrogen needed to move a fuel cell vehicle a kilometer costs approximately 8 times as much as the electricity needed to move a battery electric vehicle the same distance. Also in 2019, Katsushi Inoue, the president of Honda Europe, stated, "Our focus is on hybrid and electric vehicles now. Maybe hydrogen fuel cell cars will come, but that's a technology for the next era." A 2020 assessment concluded that hydrogen vehicles are still only 38% efficient, while battery EVs are 80% efficient.
Other fuel cell technologies based on the exchange of metal ions (e.g. zinc–air fuel cells) are typically more efficient at energy conversion than hydrogen fuel cells, but the widespread use of any electrical energy → chemical energy → electrical energy systems would necessitate the production of electricity.
Use as a transport fuel and system efficiency.
An accounting of the energy utilized during a thermodynamic process, known as an energy balance, can be applied to automotive fuels. With today's technology, the manufacture of hydrogen via methane pyrolysis or steam reforming can be accomplished with a thermal efficiency of 75 to 80 percent. Additional energy will be required to liquefy or compress the hydrogen, and to transport it to the filling station via truck or pipeline. The energy that must be utilized per kilogram to produce, transport and deliver hydrogen (i.e., its well-to-tank energy use) is approximately 50 MJ using technology available in 2004. Subtracting this energy from the enthalpy of one kilogram of hydrogen, which is 141 MJ, and dividing by the enthalpy, yields a thermal energy efficiency of roughly 60%. Gasoline, by comparison, requires less energy input, per gallon, at the refinery, and comparatively little energy is required to transport it and store it owing to its high energy density per gallon at ambient temperatures. Well-to-tank, the supply chain for gasoline is roughly 80% efficient (Wang, 2002). Another grid-based method of supplying hydrogen would be to use electrical to run electrolysers. Roughly 6% of electricity is lost during transmission along power lines, and the process of converting the fossil fuel to electricity in the first place is roughly 33 percent efficient. Thus if efficiency is the key determinant it would be unlikely hydrogen vehicles would be fueled by such a method, and indeed viewed this way, electric vehicles would appear to be a better choice except for large trucks where the weight of batteries is less efficient. However, as noted above, hydrogen can be produced from a number of feedstocks, in centralized or distributed fashion, by methane pyrolysis with zero pollution, and these afford more efficient pathways to produce and distribute the fuel.
In 2006 a study of the well-to-wheels efficiency of hydrogen vehicles compared to other vehicles in the Norwegian energy system indicates that hydrogen fuel-cell vehicles (FCV) tend to be about a third as efficient as EVs when electrolysis is used, with hydrogen Internal Combustion Engines (ICE) being barely a sixth as efficient. Even in the case where hydrogen fuel cells get their hydrogen from natural gas reformation rather than electrolysis, and EVs get their power from a natural gas power plant, the EVs still come out ahead 35% to 25% (and only 13% for a H2 ICE). This compares to 14% for a gasoline ICE, 27% for a gasoline ICE hybrid, and 17% for a diesel ICE, also on a well-to-wheels basis.
In 2007 Hydrogen was called one of the least efficient and most expensive possible replacements for gasoline (petrol) in terms of reducing greenhouse gases; other technologies may be less expensive and more quickly implemented. A 2010 comprehensive study of hydrogen in transportation applications has found that "there are major hurdles on the path to achieving the vision of the hydrogen economy; the path will not be simple or straightforward". Although Ford Motor Company and French Renault-Nissan cancelled their hydrogen car R&D efforts in 2008 and 2009, respectively, they signed a 2009 letter of intent with the other manufacturers and Now GMBH in September 2009 supporting the commercial introduction of FCVs by 2015. A study by The Carbon Trust for the UK Department of Energy and Climate Change suggests that hydrogen technologies have the potential to deliver UK transport with near-zero emissions whilst reducing dependence on imported oil and curtailment of renewable generation. However, the technologies face very difficult challenges, in terms of cost, performance and policy.
An Otto-cycle internal-combustion engine running on hydrogen is said to have a maximum efficiency of about 38%, 8% higher than a gasoline internal-combustion engine.
In the short term hydrogen has been proposed as a method of reducing harmful diesel exhaust.
Safety.
Hydrogen has one of the widest explosive/ignition mix range with air of all the gases with few exceptions such as acetylene, silane, and ethylene oxide. This means that whatever the mix proportion between air and hydrogen, when ignited in an enclosed space a hydrogen leak will most likely lead to an explosion, not a mere flame. This makes the use of hydrogen particularly dangerous in enclosed areas such as tunnels or underground parking. Pure hydrogen-oxygen flames burn in the ultraviolet color range and are nearly invisible to the naked eye, so a flame detector is needed to detect if a hydrogen leak is burning. Like natural gas, hydrogen is odorless and leaks cannot be detected by smell. This is the reason odorant chemical is injected into the natural gas to deliver the rotten-egg odor.
Hydrogen codes and standards are codes and standards for hydrogen fuel cell vehicles, stationary fuel cell applications and portable fuel cell applications. There are codes and standards for the safe handling and storage of hydrogen, for example the standard for the installation of stationary fuel cell power systems from the National Fire Protection Association.
Codes and standards have repeatedly been identified as a major institutional barrier to deploying hydrogen technologies and developing a hydrogen economy. international standards are needed for the transport, storage and traceability of environmental impact.
One of the measures on the roadmap is to implement higher safety standards like early leak detection with hydrogen sensors. The Canadian Hydrogen Safety Program concluded that hydrogen fueling is as safe as, or safer than, compressed natural gas (CNG) fueling. The European Commission has funded the first higher educational program in the world in hydrogen safety engineering at the University of Ulster. It is expected that the general public will be able to use hydrogen technologies in everyday life with at least the same level of safety and comfort as with today's fossil fuels.
Costs.
Although much of an existing natural gas grid could be reused with 100% hydrogen, eliminating natural gas from a large area such as Britain would require huge investment. Switching from natural gas to low-carbon heating is more costly if the carbon costs of natural gas are not reflected in its price.
Power plant capacity that now goes unused at night could be used to produce green hydrogen, but this would not be enough; therefore turquoise hydrogen from non-polluting methane pyrolysis or blue hydrogen with carbon capture and storage is needed, possibly after autothermal reforming of methane rather than steam methane reforming.
 green hydrogen costs between $2.50-6.80 per kilogram and turquoise hydrogen $1.40-2.40/kg or blue hydrogen $1.40-2.40/kg compared with high-carbon grey hydrogen at $1–1.80/kg. Deployment of hydrogen can provide a cost-effective option to displace carbon polluting fossil fuels in applications where emissions reductions would otherwise be impractical and/or expensive. These may include heat for buildings and industry, conversion of natural gas-fired power stations, and fuel for aviation and importantly heavy trucks.
In Australia, the Australian Renewable Energy Agency (ARENA) has invested $55 million in 28 hydrogen projects, from early stage research and development to early stage trials and deployments. The agency's stated goal is to produce hydrogen by electrolysis for $2 per kilogram, announced by Minister for Energy and Emissions Angus Taylor in a 2021 Low Emissions Technology Statement.
Examples and pilot programs.
The distribution of hydrogen for the purpose of transportation is currently being tested around the world, particularly in the US (California, Massachusetts), Canada, Japan, the EU (Portugal, Norway, Denmark, Germany), and Iceland, but the cost is very high.
Several domestic U.S. automobile have developed vehicles using hydrogen, such as GM and Toyota. However as of February 2020, infrastructure for hydrogen was underdeveloped except in some parts of California. The United States have their own hydrogen policy. A joint venture between NREL and Xcel Energy is combining wind power and hydrogen power in the same way in Colorado. Hydro in Newfoundland and Labrador are converting the current wind-diesel Power System on the remote island of Ramea into a Wind-Hydrogen Hybrid Power Systems facility. A similar pilot project on Stuart Island uses solar power, instead of wind power, to generate electricity. When excess electricity is available after the batteries are fully charged, hydrogen is generated by electrolysis and stored for later production of electricity by fuel cell. The US also have a large natural gas pipeline system already in place.
Countries in the EU which have a relatively large natural gas pipeline system already in place include Belgium, Germany, France, and the Netherlands. In 2020, The EU launched its European Clean Hydrogen Alliance (ECHA).
The UK started a fuel cell pilot program in January 2004, the program ran two Fuel cell buses on route 25 in London until December 2005, and switched to route RV1 until January 2007. The Hydrogen Expedition is currently working to create a hydrogen fuel cell-powered ship and using it to circumnavigate the globe, as a way to demonstrate the capability of hydrogen fuel cells.
Western Australia's Department of Planning and Infrastructure operated three Daimler Chrysler Citaro fuel cell buses as part of its Sustainable Transport Energy for Perth Fuel Cells Bus Trial in Perth. The buses were operated by Path Transit on regular Transperth public bus routes. The trial began in September 2004 and concluded in September 2007. The buses' fuel cells used a proton exchange membrane system and were supplied with raw hydrogen from a BP refinery in Kwinana, south of Perth. The hydrogen was a byproduct of the refinery's industrial process. The buses were refueled at a station in the northern Perth suburb of Malaga.
Iceland has committed to becoming the world's first hydrogen economy by the year 2050. Iceland is in a unique position. Presently, it imports all the petroleum products necessary to power its automobiles and fishing fleet. Iceland has large geothermal resources, so much that the local price of electricity actually is "lower" than the price of the hydrocarbons that could be used to produce that electricity.
Iceland already converts its surplus electricity into exportable goods and hydrocarbon replacements. In 2002, it produced 2,000 tons of hydrogen gas by electrolysis, primarily for the production of ammonia (NH3) for fertilizer. Ammonia is produced, transported, and used throughout the world, and 90% of the cost of ammonia is the cost of the energy to produce it.
Neither industry directly replaces hydrocarbons. Reykjavík, Iceland, had a small pilot fleet of city buses running on compressed hydrogen, and research on powering the nation's fishing fleet with hydrogen is under way (for example by companies as Icelandic New Energy). For more practical purposes, Iceland might process imported oil with hydrogen to extend it, rather than to replace it altogether.
The Reykjavík buses are part of a larger program, HyFLEET:CUTE, operating hydrogen fueled buses in eight European cities. HyFLEET:CUTE buses were also operated in Beijing, China and Perth, Australia (see below). A pilot project demonstrating a hydrogen economy is operational on the Norwegian island of Utsira. The installation combines wind power and hydrogen power. In periods when there is surplus wind energy, the excess power is used for generating hydrogen by electrolysis. The hydrogen is stored, and is available for power generation in periods when there is little wind.
India is said to adopt hydrogen and H-CNG, due to several reasons, amongst which the fact that a national rollout of natural gas networks is already taking place and natural gas is already a major vehicle fuel. In addition, India suffers from extreme air pollution in urban areas.
Currently however, hydrogen energy is just at the Research, Development and Demonstration (RD&D) stage. As a result, the number of hydrogen stations may still be low, although much more are expected to be introduced soon.
The Turkish Ministry of Energy and Natural Resources and the United Nations Industrial Development Organization have signed a $40 million trust fund agreement in 2003 for the creation of the International Centre for Hydrogen Energy Technologies (UNIDO-ICHET) in Istanbul, which started operation in 2004. A hydrogen forklift, a hydrogen cart and a mobile house powered by renewable energies are being demonstrated in UNIDO-ICHET's premises. An uninterruptible power supply system has been working since April 2009 in the headquarters of Istanbul Sea Buses company.
Another indicator of the presence of large natural gas infrastructures already in place in countries and in use by citizens is the number of natural gas vehicles present in the country. The countries with the largest amount of natural gas vehicles are (in order of magnitude):
Iran, China, Pakistan, Argentina, India, Brasil, Italy, Colombia, Thailand, Uzbekistan, Bolivia, Armenia, Bangladesh, Egypt, Peru, Ukraine, United States. Natural gas vehicles can also be converted to run on hydrogen.
Some hospitals have installed combined electrolyser-storage-fuel cell units for local emergency power. These are advantageous for emergency use because of their low maintenance requirement and ease of location compared to internal combustion driven generators.
Also, in some private homes, fuel cell micro-CHP plants can be found, which can operate on hydrogen, or other fuels as natural gas or LPG. When running on natural gas, it relies on steam reforming of natural gas to convert the natural gas to hydrogen prior to use in the fuel cell. This hence still emits CO2 (see reaction) but (temporarily) running on this can be a good solution until the point where the hydrogen is starting to become distributed through the (natural gas) piping system.
Partial hydrogen economy.
Hydrogen is simply a method to store and transmit energy. Energy development of various alternative energy transmission and storage scenarios which begin with hydrogen production, but do not use it for all parts of the store and transmission infrastructure, may be more economic, in both near and far term. These include:
Ammonia economy.
An alternative to gaseous hydrogen as an energy carrier is to bond it with nitrogen from the air to produce ammonia, which can be easily liquefied, transported, and used (directly or indirectly) as a clean and renewable fuel. For example, researchers at CSIRO in Australia in 2018 fuelled a Toyota Mirai and Hyundai Nexo with hydrogen separated from ammonia using a membrane technology.
Hybrid heat pumps.
Hybrid heat pumps (not to be confused with air water hybrids) also include a boiler which could run on methane or hydrogen, and could be a pathway to full decarbonisation of residential heating as the boiler would be used to top up the heating when the weather was very cold.
Bio-SNG.
 although technically possible production of syngas from hydrogen and carbon-dioxide from bio-energy with carbon capture and storage (BECCS) via the Sabatier reaction is limited by the amount of sustainable bioenergy available: therefore any bio-SNG made may be reserved for production of aviation biofuel.


Potassium hydrogenoxalate

Potassium hydrogenoxalate is a salt with formula KHC2O4 or K+·HO2C-CO2−. It is one of the most common salts of the hydrogenoxalate anion, and can be obtained by reacting potassium hydroxide with oxalic acid in 1:1 mole ratio.
The salt is also known as: potassium hydrogen oxalate, potassium bioxalate, acid potassium oxalate, or monobasic potassium oxalate. In older literature, it was also called: Salt of sorrel, sorrel salt, sel d'oseille, sal acetosella; or, "inaccurately, salt of lemon" (due to the similar acidic "“lemony”" taste of the edible "common sorrel" or "garden sorrel"; see "sorrel" below).
Potassium hydrogenoxalate occurs in some plants, notably sorrel. It is a commercial product used in photography, marble grinding, and removing ink stains.
Properties.
The anhydrous product is a white, odorless, crystalline solid, hygroscopic and soluble in water (2.5 g/100 g at room temperature). The solutions are basic. Below 50 °C the much less soluble "potassium tetraoxalate" • forms and precipitates out of solution.
The monohydrate KHC2O4·H2O starts losing the water at 100 °C.
The anhydrous salt was found to have remarkable elastic anisotropy, due to its crystal structure that consists of relatively rigid columns of hydrogen-bonded hydrogenoxalate anions, joined into sheets by ionic K–O bonds.
Toxicity.
Potassium hydrogenoxalate is strongly irritating to eyes, mucoses and gastrointestinal tract. It may cause cardiac failure and death.


Caesium sulfate

Caesium sulfate or cesium sulfate is the inorganic compound and salt with the formula Cs2SO4. It is a white water-soluble solid that is used to prepare dense aqueous solutions for use in isopycnic (or "density-gradient") centrifugation. It is isostructural with potassium salt.


Vinyllithium

Vinyllithium is an organolithium compound with the formula LiC2H3. A colorless or white solid, it is encountered mainly as a solution in tetrahydrofuran (THF). It is a reagent in synthesis of organic compounds.
Preparation and structure.
Solutions of vinyllithium are prepared by lithium-halogen exchange reactions. A halide-free route entails reaction of tetravinyltin with butyllithium:
The reaction of ethylene and lithium affords vinyl lithium and lithium hydride, together with other organolithium compounds,
Like most organolithium compounds, vinyllithium crystallizes from THF as a cluster compound as a cubane-type cluster.
Reactions.
Vinyllithium is used to install vinyl groups on metal-based reagents, being a precursor to vinylsilanes, vinylcuprates, and vinylstannanes. It adds to ketones compounds to give allylic alcohols. Vinylmagnesium bromide is often used in place of vinyllithium.


Silanization

Silanization is the covering of a surface with organofunctional alkoxysilane molecules. Mineral components like glass and metal oxide surfaces can all be silanized, because they contain hydroxyl groups which attack and displace the alkoxy groups on the silane thus forming a covalent -Si-O-Si- bond. The goal of silanization is to form bonds across the interface between mineral components and organic components present in paints, adhesives, etc. Silanization (or siliconization) of glassware increases its hydrophobicity and is used in cell culturing to reduce adherence of cells to flask walls.
Aside from clear applications in coatings and material science, the silanization process is also used in biomedical fields to anchor DNA to substrates.
Properties.
Organofunctional alkoxysilane molecules have both organic and inorganic properties. Silanized surfaces are usually hydrophobic, but the surface properties can be adjusted by varying the side chains of the silane compound. Many common silane compounds have alkyl groups (containing only carbon and hydrogen) which are more nonpolar than the hydroxyl (-OH) groups on the untreated surface, creating a hydrophobic surface.
Once the surface has been functionalized, further reactions can be performed to graft molecules with properties such as hydrophilicity, hydrophobicity, self cleaning, photocatalytic, and more onto the substrate.
Mechanism.
  Silanization begins with activating the desired material to expose surface hydroxyl (-OH) groups. The activated substrate, or material, is then placed in a silane solution to react; often, chlorosilanes are used due to their extreme reactivity. The silane is linked to the oxygen in the hydroxyl group, producing hydrochloric acid and a stable Si-O bond. This reaction occurs spontaneously and no catalyst is needed.
Organofunctional alkoxysilanes.
The alkoxy groups usually used are the methoxy (-OCH3) and the ethoxy (-OCH2CH3) groups. The organofunctional alkoxysilanes are classified according to their organic functions:
Aminosilanes.
The organic function is a primary or secondary amine:
Glycidoxysilanes.
The organic function is an epoxide:
Mercaptosilanes.
The organic function is a thiol:


Skaergaardite

Skaergaardite is an intermetallic platinum group mineral with the general chemical formula PdCu. The mineral is named after its discovery location: the Skaergaard intrusion, Kangerdlugssuaq area, East Greenland. The mineral name was approved by the International Mineralogical Association in 2003. The mineral has also been reported in the Duluth intrusion in Minnesota and the Rum layered intrusion in Scotland.
Occurrence.
Skaergaardite is associated with igneous intrusions containing well-preserved, oxide-rich, tholeiitic gabbro. It is found as inclusions in titanian magnetite, ilmenite, pyroxenes, and plagioclase. Skaergaardite can occur as an inclusion by itself, but is more commonly found in composite microglobule inclusions of copper iron sulfide minerals and other precious metal bearing minerals.
Crystallography and symmetry.
The crystallography of skaergaardite was determined using x-ray powder diffraction data. It has an isometric (cubic) crystal system and a hexoctahedral crystal class (Hermann–Mauguin notation: 4/m2/m). Skaergaardite can appear in various forms including: droplets; cubic grains with rounded outlines; euhedral to subhedral grains; and irregular grains or aggregates.
Optical properties.
When viewed under a microscope in plane polarized light, skaergaardite appears to be bright creamy white (in the presence of bornite or chalcopyrite) or bright white (in the presence of digenite or chalcocite). When the mineral is rotated on the microscope stage its color does not change, indicating that it is non-pleochroic.
Under crossed polar light, skaergaardite appears completely dark no matter the direction the stage is rotated, indicating that the mineral is isotropic. As skaergaardite is isotropic, it is also non-birefringent.
Importance.
Skaergaardite contains palladium (Pd), one of the six platinum group metals (PGM) that are some of the rarest elements on earth. With the cost of palladium expected to increase as demand becomes greater, Skaergaardite could begin to be mined for its valuable palladium resources.
The Skaergaard intrusion is the only known source of skaergaardite large enough to be mined. Skaergaardite is the most common PGM mineral in the intrusion, making up over 90% of all the PGM observed. The most mineral-rich layer of the intrusion could contain over 1000 tons of skaergaardite. In addition to palladium: gold, platinum, and other precious metals have been found in the intrusion. Interest has been increasing for an underground mine in the Skaergaard intrusion. A pre-feasibility study is currently under way and is scheduled for completion by December 2011.


Rameauite

Rameauite is a hydrated complex uranyl oxide mineral with formula K2Ca(UO2)6OH16·H2O or K2CaU6+6O20·9H2O.
Crystallography.
Rameauite has four observed forms which are {010}, {100}, {001} and {110}. The angles between these faces are {100}^{001} = 58°40' and {010}^{110} = 49° 50'. The crystals are always twinned on {100} and they are flattened parallel to {010}, and elongated parallel to {001}. The mineral rameauite is an example of a monoclinic mineral and appears pseudo-hexagonal. I has unit cell dimensions of: a= 13.97, b= 14.26, c= 14.22 with β = 121.02°.
Occurrence.
It was first described in 1972 for an occurrence in the Margnac Mine, Compreignac, Haute-Vienne, Limousin, France and named after Jacques Rameau (1926–1960), French prospector at the "Commissariat à l'Energie Atomique", who discovered the deposit where the mineral occurs.
In addition to the type locality in France it has been reported from the Orphan Mine on the south rim of the Grand Canyon in Arizona and on Rhyolite Ridge, Esmeralda County, Nevada.


Xanthoconite

Xanthoconite is a sulfosalt mineral with the chemical formula Ag3AsS3.


Sodium arsenide

Sodium arsenide, also known as trisodium arsenide, is the inorganic compound of sodium and arsenic with the formula Na3As. It is a dark colored solid that degrades upon contact with water or air. It is prepared by the reaction of the elements at 200–400 °C. The compound is mainly of interest as exhibiting an archetypal structure. The normal pressure "sodium arsenide" phase is adopted by many alkali metal pnictides. At 3.6 gigapascals, Na3As adopts the Li3Bi structure, which is another archetypal structure. Sodium arsenide is a crystalline solid used as a semiconductor and in photo optic applications. Its IUPAC name is disodioarsanylsodium.


Fluoroacetyl chloride

Fluoroacetyl chloride is an acyl chloride.
In 1948, William E. Truce of Purdue University described a synthesis of fluoroacetyl chloride which was undertaken "because of its potential value for introducing the group, —COCH2F, into organic molecules." In this synthesis, he reacted sodium fluoroacetate with phosphorus pentachloride to obtain the desired compound.


Tris(dimethylamino)gallium dimer

Tris(dimethylamino)gallium dimer, formally bis(μ-dimethylamino)tetrakis(dimethylamino)digallium, is an amide complex of gallium. This compound may be used as a precursor to other gallium complexes.
Commercially available, this compound may be prepared from lithium dimethylamide and gallium trichloride.


Abernathyite

Abernathyite is a mineral with formula K(UO2)(AsO4)·3H2O. The mineral is named after Jesse Evrett Abernathy (1913–1963) who first noted it in 1953 in the U.S. State of Utah. It was described as a new mineral species in 1956. Abernathyite is yellow and occurs as small crystals.
Description.
Abernathyite is a transparent, yellow mineral that occurs as tabular crystals up to . The mineral has a single perfect cleavage on {001}. Abernathyite fluoresces yellow-green in longwave and shortwave ultraviolet. Because of its uranium content, the mineral is radioactive.
Occurrence and formation.
Abernathyite forms as a coating on fractures of asphaltic sandstone containing uranium deposits. The mineral occurs in association with heinrichite, scorodite, and zeunerite. Abernathyite is known from France, Germany, Poland, South Africa, and the United States.
Structure and formula.
When first described in 1956, the formula was identified as K(UO2)(AsO4)·4H2O. However, only about 25 milligrams of the mineral was available for analysis, so a number of precautions were taken by running duplicate analyses and using artificial mixtures. In 1964, further study of the mineral identified inconsistencies between electron-density subtraction maps and the chemical evidence that abernathyite contains potassium. This led the authors to revise the formula as K(UO2)(AsO4)·3H2O.
Abernathyite crystallizes in the tetragonal crystal system.
History.
Jess Abernathy was the operator of the Fuemrol mine in Emery County, Utah. In the summer of 1953, he noted yellow crystals coating sandstone at the mine which he thought might be mineralogically significant. The specimens were sent to Grand Junction, Colorado, for study by United States Atomic Energy Commission (AEC) mineralogist E. B. Gross. He could not match the mineral's optical properties with any known species, so he sent the specimens to Washington D.C. where adequate facilities were available for further investigation. Mineralogists A. D. Weeks and M. E. Thompson of the United States Geological Survey studied the mineral on behalf of the AEC's Raw Materials Division.
Abernathyite was described in the journal "American Mineralogist" in 1956. The mineral was named "abernathyite" in honor of discoverer Jess Abernathy. Type specimens are held in the National Museum of Natural History in Washington, D.C.


Potassium nitride

Potassium nitride is an unstable chemical compound. Several syntheses were erroneously claimed in the 19th century, and by 1894 it was assumed that it did not exist.
However, a synthesis of this compound was claimed in 2004. It is observed to have the anti- structure below , although a -type structure should be more stable. Above this temperature, it converts to an orthorhombic phase.


Stannane

Stannane or tin hydride is an inorganic compound with the chemical formula . It is a colourless gas and the tin analogue of methane. Stannane can be prepared by the reaction of SnCl4 and LiAlH4.
Stannane decomposes slowly at room temperature to give metallic tin and hydrogen and ignites on contact with air.
Variants of stannane can be found as a highly toxic, gaseous, inorganic metal hydride and group 14 hydride.