Homogeneous catalysis heterogeneous catalysis is the petrochemical alkylation process, where the liquid reactants are immiscible with a solution containing the catalyst. Heterogeneous catalysis offers the advantage that products are readily separated from the catalyst, and heterogeneous catalysts are often more stable and degrade much slower than homogeneous catalysts. However, heterogeneous catalysts are difficult to study, so their reaction mechanisms are often unknown. Enzymes possess properties of both homogeneous and heterogeneous catalysts. As such, they are usually regarded as a third, separate category of catalyst. Homogeneous catalysis In chemistry, homogeneous catalysis is catalysis in a solution by a soluble catalyst. Homogeneous catalysis refers
Phomoxanthone A PXA and PXB were discovered in 2001, and their preparation by isolation from "Phomopsis" fungal cultures was described in the corresponding publication. Briefly, a MeOH extract of a "Phomopsis" culture is mixed with HO and washed with hexane. The aqueous phase is then dried and the residue is dissolved in EtOAc, washed with HO, concentrated and repeatedly purified by size-exclusion chromatography. The resulting mixture of PXA and PXB is separated by HPLC. A modified method, in which the initial extraction is done with EtOAc instead of MeOH and the drying step is skipped, was described in 2013. Phomoxanthone A was