Synthesis of ordered mesoporous MFI zeolite using CMK carbon templates
Abstract Suitability of the ‘dry-gel synthesis method’ has been investigated for the synthesis of ordered mesoporous MFI zeolite using CMK-type mesoporous carbons as a template. Ordered mesoporous carbons with various pore diameters and topologies were infiltrated with a zeolite precursor sol, which was composed of tetrapropylammonium hydroxide, tetraethoxysilane, aluminum isopropoxide and H2O. The porous carbon with the zeolite precursor was heated inside an autoclave under a controlled humidity condition at 443 K. The resultant product indicated that the zeolite precursor migrated onto the external surface of the carbon template to form a bulk zeolite when the relative humidity was excessively high (⩾95%). A highly ordered mesoporous zeolite was synthesized in a carbon template with 10-nm pores when the humidity was lowered to 80–85%. A crystalline zeolite framework was not generated in the case of 2.5-nm pores with rigid walls. When a CMK-3 carbon with 4-nm pores was used as the template, the template walls were destroyed so that the zeolite crystalline domain was several times larger than the diameter of a single pore. Thus, humidity, template pore diameters and framework rigidity should be taken into account for application of the dry-gel synthesis method.