Synthesis of ordered mesoporous MFI zeolite using CMK carbon templates

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.

Ordered mesoporous MFI zeolite that is constructed by with crystalline zeolite framework was synthesized by following dry-gel conversion method and using CMK-type carbon as template.Figure optionsDownload as PowerPoint slideHighlights
► Ordered mesoporous MFI zeolite was synthesized using CMK carbons as the template.
► Dry-gel synthesis condition was studied for ordered mesoporous MFI zeolite.
► Ordered mesoporous MFI zeolite was prepared when the humidity was lowered to 85%.
► Crystalline zeolite framework was not generated in 2.5-nm template pores.
► Wall of template should be rigid to prevent ordered mesostructure from collapsing.