The Effect of Silanisation on the Catalytic and Sorption Properties of Zeolites

Abstract

Silanising zeolites can result in significant beneficial changes to their catalytic and sorptive properties. It is, however, necessary to carefully control the reaction conditions when silanising a zeolite. Apart from the different effects of using vapour or liquid deposition procedures and static or flow systems, the deposition temperature and the number of silanisation/calcination cycles are of great importance. By careful control of these conditions, it is possible to systematically modify the diffusional properties of the zeolite while at the same time inertizing the external surface acidity. The diffusional changes are more likely due to a blockage of pore entrances, resulting in a greater diffusion pathway, than to a controlled narrowing of the pore openings. By careful control of the number of silanisation/calcination cycles, it is possible to systematically change the diffusional properties. The amount of Si deposited/nm² is a good indicator of the process of silanisation. Silanised zeolites are able to significantly increase the yield of particular isomers as a result of the diffusional constraints.