Effect of mesoporosity against the deactivation of MFI zeolite catalyst during the methanol-to-hydrocarbon conversion process

The effects of mesoporosity on catalyst longevity of methanol-to-hydrocarbon (MTH) reactions have been investigated using a number of MFI zeolites with different degrees of mesoporosity, which were obtained via the post-synthetic desilication, dry-gel conversion in nanocarbon templates, and hydrothermal synthesis with the addition of organosilane surfactants. The MTH catalytic lifetime could be increased by more than three times due to the generation of mesopores. The cause for catalyst longevity was investigated by probing the location of coke that formed during the reaction using argon adsorption measurements. The result showed that the coke formed mainly on mesopore walls in the case of mesoporous zeolite. On the other hand, the coke was more heavily deposited inside micropores in the case of solely microporous zeolites. The short diffusion path lengths and hence facile diffusion of coke precursors were most likely the cause of the improvement in the catalytic lifetime.