Comparison of the iso-structural H-SAPO-37 and H-faujasite as catalysts for the isobutane/2-butene alkylation

A study on the dimerization of 1-butene over Beta zeolite

“…Over the less acidic H-Beta-240 h, the trimer fraction (C 12 -C 14 ) is more abundant while cracking products, i.e. olefins lighter than octenes, are favored over H-Beta-96 h. Our experimental findings are in line with Lercher and coworkers [8] who for large-pore zeolites demonstrated that different acid sites are involved in different reactions: the weak ones catalyze dimerization/oligomerization [9] while the strong sites favor (multiple) cracking and alkylation. It is thus reasonable to assume that strong Brønsted acid sites are predominantly responsible of cracking reactions in the dimerization of 1-butene.…”

On the mechanism of catalyzed isobutane/butene alkylation by zeolites

“…Weak Brønsted acid sites catalyze dimerization [24]. The more demanding reactions cracking and hydride transfer do not proceed on these sites.…”

Hydrocracking

“…As yet, the influence of zeolite-Y mesopore structure has not been considered in model studies. A comparison with SAPO-37 (FAU structure, weaker acidity than Y [55] is also instructive: its large (a few microns), mesoporefree crystallites lead to mass-transport hindrances, so that despite the relatively low (52) activity, dictated by the low intrinsic acidity, secondary cracking occurs to a considerable extent (high gas make).…”