Insight into the Acid Sites over Modified NaY Zeolite and Their Adsorption Mechanisms for Thiophene and Benzene

Series of HY sorbents with different amounts and strength of Brønsted and Lewis acidic sites were prepared. Their adsorption performance in thiophene–benzene solution, pure benzene, and pure thiophene were evaluated, and the desulfurization mechanisms were studied. The results show that both thiophene and benzene could be effectively adsorbed through the interaction between Lewis acid sites and the conjugated π bond in these two molecules, and thus thiophene adsorption could be obviously competed by benzene on Lewis acidic sites. By contrast, on Brønsted acidic sites, thiophene can be efficiently adsorbed via H–S bond, which is stronger than the former interaction. Moreover, the middle strong Brønsted acid could cause thiophene oligomerization. Hence, for the desulfurization purpose by NaY zeolite in aromatic free system, its weak and middle strong Lewis acid should be increased, and for that in aromatic existing system, the Brønsted acid site with relative low strength should be promoted.