Deactivating effect of quinoline during the methylcyclohexane transformation over H-USY zeolite

The influence of 0.5 wt.% of quinoline (540 ppm of nitrogen) in the feed was tested for the methylcyclohexane transformation at 350 °C over an H-USY zeolite (framework Si/Al ratio of 5.4). The selectivities for the fresh catalyst do not seem to be altered by the presence of quinoline. Oppositely, for the deactivated zeolite, the aromatics yield increases for the tests performed with quinoline. Deactivation with time on stream is very pronounced, even for tests carried out without the base molecule; this can be attributed to the formation of highly polyaromatic coke molecules that block the acid sites and the microporous structure. In presence of quinoline, deactivation is enhanced due to its cumulative poisoning effect, especially for smaller contact times. This deactivation is caused by the strong interaction of the nitrogen base with the Brønsted acid sites responsible for the cracking mechanism. Quinoline molecule also participates in coke formation reactions, leading to an increase in the produced amount of coke, particularly of the more polyaromatic compounds insoluble in dichloromethane.