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

Abstract

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.

Effect of Content of Cerium Ion on Brönsted‐Acid‐Catalyzed Reaction of Thiophene over CeY Zeolite Studied by In Situ FTIR Spectroscopy

“…Combined with the result of Py‐FTIR, it can be deduced that oligomerization (1503 cm −1 ) of TP mainly takes place on medium and strong acid sites. This finding is consistent with the report by Guo et al that the decrease of B acid sites in HY zeolite by improving the calcination temperature would obviously reduce its TP adsorption capacity. It also implies that the increase of c may is not sufficient to improve desulfurization performance of CeY zeolite when the concentration exceeds 0.08 mol⋅L −1 .…”

Enhanced Adsorption Desulfurization Performance over CuCeY Zeolites Prepared by Low‐Temperature Calcination under H2 Atmosphere

“…1452 cm −1 can be assigned to the Py adsorbed on the Cu species or extra‐framework aluminum (EFAL) species, while ca. 1442 cm −1 can be assigned to the Py adsorbed on the Ce species or Na + ions [3,38,43,45,78,82] . It can be found from Figure 14 that Ce ions could lead to more B acidity whereas Cu ion could lead to more L acidity, which is similar to our previous results [3,38] .…”

“…1442 cm À 1 can be assigned to the Py adsorbed on the Ce species or Na + ions. [3,38,43,45,78,82] It can be found from Figure 14 that Ce ions could lead to more B acidity whereas Cu ion could lead to more L acidity, which is similar to our previous results. [3,38] According to the previous literatures, [3,17,43,45,82] the high medium and stronge B acid content in Cu 0.015 Ce 0.04 Y zeolite will result in the alkylation between thiophene and 1-hexene and the oligomerization of thiophene or 1-hexene by themselves and thus reduce sulfur adsorption capacity of Cu 0.015 Ce 0.04 Y zeolite.…”

“…It can be found from Figure 14 that Ce ions could lead to more B acidity whereas Cu ion could lead to more L acidity, which is similar to our previous results [3,38] . According to the previous literatures, [3,17,43,45,82] the high medium and stronge B acid content in Cu 0.015 Ce 0.04 Y zeolite will result in the alkylation between thiophene and 1‐hexene and the oligomerization of thiophene or 1‐hexene by themselves and thus reduce sulfur adsorption capacity of Cu 0.015 Ce 0.04 Y zeolite. Especially, the existence of H 2 O in Cu 0.015 Ce 0.04 Y zeolite can further enhance the catalytic activity of B acid centre [83] .…”

“…These hydroxyl groups may be an important factor of the increase of sulfur adsorption selectivity of CuCeY zeolites for TAMO. [11,39,82] It needs to be further studied in detail by coadoption of sulfur compounds and aromatics or and olefins over CuCeY zeolites by using FTIR as before. [78]…”