Fabrication of effective desulfurization species active sites in the CeY zeolites and the adsorption desulfurization mechanisms

Abstract

A series of CeY zeolites with different cerium loadings and calcined at different temperatures were prepared and used as the adsorbent for the desulfurization of thiophene containing model oil. The CeY zeolites were characterized by XRD, N2 sorption, FT-IR spectroscopy and GC-SCD and GC-MSD techniques. The effects of aromatics and olefins on the adsorption desulfurization performance were investigated and the active species and reaction mechanism for the adsorption desulfurization on CeY zeolites were probed. The results indicate that the CeY zeolite calcined at 150°C is provided with a large number of Brönsted acid sites and hydroxylated cerium species in the supercages, which can synergistically promote the thiophene oligomerization and then enhance the sulfur breakthrough adsorption capacity (18.45 mg(S)/g). However, a further increase in the calcination temperature and cerium loading may greatly reduce the number of active sites for the adsorption desulfurization and suppress the thiophene oligomerization reaction, leading to a significant decrease in the sulfur breakthrough adsorption capacity (4.03 mg(S)/g). For the thiophene model oils containing low concentration of 1-hexene (< 1.0%) or benzene (< 0.1%), the CeY-12.3-150 zeolite (with a cerium loading of 12.3% and calcined at 150°C) also exhibits a relatively high sulfur breakthrough adsorption capacity. However, a further increase in the content of 1-hexene or benzene in the feed may lead to a sharp decrease in the sulfur breakthrough adsorption capacity, due to the alkylation of thiophene and the adsorption mode of “S–H” bonding.