Adsorption and catalytic conversion of thiophene on Y-type zeolites modified with rare-earth metal ions

Rare earth metal modified Y zeolites (L-CeY) and USY zeolites (HRSY-3) were characterized by XRD, N₂ adsorption, NH₃-TPD, and in-situ Py-FTIR; the adsorption and catalytic conversion behavior of thiophene on the modified zeolites were investigated by using the in situ FT-IR combined with TG-MS analysis. The results indicated that the original crystal structures of the zeolites remain unchanged after the modification with the rare earth metal ions; however, the modification results in the formation of partial mesoporous structure and weak Lewis acid sites related to the rare-earth ion species as well as certain decrease of the acidic strength of the strong acid sites. Thiophene molecules can be activated via protonization upon the Brönsted acid sites of the USY and HY zeolites; however, the rare earth metal ions are able to promote the hydrogen transfer and oligomerization reactions, which can then enhance the catalytic cracking of thiophene reactions.