日本ゼオライト学会　刊行物 Publication of Japan Zeolite Association

Zeolites are aluminosilicate crystallines and their crystal structure, surface nature and catalytic properties, etc. are well defined in comparison with other solid materials. By these reasons, the catalyst design based on molecular or atomic levels is possible for the development of zeolite-based highly active catalysts. On the other hand, the invesigation of catalytic desulfurization is an important subject for the development of highly active hydrodesulfurization catalysts to produce enviromental friendly super clean fuels.

The authors have systematically investigated the active sites and reaction mechanisms in the dehydrosulfurization of aliphatic thiols and hydrodesulfurization of thiophene over various zeolites in order to develop highly active zeolite-based hydrodesulfurization catalysts. We revealed that the acid sites of HY and MeY zaolites act as the active site for the dehydrosulfrization of alliphatic thios. In the hydrodesulfurization of thiophene over zeolites, the reduced MeY zeolites (Me⁰Y) were effective for the hydrodesulfurization of thiophene and both Brönsted acid sites and metal particles on Me⁰Y zeilites act as active sites for the hydrodesulfurization of thiophene. From our systematic studies concerning these catalytic desulfurization reactions over zeolites, a general rule was derived that the combination of strong Brönsted acid sites and highly dispersed metal particles with high ability for hydrogenation on zeolites provide high catalytic activity for the hydrodesulfurization of organic sulfur compounds. On the basis of this rule for the development of highly active hydrodesulfurization catalysts, we could develop much more active Rh/USY catalyst than commercial CoMo/Al₂O₃ catalyst as second generation highly active zeolite-based hydrodesulfurization catalysts.