Hydrodesulfurization of benzothiophenes catalyzed by molybdenum/cobalt/ruthenium

Abstract

In this work, hydrodesulfurization of benzothiophenes using monometallic and multimetallic catalysts were studied. [Cp*RuCl2]2, Cp*RuCl(PPh3)2 , [CpMo(CO)3]2 and CpMo(CO)3H were prepared. The temperature, hydrogen pressure and BT/Ru mole ratio affected the catalytic activity. For the monometallic catalysts containing ruthenium: the results indicated that [Cp*RuCl2]2 was inactive catalyst. The hydride complex, Cp*RuH3(PPh3) showed catalytic activity. The Cp*RuCl(PPh3)2 in liquid-biphase system can catalyze the hydrodesulfurization of benzothiophene to give dihydrobenzothiophene (product from hydrogenation) and ethylbenzene (product from hydrogenolysis), this catalyst showed higher %conversion than Ru(PPh3)3Cl2 which gave only dihydrobenzothiophene. For molybdenum complexes, the reaction using [CpMo(Co)3]2 in toluene resulted in higher %conversion than in liquid-biphase system. Using CpMo(CO)3H, yielded lower amount of product. Comparing between ruthenium and molybdenum complexes, the former is more effective catalyst. It might be due to the hydrogenation ability of ruthenium and the bond cleavage ability of Cp*. However, the reaction catalyzed by the molybdenum catalyst occurred via hydrogenolysis, yielding ethylbenzene as product. Catalysts containing more than one metal were also investigated for the catalytic activity, bimetallic catalysts, Cp*RuCl(PPh3)2 + Mo(CO)6 or [CpMo(CO)3]2 or Co2(CO)8 and trimetallic catalyst, Cp*RuCl(PPh3)2 + [CpMo(CO)3]2 + Co2(CO)8 were used. The results indicated lower %conversion than those of monometallic catalysts