Selective Hydrogenation of Benzene to Cyclohexene over 2Ru/La2O3-ZnO Catalyst without Additional Modifiers

Selective benzene (BEN) hydrogenation to cyclohexene (CHE) has been studied in a complex four-phase system by using 2Ru/La2O3-ZnO as the catalyst. The catalyst is highly efficient (yield of desired cyclohexene=28%) and stable for about five cycles. Characterizations reveal formation of La(OH)(3) on the catalyst surface and formation of Zn(OH)(3)(-) during the reaction, which play a key role in the formation of CHE. For the first time, the reaction mixture can be observed in situ, showing the emulsion of this complicated four-phase system. The droplet size of the organic compound and the rate of hydrogenation are correlated with different stirring rates excluding mass transfer limitations.