Influence of cadmium on Ru/xCd/Al2O3 catalyst for benzene partial hydrogenation

The thermodynamic of the partial hydrogenation of benzene with ruthenium catalyst drives the reaction to the cyclohexane formation. To stop the reaction in cyclohexene, promoters such as zinc are added. In this work, we carried out a preliminary DFT study showing that the addition of cadmium to a structure containing Ru and Al could be as effective or better than zinc in promoting partial hydrogenation of benzene. Experimentally, Ru/Al2O3 catalysts with 1% Ru and different cadmium contents were prepared by successive impregnations of CdCl2 and RuCl3 and characterized by textural analysis, XRD, EDXRF, SEM-EDS, DRS, TPR and H-2-chemisorption. The catalysts were subjected to partial hydrogenation of benzene in batch reactor at 150 degrees C and 50 bar H-2. The catalysts presented RuO2 and RuCl3 in function of the remaining chlorine content after calcination. The Ru0.2CdAl catalyst with Cd:Ru ratio 0.2:1 presented 2-fold higher activity and cyclohexene yield than Ru/Al2O3 without cadmium. This catalyst presented highest reducibility with Ru-o, Ru-Cd interaction and higher H-2 chemisorption. Additionally, a reaction with benzene and water showed that the Ru0.2CdAl catalyst obtained twice the activity of the same catalyst with pure benzene.