Role of the Feed Gas on the Selective Catalytic Dehydrogenation of Benzyl Alcohol over Cu/Hydrotalcite Catalyst

The present work highlights the utilization of CO2 as feed gas for the catalytic dehydrogenation of benzyl alcohol to benzaldehyde over supported Cu catalysts in continuous process. Powder X-Ray Diffraction (XRD) patterns, N2O pulse chemisorption results, H2-Temperature Programmed Reduction (H2-TPR) profiles and Transmission Electron Microscopy (TEM) analysis suggests that Cu/hydrotalcite possess high dispersion with small Cu atoms. Due to the united effects of high metal dispersion and bifunctional acid base properties (as evidenced by Temperature Programmed Desorption (TPD) of CO2 and NH3), Cu/hydrotalcite catalyst offers better activity than Cu/Al2O3 and Cu/MgO. The presence of CO2 promotes reverse water gas shift reaction by consuming the in-situ generated H2 in dehydrogenation process and maintains stable benzaldehyde selectivity. Whereas the presence of N2 promotes the disproportionation reaction and leads to decrease in benzaldehyde selectivity.