Phenylacetylene hydrogenation coupled with benzyl alcohol dehydrogenation over Cu/CeO2 : a consideration of Cu oxidation state

We shall acknowledge the Engineering and Physical Sciences Research Council, University of Heriot-Watt, and CRITICAT Centre for Doctoral Training for financial support [Ph.D. studentship to Chiara Pischetola; Grant EP/L016419/1].We have examined the effect of copper oxidation state in the continuous gas phase coupled phenylacetylene hydrogenation (to styrene) with benzyl alcohol dehydrogenation (to benzaldehyde) over Cu/CeO2. Analysis by H2-TPR, XPS, XRD and STEM-EDX analyses demonstrates the generation of a range of Cu oxidation states (Cu0 (13-77%), Cu+ (13-74%), Cu2+ (0-55%)). The stepwise formation of styrene and ethylbenzene was promoted in the stand-alone phenylacetylene hydrogenation. An increase in Cu0/Cu+ (from H2-TPR and XPS) enhanced H2 chemisorption and styrene TOF, but with low hydrogen utilisation efficiency. The formation of benzaldehyde and toluene was promoted in the stand-alone dehydrogenation of benzyl alcohol, where benzaldehyde selectivity and TOF correlate with the concentration of Cu0. Full hydrogen utilisation, exclusive benzaldehyde/styrene formation and a (3-fold) greater styrene TOF (to attain 100% yield) was achieved in the coupled process, where hydrogenation/dehydrogenation activity correlates with Cu+/Cu0. This opens new directions for sustainable “hydrogen free” hydrogenations over non-noble Cu catalysts.PostprintPeer reviewe