Selective Oxidation Of Ethanol To Acetaldehyde By Gold-copper Bimetallic Catalyst

As the depletion of fossil resource, and the environment problem caused by fossil resources increasingly severe, the oxidation of biomass-derived ethanol to produce acetaldehyde has increasingly attract the attention of researchers. Compared with dehydrogenation process, oxidation of ethanol is not limited by thermodynamics, which could reduce reaction temperature and improve ethanol conversion. We try to find an effective catalyst for ethanol oxidation at low temperature by change the support using Au-Cu bimetal as active component. And try to study the synergy mechanism of gold and copper.We chose Al2O3 Med gold-copper bimetallic catalyst for selective oxidation of ethanol to acetaldehyde. Through tuning Au and Cu loading, we found that Cu/Al2O3 or Au/Al2O3 catalyst has much lower ethanol conversion than Au-Cu/Al2O3, indicating that Au and Cu has synergistic effect in the ethanol oxidation reaction. Through using different shaped Al2O3 as support, we find that spherelike Al2O3 supported Au-Cu catalyst has best catalytic performance, which could get 70.5% ethanol conversion and 94.1% acetaldehyde selectivity at 180?, and it demonstrated that support shape has great influence on the catalyst. However, there are many by-products such as ethyl acetate, acetic acid, propion aldehyde, acetone, butanol, carbon dioxide, due to the acid site on the Al2O3 surface.In order to improve the ethanol conversion at low temperature and reduce the side reaction on Al2O3 supported Au-Cu catalysts, we chose a new support, which possesses high excellent chemical and thermal stability. Optimal Au/Cu ratio was determined by tuning Au and Cu loading. Among them,2 wt%Au-1 wt%Cu/M catalyst can get 76.9% ethanol conversion and 94.0% acetaldehyde selectivity at 180?. At same reaction conditions, Au-Cu/M catalysts exhibit more excellent catalytic performance than Au-Cu/Al2O3 and Au-Cu/SiO2 catalysts. To investigate the stability of the Au-Cu/M catalyst for the oxidation of ethanol, the catalyst was run on stream at a constant temperature of 180? for 80 h, it keeps high ethanol conversion and acetaldehyde selectivity. According to the experimental results and the literature, we conclude that Cu could active O2, and Au could promote the elimination of ?-H.