The Modification Of Cu/TiO₂ Catalysts And Its Application For Methanol Synthesis Via CO₂ Hydrogenation

Synthesis of methanol from the catalytic hydrogenation of the carbon dioxide is of great importance for the development of economy and the protection of environment.In this article,MgO-modified Cu/TiO₂ catalysts were prepared and used for methanol synthesis from CO₂ hydrogenation.The effects of surface MgO modification?using impregnation method?and bulk MgO doping?using hydrothermal method?on the properties of Cu/TiO₂ catalysts has been investigated.Furthermore,reduced Cu/TiO₂ catalysts were prepared with a hydrothermal method.The main results obtained are as follows.1.The effect of surface MgO modification on the physichemical and catalytic properties of Cu/TiO₂ catalysts.A serials of copper catalysts supported on TiO₂ modified with different amount of MgO were prepared by an impregnation method?MgO/TiO₂?.With the increase in MgO amount,the Cu surface area increases first and then decreases.The modification of TiO₂ with MgO hinders the interaction between CuO and TiO₂,resulting in a decline in the reducibility of CuO.Furthermore,the number and strength of the moderate and strong basic sites over the surface of catalyst increase with increasing the MgO loading.The copper catalyst exhibits an optimum catalytic activity as the content of MgO is 1 wt%.The CO₂ conversion is a result of the synergetic effect of the Cu specific surface area and the reducibility of CuO,and the CH₃OH selectivity is related to the surface basicity of catalyst.2.The effect of bulk MgO doping on the physichemical and catalytic properties of Cu/TiO₂ catalysts.The carrier of MgO-dopped TiO₂ was prepared by hydrothermal synthesis,and then CuO was loaded on the prepared support by the impregnation method.The catalysts were investigated by a serial of characterization methods.The results show that the strength of the surface basicity over catalysts increase with the loading amount of MgO.At the same time,BET surface areas increased.Moreover,the catalytic activity increased with the increase in the amount of MgO,and a maximum value was obtained when the loading amount of MgO reached 3%.3.The reduced Cu/TiO₂ catalysts were prepared by hydrothermal method.The copper in the catalyst exists in a state of CuO without pre-reduced with hydrogen.With the increase in Cu amount,the Cu surface area increases first and then decreases.The total number of the basic sites over the surface of catalyst increase with increasing the Cu loading and the strength of basic sites over the surface of catalyst decreases.The CO₂ conversion depended on the Cu specific surface area,and the CH₃OH selectivity is related to the surface basicity of catalyst.The copper catalyst exhibits an optimum catalytic activity as the content of Cu is 20 wt%.