DESIGN OF BIFUNCTIONAL CATALYST FOR LOW-TEMPERATURE HYDROGEN PRODUCTION

为了获得高反应活性的水蒸气重整制氢催化剂，对催化剂的制备及其反应机理进行了研究。首先，采用溶胶-凝胶法制备了高比表面积的氧化锆和氧化锆-氧化钇。采用浸渍法制备的Rh/ZrO_2-Y_2O_3催化剂中，Rh的粒径随载体比表面积的增加而线性减小。Rh/ZrO_2-Y_2O_3催化剂对正丁烷水蒸气重整反应表现出较好的催化性能，其催化活性与Rh/ZrO_2催化剂的粒径大小有关。结果表明，反应中间体为甲酸盐物种。Rh/ZrO2催化剂上的甲酸盐物种在低温下被反应消耗。研究还发现，碱性表面羟基具有较高的反应活性。流动实验得到的Rh/ZrO2催化剂的优良性能似乎是该催化剂具有酸碱性质的原因。

In order to obtain a catalyst with high reactivity for hydrogen production by steam reforming, studies on the catalyst preparation and the reaction mechanism were carried out.First, ZrO_2 and ZrO_2-Y_2O_3 with a high specific surface area were produced by the sol-gel method. Rhodium particle sizes of Rh/ZrO_2-Y_2O_3 catalysts prepared by the impreganation method decreased linearly with increasing specific surface areas of ZrO_2-Y_2O_3 supports. Rh/ZrO_2-Y_2O_3 catalysts showed superior performance for the steam reforming of n-butane and the catalyic activity related to rhodium particle size.Further, in situ DRIFT and TPD experiments were made to investigate the reaction mechanism of low-temperature steam reforming over Rh/ZrO_2 catalyst. It was found that the reaction intermediate was formate species. Formate species over Rh/ZrO_2 catalyst was consumed with reaction at low temperature. It was also found the basic surface hydroxyl groups had high reactivity. The superior performance of Rh/ZrO_2 catalyst obtained by using the flow experiment seemed to be responsible for the acid-base property of this catalyst.