Mn-Zr-O催化剂的制备及其催化苯甲醇氧化反应的活性

采用氧化还原沉淀法制备了一系列不同n(Mn)∶n(Zr)的Mn-Zr-O催化剂,并以分子氧为氧化剂,催化苯甲醇氧化反应。实验结果表明,当n(Mn)∶n(Zr)=3∶1时,催化剂的活性最高。在100℃下反应1 h,苯甲醇的转化率达88.3%,催化剂的质量比活性(单位质量催化剂上单位时间内的苯甲醇转化量)为17.7 mmol/(g.h)。XRD、N2物理吸附、XANES及H2-TPR表征结果显示,以+3和+4价共存的非晶态Mn氧化物是活化分子氧氧化苯甲醇的高活性物种,添加Zr能增加催化剂的比表面积,促进Mn氧化物的还原,从而显著提高催化剂在苯甲醇氧化反应中的活性。

Preparation of Mn-Zr-O Catalyst and Its Catalytic Activity in Benzyl Alcohol Oxidation

A series of mixed manganese-zirconium oxide catalysts with different n(Mn)∶n(Zr) were prepared by a redox-precipitation method.The prepared catalysts could efficiently catalyze the oxidation of benzyl alcohol with molecular oxygen to benzaldehyde as a main product.The highest activity was achieved by using a catalyst with n(Mn)∶n(Zr) of 3∶1,the conversion of benzyl alcohol and the mass specific activity were 88.3% and 17.7 mmol/(g.h) under the conditions of 1 h and 100 ℃,respectively.The characterization results of XRD,nitrogen physisorption,XANES and H2-TPR suggested that the key active component for the O2activation was the amorphous manganese oxide with the coexistence of Mn3+ and Mn4+.The addition of zirconium to the amorphous manganese oxide can increase the BET surface areas of the catalysts and promote the reduction of the manganese oxides,so the catalytic activity is enhanced.