还原温度和Cu负载量对乙二醇还原法制备的Cu/AC催化剂甲醇氧化羰基化反应性能的影响

摘要

The Cu/AC catalysts were prepared by the polyol process using activated carbon (AC) as support and ethylene glycol (EG) as reductant at different reduction temperature, and characterized by XRD, XPS, AAS, H2-TPR and TEM. The effect of reduction temperature and copper loading on the catalytic performance of Cu/AC catalysts for liquid-phase oxidative carbonylation of methanol to dimethyl carbonate was investigated. The results showed that Cu2+ were gradually reduced to Cu2O and Cu0 with the elevated reduction temperature. When the reduction temperature was 160℃, the content of Cu2O attained the highest with small crystalline size, and the corresponding catalyst exhibited the best catalytic activity. When copper loading was below 2.8% by mass, the Cu species could be highly dispersed on AC surface, resulting in catalytic activity improving with increasing Cu loading, and increasing copper loading to above 2.8% caused the agglomeration of Cu species and thus the catalytic activity decreased. Over the optimal catalyst, DMC space-time yield, selectivity and methanol conversion were 670mg·g-1·h-1, 91.7%and 6.0%, respectively.%以活性炭(AC)为载体采用乙二醇还原法在不同的还原温度制备了系列Cu/AC催化剂，采用XRD、XPS、AAS、H2-TPR和TEM对催化剂进行了表征，并考察了还原温度和铜负载量对其催化甲醇液相氧化羰基化合成碳酸二甲酯（DMC）反应性能的影响。结果表明：随着还原温度的升高Cu/AC催化剂中Cu2+逐渐被还原为低价态的Cu2O和单质Cu，其中经160℃还原制备的催化剂中Cu2O的含量达到最高且晶粒尺寸较小，此时催化剂显示出最佳的催化活性；催化剂铜负载质量分数低于2.8%时， Cu物种高度分散在AC载体表面，提高负载量有利于催化活性的提高，超过2.8%后继续提高铜负载量则导致Cu物种颗粒长大，并出现明显的团聚现象，催化剂活性下降。最佳催化剂的DMC时空产率、选择性和甲醇转化率分别为670mg/(g·h)，91.7%和6.0%。