焙烧温度对CuCe/AC催化剂甲醇氧化羰基化性能的影响

采用先浸渍Ce后浸渍Cu的方法制备了活性炭(AC)负载CuCe催化剂,考察了焙烧温度对CuCe/AC催化剂表面结构及其催化甲醇气相氧化羰基化合成碳酸二甲酯(DMC)性能的影响,并采用XRD、XPS和H2-TPR等表征分析了活性组分含量和价态等性质。结果表明,催化剂中高价态的Cu~(2+)逐渐被还原为低价态的Cu~+和Cu~0,催化剂中发生Cu~(2+)→Cu~+→Cu~0的还原变化过程。催化剂经450℃焙烧处理后,催化剂中仍然存在一定量的Cu_2O晶相,表明Ce与Cu的相互作用抑制了部分Cu_2O的还原。当焙烧处理温度为300℃时,催化剂中的Cu~+含量达到最高,此时催化剂的活性达到最优,DMC的时空收率、选择性以及甲醇转化率分别为143.4mg/(g·h)、85.2%和4.1%。

Effect of calcination temperature on catalytic performance of CuCe/AC catalysts for oxidative carbonylation of methanol

The CuCe/AC catalysts were prepared by impregnation first with Ce and then with Cu, and effect of calcination temperature on catalytic performance of the CuCe/AC catalysts for gas-phase oxidative carbonylation of methanol to dimethyl carbonate was studied. The active component content and valence state of as-prepared catalysts were characterized by XRD, XPS and H₂-TPR. The results show that Cu²⁺ is gradually reduced to Cu⁺ and Cu⁰ species. After calcinated at 450℃, some Cu₂O phase still exists in the catalyst, which indicates that interaction between Cu and Ce has suppressed the reduction of Cu₂O. As the calcination temperature of 300℃, the content of Cu⁺ achieves the highest, and the corresponding catalyst shows the best catalytic activity. The space-time yield of DMC, selectivity of DMC and conversion of methanol are 143.4mg/(g·h), 85.2% and 4.1%, respectively.