Effect of calcination temperature on catalytic performance of CuCe/AC catalysts for oxidative carbonylation of methanol
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摘要: 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Cu2+逐渐被还原为低价态的Cu+和Cu0, 催化剂中发生Cu2+→Cu+→Cu0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Cu2O晶相, 表明Ce与Cu的相互作用抑制了部分Cu2O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%。
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关键词:
- 碳酸二甲酯 /
- CuCe/AC催化剂 /
- 焙烧温度 /
- 活性组分
Abstract: 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.-
Key words:
- dimethylcarbonate /
- CuCe/AC catalyst /
- calcination temperature /
- active component
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表 1 不同焙烧温度下催化剂的Cu 2p XPS和CuLMM AES曲线拟合结果分析
Table 1 Cu 2p XPS and CuLMM AES curve-fitting analysis results of catalysts calcinated at different temperatures
Calcination
temp. t/℃BE of Cu 2p3/2 E/eV KE of CuLMM E/eV Area of Cu 2p3/2/%① Area of CuLMM/%② Cu+
/%③Cu0
/%④Cu2+ Cu+/Cu0 Cu+ Cu0 Cu2+ Cu+/Cu0 Cu+ Cu0 150 934.5 933.0 916.3 - 53.9 46.1 100 - 46.1 - 200 934.5 932.8 916.3 - 43.8 56.2 100 - 56.2 - 250 934.5 932.9 916.2 918.0 42.6 57.4 69.1 31.9 46.3 11.1 300 - 932.5 916.2 918.0 - 100 73.0 27.0 73.0 27.0 350 - 932.7 916.5 918.0 - 100 64.7 35. 3 64.7 35.3 400 - 932.8 916.3 918.1 - 100 60.1 39.9 60.1 39.9 450 - 932.6 916.3 918.0 - 100 52.7 47.3 52.7 47.3 ①area percentage calculated from Cu 2p3/2; ②area percentage calculated from CuLMM Auger; ③multiply Cu+ in area percentage of CuLMM by Cu+/Cu0 in area percentage of Cu 2p3/2; ④multiply Cu0 in area percentage of CuLMM by Cu+/Cu0 in area percentage of Cu 2p3/2 表 2 不同焙烧温度下催化剂的H2-TPR分析
Table 2 H2-TPR analysis of catalysts calcinated at different temperatures
Calcination temperature t/℃ 150 200 250 300 350 400 450 H2-consumption m/(mmol·g-1) 0.65 0.52 0.47 0.28 0.22 0.19 0.11 -
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