Cu/活性炭催化剂：水合肼还原制备及催化甲醇氧化羰基化

以活性炭为载体,水合肼为还原剂制备了负载型Cu/活性炭催化剂,考察了水合肼/硝酸铜物质的量的比对催化甲醇气相氧化羰基化性能的影响,并采用XRD、XPS、H2-TPR和SEM等手段对催化剂进行了表征。结果表明,不加入还原剂水合肼时,催化剂中仅有CuO;随着水合肼/硝酸铜物质的量的比的增加,二价铜逐步被还原为Cu2O和/或单质Cu0,未被还原的Cu(OH)2在催化剂干燥过程中分解形成分散态CuO存在于催化剂表面。当水合肼/硝酸铜物质的量的比为0.75时,催化剂的催化性能最好,碳酸二甲酯的时空收率为120.62 mg.(g.h)-1,选择性为74.51%,甲醇转化率达到3.88%。在93 h反应时间内,催化剂都保持了较高的反应活性和选择性。此时铜物种以Cu2O和分散态CuO为主,Cu2O是主要的活性物种。

Cu Supported on Activated Carbon Catalyst Prepared by Hydrazine Hydrate Reduction for Catalyzing Oxidative Carbonylation of Methanol

The Cu/activated carbon(AC) catalyst was prepared by hydrazine hydrate reduction for catalyzing oxidative carbonylation of methanol to dimethyl carbonate (DMC). The effects of the molar ratio of hydrazine hydrate to copper nitrate on the catalytic properties were investigated, and the catalyst was characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction. The results show that Cu²⁺ is gradually reduced to Cu₂O and/or Cu⁰ with increasing the molar ratio of hydrazine hydrate to copper nitrate. During drying process of the catalyst, the unreduced Cu(OH)₂ decomposed to CuO and highly dispersed on the surface of AC. When the molar ratio of hydrazine hydrate to copper nitrate was 0.75, the catalytic activity for oxidative carbonylation of methanol was the highest, the space-time yield of DMC, selectivity of DMC and conversion of methanol reached 120.62 mg·g^-1·h^-1, 74.5% and 3.88%, respectively, and the activity and selectivity had maintained during 93 h running time. Cu₂O and dispersed CuO were proved as main copper species, and Cu₂O as main catalytic active centre.