溶剂极性对微波辐射老化制备前驱体及CuO/ZnO/Al2O3催化剂结构的影响

在制备CuO/ZnO/Al2O3催化剂的老化过程中,采用微波辐射老化技术,着重研究了溶剂极性对前躯体物相组成,烧后CuO/ZnO/Al2O3催化剂结构及其在浆态床合成甲醇工艺中催化性能的影响。通过XRD、DTG、H2-TPR,FTIR、HR-TEM和XPS对前驱体及催化剂表征表明,沉淀母液在微波辐射条件下进行老化,溶剂的极性对前躯体物相组成及催化剂结构影响显著。随着溶剂极性的增大,Zn2+/Cu2+取代Cu2(CO3)(OH)2/Zn5(CO3)2(OH)6中Cu2+/Zn2+的取代反应增强,使得前躯体中(Cu,Zn)5(CO3)2(OH)6和(Cu,Zn)2(CO3)(OH)2物相的含量增多,结晶度提高,导致烧后CuO/ZnO/Al2O3催化剂中CuO-ZnO协同作用增强,且CuO晶粒减小,表面Cu含量增加,催化剂活性和稳定性提高。水溶剂的极性最大,制备的催化剂活性和稳定性最好,甲醇的时空收率(STY)和平均失活率分别为320 mg.g-1.h-1和0.11%.d-1。

Influence of Solvent Polarity on Microstructure of Precursors and CuO/ZnO/Al2O3 Catalysts Aged under Microwave Irradiation

In the preparation of a CuO/ZnO/Al₂O₃ catalyst for slurry methanol synthesis, microwave irradiation was introduced into the aging process. The effect of solvent polarity was studied on phase composition of the precursor, microstructure of the calcined CuO/ZnO/Al₂O₃ catalyst and catalytic performance for slurry methanol synthesis. The characterization by XRD, FTIR, DTG, HR-TEM, H₂-TPR and XPS showed that the solvent polarity had a significant effect on the composition of the precursor aged under microwave irradiation. The results indicated that solvent polarity benefited to the substitution of Cu²⁺/Zn²⁺ in Cu₂(CO₃)(OH)₂/Zn₅(CO₃)₂(OH)₆ by Zn²⁺/Cu²⁺. With the increasing of the solvent polarity, the content and crystallization degree of (Cu, Zn)₂(CO₃)(OH)₂ and (Cu, Zn)₅(CO₃)₂(OH)₆ became higher in the precursor, the interaction of CuO/ZnO/Al₂O₃ between CuO and ZnO became stronger, CuO crystal particles dispersed better and surface CuO content became higher. The performance of CuO/ZnO/Al₂O₃ catalyst using water as solvent is the best, the methanol sapce-time yield (STY) and deactivation rate of the catalyst were 320 mg· g^-1·h^-1 and 0.11%·d^-1, respectively.