并流淤浆混合法制备铜基甲醇合成催化剂及助剂Al_2O_3的作用研究

Preparation of CuO/ZnO/γ-Al_2O_3 catalysts for methanol synthesis using parallel-slurry-mixing method

采用并流淤浆混合法制备了一系列具有不同铜锌铝比的铜基甲醇合成催化剂CuO/ZnO/Al2O3,测试了其催化性能(甲醇收率和CO转化率)及物相结构,并对该制备方法进行评价。Cu∶Zn∶Al摩尔比为4∶5∶1的铜基催化剂显示了最好的催化活性。通过对催化剂前驱物煅烧过程进行DTA分析及对前驱物进行XRD分析表明,催化剂前驱物的物相与Al2O3的量有关。当Al2O3的量较低时,前驱物的物相以(Cu0.3Zn0.7)5(CO3)2(OH)6为主;当Al2O3的量较高时,前驱物中物相(Cu0.3Zn0.7)5(CO3)2(OH)6的量下降,而物相Cu2CO3(OH)2的量增加。物相(Cu0.3Zn0.7)5(CO3)2(OH)6对终态催化剂的活性是十分有利的。

A series of CuO/ZnO/γ-Al2O3 catalysts with different Al2O3 contents were prepared using parallel-slurry-mixing method,in which an aqueous solution of Cu2＋ and Zn2＋ mixed nitrates and an aqueous solution of Na2CO3 were poured into a precipitation vessel containing γ-Al2O3 slurry in a parallel-flow manner.The catalyst structure and its performance for methanol synthesis were investigated.The results indicated that Al2O3 as a structural promoter can inhibit CuO and ZnO crystallites from enlarging during calcination.The catalyst with a Cu∶Zn∶Al ratio of 4∶5∶1 exhibits the highest catalytic activity.With an increase in Al content, the amounts of（Cu0.3Zn0.7）5（CO3）2（OH）6 phase in the catalyst precursor before calcination shows a decrease,whereas those of Cu2CO3（OH）2 phase shows an increase;（Cu0.3Zn0.7）5（CO3）2（OH）6 in the precursor is beneficial to the catalytic activity of the final Cu/ZnO/γ-Al2O3 catalyst.