铝添加量对Cu/ZnO/Al_2O_3甲醇合成催化剂性能的影响

采用分步沉淀法制备出一系列不同铝含量的催化剂样品,通过X射线衍射(XRD)、热重-质谱(TG-MS)、荧光光谱仪(XRF)、N_2物理吸附、氢气程序升温还原(H_2-TPR)对样品进行表征,考察了不同铝添加量对铜基甲醇催化剂性能的影响。结果表明,铝元素的添加对前驱物中碱式碳酸盐组分产生作用,促进了焙烧后样品中高温碳酸盐的形成,进而影响到催化剂的性能。随着铝元素的添加,焙烧后催化剂的比表面积、催化剂活性和热稳定性均有增加。当Al~(3+)/(Cu~(2+)+Zn~(2+)+Al~(3+))物质的量比增加至30%时,催化剂在230℃、4 MPa和合成气(13%CO、1.2%CO_2、80%H_2、5.8%Ar)的评价条件下,热处理前后的CO转化率分别为76%和67%,仍保持着较高的活性和热稳定性。

Effect of aluminum proportion on the Cu/ZnO/Al2O3 methanol-synthesis catalyst

The objective of this work is to investigate the effect of Al contents on the performance of methanol-synthesis catalysts. A series of catalyst samples with various Al contents were prepared with fractional precipitation method, and characterized with methods including XRD, TG-MS, XRF, N₂ physisorption and H₂-TPR. Results show that Al addition affected the subcarbonate structure in precursors, which promoted the formation of high temperature carbonates, and thus has an effect on the catalyst performance. With Al addition, the BET surface area of the calcined catalysts, catalyst activity and thermostability increased to different degrees. When the molar ratio of Al³⁺ in catalyst increased to 30%, the CO conversions before and after heat treatment were 76% and 67%, respectively, at the conditions of 230 ℃, 4 MPa and syngas composition of 13%CO, 1.2%CO₂, 80%H₂ and 5.8%Ar. The catalyst sample with 0.3 of Al³⁺/(Cu²⁺+Zn²⁺+Al³⁺) molar ratio remains good catalyst performance.