载体改性对Cu/B/Al2O3结构及其催化醋酸仲丁酯加氢性能的影响

以γ-Al₂O₃为载体采用分步浸渍法制备了不同金属氧化物进行载体改性的Cu/B/M/Al₂O₃(M=Mg,Ca,Ni)催化剂,并测试了其催化醋酸仲丁酯加氢反应的性能。结果表明,以NiO进行载体改性的催化剂导致酯加氢反应中大量酸催化产物及烃类出现;以MgO进行载体改性不利于金属Cu的分散且催化剂的结构稳定性较差;以CaO对γ-Al₂O₃载体进行改性不仅能够促进金属Cu的分散,提高催化剂的酯加氢活性和产物选择性,而且可以有效减少反应中非活性碳物种在催化剂表面的沉积。

Effects of support modifications on catalyst structure and catalytic performance for hydrogenation ofsec-butyl acetate over Cu/B/Al2O3 catalyst

Cu-based catalysts(Cu/B/M/Al₂O₃, M = Mg, Ca, Ni)supported on the modified γ-Al₂O₃ by incorporating MgO, CaO or NiO were prepared by an incipient wetness impregnation method, of which each active component was solely deposited on support. The catalysts were characterized by scanning electron microscopy(SEM), X-ray diffraction(XRD), NH₃ temperature-programmed desorption(NH₃-TPD), H₂ temperature-programmed reduction(H₂-TPR)and X-ray photoelectron spectroscopy(XPS)techniques. It showed that effects of the modifications of γ-Al₂O₃ support with varied metal oxides on the structure of Cu-based catalysts and the catalytic performances for the hydrogenation of sec-butyl acetate(SBA)were significant. NiO-modified catalysts exhibited dramatic increases in the yields of both ethyl acetate and butane, due to the intrinsic activity of Ni metal for alkene hydrogenation and the acidic support beneficial to transesterification and sec-butanol dehydration, while the modification with MgO resulted in a poor dispersion of Cu metal on support and an inferior catalyst stability for the SBA hydrogenation. For above two catalysts, the modification of NiO or MgO was conducted after loading B₂O₃ and Cu precursors on support. On the contrary, the modification with CaO was done before loading B₂O₃ and Cu precursors, which facilitated the Cu dispersion on support and improved both SBA conversions and the selectivity to sec-butanol. Moreover, formation and accumulation of non-reactive carbonaceous species on the surface of CaO-modified catalyst might be effectively minimized.