甲烷氧化偶联制C_2烃La_2O_3基催化剂的研究

Study of Lanthania-Based Catalysts for Oxidative Coupling of Methane to C_2-Hydrocarbons

本文的实验结果表明,具有开放型本征构型的La_2O_3对甲烷氧化偶联反应有相当好的活性和选择性,在750℃、原料气空速6.O×10~4ml.g^(-1).h^(-1),CH_4:O_2:N_2=3.7:l.0:9.0(V/V)的反应条件下,氧接近全部转化,甲烷转化率达25.4％,C_2烃选择性为43.6％,添加碱土金属(Ca、Sr、Ba)氧化物或碳酸盐能显著地改善催化剂的性能,在上述反应条件下,60mol％Ba-La_2O_3催化剂的C_2烃选择性达到58％。

The experimental results of the present work indicated that lanthania (La2O3) with layer-type structure, which is extremely open to oxygen chemisorption. showed considerable efficacy for catalyzing the methane-oxidative-coupling (MOC) reaction. Under the reaction conditions of 75℃ , CH4/O2/N2 = 3. 7/1. 0/9. 0(V/V),and GHSV = 6 x 104 ml · g-1 · h-1,nearly 100% O2-conversion,25. 4% CH4-conversion,43. 6% C2-selectivity and 11. 0% C2-yield were reached. Addition of alkaline-earth oxides of carbonates improved markedly the MOC performance of the catalysts, with 58% C2-selectivity and 17. 4% C2-yield being reached for 60 mol % Ba-La2O3 catalyst. The promoter effects were found to increase with increasing cationic sizes,i.e. , Ca2+-<Sr2+<Ba2+. This may be correlated to the increasing tendencies towards the formation of the corresponding metal-superoxides and, in turn, to the increasing cationic polarizabilities.