LiMn_2O_4/TiO_2催化剂上甲烷氧化偶联反应性能的研究  

Performance of oxidative coupling of methane on LiMn_2O_4/TiO_2 catalysts

作　　者：刘玉兰[1] 张泽凯[1] 倪光[1] 刘华彦[1] 陈银飞[1] 

机构地区：[1]浙江工业大学化学工程学院能源化学工程系,浙江杭州310014

出　　处：《燃料化学学报》2016年第6期703-709,共7页Journal of Fuel Chemistry and Technology

摘　　要：采用固相反应法制备了具有尖晶石结构的LiMn_2O_4/TiO_2系列催化剂,探讨了TiO_2、Li/TiO_2、Mn/TiO_2、LiMn_2O_4及LiMn_2O_4/TiO_2等不同组成催化剂的甲烷氧化偶联反应性能,采用XRD、XPS、CO_2-TPD和H_2-TPR等表征方法对该系列催化剂进行了分析。结果表明,具有尖晶石结构的LiMn_2O_4化合物具有较高的甲烷氧化偶联催化活性,在775℃、0.1MPa、7200mL/(h·g),CH_4∶O_2(体积比)为2.5的条件下,甲烷转化率可达25.8%,C2选择性可达43.2%。TiO_2的存在不仅进一步提高了甲烷转化率和C2选择性,还有效抑制了甲烷完全氧化形成CO_2的过程。负载8%LiMn_2O_4的LiMn_2O_4/TiO_2催化剂性能达到最优,此时甲烷转化率达到31.6%,C2选择性为52.4%,CO_2选择性降低到26.3%。考察了不同焙烧温度对催化剂活性的影响,850℃为LiMn_2O_4/TiO_2催化剂的最佳焙烧温度。A series of LiMn_2O_4/TiO_2 catalysts with spinel crystal structure were prepared by solid state reaction method,and the catalytic performance of oxidative coupling of methane on the different catalysts,such as TiO_2,Li / TiO_2,Mn /TiO_2,Li Mn_2O_4 as well as LiMn_2O_4/ TiO_2,was evaluated.The catalysts were characterized by Xray diffraction,X-ray photoelectron spectroscopy,CO_2 temperature programmed desorption and H2 temperature programmed reduction.It is found that Li Mn2O4 with spinel structure has high catalytic activity in oxidative coupling of methane reaction.25.8% of CH4 conversion,43.2% of C_2 selectivity was obtained under the reaction conditions of 775 ℃,0.1 MPa,7 200 m L·h^（-1）·g^（-1）,CH_4∶ O2（ volume ratio） = 2.5.The introduction of TiO_2 support can not only improve CH_4 conversion and C2 selectivity,but also restrain the deep oxidation of methane to CO_2.The LiMn_2O_4/ TiO_2 with 8% loading amount showed the best activity,on which 31.6% of CH_4 conversion,52.4% of C_2 selectivity were obtained and CO2 selectivity was decreased to 26.3%.The effect of calcination temperature on the activity of LiMn_2O_4/ TiO_2 catalysts was investigated.850 ℃ is the optimal calcination temperature.

关 键 词：甲烷氧化偶联 尖晶石 LIMN2O4 TIO2 协同作用 

分 类 号：O643[理学—物理化学]