纳米La_2O_3催化剂上低温甲烷氧化偶联和乙烷氧化脱氢

采用沉淀法制备了纳米La2O3催化剂,并考察了该催化剂对甲烷氧化偶联和乙烷氧化脱氢反应的催化性能。实验结果表明,对于甲烷氧化偶联反应,在450℃、气态空速(GHSV)=7.5L/(g.h)、n(CH4)∶n(O2)=3.0的条件下,甲烷转化率和C2烃收率分别达到26.6%和10.8%,比商品化的La2O3催化剂的启动温度低100℃,具有较好的低温甲烷氧化偶联反应性能;对于乙烷氧化脱氢反应,在450℃、GHSV=10L/(g.h)、n(C2H6)∶n(O2)∶n(N2)=1∶1∶4的条件下,乙烷转化率和乙烯收率分别为49.1%和25.9%,明显优于商品化的La2O3催化剂。对纳米La2O3催化剂的表征结果显示,沉淀法制备的纳米La2O3催化剂颗粒较小(粒径30~50nm)、比表面积较大(12.0m2/g),具有较强的吸附O2能力,因此能在较低温度下活化甲烷和乙烷,具有较好的低温催化性能。

Oxidative Coupling of Methane and Oxidative Dehydrogenation of Ethane over La2O3 Nano-Catalyst at Low Temperature

La2O3 nano-catalyst was prepared by precipitation method.Performance of the catalyst in oxidative coupling of methane(OCM) and oxidative dehydrogenation of ethane(ODE) at low temperature was studied.As OCM is concerned under conditions of gas hourly space velocity(GHSV) 7.5 mL/(g·h),n(CH4) ∶n(O2) 3.0 and 450 ℃,which is 100 ℃ lower than startup temperature of commercial La2O3 catalyst used in OCM,conversion of CH4 and yield of C2 hydrocarbon are 26.6% and 10.8 %,respectively.As ODE is concerned under conditions of 450 ℃,GHSV 10 mL/(g·h) and n(C2H6) ∶n(O2) ∶n(N2) 1 ∶1 ∶4,conversion of C2H6 and yield of C2H4 are 49.1% and 25.9% respectively.The results in both cases are superior to commercial La2O3 catalyst.Both commercial and La2O3 nano-catalysts were characterized by means of XRD,BET,TEM and O2-TPD.Average size and specific surface area of La2O3 nano-catalyst are 30-50 nm and 12.0 m2/g respectively,which would be favorable to absorption and activation of O2.