Mo/La-Co-O催化剂上甲烷选择氧化制甲醇反应  

Studies on Selective Oxidation of Methane to Methanol over Mo/La-Co-O Catalyst

作　　者：张昕[1] 贺德华[1] 张启俭[1] 叶青[1] 徐柏庆[1] 朱起明[1] 

机构地区：[1]清华大学化学系一碳化学与化工国家重点实验室,北京100084

出　　处：《催化学报》2003年第4期305-311,共7页

基　　金：国家重点基础研究发展规划项目 (G19990 2 2 40 6)

摘　　要：制备了一系列Mo/La Co O催化剂 ,考察了催化剂对甲烷选择氧化制甲醇反应的催化性能 ,并用BET ,XRD ,LRS ,H2 TPR和XPS等技术研究了催化剂的结构和性质 .结果表明 ,在n(CH4 ) ∶n(O2 ) ∶n(N2 ) =10∶1∶1,SV =14 4L/ (g·h) ,p =4 2MPa和θ =4 2 0℃的反应条件下 ,7%Mo/La Co O催化剂表现出较好的催化性能 ,甲醇选择性为 6 0 % ,甲醇收率为 6 7% .Mo负载于La Co O上以后 ,Mo O物种以无定形的状态存在于La Co O表面 ,并与La Co O发生相互作用 .Mo的负载量影响Mo O物种的结构及催化剂的性质 .催化剂的还原性和表面O-/O2 -比影响催化剂上甲烷选择氧化制甲醇反应的性能 .The La Co O (perovskite type oxide), being selected as catalyst support for its high ability in activation of O 2, was prepared by sol gel method using citric acid. A series of Mo/La Co O catalyst samples with different Mo loading were prepared by wetness impregnation method. The catalytic performance of the catalyst samples in selective oxidation of CH 4 to CH 3OH was tested. The reaction resulted in products CH 3OH, CO and CO 2 over these catalyst samples. With the increase of Mo loading, CH 4 conversion gradually increased and CH 3OH selectivity gave maximum value on 7%Mo/La Co O catalyst. The CH 3OH selectivity of ca 60% and its yield of ca 6 7% were achieved under the conditions of n (CH 4) ∶ n (O 2) ∶ n (N 2) =10∶1∶1, SV=14 4 L/(g·h) , p =4 2 MPa and θ =420 ℃. And the CH 3OH selectivity and yield continuously increased with the increase of reaction temperature on 7%Mo/La Co O catalyst. The properties of the catalyst, such as structure, reducibility, oxidation state of surface ions, surface composition etc , were characterized by using BET, XRD, LRS, H 2 TPR and XPS techniques. The catalyst is mainly composed of LaCoO 3 and Co 3O 4. The molybdena is amorphous and is well dispersed when it is loaded on La Co O. On the other hand, there exists interaction between the loaded Mo and the support La Co O, and thus modifies the properties of the catalyst. With the increase of Mo loading, the reducibility of the catalyst is improved, and the O -/O 2- ratio on the catalyst surface decreases. The reducibility and the O -/O 2- ratio can determine the catalytic performance of Mo/La Co O catalyst in the selective oxidation of CH 4 to CH 3OH. The proper reducibility and proper O -/O 2- ratio of the catalyst can enhance the selectivity and yield of CH 3OH.

关 键 词：Mo/La-Co-O催化剂 甲烷 选择氧化 甲醇 氧化钼 氧化镧 氧化钴 

分 类 号：O643.3[理学—物理化学]