负载型La_(1-x)Sr_xMnO_3催化剂CO氧化性能的研究

THE OXIDATION ACTIVITY OF SUPPORTED La_(1-x) Sr_x MnO_3 CATALYSTS

用Mn_2O_3改性微球硅酸铝(SAMy,y为预载量)作载体,La_(1-x)Sr_xMnO_3催化剂CO氧化活性显著提高。Mn_2O_3除本身有一些CO氧化活性外,XRD结果表明主要是在SAMy载体上被载活性组分La_(1-x)Sr_xMnO_3氧化物相对含量和催化剂比表面有所提高,在所考察条件下,y=10为最佳。XPS研究表明:样品表面上的氧有吸附氧和晶格氧两种状态,Sr掺杂引起La_(1-x)Sr_xMnO_3化合物表面的锰以Mn^(3+)和Mn^(4+)价态并存,同时随x增加晶格氧空位增加,水热处理对500～650℃活性影响不大,而且14h后催化剂活性趋于稳定。使用热重仪研究了载体及催化剂在H_2气流及不同温度下的还原特性。

The oxidation activity of supported La_(1-x)Sr_xMnO_3 has been greatly improved by modifying the support silica-alumina (SA) , with Mn_2O_3, designated as SAM_y (y is Mn_2O_3 loadings) .Results of XRD showed that the content of La_(1-x)Sr_xMnO_3 and the surface area of the catalyst is higher when SAMy is used as the support instead of SA. Maximum activty of La_(1-x)Sr_xMnO_3 SAMy was obtained for y=10. The activity of La_(1-x)Sr_xMnO_3 was also affected by doping with Sr. The best one was obtained at x=0.4. Characterization of La_(1-x)Sr_xMnO_3/SAMy (SA) by XPS demonstrated that oxygen at the surface of the catalysts is Present in two states—absorbed oxygen and oxygen in lattice. Strontium doping of LaMnO_3 resulted in the coexistance of Mn^(3+) and Mn^(4+) at the surface, and oxygen vacancies in the lattice of La_(1-x)Sr_xMnO_3 increased with increasing Sr content. Hydrothermal treatment of the catalyste at 750℃ showed that the activity decreased slightly at 500～650℃, and approached a stable value after 14 hours of treatment. The reduction property of the catalysts in H_2at different temperatures has been correlated with changes of catalytic activity.