La_2O_3/碱土金属氧化物催化剂的甲烷氧化偶联性能与结构

STRUCTURE AND PERFORMANCE OF La_2O_3 PROMOTED ALKALINE EARTH OXIDE CATALYSTS FOR THE OXIDATIVE COUPLING OF METHANE

La2O3具有较高的甲烷氧化偶联活性,碱士金属氧化物（CaO,BaO,SrO）具有较高的选择性,La2O3修饰的碱土金属氧化物具有很高的反应活性和较好的选择性。目前对该催化剂体系的基础研究工作尚不多。尤其对催化剂各组分的作用。

There exists a good linear relationship between the XRD intensity ratio of La2O3 (d = 2.967) to CaO (d=2.4) (or SrO(d=2.816)) and the content of La2O3 (see Fig. 3). The XPS intensity ratio of La3d5/2 to Sr3d5/2 and the content of La2O3 also shows a good linear relationship (see Fig. 4). It indicates that there is no new crystal phase or new compound formed in the La2O3/alkaline earth oxide catalysts, which are composed of the uniform crystal mixture of La2O3 and alkaline earth oxides. Because the catalysts were prepared by the coprecipitation method, the crystal mixtures are expected to be quite uniform. The study of the structure and performance of La2O3 promoted alkaline earth oxide catalysts indicates that the effects of La2O3 on the catalyst performance include three aspects; (a) the addition of La2O3 enlarges the catalyst surface, and then its activity increases) (b) La2O3 itself is a high active component, and it exists in an isolated form in the catalysts, thus, the added La2O3 enhances the activity; (c) the partial coverage of SrO surface by La2O3 may be important at low La2O3 content.