对甲烷氧化偶联La_2O_3/BaCO_3催化剂稳定性的考察

THE STABILITY TEST OF La_2O_3/BaCO_3 CATALYST FOR THE OXIDATIVE COUPLING OF METHANE

在前一阶段的工作中,发现La_2O_3/BaCO_3作为甲烷氧化偶联制乙烯的催化剂具有良好的活性与选择性。本文在对这一体系催化剂进行筛选、评价的基础上,选择其中编号为C82的催化剂进行了稳定性考察,并对500小时稳定性试验后的催化剂进行了一系列反应条件试验与红外光谱和x-光衍射分析。

Lanthanum - promoted barium carbonate prepared by coprecipitati-on method ( designed as C82 ) are active and selective catalysts for the partial oxidation of methane to ethane and ethylene using oxygen as an oxidant. This paper gives the results of the stability test of this catalyst for the title reaction. In a conventional fixed-bed flow reactor, operating at atmospheric pressure, a 70% C2 ( sum of ethane and ethylene) selectivity was achieved at a 25% methane conversion over 0.25g of La2O3/BaCO3 catalyst at 780℃ with a gas mixture of CH4/ air= 1:1, 4.77×104 gas hourly space velocity. During the period of 500 hours reaction, the above results were always remained. Followed by catalytic stability test, we examined the effect of reaction conditions on the results. It appears that C2 selectivity increased as GHSV and reaction temperature are increased, an increase of the oxygen concentration in the reactor feed gives an adverse effecs on C2 selectivity. To compare the difference of the fresh catalyst with post reaction sample, the FT - IR and XRD results are presented in this paper. This result affirmed that the structure of post reaction catalyst is completely same as the fresh sample. No formation of either solid solution or new compound is observed. Therefore, the good stability of the catalyst is originated from its high structural stability.