A STUDY OF THE OXIDATIVE COUPLING OF METHANE OVER SRO-LA2O3/CAO CATALYSTS BY USING CO2 AS A PROBE

	A STUDY OF THE OXIDATIVE COUPLING OF METHANE OVER SRO-LA2O3/CAO CATALYSTS BY USING CO2 AS A PROBE
	XU, YD; YU, L; CAI, C; HUANG, JS; GUO, XX
刊名	CATALYSIS LETTERS
	1995
卷号	35 期号:3-4 页码:215-231
关键词	Oxidative Coupling Of Methane (Ocm) Sro-la2o3/cao Basicity Co2-tpd Carbonates In Situ Ft-ir Co2 Adspecies
ISSN号	1011-372X
文献子类	Article
英文摘要	20%SrO-20%La2O3/CaO catalyst (SLC-2), prepared by impregnation, has shown 18% CH4 conversion and 80% C-2-selectivity for the oxidative coupling of methane (OCM) at 1073-1103 K with CH4 : O-2 molar ratio = 9 : 1 and total flow rate of 100 ml/min. Addition of SrO onto La2O3/CaO (LC) catalyst strengthens the surface basicity and leads to an increase in CH4 conversion and C-2-selectivity. Meanwhile, the reaction temperature required to obtain the highest C-2-yield increases with increasing SrO content. The formation of carbonate on the catalyst surface is the main reason for the deactivation of LC and SLC catalysts. If the amount of CO2 added into the feed is appropriate and the reaction temperature is high enough, there is no deactivation at all. In such case, the added CO2 will suppress the formation of CO2 produced via the OCM reaction, therefore, improves the C-2-selectivity. The FT-IR spectra of CO2 adspecies recorded at different temperatures show that CO2 interacts easily with the catalyst surface to form different carbonate adspecies. Unidentate carbonate is the main CO2 adspecies formed on the catalyst surface. On the LC catalyst surface, the unidentate carbonate was first formed on Ca2+ cations at room temperature. If the temperature is higher than 473 K, it will form on La3+ cations. On the SLC catalyst surface, if the temperature is lower than 573 K, only the unidentate carbonate formed on Ca2+ cations could be observed. When the temperature is higher than 673 K, it will then form on Sr2+ cations. This suggests that the unidentate carbonate can migrate on the LC and SLC catalyst surface on one hand, and on the other hand, that the surface composition of SLC catalysts is dynamic in nature. On the basis of both the decomposition temperatures of the carbonate species, and the temperature dependence of the Delta upsilon value which is the difference of symmetric and asymmetric stretching frequencies of surface carbonates, the in situ FT-IR technique offered two approaches to measure the surface basicity of the SLC catalyst. The results thus obtained are in good agreement with that of CO2-TPD. The role of the surface basicity of the SLC catalyst is also discussed.
WOS关键词	MAGNESIUM-OXIDE CATALYST ; LANTHANIDE OXIDES ; CARBON-DIOXIDE ; DIMERIZATION ; ALUMINA
WOS研究方向	Chemistry
语种	英语
出版者	BALTZER SCI PUBL BV
WOS记录号	WOS:A1995TH73400003
内容类型	期刊论文
源URL	[http://cas-ir.dicp.ac.cn/handle/321008/167864]
专题	大连化学物理研究所_中国科学院大连化学物理研究所
通讯作者	XU, YD
推荐引用方式 GB/T 7714	XU, YD,YU, L,CAI, C,et al. A STUDY OF THE OXIDATIVE COUPLING OF METHANE OVER SRO-LA2O3/CAO CATALYSTS BY USING CO2 AS A PROBE[J]. CATALYSIS LETTERS,1995,35(3-4):215-231.
APA	XU, YD,YU, L,CAI, C,HUANG, JS,&GUO, XX.(1995).A STUDY OF THE OXIDATIVE COUPLING OF METHANE OVER SRO-LA2O3/CAO CATALYSTS BY USING CO2 AS A PROBE.CATALYSIS LETTERS,35(3-4),215-231.
MLA	XU, YD,et al."A STUDY OF THE OXIDATIVE COUPLING OF METHANE OVER SRO-LA2O3/CAO CATALYSTS BY USING CO2 AS A PROBE".CATALYSIS LETTERS 35.3-4(1995):215-231.