物理化学学报 >> 1995, Vol. 11 >> Issue (10): 902-906.doi: 10.3866/PKU.WHXB19951009

研究论文 上一篇    下一篇

红外光谱研究甲烷和氧与SrO-La2O3/CaO表面的相互作用

余林,徐奕德,郭燮贤   

  1. 中国科学院大连化学物理研究所催化基础国家重点实验室，大连 116023
  • 收稿日期:1994-11-19 修回日期:1995-03-15 发布日期:1995-10-15
  • 通讯作者: 徐奕德

A FT-IR Study on the Interaction of CH4 and O2 with the Surface of SrO-La2O3/CaO Catalysts

Yu Lin,Xu Yi-De,Guo Xie-Xian   

  1. State Key Laboratory of Catalysis,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian 116023
  • Received:1994-11-19 Revised:1995-03-15 Published:1995-10-15
  • Contact: Xu Yi-De

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摘要：

在甲烷氧化偶联（OCM）反应条件下，用原位红外光谱研究SrO-La2O3／CaO催化剂，结果表明，晶格氧使甲烷深度氧化. La2O3和CaO具有活泼的晶格氧，SrO的晶格氧比较稳定，气相氧通过补充催化剂表面消耗掉的晶格氧，加速了甲烷的深度氧化．另一方面，催化剂表面的碳酸根物种在氧气氛下分解. 在La2O3和LC催化剂中，催化剂表面La2O2（CO3）的分解形成配位不饱和的晶格氧O2-，并为气相氧吸附提供氧空穴．气相氧在氧空穴上吸附和配位不饱和晶格氧向吸附氧转移电荷，产生活性氧物种（可能为O2-）．红外光谱能检测到波数为1118cm-1的吸收峰. 在CaO，SrO和SLC催化剂上，未能用FT－IR检测到类似的活性氧物种，但有C2产物生成，推测表面碳酸根分解可能直接产生活性氧物种（可能为O22-）．

关键词: SrO-La2O3/CaO, 原位红外光谱, 甲烷氧化偶联, 晶格氧, 佩位不饱和晶格氧, 活性氧物种, 表面碳酸根物种

Abstract:

 SrO-La2O3/CaO(SLC) catalysts have been found to be active for the oxidative coupling of methane (OCM), but the lattice oxygen of them is only active for total oxidation as revealed by the studies of in - situ FT-IR on the interaction between CH4 and the oxide surface concerned.
The results of an in - situ FT-IR study on the interaction of the mixture of CH4 and O2 with the catalyst surface show that the oxygen in gas phase can accelerate the total oxidation of CH4 via replenishing the lattice oxygen consumed on the hand, and on the other hand, it will promote the decomposition of surface carbonates formed during the reaction. For La2O3 and LC catalysts, the decomposition of surface La2O2(CO3) carbonate results in the formation of coordination unsaturated oxygen species and oxygen vacancy, and then the oxygen in gas phase could be adsorbed on the oxygen vacancy and electron transfer from coordination unsaturated oxygen species to the oxygen adspecies takes place to produce active oxygen species, probably in the form O2-, with the characteristic IR band at 1180cm-1. Meanwhile on the surfaces of CaO, SrO and SLC catalysts, although no any active oxygen species could be detected, the formation of C2H4 product still is observed at high temperatures. Therefore, it is speculated that the decomposition of furface carbonates directly leads to the formation of active oxygen species, O22-.

Key words: SrO-La2O3/CaO, Oxidative coupling of methane, FT-IR, Lattice oxygen, Coordination unsaturated oxygen species;Surface carbonates