甲烷氧化偶联催化剂和部分氧化反应机理的原位及非原位谱学表征

采用原痊红外和原位显微Raman光谱技术及XPS、吡啶（Py)吸附的漫反射UV谱、Py-TPD、CO2-TPD等方法对含氟稀土基催化剂上甲烷氧化偶联（OCM）反应活性氧物种、催化剂表面酸碱性进行了考察。在O2预处理和/或工作条件下的SrF2/La2O3,SrF2/Nd2O3,LaOF,BaF2/LaOF和BaF2/CeO2等催化剂上原位观测到超氧物种（O2^-)，并在其中前4种催化剂上检测到O2^-物种与CH4反应生成的气相C2H4，CO2和表面碳酸盐等OCM反应主、副产物。这些结果为O2^-是相应催化剂上OCM反应的活性氧物种首次提供了直接的光谱证据。研究结果表明，催化剂的OCM反应性能与其表面酸碱性的强弱并无简单的对应关系。采用原拉时间分辨红外光谱和原位显微Raman光谱技术对SiO2和γ-Al2O3负载的Rh、Ru催化剂上甲烷部分氧化（POM）制合成气反应的研究表明，由CH4直接氧化生成CO和H2是Rh/SiO2上POM反应的主要途径，而燃烧-重整机理是Ru/γ-Al2O3和Ru/SiO2上CO和H2生成的主要途径，反应条件下催化剂表面氧（O^2-)物种浓度的差异很可能是导致这两种催化剂体系上POM反应机理不同的主要原因，其本质可能源于Rh和Ru对氧的亲合力的不同。

In situ and ex situSpectroscopic Characterization on the Catalysts for Methane Oxidative Coupling and on theMechanism of Methane Partial Oxidation

Active oxygen specie and surface acid/base properties of fluoride-containing rare earth-based catalysts for methane oxidative coupling (OCM) reaction were studied using in situ IR and in situ microprobe Raman spectroscopies, XPS, UV spectra of pyridine (Py) adsorption, Py- and CO2-TPD. O-2 species was detected over O2 and/or CH4/O2 pretreated SrF2/La2Oa, SrF2/Nd2O3, LaOF, BaF2/LaOF and BaF2/CeO2 catalysts at OCM reaction temperature, and the reactions between O-2 species and CH4 to form C2H4 and corresponding side-products of OCM reaction such as CO2 and surface carbonate were observed over SrF2/La2O3, SrF2/Nd2O3, LaOF, BaF2/LaOF catalysts. These results, for the first time, provide direct spectroscopic evidences which suggest that O-2 is the active oxygen species for OCM reaction over the corresponding catalysts. It is also found that the surface basicity is not always a requisite attribute for a good OCM catalyst. The results of in situ time-resolved FTIR and in situ microprobe Raman spectroscopic characterizations on the partial oxidation of methane (POM) reaction indicate that direct oxidation of CH4 to synthesis gas is the main pathway of POM reaction over Rh/SiO2 catalyst, while the combustion-reforming scheme is the dominant pathway of synthesis gas formation over Ru/γAl2Oa and Ru/SiO2 catalysts. The significant difference in the reaction schemes of POM reaction over SiO2 and γ-A12O3 supported Rh and Ru catalysts may be related to the difference in surface concentration of oxygen species (O2-) over the catalysts under the reaction conditions mainly due to the difference in oxygen affinity of the two metals