As one of the key technologies of natural gas chemical industry, oxidative coupling of methane (OCM) catalyzed by La2O3 is an important way to efficiently prepare low-carbon olefins. In this work, online mass spectrometry and micro reactor with optimal heat exchange and temperature control were used to track the activation process. The customized reactor design eliminates exothermal effect in OCM and provides more insight of reaction behavior from 400 to 700°C. The real temperature dependence of the catalyst performance with detailed high temporal resolution online MS data was obtained, thus the experimental reaction parameters were optimized. The experiment results show that C2 selectivity and CH4 conversion are found the highest when methane/oxygen ratio at 3:1 and GHSV at 50 -100 L/g/h. In addition, extra low concentration of H2O and CO in the initial reactant also significantly improve the performance of the catalyst, esp. in lower temperature region around 650°C. The dependence of the obtained catalytic performance on environmental and reaction factors provides more parameter choices for optimization and important clues for further understanding of the catalytic mechanism.

Online MS kinetics study with real temperature dependence of oxidative coupling of methane (OCM) on La2O3

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