Impact of chloride ions on the oxidative coupling of methane over Li/SnO2 catalyst
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The catalytic performance for the oxidative coupling of methane (OCM) over chloride-containing Li/SnO2 was investigated experimentally and the mechanism of OCM was further suggested. Cl− ions exerted remarkable influence on the catalytic performance of Li/SnO2, with that at 750 °C displaying the highest catalytic activity (18.5% C2 yield) for OCM. The prepared catalysts were characterized with N2 physisorption, X-ray diffraction, O2-temperature programmed desorption, X-ray photoelectron spectroscopy and H2 temperature programmed reduction measurement to elucidate the effect of Cl− ions on its properties and catalytic performance. The results showed that the enhanced OCM catalytic activity of the chloride-containing Li/SnO2 catalysts compared with pure Li/SnO2 catalyst may originate from the higher concentration of anion vacancies, more rapid oxygen mobility and improved redox ability of tin. In addition, characterization by CO2-temperature programmed desorption, infrared spectroscopy and O2 frequency pulse reactions results illustrated that adding Cl− ions improved performance of Li/SnO2, which not only reduced strong basic sites to prevent the formation of poisoning carbonate, but also facilitated the formed chloromethane to convert quickly to ethylene.
KeywordsOCM Active oxygen Chloride-containing Lithium oxide Pulse reaction
This work was supported by the “Strategic Priority Research Program” of the Chinese Academy of Sciences (No. XDA09030101) and the Petro China Innovation Foundation (No. 2016D-5007-0506).