Impact of chloride ions on the oxidative coupling of methane over Li/SnO2 catalyst

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 degrees C displaying the highest catalytic activity (18.5% C-2 yield) for OCM. The prepared catalysts were characterized with N-2 physisorption, X-ray diffraction, O-2-temperature programmed desorption, X-ray photoelectron spectroscopy and H-2 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 O-2 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.