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SnO2-based catalysts with low temperature performance for oxidative coupling of methane: insight into the promotional effects of alkali metal oxides
European Journal of Inorganic Chemistry ( IF 2.3 ) Pub Date : 2018-03-06 , DOI: 10.1002/ejic.201701440 Liang Peng 1 , Junwei Xu 1 , Xiuzhong Fang 1 , Wenming Liu 1 , Xianglan Xu 1 , Liang Liu 1 , Zhongchen Li 1 , Honggen Peng 1 , Renyang Zheng 2 , Xiang Wang 1
European Journal of Inorganic Chemistry ( IF 2.3 ) Pub Date : 2018-03-06 , DOI: 10.1002/ejic.201701440 Liang Peng 1 , Junwei Xu 1 , Xiuzhong Fang 1 , Wenming Liu 1 , Xianglan Xu 1 , Liang Liu 1 , Zhongchen Li 1 , Honggen Peng 1 , Renyang Zheng 2 , Xiang Wang 1
Affiliation
To develop reactive catalysts for oxidative coupling of methane at low temperatures, different alkali-metal oxides are adopted in this study to modify the surface of SnO2. In comparison with the unmodified SnO2, the reaction performance of all of the modified catalysts can be significantly improved, among which lithium oxide shows the best promotional effects, and the optimal catalyst is achieved with a Sn/Li molar ratio of 5:5. With this catalyst, the highest C2 product yield of 16 % is achieved at 750 °C. The XPS and CO2-TPD results reveal that for those catalysts with evident enhanced OCM reaction performance, the coexistence of a suitable amount of surface alkaline and electrophilic oxygen sites is indispensable. Furthermore, with the catalysts modified by different amounts of lithium oxide, the C2 yield at different temperatures is nearly proportional to the amounts of both surface intermediate alkaline sites and electrophilic oxygen species. Therefore, it is concluded that the abundance and the concerted interaction of these two types of surface active sites are the major factors determining the reaction performance of the SnO2 based catalysts. Last, but not least, the optimized catalyst, which has a Sn/Li molar ratio of 5:5 and also contains equal amounts of SnO2 and Li2SnO3 crystalline phases, exhibits much better reaction performance than Mn/Na2WO4/SiO2, the most promising catalyst at present, in the low-temperature region (below 750 °C). After all, this may give people some new insight into developing new types of OCM catalysts that can operate at low temperatures and thereby facilitate the industrialization process of this important chemical engineering reaction.
中文翻译:
用于甲烷氧化偶联的低温性能 SnO2 基催化剂:深入了解碱金属氧化物的促进作用
为了开发低温下甲烷氧化偶联的反应性催化剂,本研究采用不同的碱金属氧化物来改性 SnO2 的表面。与未改性的 SnO2 相比,所有改性催化剂的反应性能均得到显着提高,其中氧化锂的促进效果最好,在 Sn/Li 摩尔比为 5:5 时达到最佳催化剂。使用这种催化剂,在 750 °C 时可实现 16% 的最高 C2 产物产率。XPS 和 CO2-TPD 结果表明,对于那些具有明显增强的 OCM 反应性能的催化剂,适量的表面碱性和亲电氧位点的共存是必不可少的。此外,通过不同量的氧化锂改性催化剂,不同温度下的 C2 产率几乎与表面中间碱性位点和亲电子氧物种的数量成正比。因此,可以得出结论,这两种表面活性位点的丰度和协同相互作用是决定 SnO2 基催化剂反应性能的主要因素。最后但并非最不重要的是,优化的催化剂,其 Sn/Li 摩尔比为 5:5,还含有等量的 SnO2 和 Li2SnO3 晶相,表现出比最有前途的催化剂 Mn/Na2WO4/SiO2 更好的反应性能目前,在低温区(750℃以下)。毕竟,
更新日期:2018-03-06
中文翻译:
用于甲烷氧化偶联的低温性能 SnO2 基催化剂:深入了解碱金属氧化物的促进作用
为了开发低温下甲烷氧化偶联的反应性催化剂,本研究采用不同的碱金属氧化物来改性 SnO2 的表面。与未改性的 SnO2 相比,所有改性催化剂的反应性能均得到显着提高,其中氧化锂的促进效果最好,在 Sn/Li 摩尔比为 5:5 时达到最佳催化剂。使用这种催化剂,在 750 °C 时可实现 16% 的最高 C2 产物产率。XPS 和 CO2-TPD 结果表明,对于那些具有明显增强的 OCM 反应性能的催化剂,适量的表面碱性和亲电氧位点的共存是必不可少的。此外,通过不同量的氧化锂改性催化剂,不同温度下的 C2 产率几乎与表面中间碱性位点和亲电子氧物种的数量成正比。因此,可以得出结论,这两种表面活性位点的丰度和协同相互作用是决定 SnO2 基催化剂反应性能的主要因素。最后但并非最不重要的是,优化的催化剂,其 Sn/Li 摩尔比为 5:5,还含有等量的 SnO2 和 Li2SnO3 晶相,表现出比最有前途的催化剂 Mn/Na2WO4/SiO2 更好的反应性能目前,在低温区(750℃以下)。毕竟,