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首页> 外文期刊>Journal of industrial and engineering chemistry >Effect of promoter in the oxidative coupling of methane over synthesized Mn/SiO2 nanocatalysts via incipient wetness impregnation
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Effect of promoter in the oxidative coupling of methane over synthesized Mn/SiO2 nanocatalysts via incipient wetness impregnation

机译：初湿浸渍下助催化剂对合成的Mn / SiO2纳米催化剂上甲烷氧化偶联的影响

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摘要

The M-Na-Mn/SiO2 nanocatalysts (M = W, Mo, Nb, V, Cr) were synthesized with the size of 12-92 nm by incipient wetness impregnation method to study the effect of different promoters on the catalytic performance in the oxidative coupling of methane. The results at 1 atm, 1048 K, 2500 ml h~(-1) g~(-1) and CH4/O2/N2 = 2/2/1 revealed that C2 selectivity was significantly increased (31.6%) in the order of W > Mo > Nb > Cr > V whereas moderate enhancement (12.6%) was observed in the CH4 conversion in the order of W > Cr > Nb > Mo > V. The results of the characterization techniques (Raman, FT-IR, BET, TGA/DTA and XRD) demonstrated that Mn2O3 and α-cristobalite were the predominant species and active sites in the nanocatalyst surface and Na2MoO4, Na2WO4 and Mn2O3 crystalline phases contributed to achieving high selectivity of C2 products. The redox mechanism involving two metal sites such as Mn~(3+/2+) and W~(6+/5+) or Mn~(3+/2+) and Mo~(6+/5+) was found to be the most compatible route with the OCM reaction path in which CH4 and O2 adsorption was the controlling step.
机译：初湿浸渍法合成了M-Na-Mn / SiO2纳米催化剂（M = W，Mo，Nb，V，Cr），尺寸为12-92nm，研究了不同助催化剂对催化剂性能的影响。甲烷的氧化偶联。在1 atm，1048 K，2500 ml h〜（-1）g〜（-1）和CH4 / O2 / N2 = 2/2/1的结果表明，C2选择性按以下顺序显着提高（31.6％）。 W> Mo> Nb> Cr> V，而在CH4转化中观察到中等增强（12.6％），顺序为W> Cr> Nb> Mo>V。表征技术的结果（拉曼，FT-IR，BET （TGA / DTA和XRD）证明，Mn2O3和α-方石英是纳米催化剂表面的主要物种和活性中心，Na2MoO4，Na2WO4和Mn2O3晶相有助于实现C2产品的高选择性。发现了涉及两个金属位点的氧化还原机理，例如Mn〜（3 + / 2 +）和W〜（6 + / 5 +）或Mn〜（3 + / 2 +）和Mo〜（6 + / 5 +）这是与OCM反应路径最兼容的途径，其中CH4和O2的吸附是控制步骤。

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