The relationship between the structure and the performance of Na-W-Mn/SiO2 catalysts for the oxidative coupling of methane

Oxidative Coupling of Methane Over Na–W–Mn–Zr–S–P/SiO2 Catalyst: Effect of S, P Addition on the Catalytic Performance

“…Over the Cat4 containing no S and P, CH 4 conversion and C 2 yield is only 16.4% and 11.4%. However, in comparison with the activity of 4.6%Na-3.1%W-2%Mn/SiO 2 catalyst [4], on which CH 4 conversion was 12.0% and C 2 yield 7.3%, the performance of catalyst has been enhanced ca. 25%.…”

“…It can be seen that all samples possess the phase of Na 2 WO 4 , ZrO 2 and a-cristobalite. Ji and his co-workers [4] suggested that Na-O-W species were the most probable active sites of the Na-W-Mn/SiO 2 catalysts for OCM. In addition, ZrO 2 was reported as an effective crystal phase for activation of methane [13,14].…”

“…Among the catalysts tested, some multi-component catalysts, such as Na 4 P 2 O 7 -ZrOCl 2 [2,3], Na-Mn-W/ SiO 2 [4,5] and Na-Mn-S/SiO 2 [6] have been found to exhibit promising catalytic performance. In the literature [2], the researchers concluded that sodium was a key element in the catalysts and the active phase for OCM were NaZr 2 (PO 4 ) 3 and Na 2 Zr(PO 4 ) 2 .…”

“…In the literature [2], the researchers concluded that sodium was a key element in the catalysts and the active phase for OCM were NaZr 2 (PO 4 ) 3 and Na 2 Zr(PO 4 ) 2 . Ji et al [4] have reported that sodium and manganese played great roles over the Na-W-Mn/SiO 2 catalyst and the addition of tungsten could enhance the stability of catalyst. The active phase in Na-W-Mn/SiO 2 was identified as Na-O-Mn and Na-O-W species.…”

Effect of CO2 on the structural variation of Na2WO4/Mn/SiO2 catalyst for oxidative coupling of methane to ethylene

“…They found that the combination of tetrahedral metallic core of WO 4 and octahedral metallic core of MnO 6 with different oxidation states was responsible for the catalysis in OCM reaction. Ji et al [29,30] reported that both Na-O-Mn and Na-O-W acted as the active phase, and WO 4 tetrahedron (Na 2 WO 4 or Na 2 W 2 O 7 ) on the catalyst surface appeared to play an essential role in achieving high CH 4 conversion and high selectivity to C 2 hydrocarbons. Theoretical calculations suggested that the transition state formed via the interaction of WO 4 with CH 4 could be more stable than that of WO 6 with CH 4 , demonstrating that WO 4 tetrahedron had suitable geometry and energy matching with CH 4 , and this might account for the high OCM activity.…”