Effects of operating parameters on oxidative coupling of methane over Na-W-Mn/SiO2 catalyst at elevated pressures

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

“…The presence of Na 2 WO 4 crystal on fresh catalyst showed that Na + had a higher affinity than Mn 2+ for combining with WO 4 2− . For the catalyst after 10 h OCM reaction without dilution (CH 4 /O 2 /CO 2 = 3/1/0), it was shown that part of α-cristobalite was transformed into tridymite and SiO 2 quartz, which was in accordance with the results of Ahari et al and Li [37,38]. At the same time, Mn 2 O 3 crystal disappeared after 10 h reaction.…”

Oxidative condensation of methane in the presence of modified MnNaW/SiO2 catalysts

“…Published data on the operational stability of the MnNaW/SiO 2 catalyst are scanty and very contradic tory [32][33][34][35][36][37][38][39]. In particular, it was found that the catalyst retained its initial activity for a long time (20-97 h [32][33][34], 450 h [36], or 500 h [35]).…”

“…In particular, it was found that the catalyst retained its initial activity for a long time (20-97 h [32][33][34], 450 h [36], or 500 h [35]). On the contrary, accord ing to published data [37][38][39], the yield of C 2 hydrocarbons began to decrease even after a 14 h long OCM reaction.…”

Phase states of Na/W/Mn/SiO2 composites at temperatures of catalytic oxidative coupling of methane

“…3 (see Fig. 2) are represented using the first letters of the symbols of cations and subscripts: N 4 S, N 6 S 2 , N 2 S, and N 2 S 2 represent the sodium silicates Na 4 SiO 4 , Na 6 ( Fig. 3a) near the q SiO 2 corner, because the SiO 2 content of the composites exceeds 90 mol %.…”

“…Na/W/Mn/SiO 2 oxide composite catalysts enable the C 2+ (ethylene, ethane, and heavier hydrocarbons) yield in oxidative coupling of methane (OCM) in a continuous mode to reach 24-26% [1][2][3][4][5][6][7], or even 28-32% in some instances [8][9][10]. It is hardly reason able to correlate OCM results with the cation stoichi ometry of Na/W/Mn/SiO 2 or with the chemical for mulas of the oxides present in the composite, the more so because the oxygen nonstoichiometry plays a signif icant role.…”