Mn_2O_3-Na_2WO_4/SiO_2 is considered as the most promising catalyst for the oxidative coupling of methane（OCM） process; however, it only has a better catalytic performance over 800 °C. To improve its low-temper...Mn_2O_3-Na_2WO_4/SiO_2 is considered as the most promising catalyst for the oxidative coupling of methane（OCM） process; however, it only has a better catalytic performance over 800 °C. To improve its low-temperature performance, an attempt has been made to modify the Mn_2O_3-Na_2WO_4/SiO_2 catalyst using TiO_2, MgO, Ga_2O_3, and ZrO_2. Among the synthesized catalysts, the TiO_2-modified Mn_2O_3-Na_2WO_4/SiO_2 catalyst shows markedly improved low-temperature OCM performance,achieving a high CH_4 conversion of ~23% and a good C_2-C_3 selectivity of ~73% at 700 °C（the catalyst bed temperature）, along with promising stability for at least 300 h without signs of deactivation.In comparison with the unmodified Mn_2O_3-Na_2WO_4/SiO_2 catalyst, the TiO_2 modification results in significant improvement in the low-temperature activity/selectivity, whereas the MgO modification has almost no impact and the Ga_2O_3 and ZrO_2 modifications have a negative effect. The X-ray diffraction（XRD） and Raman results reveal that the formation of a MnTiO_3 phase and a MnTiO_3-dominated catalyst surface is crucial for the improvement of the low-temperature activity/selectivity in the OCM process.展开更多
文摘Mn_2O_3-Na_2WO_4/SiO_2 is considered as the most promising catalyst for the oxidative coupling of methane（OCM） process; however, it only has a better catalytic performance over 800 °C. To improve its low-temperature performance, an attempt has been made to modify the Mn_2O_3-Na_2WO_4/SiO_2 catalyst using TiO_2, MgO, Ga_2O_3, and ZrO_2. Among the synthesized catalysts, the TiO_2-modified Mn_2O_3-Na_2WO_4/SiO_2 catalyst shows markedly improved low-temperature OCM performance,achieving a high CH_4 conversion of ~23% and a good C_2-C_3 selectivity of ~73% at 700 °C（the catalyst bed temperature）, along with promising stability for at least 300 h without signs of deactivation.In comparison with the unmodified Mn_2O_3-Na_2WO_4/SiO_2 catalyst, the TiO_2 modification results in significant improvement in the low-temperature activity/selectivity, whereas the MgO modification has almost no impact and the Ga_2O_3 and ZrO_2 modifications have a negative effect. The X-ray diffraction（XRD） and Raman results reveal that the formation of a MnTiO_3 phase and a MnTiO_3-dominated catalyst surface is crucial for the improvement of the low-temperature activity/selectivity in the OCM process.
