Chemical Role of Alkali Ion by In Situ Electrical Conductivity Measurements–Catalytic Performance Studies over (Mn+A+W)/SiO2 Catalysts for Oxidative Coupling of Methane Reaction

فاقد چكيده

Oxidative coupling of methane (OCM) reaction were studied over (4wt%Mn+0.1wt%A+3.13wt%W)/SiO2 catalysts under GHSV of 13200 mL/grCat.h. Here A is an alkali ion of Li, Na, K or Cs. The chemical role of alkali ion is researched as the main goal. Electric conductivity of catalysts was measured under the OCM reaction conditions. Crystalline structure of catalysts, a requirement for the formation of a selective OCM catalyst, depends on the alkali ion, is observed to be quartz and α–cristobalite in case of Li and the other alkali ions, respectively and promoted under the OCM reaction conditions. Metal oxide–Na2WO4/SiO2 interaction of catalysts is determined to depend on the alkali ion by TPR studies. Oxygen activation property of catalyst, increasing by the presence of metal oxide on Na2WO4/SiO2 catalyst, is a parameter that improves the OCM catalytic performance. The oxy–anion acceptance capacity of Na2WO4/SiO2 in catalyst containing different metal oxides, however, is the other important parameter, affecting the catalyst activity and selectivity.