Investigation of the surface reaction network of the oxidative coupling of methane over Na2WO4/Mn/SiO2 catalyst by temperature programmed and dynamic experiments

• Reactions of CXHY on Na2WO4/Mn/SiO2 in temperature programmed methods were studied.
• CH4 is converted into C2 and COX, while C2H6 is oxidized to C2H4 by two mechanisms.
• Dynamic experiments support a MvK mechanism for the OCM on Na2WO4/Mn/SiO2.
• Calculated EA for selective CH4 activation, by strongly bound O*, is 275 kJ/mole.
• Partial pressure variation experiments show linear correlation for CH4 activation.

In this work a series of temperature programmed experiments were carried out on a Na2WO4/Mn/SiO2 catalyst. In TPR experiments we tested the reducibility of this catalyst and O2 desorption behavior was investigated by TPD. TPSR experiments in a flow of methane, ethane or ethene gave information about the reaction network of OCM on the catalyst surface, without the presence of gas phase reactions, induced by gas phase oxygen. We found indications of involvement of two different active oxygen species on the catalyst surface. Furthermore an activation energy of 275 kJ/mole for selective methane activation was determined. Dynamic experiments were performed to determine the amount of available oxygen species for the OCM reaction. Variation of methane partial pressure and flow rate showed a linear correlation between methane partial pressure and surface oxygen conversion in dynamic experiments.

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