Catalytic Partial Oxidation of Methane over Fe2(MoO4)3 Catalysts

The study of new energy carriers for sustainable energy conversion processes is a hot research area. Among the potential energy carriers one finds biogas, containing a large fraction of methane, which attracts high interests worldwide. However, to be more useful, e.g., concerning storage and transportation, conversion of gaseous methane fuel into liquid fuel like methanol is desired. The conventional route for production of methanol from methane is a two-step process including energy intensive syngas production. To reduce energy costs, direct catalytic conversion of methane to methanol provides an attractive possibility to circumvent syngas production provided proper catalysts can be found. In this work, Fe2(MoO4)3 catalysts were hydrothermally synthesized and tested as potential methanol production catalysts. By employing different pH value of the precursor solution different catalysts were formed, i.e., pale green (pH=1.65) and brown (pH=3) colored iron molybdate samples. Transient (pulse-response) methane oxidation experiments were performed in a continuous gas-flow reactor connected with a mass spectrometer. Essentially five parameters were studied: i) reaction temperature, ii) catalyst preparation route, iii) CH4/O2 ratio iv) H2 addition and v) the concentration of hydrogen. Analysis of BET surface area and XRD patterns for fresh and treated samples was performed as well. The pulse-response experiments show that the reaction is promoted by high temperature and also is very sensitive to the reactant composition. Addition of hydrogen shifts the product selectivity to some extent. Both samples seem to have the ability to store and release oxygen during lean/rich cycling. The study shows that methanol may be produced in small amounts for certain reaction conditions.