Methane coupling by membrane reactor. First quarterly report, 1997

The Mn-W-Na/SiO{sub 2} catalyst was studied by running the methane coupling reactions at different methane to oxygen ratios, temperatures and dilution gas flow rates. For methane to oxygen ratios less than 3, the C{sub 2} yield was almost the same; and C{sub 2} yield began to decrease as the methane to oxygen ratio was further increased. The optimal temperature observed was around 800{degrees}C, where the C{sub 2} yield reached a maximum value. Increasing the dilution gas (helium) flow rate resulted in higher C{sub 2} selectivity; however, after a certain dilution gas flow rate the C{sub 2} yield began to decrease due to a decrease in methane conversion as a result of the reduced contact time. The stability study of the catalyst showed that, after five successive run cycles, the C{sub 2} yield obtained decreased from 24% to 19% at 780 {degrees}C, and methane, oxygen and helium flow rates of 12.2, 4.1, and 44. 3 mm/min, respectively. XRD analysis showed that, after the reaction, the XRD peaks of the cristabolite and Na{sub 2}WO{sub 4} phases in the catalyst became smaller than those in the fresh catalyst, and that at least one new, unidentified phase was observed. Mn-W-Na/SiO{sub 2} catalyst was used as the methane oxidative coupling catalyst in a porous membrane reactor and its performance was compared with a packed reactor operated at similar conditions. Although the membrane reactor showed lower methane conversion at the same reaction conditions, it gave higher C{sub 2} selectivity and C{sub 2} yield at similar methane conversions