Oxidative coupling of methane over molybdates: catalyst performance and characterization

Abstract

The effect oxidative coupling of methane, a variety of molybdates were used as catalysts with sustained activity for more than 280 h. The reaction was studied by cofeeding methane and oxygen at atmospheric pressure, through continuous conventional flow reactors containing the catalyst. The effects of operating conditions were studied and the optimum reactor temperature to achieve high yields of ethane and ethylene was ca. 700-780 {degrees}C, depending on the reactor dimensions. The influence of reactor dimensions on the distribution of products is also reported. Molybdate catalysts are active and yet resistant to deactivation and sintering. Selectivities X(C{sub 2})% up to 20.0 and 7.0% were observed, respectively. The reactor feed had a CH{sub 4} to O{sub 2} ratio of ca. 1.1. The authors results present the effects of varying several operating conditions and the significant gas-phase products observed were H{sub 2}, C{sub 2}H{sub 4}, C{sub 2}H{sub 6}, C{sub 3}H{sub 6}, H{sub 2}O, and traces of HCHO and CH{sub 3}OH. C{sub 2}H{sub 2} formation was not observed. The main oxidation products were CO{sub 2} and CO. Structural characterization of the molybdates was carried out by elemental analysis, infrared spectroscopy (IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). 46 refs., 8 figs.,more » 2 tabs.« less