A High-Temperature Infrared Cell for In Situ Studies: Application to Methane Oxidative Dehydrogenation Catalysts

There has recently been an increased interest in the direct conversion of methane to higher hydrocarbons over catalysts at up to 1073 K. Among the best performing catalysts for the oxidative dehydrogenation reaction are Li2CO3/MgO, LiCl/MgO, LaAlO3, and Mn/Na4P2O7/SiO2 systems. The alkali earth metal carbonates and the rare earth oxides were also found to show significant activity. A general observation made in the various studies is that the presence of alkali, which was introduced as hydroxide, nitrate, or carbonate, resulted in higher selectivity to hydrocarbons. This behavior was also normally followed by a decrease in activity. It was also noted that, for most of the effective catalysts, some of their components melt at less than 100 K above the reaction temperature. Hence, it is possible that under reaction conditions these catalysts manifest the properties of a transitory phase or even a melt instead of that due to the stable solid. In order to probe the nature of the catalysts under reaction conditions, we have constructed an infrared (IR) cell for in situ high-temperature studies up to 1073 K.