The oxidative coupling of methane by metal oxides and phosphates

Experimental studies of the catalytic oxidation of methane to ethane, ethylene, water, carbon monoxide and dioxide have been performed over metal oxides and phosphates. The purpose of this investigation is to determine the chemical and catalytic effect of phosphorus addition to metal oxides for oxidative catalysis. Addition of phosphorus is also used to examine the nature of the active surface oxygen species in the activation of methane and examine the feasibility of synthesizing catalysts of improved activity, selectivity and durability.;Iron, lead, barium and calcium oxides and phosphates are examined in a fixed bed reactor in a helium-diluted 2:1 methane:oxygen feed at one atmosphere between 600 and 750;Reductive titration of the catalysts with methane was used to examine the variation in the mobility of the lattice oxygen and the reducibility of the metal cation with phosphorus addition. We find that lead and iron oxides have mobile lattice oxygen which directly participates in the oxidation of methane. Phosphates of lead and iron have more stable lattice oxygen resulting in increased selectivity to partial oxidation products. The introduction of phosphorus to these oxides also stabilizes the metal cations at their highest oxidation state. Study of selectivities under aerobic and anaerobic conditions suggest that the source of carbon dioxide over lead and iron phosphates and barium and calcium oxides and phosphates is weakly held oxygen not associated with the surface lattice.