High-temperature reactions on metal oxides of CH 4 with H 2O to form C 2H 4, CO and H 2

Abstract

The following reaction has been investigated over various metal oxides for the purpose of utilizing solar or nuclear heat as an energy source: (2 + x) CH 4 + xH 2O→C 2H 4 + xCO + (3 x + 2)H 2. Oxides of Zn, Mn, Co, Ni, Mg and Fe were used at 900°C. The greatest activity for C 2H 4 formation was observed with Fe 3O 4 (magnetite); ZnO, Mn 3O 4, Co 3O 4, NiO, and MgO showed little or no activity. Substitution of Mn(II) for Fe(II) in magnetite depressed CO 2 formation and improved CO selectivity (25%), while the activity (48 nmole m 2s −1) and selectivity (33%) for C 2H 4 formation remained almost the same. The surface-lattice oxygens of the wustite (FeO) phase formed by the reduction of MFe 2O 4 ( M = Fe, Zn, Mn) with CH 4 are believed to be active in the oxidation of CH 4 to C 2H 4. Lattice oxygen consumed in the oxidation of methane are readily replenished by H 2O splitting and C 2H 4 continues to form over the active wustite phase when CH 4H 2O mixture is passed over the hot metal oxide. The high-temperature CH 4H 2O reaction using MnFe 2O 4 corresponds roughly to 13CH 4 + 14H 2O→2C 2H 4 + 4CO + 5CO 2 + 36H 2.