HIGH-TEMPERATURE REACTIONS ON METAL-OXIDES OF CH4 WITH H2O TO FORM C2H4, CO AND H-2

The following reaction has been investigated over various metal oxides for the purpose of utilizing solar or nuclear heat as an energy sourc e: (2 + x) CH4 + xH(2)O-->C2H4 + xCO + (3x + 2)H-2. Oxides of Zn, Mn, Co, Ni, Mg and Fe were used at 900 degrees C. The greatest activity fo r C2H4 formation was observed with Fe3O4 (magnetite); ZnO, Mn3O4, Co3O 4, NiO, and MgO showed little or no activity. Substitution of Mn(II) f or Fe(II) in magnetite depressed CO2 formation and improved CO selecti vity (25%), while the activity (48 nmole m(2) s(-1)) and selectivity ( 33%) for C2H4 formation remained almost the same. The surface-lattice oxygens of the wustite (FeO) phase formed by the reduction of MFe2O4 ( M = Fe, Zn, Mn) with CH4 are believed to be active in the oxidation of CH4 to C2H4. Lattice oxygen consumed in the oxidation of methane are readily replenished by H2O splitting and C2H4 continues to form over t he active wustite phase when CH4-H2O mixture is passed over the hot me tal oxide. The high-temperature CH4-H2O reaction using MnFe2O4 corresp onds roughly to 13CH(4) + 14H(2)O-->2C(2)H(4) + 4CO + 5CO(2) + 36H(2). (C) 1997 Elsevier Science Ltd.