DIRECT PARTIAL OXIDATION OF METHANE OVER ZSM-5 CATALYST - METALS EFFECTS ON HIGHER HYDROCARBON FORMATION

The direct partial oxidation (DPO) of CH4 with O2 to higher hydrocarbons, and in particular C5+ liquids, over metal-containing ZSM-5 catalysts is reported. At 960 psig, 4600 hr-1 GHSV, 7 vol% O2, and temperatures sufficient for 100% O2 conversion (440-465-degrees-C), our studies with first row transition metals supported on ZSM-5 showed that Cu, Ni, and Zn oxides produced C5+ liquids (Fe-ZSM-5 produced C2-C4 hydrocarbons) without the need for a feed additive. Co-, Cr-, and Mn-ZSM-5 catalysts under the same conditions produced no higher hydrocarbons. It is believed that conversion of the CH3OH formed in the system to higher hydrocarbons over metal-containing ZSM-5 is made possible by two metal functions. Initial trace dehydrogenation of CH4 (or of minute C2+ feed components) to olefins provides initiation of the methanol-to-gasoline (MTG) reaction but survival of olefins in the system is a function of the olefin oxidation activity of the metal oxide. Further experimentation using Ga-, Pt-, and Ag-ZSM-5 catalysts was consistent with this hypothesis. Thus, metal-containing ZSM-5 catalysts can produce C5+ liquids from CH4 and O2 if dehydrogenation and oxidation functions of the metal are in balance. (C) 1994 Academic Press, Inc