The direct partial oxidation of methane to liquid hydrocarbons over HZSM-5 zeolite catalyst

Abstract

The direct partial oxidation (DPO) of CH 4 with O 2 in the presence of a C 3 additive over HZSM-5 zeolite catalyst at 960 psig produced C 5 + liquid hydrocarbons at the expense of the initially formed CH 30H. Previous experiments with pure CH4 and Oz feed and with a sand-packed reactor conclusively showed the need for both the C 3 additive and the zeolite in the system to produce C 5 + liquids. Evidence of CH 4 incorporation into the liquid products was given by selectivity calculations which indicated the C 3 alone could not account for the CS hydrocarbons. CH4 incorporation has been conclusively confirmed by mass spectral analyses of tetramethylbenzene produced in a run with 13CH 4 under identical conditions which show significant 13C enrichment in the C 9H 11 + and C 6H 5 + fragments. While CH 4 undergoes DPO to CH 30H in the system, two possible reaction mechanisms can explain the role of C 3; one involves initiation of methanol conversion to gasoline (MTG) by alkenes and the second involves C 3 aromatization followed by aromatics alkylation with CH 30H. Studies on this system with HZSM-5 catalysts having varying Al contents indicate a sensitivity to zeolite acidity except at high Al concentrations.