Direct partial oxidation of methane over ZSM-5 catalyst: effects of additives

Previously, it was reported that the direct partial oxidation (DPO) of CH₄ with O₂ over HZSM-5 catalysts produces C₅₊ hydrocarbon liquids when the feed contains a propane or propene additive. This work studies additive effects on C₅₊ production in this system by processing a CH₄/C₃H₈ feed with subsequent removal of the C₃ additive and by processing natural gas feed. Results show C₅₊ production is maintained at constant yields for HZSM-5 catalysts having different zeolitic Al contents after removal of the C₃ additive. Mechanistic implications are discussed. Natural gas DPO consistently produced C₅₊ liquids due to the presence of C₂₊ components in the feed. While C₅₊ yields from natural gas DPO are higher than those observed for CH₄/C₃ feeds, increasing feed O₂ concentration, and thus conversion, deleteriously affected C₅₊ selectivity.