Surface oxygen vacancy induced selective conversion of syngas to propane over ZnM₂O₄ spinel/SAPO-34 composite catalysts

Converting syngas to high-valued hydrocarbons is considered an ideal route to alleviate the excessive use of oil resources. However, regulating the hydrocarbon product distribution, especially for a high selectivity of a single product, remains a great challenge. Herein, we report a series of composite catalysts integrated with Zn-based spinel oxide (ZnM₂O₄) and zeolites for the highly selective synthesis of propane from syngas. A high selectivity of 68.6 % for propane and 77.5 % selectivity for LPG (propane and butane) in hydrocarbons (CO₂ free) are obtained over ZnAl₂O₄/SAPO-34 composite catalyst at CO conversion of 41.1 %. Moreover, such performance is virtually unchanged in 100 hours of reaction evaluation. Studies of the microstructure and chemical properties of the ZnAl₂O₄ spinel oxide catalyst show that the strong electron interaction between Zn–O–Al creates more abundant oxygen vacancies and stronger hydrogen dissociation capacity. Consequently, more adsorbed CO is stepwise activated and hydrogenated with the dissociated H species to HCOO*, CH₃O* intermediates and methanol, which are further transformed to propane on the acid site of SAPO-34 zeolite.