Selective Conversion of Syngas into Higher Alcohols via a Reaction-Coupling Strategy on Multifunctional Relay Catalysts

Abstract

Direct conversion of syngas (CO/H2) into higher alcohols is highly desirable but remains challenging due to the low C2+OH selectivity. Herein, an effective strategy was developed through the combination of partially reduced Zn-Cr-Al trinary oxides (ZnCrAlOx) and Mo-based sulfides to significantly raise the alcohol selectivity. The introduction of K on Mo-based sulfides suppresses the acid sites and stabilizes alkoxy species (CHxO*), which greatly enhances the selectivity of alcohols. The close proximity of the two components on the multifunctional relay catalyst ZnCrAlOx|KNiMoS-MMO-5 can effectively promote the migration of reaction intermediates by shifting the DME formation equilibrium on ZnCrAlOx, achieving an alcohol selectivity of 60.4% with more than ∼72.7% of C2+OH selectivity in alcohols under a CO conversion of 9.8%, and significantly improves the turnover frequency (TOF) of C2+OH (71.9 h–1). A plausible reaction mechanism is also proposed on the multifunctional relay catalyst ZnCrAlOx|KNiMoS-MMO-5. This work provides a promising avenue to improve the selectivity of higher alcohols through a multifunctional relay catalyst affording multiple types of active sites.