Alkali carbonate induced N-doped NiSn@NC for direct aqueous ethanol coupling to C6+ higher alcohols

Abstract

Synthesis of C₆₊ higher alcohols from readily-accessible aqueous ethanol is an alternative route of great potential for blending-fuel, plasticizer, surfactant and medicine precursors, but the direct coupling of aqueous ethanol to C₆₊ higher alcohols is still challenging. Herein, the alkali carbonate induced N-doping of a NiSn@NC catalyst was achieved by a facile gel-carbonization strategy, and the effect of alkali salt inductors was examined for the direct coupling of 50 wt% aqueous ethanol. Noteworthily, C₆₊ higher alcohol selectivity of 61.9% with 57.1% ethanol conversion was achieved for the first time over the NiSn@NC-Na₂CO₃-1/9 catalyst, which broke the step-growth carbon distribution of ethanol coupling to higher alcohols. The inductive effect of alkali carbonate for the N doped graphite structure from the NO₃⁻ precursor was revealed. Electron transfer from Ni to the pyridine N doped graphite layer is enhanced, thus elevating the Ni-4s band center, which lowers the dehydrogenation barrier of the alcohol substrate and further improves the C₆₊OH selectivity. The catalyst reusability was also examined. This work gained new insight into the selective synthesis of high-carbon value-added chemicals from C–C coupling of aqueous ethanol.