N-rich doping strategy for constructing Ni@NC catalysts to boost aqueous ethanol coupling towards higher alcohols by inhibiting C1 byproducts

Abstract

Aqueous coupling of biomass fermentation bio-ethanol offers a promising biorefinery pathway for manufacturing higher alcohols, but it still suffers from the poor utilization efficiency due to the excessive formation of undesired C1 byproducts (CH4, CO and CO2). Herein, N-rich Ni@NC catalysts were synthesized via a facile one-step carbonization of organic–inorganic co-assembly containing polyacrylamide and nickel acetate. Interestingly, the optimized Ni@NC catalyst exhibited excellent performance in aqueous ethanol coupling, giving 74.8 % of ethanol conversion, 49.3 % of C4+ higher alcohol yield and only 1.6 % of C1 gas byproduct selectivity after 12 h reaction at 230 °C. The experimental results and DFT calculations revealed that the regulation of N-rich doping weakened the interaction of Ni with intermediated CH3CHO for inhibiting its deep decomposition into C1 gas byproducts, thereby facilitating the coupling reaction to produce more higher alcohols. Moreover, a feasibility to scale-up the aqueous ethanol coupling was further validated through a 100-fold magnification experiment at ranges of 50–5000 mL, and the fuel properties of higher alcohols as diesel blending were also evaluated. This work opens new avenues for efficient mass-production of higher alcohols via aqueous ethanol coupling.