Upgrading of Aqueous Bioethanol to Higher Alcohols over NiSn/MgAlO Catalyst
Xiaoping Wu, Xueying Cai, Qian Zhang, Peiyan Bi, Qingwei Meng, Yunhong Pi, Tiejun Wang
Abstract
The calorific value and cetane number of C4+ long-chain higher alcohols are similar to those of diesel, blending with which can significantly reduce pollutant emissions from diesel engines. Direct upgrading of aqueous bioethanol derived from the biomass fermentation to higher alcohols faces the challenge of efficient catalysts with excellent catalytic activity and hydrothermal stability. Herein, NiSn/MgAlO catalysts prepared by loading Ni and Sn into hydrotalcite through coprecipitation and ion exchange methods were developed. Higher alcohols with a yield of 48.4 C-mol % and selectivity of 93.8% were obtained by upgrading of aqueous ethanol under hydrothermal conditions. NiSn/MgAlO catalysts exhibited excellent stability even after four recycle runs. The experiment results and catalyst characterizations revealed that the Ni(Mg)O solid solution formed by calcination of Ni(Mg)Al hydrotalcite promotes the dispersion and stability of Ni particles. Moreover, the high-valence Sn regulates the electronic structure and coordination environment of Ni (ratio of Ni0, Ni2+, Niδ+, and Ni–Sn alloys), both of which give the synergistic effect for the formation of C4+ long chain higher alcohols by selectively regulating the ethanol coupling reaction.