Engineering Sn doping Ni/chitosan to boost higher alcohols synthesis from direct coupling of aqueous ethanol: Modifying adsorption of aldehyde intermediates for C-C bond cleavage suppressing

The direct aqueous ethanol coupling to higher alcohols is an essential bridge between abundant bio-ethanol and the outstanding application of higher alcohols as alternative jet-fuel or plasticizer precursors. In this work, the Sn-Ni/CS catalysts were developed, and the synergy between Ni and doped Sn species promoted the selective upgrading of ethanol to higher alcohols. Experimental and theoretical evidence revealed that the enhanced selectivity of higher alcohols was attributed to the weakened adsorption of midbody aldehydes over the catalyst and the suppression of the gas by-products, which was due to the change of the electron density around the Ni active site by Sn doping causing a rich electron set around Ni specie. Benefiting from the Sn doping, the Sn-Ni/CS-500-1/1 catalyst achieved >85% selectivity for higher alcohols with 60% ethanol conversion at 230 o C. • A Sn doping Ni/chitosan catalyst boosting the higher alcohols synthesis from direct ethanol coupling. • The C-C bond breaking side reaction was effectively suppressed. • Electron transfer and electron repulsion effect over Sn doped Ni sites was proposed. • 37.3% C4+ higher alcohols yield and gas by-products selectivity as low as 1.2% were achieved.