Enhanced Conversion of Ethanol into n‑Butanol over NiCeO2@CNTs Catalysts with Pore Enrichment Effects

The determining role of the pore structure in controlling the activity of porous catalysts has been observed in a variety of reactions. However, it is still a challenge to unveil the underlying reasons for the enhancements, especially for ethanol conversions. Herein, carbon nanotubes (CNTs) with different outer diameters were employed to prepare NiCeO2 catalysts for upgrading ethanol to n-butanol. According to physicochemical characterizations and reactant adsorption results, Ni and CeO2 species were encapsulated in CNTs of 4–6 nm outer diameter with confined micropores of 1.8 nm, which enriched the adsorption of acetaldehyde and correspondingly accelerated ethanol conversion. Moreover, the highly dispersed CeO2 in CNTs produced abundant acid and strong base pairs, which condensed the local concentrated acetaldehyde into n-butanol with the assistance of hydrogenation sites. By coupling the pore enrichment effect and improved acid–base pairs, the ethanol conversion was nearly doubled with improved n-butanol selectivity over NiCeO2@CNTs catalysts compared to that of the counterpart NiCeO2/CNTs catalysts.