Efficient Catalytic Upgrading of Ethanol to Higher Alcohols via Inhibiting C-C Cleavage and Promoting C-C Coupling over Biomass-Derived NiZn@NC Catalysts

The conversion of renewable bioethanol into highenergy-density higher alcohols has become essential for meeting the increasing global demand to achieve carbon neutrality. In this study, Zn-and nitrogen-codoped Ni-based lignin-derived carbon catalysts (NiZn@NC) were prepared by solvent volatile self assembly and in situ reductive carbonization using pulp and paper waste stream alkali lignin as the carbon source. Lignin amphipathic derivatives with -COOH and -NH2 groups would coordinate with metal ions to form a stable lignin-metal framework; thus, the lignin-derived carbon layer disperses the NiZn bimetallic catalyst and prevents from corroding. At an amination reagent/lignin mass ratio of 1:2, an ethanol conversion of 75.2% and a high alcohol yield of 41.7% were achieved over the Ni20Zn1@NC catalyst. Experimental results and density functional theory calculations showed that Zn doping improved the electronic environment and defect structures of metallic Ni and carbon carrier, which effectively inhibited C-C cleavage and suppressed the byproduct formation, such as methane. Thereby, the synergetic effect between Ni and Zn facilitated the efficient conversion of aqueous ethanol into higher alcohols by the Guerbet reaction. This work provides a strategy of in situ pyrolytic doping and stabilizing of renewable biomass macromolecules as the frameworks for the construction of highly active and cost-efficient catalysts for ethanol upgrading.

Automated summary

In this study, nitrogen-doped and zinc-doped Ni-based lignin-derived carbon catalysts were prepared, leading to an improvement in ethanol conversion rate and alcohol yield. Experimental results showed that zinc doping improved the structure of metal Ni and carbon carrier, effectively inhibiting byproduct formation. This research provides a strategy for constructing highly active and cost-efficient catalysts using renewable biomass as the framework.