The conversion of renewable bioethanol into high-energy-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.
An efficient and stable catalyst
to produce higher alcohols with
a higher heat value and cetane number and less corrosive to engines
from aqueous ethanol is still facing challenges. Here, a novelty of
NiSn bimetallic catalysts encapsulated in a nitrogen-doped lignin-based
carbon material (NiSn@NC) was prepared by modified biorefinery lignin
and further precisely coordinated with metal ions to form a lignin-metal
supramolecular material followed by in situ calcining. Results showed
that the optimized Ni20Sn1@NC catalyst exhibited
a superior ethanol conversion (68.5%), a C4+ higher alcohol
yield of 31.8%, and a ratio of iso to normal alcohol of 0.52. Moreover,
it also exhibited excellent stability even after four-cycle runs.
Structural analysis revealed that the Sn/N-doping lignin-based carbon
material improved the Ni dispersion and basic site density, which
adjusted efficiently the electronic structure of the metallic active
site. Therefore, the NiSn@NC bimetallic catalysts showed satisfactory
conversion and stability of aqueous ethanol upgrading to C4+ higher alcohols.
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