One-pot
complete catalytic ethanolysis of Kraft lignin into C6–C10
chemicals, that is, aliphatic alcohols, esters, phenols, benzyl alcohols,
and arenes, is achieved with a batch reactor over a number of supported
molybdenum-based catalysts at 553 K in pure ethanol under autogenous
pressure of 10.6 MPa. Metallic molybdenum, its carbide, and nitride
all show remarkable activity, with the carbide and metallic catalysts
giving the higher overall yields: 1640 and 1390 mg/g lignin, respectively.
The major phases composing the catalysts are well-preserved after
the reaction; however, the detection of Mo(V) species verifies the
partial oxidation of molybdenum, which leads to the formation of the
dissociative Mo species, such as molybdenum V ethoxide, in the fluid
phase. Through the product analysis and catalyst characterization,
the common route of lignin conversion to value added chemicals over
the Mo-based catalyst is presented in detail. Kraft lignin is first
fragmented into segments with m/z ∼ 700–1400 via a noncatalytic ethanolysis process.
Meanwhile, the main active Mo(V) species dissociate from the solid
catalyst into the fluid due to the interaction of ethanol. Then mainly
the dissociative species catalyze, with the participation of the radicals,
the further degradation of the segments into small molecules.
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