Valorization of native birch wood lignin into monomeric phenols over nickel-based catalysts has been studied. High chemoselectivity to aromatic products was achieved by using Ni-based catalysts and common alcohols as solvents. The results show that lignin can be selectively cleaved into propylguaiacol and propylsyringol with total selectivity >90% at a lignin conversion of about 50%. Alcohols, such as methanol, ethanol and ethylene glycol, are suitable solvents for lignin conversion. Analyses with MALDI-TOF and NMR show that birch lignin is first fragmented into smaller lignin species consisting of several benzene rings with a molecular weight of m/z ca. 1100 to ca. 1600 via alcoholysis reaction. The second step involves the hydrogenolysis of the fragments into phenols. The presence of gaseous H2 has no effect on lignin conversion, indicating that alcohols provide active hydrogen species, which is further confirmed by isotopic tracing experiments. Catalysts are recycled by magnetic separation and can be reused four times without losing activity. The mechanistic insights from this work could be helpful in understanding native lignin conversion and the formation of monomeric phenolics via reductive depolymerization.
The sensing of electrons confined inside surface defect sites has been demonstrated. Tetracyanoethylene was employed as a single-electron acceptor to characterize the reduction of fully oxidized MoO3. Electron transfer deposits negative charge on closely contacted gold nanoparticles on the surface, which explains the high catalytic activity in the aerobic oxidation of alcohols.
We report a strategy for the catalytic conversion of lignosulfonate into phenols over heterogeneous nickel catalysts. Aryl–alkyl bonds (C–O–C) and hydroxyl groups (–OH) are hydrogenated to phenols and alkanes, respectively, without disturbing the arenes. The catalyst is based on a naturally abundant element, and is recyclable and reusable.
Design, synthesis and characterization of nanosized Mo-V-O oxides and their catalytic applications in C-H bond activation reactions
Synthesis of nanostructured molybdenum trioxides and their catalytic performance in carbon-carbon coupling reactions
Catalytic conversion of glycerol over V-P-O catalysts
A catalyst with nanosized FeOX domains embedded in the surface of FeVO4 phase is active for oxidative dehydration of glycerol to acrolein and acrylic acid
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