Investigating homogeneous Co/Br⁻/H₂O₂ catalysed oxidation of lignin model compounds in acetic acid

Abstract

The catalytic oxidation of lignin model compounds by Co/Br−/H2O2 is investigated; substituting Br− for N-hydroxyphthalimide improved substrate conversion and product yield.

Catalytic carbon–carbon bond cleavage in lignin via manganese–zirconium-mediated autoxidation

“…While oxidations of lignin models and lignin have been studied with Co/Mn/Br and Co/Br catalysts 36 , 37 , 55 , the target of those studies was not C–C bond cleavage. Rather, the goal was to increase monomer yields from the oxidation of β-O-4-containing substrates by acetylation of the generated phenolic products in situ prior to their degradation under the oxidation conditions.…”

Oxidative depolymerization of Kraft lignin to high-value aromatics using a homogeneous vanadium–copper catalyst

“…Among homogeneous catalysts, Cu-, Mn-, Co-, Fe-and Vbased catalysts showed promising catalytic activity in depolymerizing lignin into valuable aromatic compounds. 4,19,[29][30][31][32] Copper and vanadium catalysts have shown to selectively cleave the C-C bonds in the oxidative depolymerization reactions. [33][34][35] Reaction mechanisms for vanadium-catalyzed oxidative cleavages have been proposed.…”

Autoxidation Catalysis for Carbon–Carbon Bond Cleavage in Lignin

“…Br and oxygen-centered radicals contribute to hydrogen-atom transfer from the organic substrate in the catalytic oxidation process. The Co and Mn catalysts support the autoxidation through activation of O 2 , oxidation of HBr, and selective conversion of reaction intermediates, such as organic hydroperoxides, into the oxidized products. , Lignin has been subjected to related conditions, but monomer yields did not exceed the monomer content of the lignin substrate. , We postulated, however, that lignin oligomers derived from RCF treatment of biomass would be more amenable to such treatment and undergo successful conversion into aromatic monomers. The results outlined herein validate this hypothesis, showing that a Co/Mn/Br-based catalyst system converts RCF-derived oligomers from poplar into aromatic monomers, which are then used as substrates for bioconversion to cis , cis -muconate, a precursor to bioderived polymers (Figure ).…”

“…26,27 Lignin has been subjected to related conditions, but monomer yields did not exceed the monomer content of the lignin substrate. 28,29 We postulated, however, that lignin oligomers derived from RCF treatment of biomass would be more amenable to such treatment and undergo successful conversion into aromatic monomers. The results outlined herein validate this hypothesis, showing that a Co/Mn/Br-based catalyst system converts RCF-derived oligomers from poplar into aromatic monomers, which are then used as substrates for bioconversion to cis,cis-muconate, a precursor to bioderived polymers (Figure 1).…”