5155-64-6Relevant academic research and scientific papers
Selective production of bio-based aromatics by aerobic oxidation of native soft wood lignin in tetrabutylammonium hydroxide
Hosoya, Takashi,Miyafuji, Hisashi,Yamada, Tatsuhiko,Yamamoto, Kohei
, p. 19199 - 19210 (2020/06/04)
Aerobic oxidation of native soft wood lignin in an aqueous solution of Bu4NOH facilitates efficient production of vanillin (4-hydroxy-3-methoxybenzaldehyde), which is one of the platform chemicals in industry. Oxidation of Japanese cedar (Cryptomeria japonica) wood flour at 120 °C for 4 h under O2in Bu4NOH-based aqueous solutions produced vanillin in 23.2 wt% yield based on the Klason lignin content of the starting material. This yield was comparable to that in alkaline nitrobenzene oxidation of the same material (27.2%), which indicated that our aerobic oxidation exploited the full potential of the wood flour for vanillin production. Further mechanical investigation with lignin model compounds suggested that the vanillin formation occurred mainly through following successive reactions: alkaline-catalyzed degradation of ?-ether linkages in middle units of lignin polymer to form a glycerol end group, oxidation of the glycerol end group by O2to a HCa?O moiety, and release of vanillin from the HCa?O end. One of the reasons for the high performance of Bu4NOH for the vanillin production was explained by the general understanding in organic chemistry that Bu4OH is a stronger base than simple alkali,e.g.NaOH. The other more fundamental mechanical aspect was that Bu4N+suppressed disproportionation of the vanillin precursor (the CaHO end group) probably due to strong interaction between the cation and the HCa?O end group.
Lignin Depolymerization with Nitrate-Intercalated Hydrotalcite Catalysts
Kruger, Jacob S.,Cleveland, Nicholas S.,Zhang, Shuting,Katahira, Rui,Black, Brenna A.,Chupka, Gina M.,Lammens, Tijs,Hamilton, Phillip G.,Biddy, Mary J.,Beckham, Gregg T.
, p. 1316 - 1328 (2016/02/18)
Hydrotalcites (HTCs) exhibit multiple adjustable parameters to tune catalytic activity, including interlayer anion composition, metal hydroxide layer composition, and catalyst preparation methods. Here, we report the influence of several of these parameters on β-O-4 bond scission in a lignin model dimer, 2-phenoxy-1-phenethanol (PE), to yield phenol and acetophenone. We find that the presence of both basic and NO3- anions in the interlayer increases the catalyst activity by 2-3-fold. In contrast, other anions or transition metals do not enhance catalytic activity in comparison to blank HTC. The catalyst is not active for C-C bond cleavage on lignin model dimers and has no effect on dimers without an α-OH group. Most importantly, the catalyst is highly active in the depolymerization of two process-relevant lignin substrates, producing a significant amount of low-molecular-weight aromatic species. The catalyst can be recycled until the NO3- anions are depleted, after which the activity can be restored by replenishing the NO3- reservoir and regenerating the hydrated HTC structure. These results demonstrate a route to selective lignin depolymerization in a heterogeneous system with an inexpensive, earth-abundant, commercially relevant, and easily regenerated catalyst.
Lignin-Feruloyl Ester Cross-links in Grasses. Part 2. Model Compound Syntheses
Ralph, John,Helm, Richard F.,Quideau, Stephane
, p. 2971 - 2980 (2007/10/02)
Five compounds which model the various structures produced when feruloyl esters are copolymerized into lignins have been synthesized.These models represent the lignin-feruloyl-polysaccharide structures which have been theorized to exist in the Graminaceae but have yet to be isolated.Complete spectroscopic characterization provides important chemical-shift information to facilitate the identification of these linkages in native lignins and synthetic DHP polymers.Methyl 5-O-feruloyl>-α-L-arabinofuranoside, a model for the α-linkage of feruloyl esters to lignin, was prepared as a mixture of threo and erythro isomers by addition of methyl 5-O-(E)-feruloyl-α-L-arabinofuranoside (FA-Ara) to the quinone methide derived from 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)propane-1,3-diol (guaiacylglycerol-β-guaiacyl ether).Methyl 5-O-feruloyl>-α-L-arabinofuranoside, a β-aryl ether model, was prepared by a method analogous to one used for the synthesis of guaiacylglycerol-β-guaiacyl ether; FA-Ara was added to 4-acetoxy-β-bromo-3-methoxyacetophenone, and the product was hydroxymethylated and reduced.The peracetate of methyl 5-O--α-L-arabinofuranoside, a compound which models the attack of lignin radicals on the β-position of the feruloyl ester, was prepared by elimination of the β-proton from the quinone methide derived from ethyl 3-hydroxy-3-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)propanoate.As in the preparation of synthetic copolymers between coniferyl alcohol andFA-Ara, only a single geometrical isomer was produced.Synthesis of both isomers of derived compounds and detailed NMR analysis indicated that this was the expected Z-isomer.A model for β-5 coupled products, 3-acrylic acid bis(methyl 5-deoxy-α-L-arabinofuranosid-5-yl) ester, was obtained as a cis/trans mixture in 55percent yield by radical coupling of FA-Ara using silver(I) oxide.Finally, the crossed β-β-compound 4,8-exo-bis(4-hydroxy-3-methoxyphenyl)-3,7-dioxabicyclooctan-2-one (MEL) was obtained, in admixture with its isomer iso-MEL, pinoresinol, and the dilactone 4,8-exo-bis-(4-hydroxy-3-methoxyphenyl)-3,7-dioxabicyclooctan-2,6-dione, from mixed radical coupling of coniferyl alcohol and ferulic acid via silver(I) oxide.
