Lignin-first biorefinery of corn stalk via zirconium(IV) chloride/sodium hydroxide-catalyzed aerobic oxidation to produce phenolic carbonyls

Catalytic aerobic oxidation of lignin-based vanillyl alcohol under base–free conditions over an efficient and reusable LaFeO3 perovskite for vanillin production

“…O 2 , an oxidant in catalytic oxidation, is another key factor that cannot be ignored. 16 Accordingly, its effect on the oxidation of vanillyl alcohol to vanillin was also studied, and the results are presented in Fig. 2c.…”

“…With these considerations in mind, many researchers are working to develop sustainable catalysts to meet the challenges regarding the oxidative depolymerization of lignin and/or its model compounds. Until now, catalysts applied in the oxidation technique mainly include supported noble and/or metal oxides, 14,15 transition metal oxides, 16,17 rare earth perovskites, [18][19][20][21][22][23] organic complexes, 24,25 etc. In contrast, rare earth perovskites have been developed as viable alternatives due to their high oxygen mobility, high structural flexibility, low cost and outstanding redox performance.…”

Catalytic oxidative conversion of C/G-type lignin coexisting in Tung nutshells to aromatic aldehydes and acids

“…Water has been widely used in the oxidative depolymerization of lignins. 15,38,39 However, it exhibited a poor aromatic monomer yield when reacted in an aqueous phase in this work (entry 1), very likely due to the low solubility of native Tung nutshell. Several common organic solvents could effectively enhance the catalytic activity of the system (entries 2-6), and their yields of aromatic monomers were in the following order: dimethyl formamide o g-valerolactone o methanol o 1,4-dioxane o acetonitrile.…”

“…At the optimal ratio (CH 3 CN/H 2 O, 8/2, v/v), the total yield of aromatic monomers reached around 60.8 mg g À1 (or 12.9 wt% Klason lignin), which is comparable to the values reported for the oxidative catalytic fractionation of native lignocellulose (usually 10-15 wt% yield in the catalytic oxidative process). 15,[40][41][42][43][44] In this regard, a suitable CH 3 CN/H 2 O ratio is necessary for the CuCl 2 catalytic oxidative system. Water not only assists the release of lignin from native lignocellulose but also promotes the dissolution of the CuCl 2 catalyst, which would also enhance the accessibility of lignin to the catalyst.…”

“…Catalytic oxidation is a promising approach to obtaining highly functionalized aromatics. 15 On the other hand, oxidation enables the cleavage of the robust C-C bonds of the aliphatic side-chain in the lignin linkages, along with the formation of valuable aromatic aldehydes, acids, or esters. 16,17 In the last decades, great efforts have been devoted to the oxidative cleavage of the C-O and C-C bonds in H/G/S-type lignins.…”