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

Abstract

Conversion of lignin feedstocks into aromatic chemicals is a highly desirable target for biorefineries, whose depolymerization often requires high temperatures and harsh conditions.

Base metal iron catalyzed sustainable oxidation of vanillyl alcohol to vanillic acid in deep eutectic solvents and implementation of vanillic acid for fine-chemical synthesis

“…The rest of the bond distances and angles are in good agreement with those of previously reported similar iron(II) complexes with octahedral geometry. [93][94][95] It is worth mentioning that the distance between amine nitrogen (N2) and iron is 2.179 (19) Å which is similar to the previously reported Fe-N amine distances. [96][97][98] Extensive N-H/O and C-H/O hydrogen bonding interactions as well as C-H/p interactions are also observed in the solid-state structure of complex 1.…”

“…In a process of targeted oxidation of vanillyl alcohol to vanillin, vanillic acid has oen been found as an over-oxidation product. [18][19][20][21][22][23][24][25] There are few reports for the selective oxidation of vanillyl alcohol or vanillin to vanillic acid. In a very old report, a stoichiometric amount of silver oxide (in situ generated from AgNO 3 and NaOH) was used as an oxidant to convert vanillin to vanillic acid.…”

Catalytic depolymerization of calcium lignosulfonate to high-value oxygenated aromatic compounds over the efficient Fe2O3-La0.8Sr0.2FeO3

“…Therefore, the higher the proportion of Fe 2+ , the higher the concentration of oxygen vacancy. 55 After regeneration under air atmosphere, the O ads /O lat = 1.54 value of the regenerated catalyst returned to the fresh sample, indicating that gaseous oxygen was re-adsorbed on the LSF-1.0 catalyst as the adsorbed oxygen. 56 Moreover, after the reaction, the carbon deposition covered the surface of the sample, hampering partial CLS from transforming.…”

Telescoped Two-Step Continuous-Flow Synthesis of Vanillin

“…In the first reaction process, the Cannizzaro reaction of 3 with strong bases (disproportionation of aldehydes to carboxylic acids and alcohols) decreases the yield of 4a (Scheme 1b). 8 In addition, in the second reaction process, the overoxidation of vanillin results in undesired vanillic acid (5) or oligo-vanillin products, reducing the yield and purity of the vanillin (Scheme 1c). 10−14 The conventional batch process performs these reactions at lower temperatures over a longer period of time to prevent a decrease in yield caused by such side reactions.…”

“…Vanillin ( 1 ), the main extract of vanilla beans and a popular aromatic component of vanilla incense, is widely used in foods and beverages (to add flavor), cosmetics (as a fragrance), cleaning products, and pharmaceuticals. − Annual production is expected to reach 59,000 tons by 2025, due to rapidly growing demand . Over 99% of vanillin is produced through chemical synthesis; among this synthetic vanillin, 85% is derived from a two-step synthesis (as shown in Scheme ) using guaiacol ( 2 ) and glyoxylate ( 3 ) as starting materials .…”