Gas–solid conversion of lignin to carboxylic acids

Abstract

We combine thermo-chemical processes with oxidative catalysis to convert lignin to aliphatic carboxylic acids mainly C4 acids. Acid selectivity changed with catalyst.

Reductive or oxidative catalytic lignin depolymerization: An overview of recent advances

“…Later the same authors revisited the process with the aim of minimizing coke and char formation keeping the activity of the catalysts. They associated in the same reactor a two-stage gas phase catalytic process: treatment of a bed of solid lignin followed by oxidative catalytic treatment of evolved compounds [53]. Several reactor configurations were evaluated, including thermal oxidative steam cracking (T ≤ 550 °C) prior to oxidation which produced lower coke and char on the catalyst surfa ce, fa voring aromatics formation.…”

Carboxylic Acids Production via Electrochemical Depolymerization of Lignin

“…Lotfi et al . introduced a two stage gas‐phase catalytic process that produces carboxylic acids and aromatics from lignin . The production of carboxylic acids by partial wet oxidation of alkali lignin was studied by Demesa et al …”

Lignin conversion into C4 dicarboxylic acids by catalytic wet peroxide oxidation using titanium silicalite-1

“…Heteropoly acids (i.e., phosphotungstic acid (H 3 PW 12 O 40 ) and phosphomolybdic acid (H 3 PMo 12 O 40 )) showed low improvement for succinic acid yield, with disadvantages such as higher costs and recovering difficulties (Demesa et al, 2017). Other catalysts based on V and Mo oxides or pyrophosphates (deposited in materials like Al 2 O 3 , TiO 2 , and HZSM-5), used in lignin gas-phase oxidation gave rise to no more than 2% of succinic acid (Lotfi et al, 2016(Lotfi et al, , 2015. In most of these studies, significant amounts of oxalic, formic, and acetic acids were obtained (as degradation products of lignin over-oxidation).…”