Lignin depolymerisation in supercritical carbon dioxide/acetone/water fluid for the production of aromatic chemicals

Reductive de-polymerization of kraft lignin for chemicals and fuels using formic acid as an in-situ hydrogen source

“…Interestingly, increasing the reaction temperature from 300 to 330 °C resulted in a drastic increase in SR yield (from ~0 wt.% to 38 wt.%), accompanied by a marked decrease in DL yield (from ~90 wt.% to ~34 wt.%). This drastic increase in SR yield and drop of DL yield probably resulted from condensation or repolymerization of the degraded lignin intermediates to form large acetone-insoluble molecules, as was observed in some previous studies Gosselink et al, 2012). These results suggest that lignin degradation reactions are dominant at temperatures <300 °C) while repolymerization reactions become predominant at >300 °C.…”

“…However, the results in Table 3-1 show that both M n and M w level off at the FA-to-lignin mass ratio of 0.7 and actually increase slightly when further increasing the FA-to-lignin mass ratio. This can likely be attributed to the difficulty in cleaving of the C-C linkages in KL and the increased acidity at a higher FA-to-lignin mass ratio that could lead to condensation/repolymerization of the reaction intermediates (Gosselink et al, 2012). The above results suggest that FA-to-lignin mass ratio at around 0.7 (corresponding to 3 mL FA for 5.0 g KL) may be optimal for KL depolymerization.…”

Physicochemical Characterisation of Technical Lignins for Their Potential Valorisation

“…It is expected that in the near future, the advent of new biorefineries, which convert cellulosic biomass into transportation biofuels, will introduce an excess supply of various lignins into the process streams, besides the substantial amounts of lignin produced annually from pulping [1]. This turns lignin into a potentially highly available and accessible renewable feedstock for the synthesis of bulk aromatic and phenolic compounds [2]. Also, in comparison with cellulose and hemicellulose, lignin carries the highest specific energy content within the organic matrix of woody materials [3].…”

Catalytic Depolymerization of Alkali Lignin in Sub- and Super-critical Ethanol

“…In recent years, supercritical solvent is considered to be a reaction system with the capability to prevent the condensation reactions (Gosselink et al 2012;Kim et al 2015b), and increase the oil yield of lignin. Based on related research (Mahmood et al 2015;Güvenatam et al 2016a), the abundant hydrogen radicals released from the supercritical solvent can couple with the intermediate products generated from the lignin depolymerized process, thereby preventing the condensation reaction between the intermediate products.…”