Lignin‐First Fractionation of Softwood Lignocellulose Using a Mild Dimethyl Carbonate and Ethylene Glycol Organosolv Process

Abstract

A mild lignin‐first acidolysis process (140 °C, 40 min) was developed using the benign solvent dimethyl carbonate (DMC) and ethylene glycol (EG) as a stabilization agent/solvent to produce a high yield of aromatic monophenols directly from softwood lignocellulose (pine, spruce, cedar, and Douglas fir) with a depolymerization efficiency of 77–98 %. Under the optimized conditions (140 °C, 40 min, 400 wt % EG and 2 wt % H2SO4 to pinewood), up to 9 wt % of the aromatic monophenol was produced, reaching a degree of delignification in pinewood of 77 %. Cellulose was also preserved, as evidenced by a 85 % glucose yield after enzymatic digestion. An in‐depth analysis of the depolymerization oil was conducted by using GC‐MS, HPLC, 2 D‐NMR, and size‐exclusion chromatography, which provided structural insights into lignin‐derived dimers and oligomers and the composition of the sugars and derived molecules. Mass balance evaluation was performed.

Recent Advances in the Catalytic Depolymerization of Lignin towards Phenolic Chemicals: A Review

“…The same group also compared the effect of different metal triflates [M(OTf)x] on the yield of C 2 ‐aldehydes using β‐O‐4 model compounds, finding that the metal triflates Bi(OTf) 3 , Fe(OTf) 3 , and Hf(OTf) 4 showed the most promising cleavage efficiency to form C 2 ‐aldehdyes with Fe(OTf) 3 giving the highest yield (19.3 wt %) of phenolic C 2 ‐aldehydes . Recently, a mild hydrogenolysis method using H 2 SO 4 was developed with dimethyl carbonate (DMC) as solvent and ethylene glycol as stabilization agent, achieving 77–98 % yield of C 2 ‐acetal phenolic monomers …”

Toward a Consolidated Lignin Biorefinery: Preserving the Lignin Structure through Additive‐Free Protection Strategies

“…[13] Am ild organosolv extraction of lignin subsequentt oh ydrothermal pretreatment was recently reported. [14] Evenm ore recently,p olyhydroxy alcohols, such as butanediol [15] and ethylene glycol in combination with dimethyl carbonate, [16] have been used in the reactived issolution of biorefinery lignins.…”

Development of ‘Lignin-First’ Approaches for the Valorization of Lignocellulosic Biomass

“…Liquid alkylcyclohexanes, arenes, polyols, and furfural derivatives were produced [70,71]. The latest novel results were carried out using new catalysts [80,87,88] and by developing task-specific catalysts for hardwood and softwood [86], chemodivergent hydrogenolysis (for propyl-or propanol-methoxyphenol production) [87], membrane filtration [83], and applying new solvents/stabilization agent (dimethyl carbonate) [92]. The first integrated techno-economic assessment of a biorefinery process revealed that using only waste wood as feedstock can make the investment profitable [101].…”

“…Softwood lignocellulose was effectively (77-98%) depolymerized in a mild lignin-first acidolysis process (140 • C, 40 min, entry 73 in Table 1) using dimethyl carbonate and ethylene glycol solvents/stabilization agent producing high yield (9 wt %) of aromatic monophenols (2020, second row in Figure 4) and preserving cellulose as evidenced by a 85% glucose yield after enzymatic digestion [92]. The total utilization of lignin and carbohydrates in eucalyptus towards phenolics, levulinic acid, and furfural was emphasized in another paper in 2020: Pd/C catalyst in methanol solvent was used in the hydrogenolysis step, 50 wt % maximum phenolic monomers yield was achieved (entry 74 in Table 1) [93].…”