Isolation of Low Dispersity Fractions of Acetone Organosolv Lignins to Understand their Reactivity: Towards Aromatic Building Blocks for Polymers Synthesis

Abstract

Two organosolv lignins extracted during pilot runs of the Fabiola process were analyzed, fractionated and chemically modified with ethylene carbonate (EC) to produce building blocks suitable for polymer synthesis. Isolation of low dispersity fractions relied on the partial solubility of the lignins in organic solvents. Lignins solubility was first evaluated and analyzed with Hansen and Kamlet-Taft solubility parameters, showing a good correlation with the solvents dipolarity/polarizability parameter π*. The results were then used to select a sequence of solvents able to fractionate the lignins into low dispersity fractions of increasing molar masses, which were analyzed by 31 P NMR, SEC and DSC. The lignins were then reacted with EC, to convert the phenolic OH groups into primary aliphatic OH groups. The reactivity of the organosolv lignins was high, and milder reaction conditions than previously reported were sufficient to fully convert the phenolic OH groups. A gradual reduction in reactivity with increasing molar mass was evidenced and attributed to reduced solubility of high molar mass fragments in EC. Undesirable crosslinking side reactions were evidenced by SEC, but were efficiently limited thanks to a fine control of the reaction conditions, helping to maximize the benefits of the developed lignin modification with EC.

Effect of the Lignin Structure on the Physicochemical Properties of Lignin-Grafted-Poly(ε-caprolactone) and Its Application for Water/Oil Separation

“…In other words, lignin M w has a positively linear correlation with the quantity of aliphatic OH [Pearson correlation coefficient ( r ) = 1.000, regression coefficient ( R 2 ) = 1.00, P value ( P ) = 0.189] and a negatively linear correlation with the quantity of phenolic OH ( r = −0.999, R 2 = 1.00, P = 0.031) (Figure A). The phenolic OH concentration increases with the reduction of lignin M w , which may be due to the following factors: (1) β- O -4 linkages are cleaved with the addition of hexane, forming new phenolic OHs, , (2) phenolic OH itself is the chain end of the lignin oligomers, which means that the low- M w lignin fraction has a high frequency of phenolic OH . The elevation of the phenolic OH content leads to a decreased proportion of aliphatic OHs.…”

“…Grafting PCL improves lignin’s dispersity, compatibility, and hydrophobicity, and lignin enhances the anti-UV, antioxidation, anti-inflammation, osteo-conductivity, and cell-viability and -proliferation abilities of PCL. − Lignin -g- PCL typifies a star-shaped molecule with a lignin core and PCL arms. , Technical lignin is reactive to copolymerize with ε-CL irrespective of its botanical sources and extraction methods, but the lignin content negatively affects the MW and thermal properties of the lignin -g- PCLs . Moreover, the crystallinity degree ( X c ) of the PCL segments in lignin -g- PCLs depends on the ε-CL-to-lignin OH (CL/OH) molar ratio to a great extent. ,, Nevertheless, the reactivities of OHs differ among different OH types in terms of phenolic, aliphatic, and carboxylic OHs, , so simply applying CL/OH as a variant is insufficient to reveal the synthetic mechanism.…”

Synthesis of Bio-Based Photo-Cross-Linkable Polyesters Based on Caffeic Acid through Selective Lipase-Catalyzed Polymerization

“…However, propylene oxide and chloro-alcohols are both toxic. For this reason, we chose to use a cyclic carbonate that has already been described by our team for the modification of lignins. − Ethylene carbonate can react with a phenol in basic condition to yield a primary alcohol. However, the limited reactivity of coumaric derivatives toward ethylene carbonate has already been reported and systematically prevented the obtention of the desired product .…”

Laboratory- to Pilot-Scale Fractionation of Lignocellulosic Biomass Using an Acetone Organosolv Process

“…Mild acetone organosolv fractionation of herbaceous biomass and hardwood has shown promising results at the lab scale and excellent lignin solubilization. , The so-called Fabiola process aims to balance the high severity requirements for optimal biomass fractionation and mild process conditions needed to minimize sugar and lignin degradation. Replacing the state-of-the-art ethanol organosolv fractionation process by an acetone-based process prevents undesired ethylation of sugars and lignin and directly improves sustainability performance mainly via reduced energy demand and investments. , …”