Acylation of Lignin with Different Acylating Agents by Mechanical Activation-Assisted Solid Phase Synthesis: Preparation and Properties

Abstract

Acylated lignins with substituents consisting of different lengths of carbon chains were prepared by a mechanical activation-assisted solid phase synthesis (MASPS) technology with a customized stirring ball mill as a reactor. The structures and properties were analyzed by UV/Vis, FTIR, NMR, SEM, DSC, and TG. The results showed that the acylated lignins were successfully prepared with either non-cyclic or cyclic anhydrides as the acylating agents. Both aliphatic hydroxyl and phenolic hydroxyl groups of lignin reacted with non-cyclic anhydrides, and different reactivity of acylating agents resulted in different relative contents of phenolic and aliphatic substituents in the products. The reactivity of the cyclic anhydrides was weaker than that of the non-cyclic anhydrides, and the reactivity of the acylating agents decreased with increasing carbon chain length and unsaturated bonds of acyl groups. All of the acylated lignins except maleylated lignin had a lower glass transition temperature (Tg) than the original lignin. The acylated lignins prepared with non-cyclic anhydrides had better thermal stability than original lignin, and the thermal stability increased, but Tg decreased with an increasing chain length of the acyl groups. The acylated lignins prepared with cyclic anhydrides had higher a Tg than those with non-cyclic anhydrides with the same carbon number, and the thermal stability was not obviously improved.

Thermal, Physical and Mechanical Properties of Poly(Butylene Succinate)/Kenaf Core Fibers Composites Reinforced with Esterified Lignin

“…It can be observed that lignin was covered by phthalic anhydride after modification. The surface of the modified lignin became rougher, mainly due to the removal of hydroxyl groups and elimination of intermolecular hydrogen bonding by esterification reactions [39]. This finding explained the reason why T g of composites prepared by PBS/ML and PBS/ML/KCF were lower than that of unmodified samples mentioned in the above section.…”

Solid-Phase Synthesis of Cellulose Acetate Butyrate as Microsphere Wall Materials for Sustained Release of Emamectin Benzoate

“…CAB-MA prepared by the MA method was performed in a customized stirring ball mill [17]. Typically, 10.0 g of MCC mixed with butyric acid, acetic anhydride, and sulfuric acid catalyst (molar ratio of anhydroglucose unit (AGU) of MCC:butyric acid:acetic anhydride:sulfuric acid = 1:6:3:0.06) was poured into a 1200-mL jacketed stainless steel chamber containing 500 mL of zirconium oxide milling balls (Φ = 5 mm).…”

Lignin to value-added chemicals and advanced materials: extraction, degradation, and functionalization

“…The hydroxyl groups of lignin react with acid, acid anhydride and acyl chloride in the presence of catalysts such as pyridine, 4-dimethylaminopyridine, 1-or N -methylimidazole, 2-methylimidazole, and imidazole, yielding esterified lignin. 152,153 Both the aliphatic and phenolic hydroxyl groups of lignin take part in the esterification reaction (Fig. 8).…”

“…Moreover, when the length of the carbon chain and the number of unsaturated bonds in the acyl groups increased, the reactivity of the esterifying agent decreased. 153 For catalysts, 4-dimethylamino pyridine, sodium acetate, and sulfuric acid all could enhance the esterification efficiency. 154 The esterification efficiency followed the order of 4-dimethylamino pyridine > sodium acetate > sulfuric acid.…”