Room-temperature dissolution and chemical modification of cellulose in aqueous tetraethylammonium hydroxide–carbamide solutions

Abstract

The room-temperature dissolution of cellulose in aqueous tetraethylammonium hydroxide (TEAOH) in the presence of carbamides (ureas) was investigated. Without carbamide, 35 wt% TEAOH was able to dissolve cellulose (microcrystalline cellulose) up to 3 wt%, whereas carbamides-such as urea, N-methylurea, N-ethylurea, 1,3-dimethylurea, and imidazolidone-were able to improve the dissolution of cellulose. At 5 wt% cellulose concentration, the highest carbamide contents in the solvent still able to dissolve cellulose within 1 h were 56 and 55 wt% of 1,3-dimethylurea and N-methylurea, respectively. When using urea, up to 15% of cellulose could be dissolved in a solution containing 22 wt% of urea. To demonstrate the possibility of the use of a carbamidebased solvent in cellulose modification, cationic cellulose was produced using glycidyltrimethylammonium chloride (GTAC). At a molar ratio of 1:3 of cellulose and GTAC, all the studied TEAOH-carbamide solvents produce cationic cellulose with higher charge density compared to the reference NaOH-urea solvent.

Transparent lignin-containing wood nanofiber films with UV-blocking, oxygen barrier, and anti-microbial properties

“…TEAOH together with carbamides, described as aqueous deep eutectic solvent (DES), has been previously used for room temperature dissolution of low-molecular weight microcrystalline cellulose. 32 Although the dissolution of high-molecular weight cellulose, such as that present in wood, is limited, it was assumed that TEAOH with carbamides could serve as an efficient reaction medium for wood. The wood material used here was dry sawdust, which was mildly ground to a smaller size, leaving the majority of the wood components still intact.…”

A Fast Dissolution Pretreatment to Produce Strong Regenerated Cellulose Nanofibers via Mechanical Disintegration

“…TEAOH belongs to the class of aqueous tetraalkylammonium hydroxide ionic liquids that are studied for cellulose dissolution as such 35 or together with additional components, such as urea. 36 Tetraalkylammonium hydroxides are known to dissolve cellulose even at room temperature, and despite the apparent toxicity of alkyl cations, they are biodegradable. Moreover, it has been proposed that after use in dissolution and regeneration of biomass, they could be used as fertilizer.…”

Probing Interactions in Combined Hydroxide Base Solvents for Improving Dissolution of Cellulose

“…While hydrogen bonding between cellulose and urea was initially proposed, more recently weak dispersion interactions between cellulose and urea have been suggested as the reason for the observed improvement [6]. Urea and derivatives of urea have also been used as additives to improve cellulose dissolution in aqueous solutions of quaternary ammonium hydroxides (QAHs) [7,8]. The ability of aqueous QAH solutions to dissolve cellulose has been known for a long time, as seen by the patent by Leon Lilienfeld from 1924 [9].…”