Ionic Liquid as Reaction Media for the Production of Cellulose-Derived Polymers from Cellulosic Biomass

Abstract

Abstract:The most frequent polymer on nature is cellulose that is present together with lignin and hemicellulose in vegetal biomass. Cellulose can be, in the future, sustainable raw matter for chemicals, fuels, and materials. Nevertheless, only 0.3% of cellulose is processed nowadays due to the difficulty in dissolving it, and only a small proportion is used for the production of synthetic cellulosic fibers especially esters and other cellulose derivatives, normally in extremely polluting processes. The efficient and clean dissolution of cellulose is a major objective in cellulose research and development. Ionic liquids (ILs) are considered "green" solvents due to their low vapor pressure, that prevents them evaporating into the atmosphere. In addition, these molten salts present advantages in process intensification, leading to more than 70 patents in lignocellulosic biomass in ILs being published since 2005, most of them related to the production of cellulose derived polymers, e.g., acetates, benzoylates, sulfates, fuorates, phthalates, succinates, tritylates, or silylates. In this work, the use of ILs for production of cellulose derived polymers is thoroughly studied. To do so, in the first place, a brief summary of the state of the art in cellulose derivatives production is presented, as well as the main features of ILs in cellulose processing applications. Later, the main results in the production of cellulose derivatives using ILs are presented, followed by an analysis of the industrial viability of the process, considering aspects such as environmental concerns and ILs' recyclability.

The Effect of Additives on the Viscosity and Dissolution of Cellulose in Tetrabutylphosphonium Hydroxide

“…Most solvents are unable to break the strong hydrogen bonds within crystalline cellulose and thus heterogeneous modification is often limited to its surface. Only full dissolution ensures complete modification or degradation …”

“…Only full dissolutione nsures complete modification or degradation. [4] However,c ellulose presents ah ighly insoluble substance; most common solvents, such as water,c annot break the strongi ntramolecular and intermolecularh ydrogen bonds. The amphiphilic cellulosec ontains both hydrophilic and hydrophobic sites.…”

Effective Concentration of Ionic Liquids for Enhanced Saccharification of Cellulose

“…The dissolution of cellulose is a bottleneck step in the enzymatic saccharification process, in which ILs can promote the dissolution of crystalline cellulose [22]. In the absence of ILs, the saccharification could be considered as the solid-liquid reaction that happens at the crystalline cellulose surface, which usually results in less productivity of glucose.…”

Crystal structure and Hirshfeld surface analysis of a pyridiniminium bromide salt: 1-[2-([1,1′-biphenyl]-4-yl)-2-oxoethyl]-3-methyl-1,4-dihydropyridin-4-iminium bromide

“…Over the past decade, ionic liquids have been the subject of intense research as a customizable replacement for volatile organic solvents because of their negligible vapor pressure, excellent thermal stability, high ionic conductivity and solvation ability (Davis, 2004). A wide range of applications using ionic liquids has been reported in many areas, such as their use as homogeneous and heterogeneous catalysts (Dong et al, 2016) and biological reaction media (Lopes et al, 2017), and in nuclear waste treatment (Ha et al, 2010) and water purification (Fuerhacker et al, 2012;Wang & Wei, 2017).…”