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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.

Ionic liquids of the alkylmethylimidazolium chloride family are able to solubilize high amounts of cellulose and other natural polymers and have very good characteristics for their processing. Nevertheless, they present important disadvantages related to their high melting points and viscosities. Dissolution of carbon dioxide (CO2) can reduce the melting point of these ionic liquids. In this work, the effect of pressurized carbon dioxide on the melting point depression of some ionic liquids able to dissolve biopolymers was experimentally determined using the first melting point method. Five different ionic liquids were studied using a high-pressure visual cell, up to a pressure of 10 MPa. The ILs studied were four ionic liquids with chloride anion coupled with 1-butyl-3-methylimidazolium cations: [C4mim] + , 1-ethyl-3-methylimidazolium, [C2mim] + , 1-allyl-3-methylimidazolium, [Amim] + and 1-(2-hydroxyethyl)-3-methylimidazolium, [C2OHmim] + and one ammonium-based cation choline [C5H14NO] + combined with dihydrogen phosphate anion, [H2PO4] -. Melting point depression effect observed for these groups of ionic liquids were around 10 K for chloride ILs and went as high as 33.2 K for choline dihydrogen phosphate. To correlate the melting point depression of imidazolium chloride ILs, parameters for the Group Contribution Equation of State (GC-EoS) of Skjold-Jørgensen for the liquid phase plus a fugacity expression for solid phases was employed. Experimental data used for the parameterization includes literature data of binary vapor-liquid, liquid-liquid and solid-liquid equilibria, and activity coefficients at infinite dilution. Melting point depression was calculated with an average deviation of 1.7 K (0.5%) and a maximum deviation of 4.3 K (1.3%).

Deconstruction of lignocellulosic biomass with low-cost ionic liquids (ILs) has proven to be a promising technology that could be implemented in a biorefinery to obtain renewable materials, fuels and chemicals.

In this work, the performance of inorganic salt sodium chloride and ionic liquid (molten salt) ECOENG212 as salting-out media for the separation of nicotine from its aqueous solutions was examined. In this respect, liquid–liquid equilibria of the ternary solutions nicotine + water + NaCl and nicotine + water + ECOENG212 were determined at ambient pressure, 0.1 MPa, and humidity at three temperatures. The related phase diagrams were constructed by means of both cloud points and chemical analysis of phases in equilibrium (tie-line data). The latter were used to calculate two important separation parameters: partition coefficients of nicotine and separation factors. The effects of the initial compositions of the solutions and of the temperature on the phase behavior and partition coefficients were analyzed and discussed. The results obtained, particularly in the case of sodium chloride as a salt, clearly showed that both investigated salts provided good salting-out media for the efficient and sustainable separation of nicotine from solutions with water.

The effect of viscosity reduction caused by the solubilization of CO2 is studied in order to improve the biomass processing in ionic liquids. To do so, densities and viscosities of the pure ionic liquid 1-allyl-3-methylimidazolium chloride and its mixtures with CO2 up molar fractions of 0.25 and temperatures between 333 and 372 K have been experimentally determined. Viscosities were correlated as a function of temperature and CO2 molar fractions with an average relative error of 2.5%. The viscosities of other mixtures CO2 + ionic liquids were also correlated for other ionic liquids with an average relative error between 4.4 and 13%. In general these ionic liquids present a linear decrease of viscosity with CO2 molar fractions up to around 0.5 that is more pronounced at lower temperatures and depends of each ionic liquid, and can reach between 60-100% viscosi-2 ty reduction with respect the viscosity of the pure ionic liquid, making the CO2 a promising co-solvent for viscosity reduction in process with ionic liquids.