A laboratory batch simulation of the recovery and reuse of [DBNH][OAc] in the IONCELL-F process, yielding future directions for optimising the recycling process.

A thermochemical study of the protic ionic liquid 1,5-diazabicyclo­[4.3.0]­non-5-enium acetate ([DBNH]­[OAc]), a prospective cellulose solvent considered for the Ioncell-F process, was carried out. The heat capacities of 1,5-diazabicyclo[4.3.0]­non-5-ene (DBN) and [DBNH]­[OAc] were measured by differential scanning calorimetry (DSC) at 223–323 and 273–373 K temperature ranges, respectively. The enthalpies of fusion and synthesis reaction of [DBNH]­[OAc] were measured by DSC and reaction calorimetry, respectively. The gas-, liquid-, and solid-phase enthalpies of formation of [DBNH]­[OAc] and DBN were determined using calorimetric and computational methods. The enthalpy of vaporization of [DBNH]­[OAc] was estimated from the formation enthalpies. The activity coefficients at infinite dilution of 17 and the enthalpies of solution at infinite dilution of 25 organic solutes in [DBNH]­[OAc] were measured by gas chromatography and solution calorimetry methods, respectively. The obtained data will be used in the design and optimization of the Ioncell-F process.

7-Methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (mTBD) has useful catalytic properties and can form an ionic liquid when mixed with an acid. Despite its potential usefulness, no data on its thermodynamic and transport properties are currently available in the literature. Here we present the first reliable public data on the liquid vapor pressure (temperature from 318.23 K to 451.2 K and pressure from 11.1 Pa to 10 000 Pa), liquid compressed density (293.15 K to 473.15 K and 0.092 MPa to 15.788 MPa), liquid isobaric heat capacity (312.48 K to 391.50 K), melting properties, liquid thermal conductivity (299.0 K to 372.9 K), liquid refractive index (293.15 K to 343.15 K), liquid viscosity (290.79 K to 363.00 K), liquid-vapor enthalpy of vaporization (318.23 K to 451.2 K), liquid thermal expansion coefficient (293.15 K to 473.15 K), and liquid isothermal compressibility of mTBD (293.15 K to 473.15). The properties of mTBD were compared with those of other relevant compounds, including 1,5-diazabicyclo(4.3.0)non-5-ene (DBN), 1,8-diazabicyclo[5.4.0]undec-7ene (DBU), and 1,1,3,3-tetramethylguanidine (TMG). We used the PC-SAFT equation of state to model the thermodynamic properties of mTBD, DBN, DBU, and TMG. The PC-SAFT parameters were optimized using experimental data.

For ionic liquid processes to be adopted by industry there are two main challenges. First is the enormous capital and running costs when using expensive ionic liquids, compared to molecular solvents. In addition, if ionic liquids are disposed of there is great potential for environmental damage. These factors can be mitigated, by recycling ionic liquids in any process or product life cycle, as far as possible. This chapter reviews the topic of ionic liquid recycling, covering the main methods of recycling in the academic and patent literature. These include the classical methods of recycling compounds such as distillation, phase separation, extraction and crystallization. Adsorption and membrane methods are also covered. The various mechanisms of distillation will be covered, including distillation of ion pairs or dissociation of ionic liquids into volatile neutral species, which vaporize and recondense. The topic of aqueous biphasic systems is also covered, under the general method of phase separation. It is shown how even water miscible ionic liquids can be separated with the use of kosmotropic salts, commonly described in the Hofmeister series. Throughout this discussion the applicability to recycling of ionic liquids on an industrial scale is also considered.

Ionic liquids are used to dewater a suspension of birch Kraft pulp cellulose nanofibrils (CNF) and as a medium for water‐free topochemical modification of the nanocellulose (a process denoted as “WtF‐Nano”). Acetylation was applied as a model reaction to investigate the degree of modification and scope of effective ionic liquid structures. Little difference in reactivity was observed when water was removed, after introduction of an ionic liquid or molecular co‐solvent. However, the viscoelastic properties of the CNF suspended in two ionic liquids show that the more basic, but non‐dissolving ionic liquid, allows for better solvation of the CNF. Vibrio fischeri bacterial tests show that all ionic liquids in this study were harmless. Scanning electron microscopy and wide‐angle X‐ray scattering on regenerated samples show that the acetylated CNF is still in a fibrillar form. 1 D and 2 D NMR analyses, after direct dissolution in a novel ionic liquid electrolyte solution, indicate that both cellulose and residual xylan on the surface of the nanofibrils reacts to give acetate esters.

Understanding the toxicity of ionic liquids (ILs) is crucial in the search of greener chemicals. By comparing in vivo toxicity and in vitro interactions determined between compounds and biomimetic lipid membranes, more detailed toxicity vs. structure relation can be obtained. However, determining the interactions between non-surface-active compounds and liposomes has been a challenging task. Organisational changes induced by ILs and IL-like spirocyclic compounds within 1,6-diphenyl-1,3,5-hexatriene-doped biomimetic liposomes was studied by steady-state fluorescence anisotropy technique. The extent of organisational changes detected within the liposome bilayers were compared to the toxicity of the compounds determined using Vibrio Fischeri bacteria. Four liposome compositions made of pure 1-palmitoyl-2-oleyl-sn-glycero-3-phosphocoline (POPC) and mixtures of POPC, 1-palmitoyl-2-oleyl-sn-glycero-3-phosphoserine (POPS), and cholesterol (Chol) were tested as biomimetic models. Changes observed within the POPC/POPS/Chol 55:20:25 bilayers correlated the best with the toxicity results: ten out of twelve compounds followed the trend of increasing bilayer disorder – increasing toxicity. The study suggests that the toxicity of non-surface-active compounds is dependent on their ability to diffuse into the bilayers. The extent of bilayer’s organisational changes correlates rather well with the toxicity of the compounds. Highly sensitive technique, such as fluorescence anisotropy measurements, is needed for detecting subtle changes within the bilayer structures.

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