Irregular solution thermodynamics of wood pulp in the superbase ionic liquid [m-TBDH][AcO]

Knowledge of solution thermodynamics is fundamental for solution control and solvent selection processes. Herein, experimentally determined thermodynamic quantities for solutions of wood pulp (hardwood dissolving pulp, i.e. cellulose) in [m-TBDH][AcO] are presented. Model-free activities (a(i,j)) and associated mass fraction (w(i,j)) activity coefficients (omega(i,j)), are determined to quantify inherent solution non-ideality. Access to the Gibbs energy of mixing, G(mix), in combination with associated partial molar thermodynamic quantities, reveal strong enthalpically favourable (exothermic) interactions due to solvent-j and solute-i contact-encounters. Onset of an entropy driven phase instability appears at increased temperatures as excess entropic contributions dominate solvation character of the irregular solutions formed.Peer reviewe

Transesterification of cellulose with unactivated esters in superbase-acid conjugate ionic liquids

A sustainable homogeneous transesterification protocol utilizing the superbase ionic liquid [mTBNH][OAc] and unactivated methyl esters has been developed for the preparation of cellulose esters with controllable degree of substitution. [mTBNH][OAc] shows excellent recyclability with a high recovery of sufficient purity for repeated use. This reaction media allows for cellulose transesterification reactions not only using activated or cyclic esters, but also with unactivated methyl esters, which extends the substrate and application scope. Furthermore, the solubility properties of the prepared cellulose materials were tested and some intrinsic trends were observed at low degrees of substitution.Peer reviewe

Enhanced activity of hyperthermostable Pyrococcus horikoshii endoglucanase in superbase ionic liquids

Objectives Ionic liquids (ILs) that dissolve biomass are harmful to the enzymes that degrade lignocellulose. Enzyme hyperthermostability promotes a tolerance to ILs. Therefore, the limits of hyperthemophilic Pyrococcus horikoschii endoglucanase (PhEG) to tolerate 11 superbase ILs were explored. Results PhEG was found to be most tolerant to 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) in soluble 1% carboxymethylcellulose (CMC) and insoluble 1% Avicel substrates. At 35% concentration, this IL caused an increase in enzyme activity (up to 1.5-fold) with CMC. Several ILs were more enzyme inhibiting with insoluble Avicel than with soluble CMC. K-m increased greatly in the presence ILs, indicating significant competitive inhibition. Increased hydrophobicity of the IL cation or anion was associated with the strongest enzyme inhibition and activation. Surprisingly, PhEG activity was increased 2.0-2.5-fold by several ILs in 4% substrate. Cations exerted the main role in competitive inhibition of the enzyme as revealed by their greater binding energy to the active site. Conclusions These results reveal new ways to design a beneficial combination of ILs and enzymes for the hydrolysis of lignocellulose, and the strong potential of PhEG in industrial, high substrate concentrations in aqueous IL solutions.Peer reviewe

Phase-separation of cellulose from ionic liquid upon cooling : preparation of microsized particles

Cellulose is an historical polymer, for which its processing possibilities have been limited by the absence of a melting point and insolubility in all non-derivatizing molecular solvents. More recently, ionic liquids (ILs) have been used for cellulose dissolution and regeneration, for example, in the development of textile fiber spinning processes. In some cases, organic electrolyte solutions (OESs), that are binary mixtures of an ionic liquid and a polar aprotic co-solvent, can show even better technical dissolution capacities for cellulose than the pure ILs. Herein we use OESs consisting of two tetraalkylphosphonium acetate ILs and dimethyl sulfoxide or gamma-valerolactone, as co-solvents. Cellulose can be first dissolved in these OESs at 120 degrees C and then regenerated, upon cooling, leading to micro and macro phase-separation. This phenomenon much resembles the upper-critical solution temperature (UCST) type thermodynamic transition. This observed UCST-like behavior of these systems allows for the controlled regeneration of cellulose into colloidal dispersions of spherical microscale particles (spherulites), with highly ordered shape and size. While this phenomenon has been reported for other IL and NMMO-based systems, the mechanisms and phase-behavior have not been well defined. The particles are obtained below the phase-separation temperature as a result of controlled multi-molecular association. The regeneration process is a consequence of multi-parameter interdependence, where the polymer characteristics, OES composition, temperature, cooling rate and time all play their roles. The influence of the experimental conditions, cellulose concentration and the effect of time on regeneration of cellulose in the form of preferential gel or particles is discussed.Peer reviewe

Heat of mixing profile, complexation curve and spectroscopic investigation of binary mixtures containing bicyclic Bronsted superbase DBN with hydrogen ethanoate

Isothermal titration calorimetry (ITC) experiments were performed for investigation of binary mixtures comprised of the Bronsted superbase DBN with hydrogen ethanoate (AcOH). The heat of mixing (H-E) profile was recorded at (343.15 +/- 0.1) K and fitted with a 5-parameter Redlich-Kister (RK) polynomial. RK fit parameters were subsequently used to quantify partial molar heats of mixing, x(i)H(i)(E), for each component i. ITC-based complexometric titration data for the binary mixtures were recorded separately in methyl isobutyl ketone (mibk) and dodecane, to investigate the energetics of non random clustering phenomena. Variable temperature H-1-NMR in combination with ATR-FTIR spectroscopic analyses were employed in parallel for elucidation and verification of liquid state ion speciation. These investigations reveal a strongly non ideal system, and indicate "superbase" character of DBN is preserved for specific compositions where stoichiometric ionic liquids (ILs) form. Available ion speciation has been found to include [DBN-H](+), [AcO] as well as mu 2 -hydrogen-bridged, hydrogen-bonded homoassociate anions, of the type [H(OAc)(2)], with double liquid salt formation characterising various compositions based on spectroscopic determinations. (C) 2021 The Authors. Published by Elsevier Ltd.Peer reviewe

Chemical structure of the lipid a component of lipopolysaccharides of the genus pectinatus

The chemical structure of the lipid A components of smooth-type lipopolysaccharides isolated from the type strains of strictly anaerobic beer-spoilage bacteria Pectinatus cerevisiiphilus and Pectinatus frisingensis were analyzed. The hydrophilic backbone of lipid A was shown, by controlled degradation of lipopolysaccharide combined with chemical assays and P-31-NMR spectroscopy, to consist of the common beta 1-6-linked disaccharide of pyranosidic 2-deoxy-glucosamine (GlcN), phosphorylated at the glycosidic position and at position 4\u27. In de-O-acylated lipopolysaccharide, the latter phosphate was shown to be quantitatively substituted with 4-amino-4-deoxyarabinose, whereas the glycosidically linked phosphate was present as a monoester. Laser-desorption mass spectrometry of free dephosphorylated lipid A revealed that the distal (non-reducing) GlcN was substituted at positions 2\u27 and 3\u27 with (R)-3-(undecanoyloxy)tridecanoic acid, whereas the reducing GlcN carried two unsubstituted (R)-3-hydroxytetradecanoic acids at positions 2 and 3. The lipid A of both Pectinatus species were thus of the asymmetric hexaacyl type. The linkage of lipid A to polysaccharide in the lipopolysaccharide was relatively resistant to acid-catalyzed hydrolysis, enabling the preparation of a dephosphorylated and deacylated saccharide backbone. Methylation analysis of the backbone revealed that position 6\u27 of the distal GlcN of lipid A was the attachment site of the polysaccharide. Despite the quantitative substitution of the lipid A 4\u27-phosphate by 4-amino-4-deoxyarabinose, which theoretically should render the bacteria resistant to polymyxin, P. cerevisiiphilus was shown to be susceptible to this antibiotic. P. cerevisiiphilus was, however, also susceptible to vancomycin and bacitracin, indicating that the outer membrane of this bacterium does not act as an effective permeability barrie

Thorough chemical modification of wood-based lignocellulosic materials in ionic liquids

Homogenous acylation and carbanilation reactions of wood-based lignocellulosic materials have been investigated in ionic liquids. We have found that highly substituted lignocellulosic esters can be obtained under mild conditions (2 h, 70 °C) by reacting wood dissolved in ionic liquids with acetyl chloride, benzoyl chloride, and acetic anhydride in the presence of pyridine. In the absence of pyridine, extensive degradation of the wood components was found to occur. Highly substituted carbanilated lignocellulosic material was also obtained in the absence of base in ionic liquid. These chemical modifications were confirmed by infrared spectroscopy, 1H NMR, and quantitative 31P NMR of the resulting derivatives. The latter technique permitted the degrees of substitution to be determined, which were found to vary between 81 % and 95 % for acetylation, benzoylation, and carbanilation, accompanied by similarly high gains in weight percent values. Thermogravimetric measurements showed that the resulting materials exhibit different thermal stabilities from those of the starting wood, while differential scanning calorimetry showed discrete new thermal transitions for these derivatives. Scanning electron microscopy showed the complete absence of fibrous characteristics for these derivatives, but instead, a homogeneous porous, powdery appearance was apparent. A number of our reactions were also carried out in completely recycled ionic liquids, verifying their utility for potential applications beyond the laboratory bench. 1

Recovery of superbase ionic liquid using aqueous two-phase systems

Aqueous two-phase systems (ATPS) have been widely used for the purification and separation of biomolecules. However, recent studies have shown that ATPS can also be effective in the purification and recovery of other compounds, such as ionic liquids (IL). Here, we investigated the liquid-liquid phase equilibria of ATPS consisting of 5-methyl-1,5,7-triaza-bicyclo[4.3.0]non-6-enium acetate ([mTBNH][OAc]) and potassium salts (K2CO3 and K3PO4) at 293.2 K and 323.2 K. Our results indicate that both systems exhibited a high IL partition coefficient (k), exceeding 9.5, and achieved a 99.5% recovery of ionic liquid. Moreover, we found that the presence of potassium salt in the ionic liquid-rich phase had a negative impact on the IL cellulose dissolution capability. Therefore, we investigated the removal of potassium salt from the IL and successfully achieved it by using a nanoporous sodium zirconium cyclosilicate (ZS-9 or AV-13). Overall, our study suggests that ATPS can be a promising technique for the purification and recovery of ionic liquids, with potential applications in various industries.Peer reviewe