2-hydroxyethyl Ammonium Acetate Research Articles

Effect of 2-hydroxyethylammonium carboxylate protic ionic liquids on the solubility and cytotoxicity of indomethacin

Recently, there is a particular interest to utilize protic ionic liquids (PILs) in drug solubility. This study is exploring the effect of three protic ionic liquids (PILs) based on 2-hydroxyethylammonium carboxylate [2-hydroxyethylammonium acetate (MEAA), 2-hydroxyethylammonium lactate (MEAL), and 2-hydroxyethylammonium propionate (MEAP)] on the solubility of the very poorly soluble drug in water, indomethacin (IMC). The shake flask method was used to measure the experimental solubility of IMC at the different temperatures range (298.15–313.15) K. The results demonstrate significantly enhancment the solubility of IMC in PILs compared to pure water, with an approximate increase of 200 times. The experimental solubility data have been correlated using the empirical models which showed the performance as the order: Modified Apelblat–Jouyban–Acree > Van’t Hoff–Jouyban–Acree > Modified Apelblat equations and also the performance for the Wilson model indicated as the order (absolute relative deviation): 2-hydroxyethylammonium acetate (3.030) > 2-hydroxyethylammonium propionate (3.239) > 2-hydroxyethylammonium lactate (7.665). Then the thermodynamic dissolution properties were obtained by usage of Gibbs and Van’t Hoff equations to investigate the thermodynamic behavior of the IMC in the aqueous solution PILs. Eventually, the cytotoxicity of the co-solvents (PILs) under study was evaluated using a standard MTT assay. The results showed that the cell viability percentage increased in the following order: MEAA < MEAP < MEAL. These findings indicated that these PILs had low to moderate toxicity. It is noteworthy that the functional groups of the anions were not the only determinant factor of the cytotoxicity. Other factors encompassing concentration, exposure time, and cell line characteristics also had significant effects.

The use of green protic ionic liquids in the crystallization of isoniazid: Evaluation of physicochemical and biological properties of drug

This study evaluated the synthesis of protic ionic liquids (PILs), 2-hydroxy ethylammonium formate (2-HEAF) and 2-hydroxy ethylammonium acetate (2-HEAA), and their applicability in the crystallization process of the active pharmaceutical ingredient isoniazid (INH) as anti-solvent. Isoniazid is an antibiotic used in the treatment of tuberculosis infections, being used as a first-line chemotherapeutic agent against Mycobacterium tuberculosis. Futhermore, this investigation was conducted in order to evaluate how these PILs can influence the habit, solubility, stability, and therapeutic efficiency of the obtained isoniazid crystals. The 2-HEAF and 2-HEAA PILs were easily formed in reactions between ethanolamine and carboxylic acids (formic or acetic acid), and they have no toxicity against Artemia salina. The PILs were able to crystallize isoniazid, influencing the crystal habit and size. The greatest variations in the hydrogen signals of the NH2 and NH groups of the amine and low variations in the chemical shifts of the hydrogens of the cation of the ethanolamine group from 2-HEAA and 2-HEAF indicate that PILs establish possibly weak interactions with INH. The obtained crystals were amorphous and showed higher solubility in water than standard INH. Moreover, these crystals showed therapeutic efficiency inantimycobacterial activity to inhibit the growth of Mycobacterium tuberculosis. The INH:2-HEAF only degraded 5.1 % (w/w), however, INH:2-HEAA degraded 32.8 % (w/w) after 60 days in an accelerated atmosphere. Then, the 2-HEAA and 2-HEAF were able to crystallize isoniazid, being a new application for these PILs. The used PILs also influenced the characteristics of isoniazid crystals.

Chemical recycling of post-consumer poly(ethylene terephthalate) (PET) driven by the protic ionic liquid 2-HEAA: Performance, kinetics and mechanism

The circular economy is a paradigm for the upcoming industrial era, in which plastic wastes must be focused on as new resources. Chemical valorisation permits deepening into waste-to-gate schemes by obtaining new chemical platforms to be reintroduced in the production market. In this context, the potential of the protic ionic liquid 2-hydroxyethyl ammonium acetate (2-HEAA) to be used as a homogeneous catalytic co-solvent for the glycolytic conversion of post-consumer poly(ethylene terephthalate) (PET) was validated from different perspectives. Studies were performed for the reaction triplet framed under the experimental conditions (i) temperature T [160,170,180 ºC], (ii) plastic-to-solvent mass ratio P/S [1:3, 1:4,1:5] and (iii) plastic-to-ionic liquid mass ratio P/IL [2:1, 2:2, 2:3]. The reaction was confirmed in terms of the transformation of PET into BHET (bis(2-hydroxyethyl terephthalate) and a proposal of mechanism induced by the amine group of the 2-HEAA is given. The thermal kinetics were modelled and a first-order equation and an apparent activation energy of 60.5 kJ·mol-1 were obtained. A statistical Box-Behnken design of experiments explained the relationship between the factors of the glycolysis triplet by a response surface, with a maximum around {T = 170 ºC, P/S = 1:3.75 and P/IL = 2:1.75}, being T and P/S statistically relevant, whereas only the presence of 2-HEAA and not its amount P/IL was significant. Finally, the reusability of 2-HEAA after 90-min glycolytic chemical valorisations was confirmed up to 4 cycles. The results position 2-HEAA as a promising catalytic co-solvent for the scale-up of chemical valorisation of PET.

Characterization and electrochemical properties of TiO2-rNTs/SnO2–Sb/PbO2 electrodes for the mineralization of persistent organic pollutants using anodic oxidation coupled Electro-Fenton treatment: Effect of precursor selection

The present study compares the effect of using different solvents on the electrochemical properties of the reduced TiO2 nanotubes (TiO2-rNTs) layered Ti/TiO2-rNTs/SnO2–Sb/PbO2 anodes. The electrodes are prepared using three different solvent-based precursors: (i) isopropanol, (ii) ethylene glycol and citric acid (Pechini method), and (iii) 2-hydroxyethylammonium acetate (2HEAA) ionic liquid (IL) via the thermal decomposition route. The decomposition mechanism of precursor solutions was explored using the thermogravimetric (TGA) analysis. Further, the physicochemical properties of the electrodes are examined using Field emission Scanning Electron microscopy (FE-SEM), X-ray diffraction spectroscopy (XRD), and X-ray photoelectron emission spectroscopy (XPS). The results revealed that solvents with higher viscosity and slower decomposition rates support better film uniformity and higher stability of the electrode. The TiO2 -rNTs bottom layer and PbO2 top layer helped obtain higher film stability, increased working potential window (2.2 V vs. SHE) of the electrode, and the repeatability of the results. The performance of different electrodes based on the precursor solution is found as IL ≫ Pechini > Isopropanol. 4-chlorophenol (4-CP) is used as a model pollutant to test the performance of IL-Ti/TiO2-rNTs/SnO2–Sb/PbO2 anode in an anodic oxidation (AO) coupled electro-Fenton (EF) treatment. Further, the reliability of the electrode is evaluated by mineralizing other persistent organic pollutants (POPs) like tetracyclin, phenol, 2-chlorophenol (2-CP), and 2,4-dichlorophenol (2,4-DCP). Under the optimized conditions, the proposed system was able to mineralize the tetracyclin, phenol, 2-CP, 2,4-DCP, and 4-CP up to 78.91, 82.07, 74.96, 78.78, and 69.3 %, respectively. Moreover, the degradation mechanism of chlorophenols is proposed.

TiO2 nanostructures synthesized by electrochemical anodization in green protic ionic liquids for photoelectrochemical applications

This work studies the influence of the 2-hydroxyethylammonium acetate (2-HEAA) ionic liquid (IL) as an electrolyte in the electrochemical anodization of titanium for the synthesis of nanostructures for photoelectrochemical water splitting. Different 2-HEAA IL concentrations were used ranging from 0 to 4% v/v (IL-0 to IL-4) in electrolytes containing NH4F, water and ethylene glycol. Morphological, structural and electrochemical characterization of the nanostructures was carried out by means of field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and Mott-Schottky (MS) analysis. Additionally, photoelectrochemical tests were carried out in order to evaluate the efficiency of these materials as catalysts for water splitting applications. According to the obtained results, the electrolyte used for electrochemical anodization should contain little amount of NH4F (0.05 M) in order to obtain efficient nanostructures for photoelectrochemical purposes. However, small concentrations of IL (IL-0.25) resulted in nanostructures with higher photocurrents than doubling the NH4F concentration to 0.1 M. Therefore, the IL addition contributes to a more sustainable electrolyte formulation. The best photoelectrochemical response for water splitting processes was obtained for the nanostructures anodized with 1% v/v of 2-HEAA IL (IL-1) due to their high surface/area (higher pore diameters, smaller nanotubes wall thickness and higher nanotubes lengths), better crystallinity and electrochemical response, showing photocurrents more than 100% higher than the ones obtained for the nanotubes anodized without IL.

Recovery of mixture of hydroxyethylammonium carboxylate protic ionic liquids from sugarcane pretreatment liquor using activated carbon in a fixed bed column

Integrated strategies using fixed bed columns can facilitate the recovery of protic ionic liquids (PILs) used in the pretreatment of lignocellulosic biomass. In this study, we investigated the adsorption of 2-hydroxyethylammonium acetate [Mea][Ac] and 2-hydroxyethylammonium hexanoate [Mea][Hex] on activated carbon in a fixed bed column for recovering the PILs mixture present in the liquor of the pretreatment. Breakthrough curves were determined experimentally. Breakthrough time (tb), exhaustion time (te), difference between tb and te, adsorption efficiency (ϕads), column efficiency (ϕcol) and qe equilibrium capacity were evaluated as a function of simultaneous variations in superficial velocity (vs) and temperature (T) using a central composite rotatable design. The optimum conditions for PIL purification were vs = 1.66 cm/min (Q = 1.3 mL/min) and T = 20 °C. After selection of optimum operating conditions, PILs separation was evaluated in a model solution and sugarcane pretreatment liquor, with similar intervals for recover of PILs. This is the first study to develop a successful proof of concept of mixture PILs [Mea][Ac]/[Mea][Hex] recovery from sugarcane straw pretreatment liquor in a fixed-bed column of activated carbon. The results indicate that the method has great potential for industrial application.

2-hydroxyethylammoniumsulfate ionic liquid performance as simultaneous fuel and sulfating agent in tablet-like manganese and iron incorporated titania synthesis: Biodiesel production from waste oil

The efficient tablet-like manganese and iron incorporated titania catalyst was synthesized in the presence of 2-hydroxyethylammonium sulfate (ILS) as both fuel and sulfating agent via microwave for biodiesel production. Catalyst characterizations were conducted by XRD, FESEM, EDX, BET-BJH, and TPD-NH3 analyses. The catalyst was also synthesized via other fuels including urea, 2-hydroxyethylammonium acetate (ILA), and 2-hydroxyethylammonium formate (ILF). The nature of fuels affected the catalyst’s physicochemical properties and performance. Urea created a large portion of wide pores in the catalyst. ILS led to the creation of a highly acidic catalyst with an acid density of 0.804 mmol/m2. Oleic acid conversion for catalysts synthesized by urea, ILA, ILF, and ILS in the condition of 110 °C, 1.5 h, 9 wt% catalyst, alcohol to oil mole ratio of 20 was 63.5, 39.36, 48.56, and 93.11 %. MnFeTi(ILS) showed a good capability for producing biodiesel from sunflower (92.12 %) and waste oil (91.43 %). The catalyst was reused 5 times, and only a 6 % conversion loss was detected.

Techno-economic analysis of the production of 2G ethanol and technical lignin via a protic ionic liquid pretreatment of sugarcane bagasse

The increasing demand for renewable energy, fuels, and chemicals encourages the development of new biorefinery processes. This work presents a techno-economic analysis of the pretreatment of sugarcane bagasse using the protic ionic liquid 2-hydroxyethylammonium acetate ([MEA][OAc]) considering four washing methods to remove it from the pretreated pulp. In the best scenario, the increased enzymatic hydrolysis yield and the more efficient counter-current washing method contributed to an increased ethanol yield of 33 %. Despite the lower increment in ethanol yield compared with other second-generation processes, the production of technical lignin increased the reaction mass efficiency of the biorefinery by 5.6 % and led to an internal rate of return two percentage points higher. However, wastewater and vinasse production increased by 26 % and 50 %, respectively. These results indicate that protic ionic liquids are potentially good pretreatment agents to produce fuels and chemicals from biomass, thus underpinning the establishment of new biorefinery processes. • Process development to produce ethanol and technical lignin from bagasse. • Different washing steps yielded different hydrolysis and fermentation yields. • Techno-economic analysis indicates the importance of using protic ionic liquids. • Protic ionic liquid pretreatment has better economic results because of lignin. • Recycling of ionic liquid plays an important role in process economic feasibility.

Selection of protic ionic liquids for the improved production of butanol from rice straw

Biomass pretreatment with protic ionic liquids (PILs) has been proved as an economically attractive method to enhance saccharification yield. This work evaluated the use of six PILs -based on acetate and hydrogen sulfate anions - using water as cosolvent for processing a high solid loading of rice straw (RS). Among the investigated PILs, the most promising results were obtained by 2-hydroxyethylammonium acetate [MEOA][OAc] containing 20 %w/w water, achieving 87.3 % of glucose and 68.6 % of xylose yield, respectively, and 98.3 % of delignification at 150 °C for 2 h with 15 %w/w solid loading. Five recovery and reuse cycles were successfully performed with [MEOA][OAc], obtaining a delignification degree of 69.5 % after the fifth reuse. Process viability was evaluated by enzymatic hydrolysis followed by acetone-butanol-ethanol (ABE) fermentation using Clostridium beijerinckii. Similar saccharification yields (89.9 ± 6.8 % glucose and 71.5 ± 4.7 % xylose) and butanol production (7.3 ± 0.1 g/L, 81.7 ± 1.7 g butanol per kg of RS) were achieved for fresh and recycled [MEOA][OAc], demonstrating the feasibility of PIL reuse. This study showed the potential of [MEOA][OAc] as a cost-effective pretreatment agent for rice straw valorization into an advanced biofuel such as butanol.

Solubilities of caffeic acid and tyrosol in two protic ionic liquids and one deep eutectic solvent

The present work provides solubility measurements for two phenolic compounds, caffeic acid and tyrosol, in two protic ionic liquids, 2-hydroxyethylammonium formate (2HEAF) and 2-hydroxyethylammonium acetate (2HEAA), and in the Deep Eutectic Solvent (DES) choline chloride-urea (ChCl:urea (1:2)). Solubility measurements of tyrosol were also performed in ethanol and water. All measurements were conducted under atmospheric pressure and in the temperature range of 293.15–313.15 K. Moreover, densities of pure 2HEAF, 2HEAA and ChCl:urea (1:2) and the viscosity of ChCl:urea (1:2), were measured. ChCl:urea (1:2) showed the highest solvation capacity among all the solvents studied for both compounds, while tyrosol was found to be more soluble than caffeic acid in all solvents. In order to better understand the solubilization process, the van't Hoff equation was applied for calculating the apparent Gibbs energy, enthalpy and entropy of solution. Finally, correlation of the solubility data was achieved with UNIQUAC and NRTL activity coefficient models.

Stabilization of Haloalkane Dehalogenase Structure by Interfacial Interaction with Ionic Liquids

Ionic liquids attracted interest as green alternatives to replace conventional organic solvents in protein stability studies. They can play an important role in the stabilization of enzymes such as haloalkane dehalogenases that are used for biodegradation of warfare agents and halogenated environmental pollutants. Three-dimensional crystals of haloalkane dehalogenase variant DhaA80 (T148L+G171Q+A172V+C176F) from Rhodococcus rhodochrous NCIMB 13064 were grown and soaked with the solutions of 2-hydroxyethylammonium acetate and 1-butyl-3-methylimidazolium methyl sulfate. The objective was to study the structural basis of the interactions between the ionic liquids and the protein. The diffraction data were collected for the 1.25 Å resolution for 2-hydroxyethylammonium acetate and 1.75 Å resolution for 1-butyl-3-methylimidazolium methyl sulfate. The structures were used for molecular dynamics simulations to study the interactions of DhaA80 with the ionic liquids. The findings provide coherent evidence that ionic liquids strengthen both the secondary and tertiary protein structure due to extensive hydrogen bond interactions.

Ti/Ru0.7M0.3O2 (M = Ir or Ti) anodes made by Pechini and ionic liquid methods: Uneven catalytic activity and stability

• The electrode composition influences the properties conferred by the IL method. • The IL method improved the service life for the Ti/Ru 0.7 Ir 0.3 O 2 electrode. • The IL method leads to the lowest resistivity for the Ti/Ru 0.7 Ti 0.3 O 2 electrode. • The Ti/Ru 0.7 Ir 0.3 O 2 presented the best electrocatalytic performance for RB5 oxidation. • The two methods (IL and Pechini) conferred different properties to the electrocatalysts. In this work, we prepared ruthenium-based oxide (Ru 0.7 M 0.3 O 2 (M = Ir or Ti)) anodes by using the 2-hydroxyethylammonium acetate ionic liquid (IL) and the conventional polymeric precursor method. The use of IL as the solvent for the Ti/Ru 0.7 Ti 0.3 O 2 anode resulted in the outstanding charge transfer resistance reduction of 30-fold and a decrease of 1.59-fold in the voltammetric charge when compared with the conventionally-made Ti/Ru 0.7 Ti 0.3 O 2 anode. Whereas for the Ti/Ru 0.7 Ir 0.3 O 2 , the resistivity of the anode increased (2.64-fold), and the voltammetric charge decrease is low (1.25-fold) for the IL-made anode. However, the increased stability of the Ti/Ru 0.7 Ir 0.3 O 2 anode (2.2-fold) indicates a positive effect of the IL on the adhesion of the coating. Notably, the prolonged accelerated service life (~300 h) displayed for the Ti/Ru 0.7 Ir 0.3 O 2 anode made using the IL method is the highest found in the available literature for Ti/Ru 0.7 Ir 0.3 O 2 anodes. Moreover, the Ti/Ru 0.7 Ir 0.3 O 2 stands out with the better electrocatalytic performance toward the electrochemical oxidation of a model organic pollutant (Reactive Black 5 dye).

Solubility of H2S in ammonium-based ionic liquids

This work is inserted in a research program that consists mainly in the experimental and theoretical study of gas/liquid solubility in ionic liquids (ILs). In this study the experimental data of hydrogen sulfide solubility in ammonium-based ionic liquids, namely 2-hydroxyethylammonium acetate [2-HEA][Ace], bis(2-hydroxyethyl)ammonium acetate [B-2-HEA][Ace] and 2-hydroxyethyldiethylammonium hydrogen diacetate [2-HEDEA][H(Ace)2], were determined using a volumetric method in the 298 K to 318 K temperature range and at atmospheric pressure. The ionic liquids are functionalized with the OH group in the ammonium-based cations, in order to study the influence of hydroxyl group in the formation of hydrogen bonds between the IL-IL and IL-gas. The data gathered is modelled with the Cubic Plus Association Equation of State (CPA EoS), considering the association schemes four-sites (4C) for hydrogen sulfide and two-sites (2B) for the ILs ([2-HEA][Ace], [B-2-HEA][Ace] and [2-HEDEA][H(Ace)2]).

Formation of viscoelastic micellar solutions by a novel cationic surfactant and anionic salt system

A novel binary system consisting of a cationic surfactant and a counter ion that can form wormlike micelles with high viscosity is proposed. Wormlike micelles based on 2-hydroxyethyl dimethyl hexadecyl ammonium acetate (HDMHA) and sodium salicylate (NaSal) as counter ion were detected via both cryo-TEM and SANS in dilute solution. Moreover, rheological measurements of the HDMHA/NaSal system were conducted as a function of temperatures. The results demonstrate the formation of long elongated wormlike micelles in dilute solution at temperatures that exceed 60 °C.

Application of protic ionic liquids in the microwave-assisted extraction of phycobiliproteins from Arthrospira platensis with antioxidant activity

Phycobiliproteins are potential molecules for use in various applications. Although phycobiliproteins extraction classical methods are reproducible and show good yields, they are generally time-consuming and require the use of high energy consumption and/or large volumes of solvent. Therefore, it is necessary the development of new eco-friendlier process by extraction techniques, permitting the transfer of the results obtained in laboratory scale for industrial. Then, microwave-assisted extraction using protic ionic liquid as solvent was proposed and optimized to extract phycobiliproteins from Arthrospira platensis in an efficient manner. The protic ionic liquids (PILs): 2-hydroxyethylammonium acetate (2-HEAA), 2-hydroxyethylammonium formate (2-HEAF), their equimolar mixture (2-HEAA + 2-HEAF), and the commercial ionic liquid 1-butyl-3-methylimidazolium chloride [Bmim]Cl were used as solvents, and sodium phosphate buffer as a control and the conditions of extraction were evaluated. The irradiation power was the most significant variable for the extraction process, and it showed a negative effect. The process conducted at 62 W and pH 7.0, using 2-HEAA + 2-HEAF and a solvent: biomass ratio of 10 mL∙g−1, showed the highest phycobiliproteins concentrations. The purity obtained for phycocyanin, allophycocyanin and phycoerythrin were 1.22, 1.03, and 0.71, respectively. The mixture of the PILs (2-HEAA + 2-HEAF) can be reused for three cycles for extraction of allophycocyanin. The extraction of phycobiliproteins using microwave and ionic liquids was efficient and the degree of purity and antioxidant activity achieved allows the application of these pigments in food and cosmetics.

Influence of the RuO2 layer thickness on the physical and electrochemical properties of anodes synthesized by the ionic liquid method

The use of ionic liquids as solvents to prepare mixed metal oxide (MMO) anodes has proven to be a very promising alternative synthesis route. However, little attention has been dedicated to assessing the effect of the coating thickness on their activity and service life, and no detailed study of the thickness of anodes made using ionic liquids has been conducted to date. Here we studied the influence of the ruthenium oxides film thickness (8.2, 13.7, and 16.5 μm) on the physical, electrochemical, and electrocatalytic properties of Ti/RuO2 anodes. The electrodes were prepared using the 2-hydroxyethyl ammonium acetate (2HEAA) ionic liquid as the solvent of the precursor solutions. The properties of these anodes were compared with the RuO2-based commercial anode provided by De Nora® (17.7 μm of thickness). The increase in RuO2 layer thickness from 8.2 μm to 13.7 μm, and then to 16.5 μm decreases the voltammetric anode charge and increases their charge transfer resistance from 11.2 Ω to 28.2 Ω, and then to 52.7 Ω, respectively. Deactivation of the anodes was investigated by accelerated lifetime tests in H2SO4 and NaCl solutions. In acidic media, the anodes with a higher thickness (13.7 μm and 16.5 μm) presented longer service lifetimes, respectively, 1.5 and 1.4 higher than the electrode with 8.2 μm. In NaCl medium, a higher thickness improves the service life significantly. The anode with 16.5 μm of thickness has a service life up to 48.6 times higher than the anode with 8.2 μm. All anodes, including the commercial one, presented high catalytic efficiency towards the electrochemical degradation of Reactive Black 5 dye. Within only 30 min of electrochemical treatment, all anodes removed more than 94% of color. It is shown that the use of anodes with low coating thicknesses is more favorable due to reduced time and energy costs of the synthesis process while maintaining a high degradation efficiency of the dye.

Evaluating Protic Ionic Liquid for Woody Biomass One-Pot Pretreatment + Saccharification, Followed by Rhodosporidium toruloides Cultivation

Woody biomass feedstocks pose challenges in their use as sustainable carbon sources due to their recalcitrance. One-pot ionic liquid-based processes are a promising bioproduction strategy to reduce water consumption (removing the washing of biomass), reduce costs, and minimize the presence of inhibitory compounds. We evaluated the one-pot ionic liquid pretreatment + saccharification configuration as a scheme for the deconstruction and conversion of two different woody feedstocks, eucalyptus, and pine. A comparative study of protic ionic liquids 2-hydroxylethylammonium acetate-based ionic liquids, bis-2-hydroxyethylammonium acetate, and cholinium lysinate for pretreatment of eucalyptus and pine was conducted. The impact of ionic liquids at 11% w/w on the saccharification and toxicity of hydrolysates containing the ionic liquid for downstream use for microbial cultivation was evaluated. Protic ionic liquids were more effective in eucalyptus than in pine pretreatment and less toxic than cholinium lysinate at concentrations ≤10% w/w. 2-hydroxylethylammonium acetate yielded the highest digestibility, of up to 75% in eucalyptus. As a proof of concept of an integrated feedstocks-to-biofuels process, we tested the growth of the fungal strain Rhodosporidium toruloides in hydrolysates with low amounts of ionic liquids and phenolic compounds. The proof of concept demonstrated the ability of Rhodosporidium toruloides to grow in the presence of 2-hydroxyethylammonium acetate (5% w/w), the importance to adjust the pH after saccharification, and the ability to consume lignin monomers. This work offers a valid starting point for further studies aimed at increasing cellulose digestibility in a one-pot configuration in the presence of protic ionic liquids.

Uncovering the potentialities of protic ionic liquids based on alkanolammonium and carboxylate ions and their aqueous solutions as non-derivatizing solvents of Kraft lignin

The present study scrutinized in depth the ability of alkanolammonium-based Protic Ionic Liquids (PILs) with carboxylate anions to dissolve Kraft lignin at 323.15 K. A focus was put on understanding the role of both PIL ions and water on the dissolution process. The results demonstrated that the anion plays a more important role in lignin dissolution than the cation. Furthermore, lignin dissolution was favored by increasing the alkyl chain of the carboxylate anion, while a smaller cation with lower number of hydroxyalkyl groups performed better. Among the studied solvents, the 2-hydroxyethylammonium hexanoate (HEAH) displayed the highest lignin solubility (37 wt%). In general, the addition of water had a negative influence on lignin solubility with the tested PILs. A sharp decrease in lignin solubility curves of 2-hydroxyethylammonium formate (HEAF) and acetate (HEAA) was observed, while a more softly effect was observed for 2-hydroxyethylammonium propionate (HEAP) and HEAH with the addition of water. However, a distinct behavior was observed for 2-hydroxyethylammonium octanoate (HEAO) that acted as hydrotrope enhancing lignin solubility in aqueous solutions to a maximum value at 40 wt% water content. Furthermore, by increasing the temperature, the lignin solubility was favored due to endothermic behavior of lignin dissolution process.The dissolution of Kraft lignin was also performed at 393.15 K to unravel any lignin modification unleashed by PILs. GPC, FTIR-ATR and 2D NMR were employed for lignin characterization and the changes observed between native lignin and recovered lignin samples were negligible demonstrating the non-derivatizing character of the PILs. Moreover, the recycle of 2-hydroxyethylammonium propionate (HEAP) was successfully demonstrated for at least 3 cycles. In this way, PILs are herein revealed as promising solvents to apply in lignin valorization towards more efficient and eco-friendly processes.

High-pressure behavior of 2-hydroxyethylammonium acetate ionic liquid: Experiment and molecular dynamics

The behavior of 2-hydroxyethylammonium acetate ionic liquid under high-pressure was studied using a combined experimental and molecular simulation approach. PVT behavior was experimentally inferred by density measurements using high-pressure vibrating tube densimetry in the 298.15–328.15 K and 0.1–40 MPa temperature and pressure ranges. Experimental data were correlated by the use of a Tait-type equation, from which the derived mechanical coefficients were calculated. Likewise, a molecular dynamics study in the same pressure – temperature range was carried out to infer the changes in fluid’s properties upon compression. The evolution of hydrogen bonding, ions packing and additional nanoscopic features were studied by simulation results, thus allowing to analyze the relationships between micro and macroscopic features.

Dissolution of lignocellulosic biopolymers in ethanolamine-based protic ionic liquids

This work evaluates the potential use of 2-hydroxy ethylammonium-based protic ionic liquids (PILs) for dissolving the major lignocellulosic biopolymers such as cellulose, xylose and lignin. Three PILs, 2-hydroxy ethylammonium formate (2-HEAF), 2-hydroxy ethylammonium acetate (2-HEAA) and 2-hydroxy ethylammonium propionate 2-HEAPr, were synthesized and characterized (viscosity, density and conductivity). A small amount of biopolymer was added to the PILs; the biopolymers’ dissolution curves were determined from 30 °C up to 100 °C on these solvents using a hot stage coupled to an optical microscope. The results show that while xylose and lignin could be dissolved by the PILs, cellulose could not, and also that 2-HEAF—which presented the higher ionicity—was the most appropriate PIL among those tested to dissolve these biopolymers (xylose and lignin). They also show that lignin dissolution is faster when an anion with a short alkyl carbon chain is used and that higher heating rates require a somewhat higher temperature to achieve full dissolution.