Acidic Ionic Liquid Research Articles

Protic Brønsted acidic ionic liquids with variable acidity for efficient conversion of xylose and hemicellulose to furfural

Furfural (FF) is an important platform molecule originated from biomass, but it’s synthesis through the traditional acid-catalyzed dehydration reaction of xylose and hemicellulose remains problematic due to the poor activity and equipment corrosion. Therefore, a series of [HSO4]-based protic Brønsted acidic ionic liquids (BAILs) are employed as green catalysts to achieve efficient and sustainable preparation of FF from xylose or hemicellulose in this work. Furfural yields of 75.4% or 80.4% were achieved under optimal operating conditions with [Hpy][HSO4] as catalyst, hemicellulose or xylose as substrates, higher than those catalysed with most ionic liquids reported so far. The chemical structures of BAILs were confirmed by NMR and FT-IR spectroscopy, and the Hammett acidity (H0) were determined using UV–vis spectroscopy with 4-nitroaniline as probe. The acidity of BAILs were tuned through methyl substitution on the pyridinium ring, and its effect on the catalysis performance was investigated. In addition, the reaction constants and the corresponding activation energies of BAILs for dehydration of xylose to FF were calculated by kinetic equations. Overall, the highly efficient catalysis performance, good recyclability and low cost enables [Hpy][HSO4] to be potentially applied for large-scale preparation of FF.

Efficient synthesis of novel chromeno[2,3-d][1,3,4]thiadiazolo[3,2-a]pyrimidine derivatives via three-component reaction using acidic ionic liquid catalysts in ethylene glycol

Efficient synthesis of novel chromeno[2,3-d][1,3,4]thiadiazolo[3,2-a]pyrimidine derivatives via three-component reaction using acidic ionic liquid catalysts in ethylene glycol

Highly efficient and tunable catalytic addition of CO2 with epoxides over 2D Co-TCPP nanosheet at ambient condition

A series of ultrathin (∼1.11–4.80 nm) 2D porphyrinic MOF nanosheets are developed and novel synergistic systems are conveniently constructed for the facile formation of cyclic carbonates. Using n-Bu4NBr (TBAB) as a co-catalyst, ultrathin (ca. 2.58 nm) Co-TCPP exhibited high catalytic activity for the solvent-free conversion of styrene oxide to cyclic carbonate, affording 99% yield at ambient conditions (25 °C and 1 atm CO2). A relatively low energy (19.6 kcal/mol) for the rate-determining step is required for Co-TCPP/TBAB nanosystem as calculated by DFT. Notably, utilizing amino acid ionic liquid (AAIL, [Bmim][Glu] or [Bmim][His]) as the modifier, a substrate-dependent protocol was proposed to fix CO2 with terminal epoxides or cyclohexene oxide, giving cyclic carbonates in 84–99% yields under mild conditions (solvent-free, 80 °C and 1 atm CO2). 13C NMR and UV-vis studies provided insights into the vital roles of AAIL during CO2 capture via carbamate dianion and in situ fabrication of Co-TCPP-AAIL. Moreover, DFT calculations also confirmed the AAIL-regulated substrate-dependent transformation strategy.

Automation of liquid crystal phase analysis for SAXS, including the rapid production of novel phase diagrams for SDS-water-PIL systems.

Lyotropic liquid crystal phases (LCPs) are widely studied for diverse applications, including protein crystallization and drug delivery. The structure and properties of LCPs vary widely depending on the composition, concentration, temperature, pH, and pressure. High-throughput structural characterization approaches, such as small-angle x-ray scattering (SAXS), are important to cover meaningfully large compositional spaces. However, high-throughput LCP phase analysis for SAXS data is currently lacking, particularly for patterns of multiphase mixtures. In this paper, we develop semi-automated software for high throughput LCP phase identification from SAXS data. We validate the accuracy and time-savings of this software on a total of 668 SAXS patterns for the LCPs of the amphiphile hexadecyltrimethylammonium bromide (CTAB) in 53 acidic or basic ionic liquid derived solvents, within a temperature range of 25-75 °C. The solvents were derived from stoichiometric ethylammonium nitrate (EAN) or ethanolammonium nitrate (EtAN) by adding water to vary the ionicity, and adding precursor ions of ethylamine, ethanolamine, and nitric acid to vary the pH. The thermal stability ranges and lattice parameters for CTAB-based LCPs obtained from the semi-automated analysis showed equivalent accuracy to manual analysis, the results of which were previously published. A time comparison of 40 CTAB systems demonstrated that the automated phase identification procedure was more than 20 times faster than manual analysis. Moreover, the high throughput identification procedure was also applied to 300 unpublished scattering patterns of sodium dodecyl-sulfate in the same EAN and EtAN based solvents in this study, to construct phase diagrams that exhibit phase transitions from micellar, to hexagonal, cubic, and lamellar LCPs. The accuracy and significantly low analysis time of the high throughput identification procedure validates a new, rapid, unrestricted analytical method for the determination of LCPs.

Imidazolium triflimide-based Brønsted acidic ionic liquid as organocatalyst to trigger the cationic ring-opening polymerization of cyclotrisiloxanes

Brønsted acidic ionic liquid (BAIL)-catalyzed efficient ROP of D3 and/or DVi3 in bulk at moderate temperature.

Preparation and characterization of cellulose nanocrystals from corncob via ionic liquid [Bmim][HSO4] hydrolysis: effects of major process conditions on dimensions of the product.

In this study, cellulose nanocrystals were prepared via the hydrolysis of corncob (CC) biomass using Brønsted acid ionic liquid 1-butyl-3-methylimidazolium hydrogen sulfate [Bmim][HSO4]. The corncob was subjected to alkaline pretreatment, and was then hydrolysed by [Bmim][HSO4], which acted as both solvent and catalyst. The effects of process conditions, including mass percent of CC (1.0-10.0%), reaction temperature (46-110 °C), and reaction time (1.2-2.8 h) on the size of cellulose nanocrystals (IL-CCCNC) were investigated by response surface methodology-central composite design. The obtained IL-CCCNC was characterized by Fourier transforms infrared spectroscopy, zeta sizer, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and thermogravimetry. The results showed that the dimensions of the nanocellulose products were affected by the mass percent of CC and the reaction temperature, but were not significantly influenced by the reaction time under the studied conditions. The optimal conditions, estimated by the developed model, were a mass percent of 2.49%, reaction temperature of 100 °C, and reaction time of 1.5 h. The process successfully produced IL-CCCNC with a yield of 40.13%, average size of 166 nm, and crystallinity index (CrI) of 62.5%. The morphology, chemical fingerprints, and thermal properties of the obtained IL-CCCNC were comparable to those extracted by alkaline and acid hydrolysis. After the reaction, [Bmim][HSO4] could be recovered with a yield of 88.32%, making it a viable green catalyst for the hydrolysis of CC cellulose. The findings are of direct industrial relevance as optimal processes can be developed to produce nanocellulose crystals with desirable size and physicochemical characteristics.

Computational predictions on Brønsted acidic ionic liquid-catalyzed carbon dioxide conversion to five-membered heterocyclic carbonyl derivatives.

Experimentally conducted reactions between CO2 and various substrates (i.e., ethylenediamine (EDA), ethanolamine (ETA), ethylene glycol (EG), mercaptoethanol (ME), and ethylene dithiol (EDT)) are considered in a computational study. The reactions were previously conducted under harsh conditions utilizing toxic metal catalysts. We computationally utilize Brønsted acidic ionic liquid (IL) [Et2NH2]HSO4 as a catalyst aiming to investigate and propose 'greener' pathways for future experimental studies. Computations show that EDA is the best to fixate CO2 among the tested substrates: the nucleophilic EDA attack on CO2 is calculated to have a very small energy barrier to overcome (TS1EDA, ΔG‡ = 1.4 kcal mol-1) and form I1EDA (carbamic acid adduct). The formed intermediate is converted to cyclic urea (PEDA, imidazolidin-2-one) via ring closure and dehydration of the concerted transition state (TS2EDA, ΔG‡ = 32.8 kcal mol-1). Solvation model analysis demonstrates that nonpolar solvents (hexane, THF) are better for fixing CO2 with EDA. Attaching electron-donating and -withdrawing groups to EDA does not reduce the energy barriers. Modifying the IL via changing the anion part (HSO4-) central S atom with 6 A and 5 A group elements (Se, P, and As) shows that a Se-based IL can be utilized for the same purpose. Molecular dynamics (MD) simulations reveal that the IL ion pairs can hold substrates and CO2 molecules via noncovalent interactions to ease nucleophilic attack on CO2.

3D mesoporous polycalix-functionalized dual Brønsted–Lewis acidic double-charged DABCO-based ionic liquid: a powerful and recyclable supramolecular polymeric catalyst for the synthesis of spiro-fused[4H-pyran

A porous polycalix-functionalized bi-functional DABCO-based IL group (PC4RA@[SiPrDABCO@BuSO3H](FeCl4) was synthesized and characterized to show synergistic incorporation of the aromatic cavity and active sites for spiro formation.

A thermo-responsive hydrogel loaded with an ionic liquid microemulsion for transdermal delivery of methotrexate.

Systemic administration of methotrexate (MTX), the gold standard for the treatment of psoriasis, can cause adverse side effects. To address this issue, a thermally responsive hydrogel loaded with an ionic liquid microemulsion (IL-ME) was developed for the transdermal delivery of MTX. The microemulsion was prepared using water, Tween 20 and choline and geranic acid (CAGE) ionic liquid. The solubility of methotrexate in the IL-ME was 9-fold higher than that in phosphate buffer (PBS). The hydrogel (Gel) based on isopropylacrylamide and silk fibroin acts as a drug reservoir to achieve temperature-responsive drug release in the human epidermis. The loading of the IL-ME or MTX-containing IL-ME on the Gel produced a ME@Gel or MTX/ME@Gel. In vitro permeation experiments showed that the MTX/ME@Gel exhibited a 27.6% increase in MTX permeation. In addition, IL-ME exhibits strong antibacterial activity. In vivo studies indicated that when compared with the results obtained in PBS medium, the MTX/ME@Gel could effectively treat skin redness, swelling and scaling caused by imiquimod (IMQ). In general, the present study demonstrated that the MTX/ME@Gel provides vast potential to serve as a biocompatible drug carrier for the efficient delivery of poorly soluble drugs, i.e., MTX in this particular case.

Preparation of functionalised heteropolyacid ionic liquids and their application in catalytic degradation of bottle-grade polyester

This research study is related to an environmentally friendly process method for catalytic degradation of bottle-grade PET by using ionic liquid catalysts.

Preparation of a heteropoly acid ionic liquid and its application in the catalytic degradation of bottle-grade PET

A new environmentally friendly process method for catalytically degrading bottle-grade PET by utilizing ionic liquid catalysts.

Kinetic and thermodynamic studies of HMF-ester synthesis using Brønsted–Lewis acidic ionic liquid catalyst

5-HMF to HMF-ester conversion kinetics.

NANOSTRUCTURED CURCUMIN WITH CHOLINE AND GERANIC ACID IONIC LIQUID (CAGE-IL): POTENTIAL FOR INCORPORATION INTO PHARMACEUTICAL GEL FORMULATIONS

Curcumin, a phytochemical, exhibits several biological properties and has been studied for the treatment of psoriasis. To facilitate its transdermal permeation, permeation enhancers such as choline and geranic acid ionic liquid (CAGE-IL) have been studied. From this perspective, the research effort entertained herein aimed at developing and evaluating the stability of an emulsion prepared with curcumin (phytochemical from Curcuma longa L.) and locust bean gum (extracted from the seeds of the carob tree, Ceratonia siliqua), with CAGE-IL as a facilitator of transdermal permeation. Stability studies were carried out for six months, with analyses being performed at time intervals of 0 (24 h), 30, 60, 90, and 180 days. The samples were kept at 40 ± 2 °C, with 75 ± 5% relative humidity (RH). The parameters analyzed were morphological characteristics, pH (5.8-6.0), and spreadability. The samples were shown to be stable during the timeframe studied, maintaining adequate physicochemical characteristics and meeting quality specifications for cutaneous applications. CAGE-IL, in addition to facilitating permeation of the active substance, also favored the formation of a stable emulsion encompassing nanosized particles (134.3 ± 2.6 nm) in a simple fashion and with only a few components.

An efficient porous acidic ionic liquid polymer catalyst for Friedel–Crafts acylation reactions

A new function for a porous acidic ionic liquid polymer as a solid catalyst for Friedel–Crafts acylation.

Ultrafast and selective recycling of poly(p-dioxanone) to monomers by using Brønsted–Lewis acidic ionic liquids as solvents/catalysts

In the [Et3NH][ZnCl3]/pentaerythritol system, poly(p-dioxanone) is almost fully chemically recycled to the high-purityp-dioxanone monomer in several minutes.

A multi-walled carbon nanotube-supported acidic ionic liquid catalyst for the conversion of biomass-derived saccharides to 5-hydroxymethylfurfural

Herein, the surface of multi-walled carbon nanotubes (MWCNTs) was functionalized with 3-mercaptopropyltrimethoxysilane followed by anchoring of 1-vinylimidazole on the surface through the thiol–ene click reaction.

Solid ionic liquids with macro–microporous structure for efficient heterogeneous catalysis of biodiesel

Solid acidic ionic liquid (Macro-UiO-67-ILs) bearing a macroporous structure for high-performance catalytic esterification.

Polystyrene-supported imidazolium acidic ionic liquids: highly efficient catalysts for the synthesis of bisphenols

Reusable polystyrene-supported ionic liquid catalysts exhibit high catalytic activity for the synthesis of bisphenol compounds. The anions and cations of ionic liquids activate the substrates simultaneously, playing a synergistic catalytic role.

PolyE-IL Is an Efficient and Recyclable Homogeneous Catalyst for the Synthesis of 5-Hydroxymethyl Furfural in a Green Solvent.

5-Hydroxymethyl furfural (5-HMF) is a potential platform molecule with multidimensional applications and can be produced from biomass-based hexose sugars. In the present article, polyethyleneimine (PEI)-functionalized polymeric Bronsted acid ionic liquid (PolyE-IL) catalyst has been explored for fructose dehydration in the presence of isopropyl alcohol (IPA) as a green and low-boiling-point (LBP) organic solvent. The use of homogeneous PolyE-IL catalyst provides several specific advantages in terms of high yield, conversion, selectivity, ease of catalyst separation, recycle and reuse, and so forth. PEI with various Bronsted acid counterions such as H2SO4, H3PO4, TsOH, TfOH, and TFA provides the corresponding variables of PolyE-IL such as [PEI]+[HSO3]-, [PEI]+[H2PO4]-, [PEI]+[CF3CO2]-, [PEI]+[TfO]-, and [PEI]+[TsO]-, which are tested for fructose dehydration in the presence of IPA. Of the tested catalysts, only PolyE-IL with [HSO4]-, [CF3CO2]-, [TfO]-, and [TsO]- counterions showed the formation of 5-HMF. [PEI]+[HSO4]- showed the maximum yield of 5-HMF (61%) and selectivity (70%) with (87%) fructose conversion. Thus, further process optimization study was conducted to obtain the maximum yield, conversion, and selectivity. The intensified process provides a maximum yield of 5-HMF of 75% with 85% fructose conversion and 90% selectivity. The catalyst recyclability study showed the consistency in 5-HMF yield (75%), conversion (85%), and selectivity (90%) for five consecutive recycle runs. However, the study of reaction kinetics showed the first-order kinetics with an activation energy of 12.4 kJ/mole by using [PEI]+[HSO4]- catalyst. Thus, the use of an easily recyclable and robust catalyst provides an efficient route for production of 5-HMF in the presence of a green solvent.

Recovery of samarium(III) and cobalt(II) in synthetic nitric acid solutions using carboxyl functionalized ionic liquids and application to recycling SmCo permanent magnets

Samarium (Sm), as one of the lanthanide elements, has a broad application prospect in the synthesis of samarium cobalt permanent magnet materials with high temperature stability, corrosion resistance and oxidation resistance. Due to the unlimited demand of Sm(III), recycling of Sm(III) waste is an effective method to balance economy and supply. In this paper, three novel morpholine carboxylic acid ionic liquids (ILs) were rationally designed and successfully synthesized for the extraction of Sm(III). The effects of alkyl chain length of the ionic liquids, solution acidity, contact time, extractant concentration and temperature were tested in terms of the extraction performances. The results revealed that [(CH2)7COOHmor][NTf2] had the optimal extraction capacity, as well as the extraction efficiency of Sm increased with the increase of pH, reaching >99.9% when the pH was 1.8. In addition, the extraction equilibrium could be achieved within 1 min. Moreover, the slope analysis and FTIR spectral studies proposed a cation exchange extraction mechanism for Sm(III) by [(CH2)7COOHmor][NTf2]. The loaded Sm(III) in organic phase was easy to strip with 0.05 mol/L of HNO3, and the [(CH2)7COOHmor][NTf2] remained stable after 5 cycles. The research of transition metal extraction revealed that Sm(III) could be selectively separated from Ni(II) and Co(II) by adjusting the pH value of the solution. Finally, under the optimized extraction conditions, Sm2O3 with 83.9% yield was obtained by the extraction-stripping-precipitation-calcination process, through the large-scale recovery applications of the simulated waste liquid.