Alkaline Ionic Liquid Research Articles

Semi-interpenetrating polybenzimidazole membrane containing polymeric ionic liquid with high power density and enhanced proton conductivity for fuel cells

In phosphoric acid (PA)-doped polybenzimidazole (PBI) membranes designed for high-temperature proton exchange membranes (HT-PEMs), increasing the PA doping is essential. Yet, excessive PA doping causes a decline in mechanical strength, which in turn affects the cell performance. We utilize a strategy that integrates elevated PA absorption, increased mechanical strength, and enhanced PA retention. An azide-type ionic liquid (IL) containing double bonds was synthesized and crosslinked with PBI via free radical polymerization reaction. In addition, the IL can also self-polymerize to form long-chain polymeric ionic liquid (PIL). Together, the two structures together form a semi-interpenetrating polymer network (sIPN) system, which has good mechanical properties. The synthesized alkaline ionic liquid can absorb and retain a large amount of PA through acid-base interactions and inter-ionic interactions. Consequently, the proton conductivity of the amino-type polybenzimidazole (AmPBI)-polymeric ionic liquid (PIL)-30 (where 30 stands for the wt% of IL) membrane in an anhydrous environment at 180 °C reached 138.2 mS cm−1. After PA retention test at 160 °C/0 % relative humidity (RH) for 240 h, the proton conductivity reached 99.4 mS cm−1 at 180 °C. The AmPBI-PIL-10 membrane exhibited a significant power density of 635.4 mW cm−2 at 160 °C. The AmPBI-PIL-X composite membranes exhibited exceptional performance.

Unveiling the innovation: Optimized biodiesel production from emerging Acer truncatum Bunge seed oil using novel and highly effective alkaline ionic liquid catalyst

Herein, three novel alkaline ionic liquids (ILs) with nitrogen-containing heterocycles were prepared via a two-step method, which were then utilized as excellent catalysts for biodiesel synthesis through transesterification of emerging Acer truncatum Bunge seed oil (ATBSO) and methanol. The alkaline ILs exhibited favorable catalytic performance, with 1-(2,3-dihydroxy)-propyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene) hydroxide ([DPTD][OH]) exhibiting the highest catalytic efficiency among them. Furthermore, the effect of the independent variables and their interactions on biodiesel yield were assessed and optimized using response surface methodology (RSM). Under the optimal parameters, which consisted of a reaction temperature of 71 °C, a reaction time of 137 min, a substrate molar ratio of methanol to ATBSO of 12:1, and a catalyst loading of 1.3 wt%, the biodiesel yield reached a maximum of 97.3 %. The catalytic transesterification of ATBSO for the preparation of biodiesel exhibited an activation energy (Ea), enthalpy (ΔH), entropy (ΔS) and the Gibbs free energy (ΔG) of 35.14 kJ·mol−1, 32.37 kJ·mol−1, −178.80 J·mol−1·K−1 and 93.70 kJ·mol−1 at 343 K, respectively. It is worth noting that, after the reaction, an automatic phase separation between biodiesel and the catalyst occurred, minimizing the processes of product isolation and purification. Additionally, [DPTD][OH] exhibited favorable reusability over the four reaction cycles, providing a sustainable and environmentally friendly approach for biodiesel production. The biodiesel obtained from ATBSO demonstrated excellent physicochemical properties, such as good cold flow property and flash point, which conform to the biodiesel standards outlined in ASTM D6751 and EN 14212.

Alkaline Ionic Liquid Microphase Promotes Deep Reduction of CO2 on Copper.

Electrochemical reduction of CO2 to multicarbon (C2+) products using renewable energy sources is an important route to storing sustainable energy and achieving carbon neutrality. It remains a challenge to achieve high C2+ product faraday efficiency (FE) at ampere-level current densities. Herein, we propose the immobilization of an alkaline ionic liquid on copper for promoting the deep reduction of CO2. By this strategy, a C2+ FE of 81.4% can be achieved under a current density of 0.9 A·cm-2 with a half-cell energy conversion efficiency of 47.4% at -0.76 V vs reversible hydrogen electrode (RHE). Particularly, when the current density is as high as 1.8 A·cm-2, the C2+ FE reaches 71.6% at an applied potential of -1.31 V vs RHE. Mechanistic studies demonstrate that the alkaline ionic liquid plays multiple roles of improving the accumulation of CO2 molecules on the copper surface, promoting the activation of the adsorbed CO2, reducing the energy barrier of CO dimerization, stabilizing intermediates, and facilitating the C2+ product formation.

Sandwich like poly(ionic liquid)s functionalized microspheres: Efficient interfacial catalysts for preparation of biodiesel

Smart photo-responsive nanospheres azo-p(St-TMGILs)-OEt with sandwich like structure were prepared by introducing alkaline ionic liquids (TMG ILs) and a pioneering photo-responsive monomer (azo-TEPIC) on the surface of polystyrene microspheres by one-pot soap-free emulsion polymerization with free radical polymerization. Then the as-prepared nanoparticles were used as interfacial catalysts for constructing Pickering emulsions, wherein, azo-TEPIC was first obtained by using organosilane to functionalize azobenzene. Pickering emulsions can be reversibly switched between emulsification and breakage by alternate exposure to UV and visible light. The Pickering emulsion was used for the transesterification of soybean oil and ethanol to produce biodiesel and was found to give yields above 97% under mild reaction conditions with superior cycling stability of the catalyst.

One-step embedding method for immobilized bifunctional and alkaline ionic liquids as effective catalysts applied in transesterification

[Emim]Im can not only work as an active component to enhance the transesterification reaction but can also promote the hydrolysis of TEOS to enhance mass transfer.

Lignin depolymerization with alkaline ionic liquids and ethylene glycol in a continuous flow reactor

A novel alkaline ionic liquids N-allylpyridinium hydroxide ([APy]OH) was successfully designed and developed as a catalyst and co-solvent with ethylene glycol in the continuous depolymerization of lignin. Various reaction conditions, like lignin concentration, water content, and reaction temperature, were investigated under atmospheric pressure. Ethylene glycol was used as main solvent and repolymerization inhibitor of the aldehydes produced. The combination of [APy]OH and alkali metal salts exhibited a good synergistic effect for lignin depolymerization. Then, the depolymerization of three different lignins, including dealkaline lignin (DA-lignin), alkaline lignin (A-lignin), and sodium lignosulfonate (S-lignin), were also studied. S-lignin exhibited the highest yields of total liquid products (21.3 %) and aromatics (10.7 %). The change in lignin structure after depolymerization was observed by means of FT-IR and DTG-DTA techniques. Lastly, a hypothetical pathway for lignin depolymerization was proposed based on the catalytic results of lignin model compounds (LMCs) with different linkages.

DBU-assisted expeditious synthesis of highly stable IL@ZIFs intergrowth composite: A nanocatalyst for EMC production

Methyl ethyl carbonate (EMC) is the primary raw material for the electrolyte of lithium-ion batteries. It is mainly prepared by the transesterification reaction of dimethyl carbonate (DMC) and EtOH. However, homogeneous alkaline catalysts such as sodium alcohol commonly used in industry are easy to deactivate and challenging to separate and recover.Therefore, the alkaline ionic liquid decorated zeolitic imidazolate frameworks (IL@ZIFs) heterogeneous catalysts were prepared using a simple method with DBU as an inducer. In the synthetic route of IL@ZIFs, the ligand of ZIFs can form an ionic liquid with DBU, and deprotonated ligands will rapidly coordinate with metal ions at room temperature. The DBU can also play the structural guidance and stabilizer, which is conducive to the rapid and effective preparation of ZIFs materials. Meanwhile, the DBU, which has a large molecular diameter, will be trapped in the pore cage and can combine with other protic materials (imidazole, triazole, 2-methylimidazole, phenol, etc.) to form alkaline ionic liquids. The prepared DBU-IL@ZIFs were used as heterogeneous catalysts for synthesizing EMC by transesterification reaction. The DBU-PO@ZIF-8 composite with phenol as anion has better catalytic activity. Under the appropriate reaction conditions, the yield of EMC can reach 55.7% with high selectivity of 94.7%.The catalytic mechanism of DBU-PO@ZIF-8 in the transesterification reaction was also explored and revealed.

Condensation Reactions of Aromatic Aldehydes with Active Methylene Compounds: The Beneficial Sinergy of Alkaline Ionic Liquid in One Pot Synthesis

Background: In recent times, there has been on-going interest in developing convenient and environmentally friendly synthetic methods in organic chemistry. The use of ionic liquid catalysts in organic synthesis is a developing area that allows reactions to be run at low temperatures and without solvents. Literature overview revealed that room temperature supported ionic liquid catalysis is a developing field in catalytic science with huge application in organic synthesis. Hence in this current article, our focus is on the one-pot synthesis of arylidene derivatives with the use of ([bmim] OH) ionic liquid. Objectives: We describe here the use of an ionic liquid catalyst, 1-n-butyl-3-methylimidazolium hydroxide, [bmim] OH), in the convenient one pot synthesis of arylidene derivatives by the reaction of the active methylene compound, malononitrile, with pyrazole aromatic aldehydes under microwave irradiation. Methods: The functionalized ionic liquid, 1-n-butyl-3-methylimidazolium hydroxide ([bmim] OH), catalyzed Knoevenagel condensation reactions of pyrazole aromatic aldehydes with active methylene compound malononitrile carried out under microwave irradiation. The reaction progress was monitored by thin layer chromatography and the synthesized compounds were further characterized by NMR spectroscopy. Results: This proposed work demonstrates the utility of the use of the ionic liquid catalyst [bmim] OH, in the suitable, high yield (80-95%) microwave assisted reactions of pyrazole aromatic aldehydes with the active methylene compound, malononitrile. Conclusion: An eco-friendly synthesis of pyrazole derivatives has been demonstrated using ([bmim] OH) ionic liquid as a catalyst for the Knoevenagel condensation reactions of pyrazole aromatic aldehydes and malononitrile with microwave irradiation. The advantages of this green method are its convenience, mild reaction conditions, and high product yields (80-95%).

Evaluation and kinetic study of alkaline ionic liquid for biodiesel production through transesterification of sunflower oil

Biodiesel production is performed in the industry by alkaline transesterification of oils with a low amount of free fatty acids. In order to reduce the disposal of conventional catalysts used industrially, ionic liquids (ILs) have been studied to be applied as catalysts in transesterification since they can be recovered and reused in subsequent reaction cycles. In this work, the ionic liquid choline hydroxide (ChOH) was successfully applied as a catalyst for the transesterification reaction of triacylglycerols present in sunflower oil with methanol. A kinetic modeling study under the specific conditions of 2 wt% catalyst dosage, 1:10 oil/methanol molar ratio, for 0–120 min at 35–65 ℃ was conducted, and liquid–liquid extraction with water/butanol was evaluated as a process to recover the IL. A 95.0% ester yield content was achieved in this work for a short reaction time (30 min). Furthermore, the results of the kinetic study demonstrated that a first-order model was the best fit for the reaction with a rate constant (k) estimated as 0.1182 min−1 and activation energy (Ea) of 13.64 kJ/mol. For the tested conditions, the complete recovery of the IL using liquid–liquid extraction did not occur since it is noted the presence of ChOH in both phases.

Lignin Depolymerization with Alkaline Ionic Liquids and Ethylene Glycol in a Continuous Flow Reactor

Lignin Depolymerization with Alkaline Ionic Liquids and Ethylene Glycol in a Continuous Flow Reactor

Silica‐supported morpholine alkaline ionic liquid catalysts for preparation of biodiesel

AbstractBiodiesel was synthesized by transesterification of soybean oil and methanol over a silica‐supported morpholine alkaline ionic liquid catalyst (SILC). Characterization of SILC was performed using 1H‐nuclear magnetic resonance (1H‐NMR), Fourier‐transform infrared spectroscopy (FT‐IR), x‐ray diffraction, thermogravimetric analysis (XRD), and nitrogen adsorption‐desorption isotherms. Transesterification proceeded satisfactorily over SILC at ambient pressure and without simultaneous water removal. Under optimal reaction conditions, including 60°C, 4 hours, reactant/catalyst molar ratio of 14/1, and 3‐wt% catalyst, a high yield of biodiesel (94.5%) was obtained. SILC's reusability was more than six times, with no obvious decrease in catalytic activity observed.

Preparation of Biodiesel Based on Alkaline Ionic Liquid [Bmim]OH Catalyzed Castor Oil

In this experiment, a new basic ionic liquid [Bmim]OH was synthesized from 1-methylimidazole and sodium hydroxide, which was used to catalyze the preparation of biodiesel from castor oil. The catalyst of [Bmim]OH was compared with KOH and tetrabutylammonium hydroxide during the study. The experimental results showed that the latter two were better than the latter two. The orthogonal experimental design scheme was used to optimize the process conditions. The optimized catalytic conditions of alkaline ionic liquid [Bmim]OH were as follows: the catalyst dosage was 1%, the molar ratio of alcohol to oil was 6:1, the reaction temperature was 40 °C, and the reaction time was 60min. Under the optimized conditions, the crude methyl ester mixture yield is higher than 97%, the castor oil is more than 95% converted to the product methyl ester, and the catalyst of [Bmim]OH is used for six times without significant consumption, and the catalytic performance is stable.

Highly efficient cellulose dissolution by alkaline ionic liquids

Alkaline ionic liquids (ILs) with unconventional organic anions were prepared and used for cellulose dissolution studies. High concentrations of cellulose were dissolved at room temperature in the phenolate based imidazolium IL [C2mim][OPh], combined with organic solvent, and up to 45 wt-% cellulose dissolution (wt-% MCC of weight IL) was readily achieved at 100 ºC. No functionalization of the regenerated cellulose was observed during the dissolution process (FTIR). Characteristic cellulose II XRD diffraction pattern was observed after IL dissolution and regeneration of MCC. The crystallinity index (CI) of the pretreated MCC was reduced from 93.2 % to 31 %. Inert conditions were not required for the cellulose dissolution experiments. This study indicates that the IL H-bond basicity is not the only key parameter determining their cellulose dissolution ability. The alkaline ILs represent an energy efficient and sustainable approach for cellulose dissolution.

Fabrication of Tubular g‐C3N4 with N‐Defects and Extended π‐Conjugated System for Promoted Photocatalytic Hydrogen Production

AbstractSemiconductor photocatalytic hydrogen evolution from water splitting using solar energy is one of the most potential strategies for settling the energy crisis, but a bottleneck is occurred in developing a highly efficient photocatalyst. Herein, we successfully fabricated a tubular g‐C3N4 with nitrogen defects (including both nitrogen vacancies and cyano groups) and extended π‐conjugated system, wherein the nitrogen defects and extended π‐conjugated system were conveniently introduced during thermal polymerization of the pyridinium alkaline ionic liquid‐modified hydrogen‐bonding melamine‐cyanuric acid supramolecular (PHMCS) pre‐aggregates towards carbon nitride with hexagonal cylinder morphology formed by the pyridinium alkaline ionic liquid‐assisted hydrothermal process of low‐cost melamine, in which the added trace pyridinium alkaline ionic liquid serves as an all‐rounder with three roles including the promoting agent towards the transformation of melamine to cyanuric acid for constructing PHMCS, nitrogen defects making agent, and the electronic‐tuning agent regarding of the as‐formed carbon nitride. The tubular structure enhances the light scattering and improves the accessibility of active sites. Meanwhile, the high charge transfer efficiency, broad optical absorption region, and suitable energy band positions are related to both the introduction of nitrogen defects by alkali of ionic liquid and the extended π‐electron delocalization in the conjunction carbon nitride networks. As a consequence, the resulted carbon nitride using optimized amount of pyridinium alkaline ionic liquid (AIL‐2.0‐CN) photocatalyst exhibited a high hydrogen evolution rate of 1284 μmol h−1 g−1 (λ>420 nm) with an apparent quantum efficiency of 4.2 % at 420 nm, which is 13.6 times higher than that of bulk g‐C3N4 (B−CN), and even 3.5 folds much higher than the one (SHPY−CN) prepared by the similar process to that for AIL‐2.0‐CN except for the replacement of pyridinium alkaline ionic liquid by a mixture containing a corresponding amount of pyridine and sodium hydroxide, suggesting the promoting effect resulting from the unique characteristic of pyridinium alkaline ionic liquid. Based on the unique physicochemical properties and the molecules‐ adjustability, the developed alkaline ionic liquid assisted strategy can open an avenue for designing and preparing excellent g‐C3N4 based photocatalysts with tunable geometric and electronic structures for solar hydrogen production.

Alkaline Ionic Liquids Immobilized on Protective Copolymers Coated Magnetic Nanoparticles: An Efficient and Magnetically Recyclable Catalyst for Knoevenagel Condensation

A novel three-layered catalyst was successfully synthesized by the copolymerization of divinylbenzene and vinyl benzyl chloride in the presence of 3-mercaptopropyltrimethoxysilane-functionalized ma...

Electrodeposition of CdTe from BmimCl: Influence of substrate and electrolytic bath

Potentiostatic electrodeposition of Cadmium Telluride (CdTe) films from the alkaline ionic liquid (IL), butyl methyl imidazolium chloride (BmimCl) at 80 °C has been carried out at an applied potential of −1.45 V vs. platinum (Pt) wire. The influence of the substrate and electrolytic IL bath content on the morphology and composition of electrodeposited CdTe thin films has been presented. The sheet resistivity of the modified FTO substrate increases to ~17.7 Ω/sq. While treatment of the substrate prior deposition changes the individual CdTe morphology, the composition as well as the film compactness has been found to vary with the treatment of the IL based electrolytic bath. SEM micrograph shows inter-connected needle-like and herring bone morphology of electrodeposited CdTe along with agglomerated lumps of Te and flecks of Cd. Interdependency of surface morphology and elemental composition of electrodeposited CdTe films were observed by SEM & EDX analysis. It has been shown that hydroxylated FTO surface facilitates three dimensional (3D) nucleation and growth in the presence of O2 in the electrolytic bath. 3D nucleation and growth mechanism leads to Cd-rich CdTe films. Electrodeposition that does not proceed through 3D nucleation and growth shows only Te-rich layer. Also, the net charge transfer was found more in Cd-rich CdTe layers as compared with Te-rich CdTe deposits.

Alkaline Ionic Liquid Modified Pd/C Catalyst as an Efficient Catalyst for Oxidation of 5-Hydroxymethylfurfural

Conversion of HMF into FDCA was carried out by a simple and green process based on alkaline ionic liquid (IL) modified Pd/C catalyst (Pd/C-OH−). Alkaline ionic liquids were chosen to optimize Pd/C catalyst for special hydrophilicity and hydrophobicity, redox stability, and unique dissolving abilities for polar compounds. The Pd/C-OH− catalyst was successfully prepared and characterized by SEM, XRD, TG, FT-IR, and CO2-TPD technologies. Loading of alkaline ionic liquid on the surface of Pd/C was 2.54 mmol·g−1. The catalyst showed excellent catalytic activity in the HMF oxidation after optimization of reaction temperature, reaction time, catalyst amount, and solvent. Supported alkaline ionic liquid (IL) could be a substitute and promotion for homogeneous base (NaOH). Under optimal reaction conditions, high HMF conversion of 100% and FDCA yield of 82.39% were achieved over Pd/C-OH− catalyst in water at 373 K for 24 h.

Conversion of Carbohydrates into Platform Chemicals Catalyzed by Alkaline Ionic Liquids

A series of alkaline ionic liquids (ILs) including 1-butyl-3-methylimidazolium benzoate ([BMIM]PHCOO), 1-butyl-3-methylimidazolium carbonate ([BMIM]2CO3), 1-butyl-3-methylimidazolium acetate ([BMIM]OAc), 1-butyl-3-methylimidazolium hydroxide ([BMIM]OH), ethanolamine tetrafluoroborate ([MEA]BF4), and 1,1,3,3-tetramethylguanidine (TMG)-based ILs, etc., were synthesized and utilized as catalysts for the conversion of carbohydrates into 5-HMF. 1,1,3,3-tetramethylguanidine tetrafluoroborate ([TMG]BF4) was confirmed to exhibit excellent catalytic activity, and was much cheaper than other ILs such as 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) for use as a solvent in the conversion of C6 carbohydrates into 5-HMF. The 5-HMF yields from fructose, glucose, cellobiose, and microcrystalline cellulose (MCC) were 74.19%, 27.33%, 20.20%, and 17.73%, respectively. In addition, the possible pathway of carbohydrates (MCC, cellobiose, glucose, etc.) conversion into 5-HMF with [TMG]BF4 as a catalyst was speculated, and the conversion of glucose into 5-HMF was determined to likely be the committed step in the transformation of MCC catalyzed by [TMG]BF4.

Efficient conversion of Hubrid Pennisetum to glucose by oxygen-aqueous alkaline ionic liquid media pretreatment under benign conditions

To enhance the cellulose digestibility of energy grass hybrid Pennisetum (P. americanum×P. purpureum, HP) with low energy-consumption and high efficiency, a novel combinatorial pretreatment of oxygen-aqueous alkaline ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([Emim]Ac) media (OEA) was developed in this work. The combinatorial pretreatment was performed under the relatively low temperature (120°C), short retention time (30min), and 12bar oxygen pressure. The combinatorial pretreatment of OEA was demonstrated effectively for pretreatment of hybrid Pennisetum, which evidenced by the removal of lignin, degradation of carbohydrate, and porosity property of the regenerated biomass. Subsequently, a higher glucose recovery (96.9%) at a low enzyme loading (20FPU/g substrate) was obtained by the OEA pretreatment, and it was 9.1 times as much as the untreated samples. Overall, the novel OEA combinatorial pretreatment has the advantages of low thermal energy input and enzyme usage, and short retention time.

Dissolution of Eucalyptus Powder with Alkaline Ionic Liquid [Mmim]DMP under Microwave Conditions

An orthogonal design was used to study three factors—melting temperature, time, and solid-liquid ratio—and how they affected the dissolution rate of eucalyptus powder. The optimum solution conditions were 170 °C, 20 min, and a solid-liquid ratio of 1:25. Composition analysis of the residue indicated that, in the dissolving process, acid-insoluble lignin was converted into acid-soluble lignin, and a part of the lignin was degraded or modified. After dissolution, the crystalline structure of cellulose deteriorated, the relative crystallinity decreased, and the crystal form changed from type I into amorphous. Wood powder degradation occurred during dissolution, and a higher dissolution rate led to greater degradation. In a low-temperature environment below 225 °C, the residue thermal stability decreased slightly with increasing dissolution rates, but it greatly improved in a high-temperature environment of 225 to 600 °C.