Amine-functionalized Ionic Liquids Research Articles

Effective Defect Passivation via Molecular Interactions Based on Amine-Functionalized Ionic Liquid for Perovskite Solar Cells

Effective Defect Passivation via Molecular Interactions Based on Amine-Functionalized Ionic Liquid for Perovskite Solar Cells

Corrosion Behavior of S235JR and 304 SS in Amine-Functionalized Ionic Liquid Aqueous Solutions

Amine-functionalized ionic liquid (IL) aqueous systems were recently tested as a CO2 absorber. Nevertheless, equipment corrosion of CO2 capture into IL aqueous solutions is still rarely studied. In the present study, the corrosion behaviors of various concentrated dimethylethylenediamine acetate [DMEDA][CH3COO] aqueous solutions had been investigated by systematically probing the effect of IL concentrations, CO2 loading for typical mild steel S235JR and stainless steel 304 SS. The experimental results indicated that neat [DMEDA][CH3COO] showed negligible corrosivity, while high water contents would accelerate the corrosion rates. The corrosion process was controlled by charge transfer according to Tafel curves. Also, the presence of CO2 slightly altered the corrosion rates, which were quite different from the previous report that CO2-producing hydrogen protons (H+) promoted the dissolution of iron and accelerated the corrosion rates. It was likely that [DMEDA][CH3COO] was attached on the metal surface to resist the H+ attack. The corrosion behaviors suggested that [DMEDA][CH3COO]/water mixtures could be proper candidates for CO2 capture.

Efficient conversion of H2S into mercaptan alcohol by tertiary-amine functionalized ionic liquids

This work develops a novel way of H 2 S resource into mercaptan alcohol mediated by tertiary-amine functionalized protic ionic liquids. • Novel way of H 2 S resource utilization into mercaptan alcohol was developed. • The mechanism of H 2 S conversion mediated ionic liquids was proposed. • The reaction separation coupling process was proposed. The resource utilization of hydrogen sulfide (H 2 S) is of great significance in natural gas chemical industry. Described herein have developed a novel method mediated in tertiary amine-functionalized ionic liquids (ILs) to convert H 2 S into mercaptan alcohols with enols. The effect of ILs, substrate scope, and regeneration experiments have been investigated. It is found that the conversion of 3-methyl-2-buten-1-ol by H 2 S can reach 52% with a 50% (mol) catalyst loading of bis(2-dimethylaminoethyl) ether methoxyacetate within 12 h at 90 °C. The reaction mechanism was speculated based on theoretical calculation. Besides, a plausible reaction–separation-integrated strategy was further proposed. This work reveals an effective insight into the capture and catalytic conversion of H 2 S to high valuable mercaptan alcohol, which makes the utilization method of H 2 S resource universal and has the potentiality for industrial application.

Amine-functionalized ionic liquids for CO2 capture.

In petroleum industry, the release of more and more carbon dioxide (CO2) brings greenhouse effect and even results in climate change, leading CO2 capture to become an urgent issue. To design ideal and effective absorbent, interaction mechanism for CO2 capture was systematically investigated in a series of imidazolium-based ionic liquids (ILs). The potential effects of alkyl side chain, electron-philic halogen (F, Cl, Br) atom(s), electron-denoting groups OH and NH2 (bound on cation or/and anion), and water solvent were disclosed on CO2 capture using CAM-B3LYP functional with SMD-GIL solvation model, and the most potential green effective absorbent was predicted. This work provides an explicit idea and theoretical basis about the design of desired IL for CO2 capture. Graphical abstract In present work, no/halogen/amino/hydroxy-functionalized imidazolium tetrafluoroborate ILs were studied for CO2 absorption at the CAM-B3LYP/6-311++G** level of theory by SMD-GIL solvation model. NH2 is more potent group in absorbing CO2 than halogen and OH, and its number is proportional to the adsorption capacity of IL. A potentially high-capacity CO2 absorbent with four NH2 groups was predicted. In addition, the mixture of water could further enhance such chemical absorption by lowering the activation energy barriers and viscosity of IL.

A novel nanofiltration membrane with [MimAP][Tf2N] ionic liquid for utilization of lithium from brines with high Mg2+/Li+ ratio

In order to utilize lithium from brines with high Mg2+/Li+ ratio, a positively charged nanofiltration (NF) membrane was prepared by grafting amine-functionalized ionic liquid 1-(3-aminopropyl)-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([MimAP][Tf2N]) onto the surface of polyamide (PA) membrane. The effects of [MimAP][Tf2N] contents on the chemical composition, surface morphology, surface charges and separation properties of the modified PA membranes were discussed. The results of chemical composition analyses indicated reaction of the amine group of [MimAP][Tf2N] with the residual acyl chloride groups, which was existed on the surface of the nascent PA membrane. The surfaces of all the modified PA membranes were positively charged at pH = 6.4 due to the quaternary ammonium group of [MimAP][Tf2N]. In the separation process, the resulting membrane presented high water permeance (37.8 L/(m2⋅h)) and mono-/divalent cation selectivity (Li+ and Mg2+) with much higher MgCl2 rejection (83.8%) than LiCl rejection (24.4%). For a simulative brine with a Mg2+/Li+ ratio of 20, the rejections to Mg2+ and Li+ by the optimized membrane (NF-IL-2.0%) were around 81.9% and −45.2%, respectively, where the permeate with the Mg2+/Li+ ratio of 3.5 was obtained and the selectivity (SLi,Mg) was 8.12. Additionally, the optimized membrane exhibited a stable performance for Mg2+/Li+ separation. Therefore, there is a very possibility for utilization of lithium from brine with high Mg2+/Li+ ratio by using the optimized NF membrane.

Mechanistic Studies of CO2 Cycloaddition Reaction Catalyzed by Amine-Functionalized Ionic Liquids.

The homogeneous cycloaddition reaction of CO2 and epichlorohydrin catalyzed by amine-functionalized ionic liquid (AFIL) to yield cyclic carbonate is reported in this study. The AFIL has the dual function of ionic liquid and organic base. The experimental study indicates that AFIL can efficiently catalyze the conversion of CO2 and epichlorohydrin to the product 3-chloro-1,2-propylene. The mechanistic study based on DFT calculations reveals that the imidazolium ring in AFIL primarily catalyzes the ring-opening reaction of epichlorohydrin, while the protonated amine group is responsible for stabilizing the Br− anion in the nucleophilic attack. This study provides a deep insight into the catalytic roles of AFIL and also inspires us to design efficient dual function catalysts for CO2 utilization.

Ionic Liquids-Functionalized Zeolitic Imidazolate Framework for Carbon Dioxide Adsorption.

Ionic-liquid-functionalized zeolitic imidazolate frameworks (ZIF) were synthesized using the co-ligands of 2-methylimidazole and amine-functionalized ionic liquid during the formation process of frameworks. The resulting ionic-liquid-modified ZIF had a specific surface area of 1707 m2·g−1 with an average pore size of about 1.53 nm. Benefiting from the large surface area and the high solubility of carbon dioxide in ionic-liquid moieties, the synthesized materials exhibited a carbon dioxide adsorption capacity of about 24.9 cm3·g−1, whereas it was 16.3 cm3·g−1 for pristine ZIF at 25 °C under 800 mmHg. The results demonstrate that the modification of porous materials with ionic liquids could be an effective way to fabricate solid sorbents for carbon dioxide adsorption.

Co2 Capture: State of the Art

The enhanced CO2 concentration in the atmosphere is directly proportional to the global warming. The atmospheric CO2 concentration is more or less 280 to 400 ppm during pre-industrial era and expected to enlist >500 ppm by 2050 [1,2]. Emission at the current rate would lead the adverse effect in the future could be larger as compared to the last century [3]. World energy consumption will see a 48% increase from 2012 to 2040 and fossil fuel sources will still account for 78% of the world energy consumption in 2040 [3]. The Paris Accord bind countries towards reduction of CO2 emissions by at least 50% are necessary to restrict the global temperature rise to 2°C by 2050[4]. Owing of hefty challenge, it is imperative to reduce CO2 emissions from fossil fuel consumption. Overall cost and the required energy is the bottlenecks towards commercialize the CO2 capture and storage process at large scale. Few technologies for instance physical or chemical solvent scrubbing, [5-7] gas membrane separation, [8-13] pressure swing absorption, [14,15] surface absorption and adsorption, [16-19] metal organic frameworks, [20-27] amine based technology [28] have been applied to the CO2 capture. Owing of the high energy consumption, storage, cost raised concerns towards widespread implementation of carbon capture storage. Recently, ionic liquids (ILs) have been emerging as potential contenders for CO2 capture due to their superior physicochemical characteristics, including low melting point, high thermal stability, adjustable structure, and good recyclability [29,30]. However, the solubility of CO2 in conventional ILs is limited due to the physical absorption. In order to achieve better performance, some special groups (e.g.−NH2, −OH) were introduced to the anion or the action of ILs. The amine-functionalized IL has been chosen as the most promising candidate for CO2 capture.

Heterogenization of amine-functionalized ionic liquids using graphene oxide as a support material: a highly efficient catalyst for the synthesis of 3-substituted indoles via Yonemitsu-type reaction

Heterogenization of amine functionalized ionic liquid and its application as an efficient and recyclable catalyst.

Comparison of Solvation Effects on CO2 Capture with Aqueous Amine Solutions and Amine-Functionalized Ionic Liquids.

Amines are the most widely utilized chemicals for postcombustion CO2 capture, because the reversible reactions between amines and CO2 through their moderate interaction allow effective "catch and release". Usually, CO2 is dissolved in the form of an anion such as carbamate or bicarbonate. Therefore, the reaction energy diagram is potentially governed to a large extent by the polarity of the surrounding solvent. Herein, we compared aqueous amine solutions and amine-functionalized ionic liquids by investigating their dielectric constants and performing an intrinsic reaction coordinate analysis of the CO2 absorption process. Quantum mechanical calculations at the CCSD(T)/6-311++G(d,p)//B3LYP/6-311++G(d,p) level within the continuum solvation model (SMD/IEF-PCM) revealed contrasting dependencies of C-N bond formation on the dielectric constant in those solutions. Amines react with CO2 on an energy surface that is significantly affected by the dielectric constant in conventional aqueous amine solutions, whereas amine-functionalized anions and CO2 form stable C-N bonds with a comparatively lower activation energy regardless of the dielectric constant.

Thermophysical properties and CO2 absorption studies of the amine functionalized [Amim][Tf2N] and the non-functionalized counterpart [bmim][Tf2N] ionic liquids

Large scale application of physical ionic liquids (ILs) for carbon dioxide (CO2) capture from flue gas is mainly hindered by the low CO2 absorption capacity at post-combustion conditions. To overcome this problem researchers appealed to the amine chemistry by arguing that including an amine moiety to conventional ILs (amine-functionalized ionic liquids) could greatly improve CO2 absorption capacity. The present work investigates the thermophysical properties of the functionalized imidazolium based ionic liquid with an added primary amine group into the cation structure [Amim]+[Tf2N]− and the non-functionalized counterpart ionic liquid [bmim]+[Tf2N]− and compares them to the conventional amine solutions used for absorption of CO2. The thermophysical properties (densities, viscosity and surface tension) of the ionic liquids measured over the temperatures between 293.15K and 348.15K at atmospheric pressure. It was observed that a rise in temperature caused a remarkable reduction in the ionic liquid viscosity by factors of 3.75 and 3.71 for [Amim][Tf2N] and [bmim][Tf2N] respectively whereas for a similar temperature change, the viscosity of the aqueous MEA and DEA solutions decreased only by factors of 2.10 and 2.15 respectively. The surface tension–fluidity relation of the tested ionic liquids investigated. The functionalized IL showed higher CO2 solubility compared to the non- functionalized counterpart IL. The results showed that CO2 absorption behavior of the [Amim][Tf2N] was influenced by the functionalized chain (primary amine group) appended to the IL cation and probably a typical chemical enhancement of the CO2 absorption took place when the functional IL was used as absorption solvent. On mass basis (g CO2/kg IL), The [Amim][Tf2N] showed 780% and 350% more CO2 absorption capacity than the non-functionalized counterpart IL at 1.1bar and 8bar respectively at 308.15K. The isotherms of CO2-functionalized IL shows a trend which is typical for chemical absorption. At low pressure (P=1.1bar) the solubility increases sharply, while a steady increase in solubility is observed at higher pressure (from 1.1 to 8bar) due to contribution of the physical mechanism. We observed a marginal increase in volumetric CO2 load into the [bmim][Tf2N] at higher pressures which is typical for physical absorption. At pressure equal to 6bar, the CO2 loads for the functionalized ionic liquid at 308.15K is comparable to CO2 loads from 20% DEA at 323K. The results of the measured volumetric CO2 loads of the functionalized ionic liquid indicated that for representative operating conditions, (308.15K and pressures up to 8bar), the two studied ILs do not present a greater absorption capacity than the aqueous MEA solution. The ionic liquids were regenerated at vacuum (10Pa) and at 378.15K during at 16h. The next absorption experiments were performed with the regenerated samples and a reduction in CO2 absorption capacity was not observed.

Thermal reaction of the ionic liquid 1,2-dimethyl-(3-aminoethyl) imidazolium tetrafluoroborate: a kinetic and theoretical study.

Since the thermal stabilities of ionic liquids (ILs) are of significance for their application, an amine-functionalized IL 1,2-dimethyl-(3-aminoethyl) imidazolium tetrafluoroborate [aEMMIM][BF4] was chosen to study thermal decomposition mechanisms via the methods of FT-IR, (1)H NMR, TGA, TGA-MS and density functional theory (DFT) calculations. Theoretical and experimental results indicated that amine-functionalization reduces the thermal stability of [aEMMIM][BF4] compared to its non-functionalized counterpart. Moreover, we found that [aEMMIM][BF4] follows a unimolecular nucleophilic substitution (SN1) decomposition (98.8%), whereas the bimolecular nucleophilic substitution (SN2) decomposition (1.2%) is unfavorable. The SN1 and SN2 reactions were fully optimized at B3LYP/6-311++G(d,p) level, and the energies of reactant (R), intermediates (IM), transition state (TS) and product (P) were obtained and analyzed by reaction mechanism. The energy of the intermediate is higher than that of the reactants by 18.92kJmol(-1), and the energy of the TS is higher than that of the IM by 155.23kJmol(-1). This result indicates that the IM are also more stable than the P2 product, thus the reaction is endothermic. The chemical nature of the covalent and hydrogen bonds was analyzed by vibrational modes analysis (VMA), nature bond orbital (NBO) and the theory of atoms in molecules (AIM). Graphical Abstract Proposed thermal decomposition of [aEMMIM][BF4] via unimolecular ( SN1) and bimolecular( SN2) nucleophilic substitution mechanisms. The electrostatic potential surface (ESP) of the transition state illustrates that hydrogen bonds are generated when [BF4](-) is close to [aEMMIM](+), and SN1 decomposition is much favorable than SN2 decomposition.

Investigations on the thermal stability and decomposition mechanism of an amine-functionalized ionic liquid by TGA, NMR, TG-MS experiments and DFT calculations

Amine-functionalized ionic liquids (ILs) have potential applications for CO2 capture. The CO2 capture process is generally operated at a relatively high temperature for a long term, so determining the thermal stability of amine-functionalized ILs is important. In this study, the thermal stability of an amine-functionalized IL 1,2-dimethyl-(3-aminoethyl) imidazolium tetrafluoroborate [aEMMIM][BF4] was investigated by thermogravimetric analysis (TGA), thermogravimetric mass spectroscopic analysis (TG-MS), 1H nuclear magnetic resonance (NMR) experiments and density function theory (DFT) calculation. Amine-functionalization was found to reduce the thermal stability of [aEMMIM][BF4] compared to the non-functionalized counterpart. Besides that, we found that [aEMMIM][BF4] favors a unimolecular substitution nucleophilic (SN1) decomposition reaction rather than bimolecular nucleophilic substitution (SN2) reaction. Vaporization and elimination processes are negligible due to amine functionalization. Moreover, an operational temperature, Toper, is proposed for evaluating the thermal stability of ILs. Results show that Toper of [aEMMIM][BF4] only reaches 138°C, much less than that of the onset decomposition temperature, Tonset (284°C). Evaluating thermal stability of amine-functionalized ILs by Toper is more practical than by Tonset.

Efficient synthesis of 2-oxazolidinones from epoxides and carbamates catalyzed by amine-functionalized ionic liquids

The amine-functionalized ionic liquids can be an efficient catalyst for 2-oxazolidinones synthesis from epoxides and carbamates.

CO2 Capture by Novel Supported Ionic Liquid Phase Systems Consisting of Silica Nanoparticles Encapsulating Amine-Functionalized Ionic Liquids

We report novel supported ionic liquid (IL) phase systems, described as “inverse” SILPs, consisting of micron size IL droplets within an envelope of silica nanoparticles. These novel IL-in-air powders, produced by an easily scalable phase inversion process, are stable up to 60 °C and 30 bar and are proposed as a means to confront the major drawbacks of conventional SILPs for gas separation. SILPs are usually formed by filling the channels of nanoporous materials with the IL phase. In case the core space of the pores remains open, such conventional SILPs exhibit lack of gas absorption specificity, while complete pore filling leads to diffusivity that is very low compared to that for corresponding bulk ILs; the latter drop is largely due to the high tortuosity of the pore network of the support. The inverse SILPs prepared in this work exhibited promising CO2/N2 separation performance that had reached the value of 20 at absorption equilibrium and enhanced CO2 absorption capacity of 1.5–3 mmol g–1 at 1 bar and 40 °C. Moreover, the CO2 absorption kinetics were very fast compared to conventional SILP systems and to simultaneous N2 absorption; the CO2/N2 selectivity at the short times of the transient stage of absorption had reached values in excess of 200.

Efficient CO2 capture by tertiary amine-functionalized ionic liquids through Li(+)-stabilized zwitterionic adduct formation.

Highly efficient CO2 absorption was realized through formation of zwitterionic adducts, combining synthetic strategies to ionic liquids (ILs) and coordination. The essence of our strategy is to make use of multidentate cation coordination between Li+ and an organic base. Also PEG-functionalized organic bases were employed to enhance the CO2-philicity. The ILs were reacted with CO2 to form the zwitterionic adduct. Coordination effects between various lithium salts and neutral ligands, as well as the CO2 capacity of the chelated ILs obtained were investigated. For example, the CO2 capacity of PEG150MeBu2N increased steadily from 0.10 to 0.66 (mol CO2 absorbed per mol of base) through the formation of zwitterionic adducts being stabilized by Li+.

Ship-in-a-bottle synthesis of amine-functionalized ionic liquids in NaY zeolite for CO2 capture.

CO2 capture on solid materials possesses significant advantages on the operation cost, process for large-scale CO2 capture and storage (CCS) that stimulates great interest in exploring high-performance solid CO2 adsorbents. A ship-in-a-bottle strategy was successfully developed to prepare the [APMIM]Br@NaY host–guest system in which an amine-functionalized ionic liquid (IL), 1-aminopropyl-3-methylimidazolium bromide ([APMIM]Br), was in-situ encapsulated in the NaY supercages. The genuine host-guest systems were thoroughly characterized and tested in CO2 capture from simulated flue gas. It was evidenced the encapsulated ILs are more stable than the bulk ILs. These host–guest systems exhibited superb overall CO2 capture capacity up to 4.94 mmol g−1 and the chemically adsorbed CO2 achieved 1.85 mmol g−1 depending on the [APMIM]Br loading amount. The chemisorbed CO2 can be desorbed rapidly by flushing with N2 gas at 50°C. The optimized [APMIM]Br@NaY system remains its original CO2 capture capacity in multiple cycling tests under prolonged harsh adsorption-desorption conditions. The excellent physicochemical properties and the CO2 capture performance of the host-guest systems offer them great promise for the future practice in the industrial CO2 capture.

Relationship between Diffusion and Chemical Exchange in Mixtures of Carbon Dioxide and an Amine-Functionalized Ionic Liquid by High Field NMR and Kinetic Monte Carlo Simulations.

NMR exchange spectroscopy (EXSY) and NMR diffusion spectroscopy (PFG NMR) were applied in combination with kinetic Monte Carlo (MC) simulations to investigate self-diffusion in a mixture of carbon dioxide and an amine-functionalized ionic liquid under conditions of an exchange of carbon dioxide molecules between the reacted and unreacted states in the mixture. EXSY studies enabled residence times of carbon dioxide molecules to be obtained in the two states, whereas PFG NMR revealed time-dependent effective diffusivities for diffusion times comparable with and larger than the residence times. Analytical treatment of the PFG NMR attenuation curves as well as fitting of the PFG NMR effective diffusivities by KMC simulations enabled determination of diffusivities of carbon dioxide in the reacted and unreacted states. In contrast to carbon dioxide, the ion diffusivities were found to be diffusion time independent.

Carbon Dioxide Capture by an Amine Functionalized Ionic Liquid: Fundamental Differences of Surface and Bulk Behavior

Carbon dioxide (CO2) absorption by the amine-functionalized ionic liquid (IL) dihydroxyethyldimethylammonium taurinate at 310 K was studied using surface- and bulk-sensitive experimental techniques. From near-ambient pressure X-ray photoelectron spectroscopy at 0.9 mbar CO2, the amount of captured CO2 per mole of IL in the near-surface region is quantified to ~0.58 mol, with ~0.15 mol in form of carbamate dianions and ~0.43 mol in form of carbamic acid. From isothermal uptake experiments combined with infrared spectroscopy, CO2 is found to be bound in the bulk as carbamate (with nominally 0.5 mol of CO2 bound per 1 mol of IL) up to ~2.5 bar CO2, and as carbamic acid (with nominally 1 mol CO2 bound per 1 mol IL) at higher pressures. We attribute the fact that at low pressures carbamic acid is the dominating species in the near-surface region, while only carbamate is formed in the bulk, to differences in solvation in the outermost IL layers as compared to the bulk situation.

Theoretical investigations on the reaction mechanisms of amine-functionalized ionic liquid [aEMMIM][BF4] and CO2

In this study, an amine-functionalized ionic liquid 1,2-dimethyl-(3-aminoethyl) imidazolium tetrafluoroborate [aEMMIM][BF4] was designed and synthesized for better performance of CO2 capture based on previous reports. Quantum chemical calculations had been used to investigate the interactions between CO2 molecules and the as-synthesized ionic liquids. The molecular structures of the most stable conformation of [aEMMIM] cation and [aEMMIM][BF4] were optimized at B3LYP/6-311++G (d, p) level. At the same time, we had performed CO2 capture by [aEMMIM] cation. Compared with [aEMMIM][BF4], the performance of [aEMMIM] cation on CO2 capture was not as good as supposed. It was found that the anionic part of [aEMMIM][BF4] played a non-neglectful role in CO2 capture [aEMMIM][BF4] was found to capture CO2 with a 1:1mol stoichiometry by quantum calculations due to the steric effect of the methyl group on C2 position of imidazolium ring. It was consistent with the experimental results. In order to understand the reaction mechanisms, we calculated the configuration variations on the reactant, intermediate, transition state and product, as well as energy barrier and vibration frequency changes in gas phase and using the conductor-like polarizable continuum model (CPCM) in water solution. The barrier height for [aEMMIM] and ([aEMMIM][BF4]) capturing CO2 is 47.25 (38.25)kcal/mol in gas phase and 38.92 (20.02)kcal/mol in water solution. These results indicate that the polarity of the solvent has played an important role on the reaction mechanisms. Frequency analysis indicates that the experimental results of the vibration frequencies are in better agreement with the scaled calculated values.