Ionic Liquid Hydrogen Research Articles

Hydrogen solubility in ionic liquids: Application of a structure-based deep learning approach and equations of state

Following the increasing threat to the environment, the application of hydrogen as an energy carrier is one of the solutions that has received much attention. Considering the importance of gas solubility in separation and gasification processes, the solubility of hydrogen in various solvents has particular importance. In this study, an extensive database containing 580 experimental data points (13 ionic liquids (ILs)) in a vast range of temperature (278.2–453.15 K) and pressure (0.433–552 bar) was employed to determine the solubility of hydrogen in ILs using intelligent models. In this regard, four intelligent models, including Random Forest (RF), Adaptive Boosting-Support Vector for Regression (AdaBoost-SVR), Deep Belief Network (DBN), and Multivariate Adaptive Regression Splines (MARS) models, were developed with two different approaches. In the first method, the chemical substructures were considered as inputs; in the second manner, the thermodynamic attributes of ILs were considered as inputs. Temperature and pressure were also two inputs of both methods. The results show that in both methods, the DBN paradigm has the best proficiency. The best root mean square error (RMSE) and coefficient of determination (R2) values in the former way were 0.00106 and 0.9991, respectively, and in the latter way, 0.00066 and 0.9996, respectively. The findings of sensitivity analysis show that among the chemical substructures and thermodynamic properties, –CH3 and pressure, with absolute relevancy factor values of 0.425 and 0.517, respectively, have the most impression on the hydrogen solubility in ILs. Also, the investigation of the influence of different parameters on hydrogen solubility shows that raising the pressure and alkyl chain length increases the hydrogen solubility in ILs. The acquired findings were also compared with equations of state (EOSs), and it was found that the intelligent models have better performance and high efficiency than EOSs. Finally, to validate the model data, the leverage method was used, which shows that over 96.7% of the data is in the authentic domain and only about 1% of the data is in the suspected data region.

Research progress on ionic liquid mediated chemical reactions

<p indent=0mm>Ionic liquid is a low-temperature molten salt composed of organic cation and inorganic/organic anion, which has the characteristics of molecular solvent and salt. It can be used as a reaction medium in chemical reactions, and also plays a catalytic or co-catalytic role. In this paper, the research progress of our group in recent years including ionic liquid-mediated transformation of renewable carbon resources, ionic liquid-catalyzed hydration of propargylic alcohols under metal-free conditions, and ionic liquid hydrogen bonding-catalyzed chemical reaction was summarized. The problems that still exist in this field were addressed and the development prospect was also presented.

Metal alloys for the new generation of compressors at hydrogen stations: Parametric study of corrosion behavior

Compressors are one of the most costly components at hydrogen stations, which leads to the high price of hydrogen production. The substitution of a solid piston with ionic liquid is a promising option that may solve some of the challenges related to conventional reciprocating compressors and, consequently, significantly reduce the final cost of hydrogen production. The correct choice of ionic liquid and construction materials is critical for avoiding significant corrosion problems. Hence, the objective of this study is to evaluate the compatibility of various austenitic stainless steels and nickel-based alloys as construction materials in contact with 80 °C ionic liquids in an ionic liquid hydrogen compressor, considering the role of parameters such as the temperature, viscosity, ionic liquid cation and anion, and water absorption.The results show that temperature contributes to increasing the corrosion rate. However, even at 80 °C, the very low corrosion current densities proved that all of the tested alloys are safe to use as construction materials. AISI 347 showed very high corrosion resistance in all of the ionic liquids. The highest corrosion resistance among all of the tested alloys was observed in trihexyltetradecylphosphonium bis (trifluoromethylsulfonyl) imide, which had a relatively high viscosity and the lowest water content.

Corrosion behavior of construction materials for ionic liquid hydrogen compressor

The corrosion behavior of various commercially available stainless steels and nickel-based alloys as possible construction materials for components which are in direct contact with one of five different ionic liquids was evaluated. The ionic liquids, namely: 1-ethyl-3-methylimidazolium triflate, 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, trihexyltetradecylphosphonium bis (trifluoromethylsulfonyl) imide, butyltrimethylammonium bis (trifluoromethylsulfonyl) imide, methyltrioctylammonium bis (trifluoromethylsulfonyl) imide have been identified, as performance fluids in an ionic liquid hydrogen compressor. An electrochemical cell was specially designed, and steady-state cyclic voltammetry was used to measure the corrosion resistance of the alloys in the ionic liquids at 23 °C, under atmospheric pressure.The results showed a very high corrosion resistance and high stability for all the alloys tested. The two stainless steels, AISI 316L and AISI 347 showed higher corrosion resistance compared to AISI 321 in all the ionic liquids tested. It was observed that small addition of molybdenum, tantalum, and niobium to the alloys increased the corrosion stability in the ionic liquids studied. Hastelloy® C-276 showed the poorest corrosion resistance in all the ionic liquids tested. AISI 316L with high corrosion resistance and the lowest cost is recommended as the most attractive construction material for all the components, in an ionic liquid hydrogen compressor, which are in direct contact with ionic liquids used in this study.

Mass Transport Studies and Hydrogen Evolution at a Platinum Electrode Using Bis(trifluoromethanesulfonyl)imide as the Proton Source in Ionic Liquids and Conventional Solvents

The hydrogen evolution reaction at a platinum electrode and proton transport using bis(trifluoromethanesulfonyl)imide (H[NTf2]) as the proton source has been investigated in six aprotic [NTf2]− ionic liquids (ILs), a protic [NTf2]− IL, propylene carbonate, and water. Proton reduction to form hydrogen in ILs is highly sensitive to the surface state of the platinum electrode, requiring oxidative preconditioning at ∼2 V versus Fc/Fc+ (Fc = ferrocene) to “activate” the electrode and achieve reproducible voltammetry. The hydrogen evolution reaction at a preconditioned electrode in ILs has been simulated by combining the classical Volmer, H+ + e– ⇌ H* (E10,ks,1,α1), and Heyrovsky reactions, H+ + H* + e– ⇌ H2 (E20,ks,2,α2), where E0, ks, and α are the standard potential, standard heterogeneous electron-transfer rate constant, and charge transfer coefficient, respectively. The Volmer reaction is the rate-determining step on platinum in IL media and the formal potential of the H+/H2 process is insensitive to the identity of the IL cation, lying at approximately −30 mV with respect to the Fc/Fc+ process. Proton transport in the ILs investigated obeys the Stokes–Einstein equation. Furthermore, the proton diffusion coefficient (measured electrochemically) is essentially identical to the self-diffusion coefficient of [NTf2]− (measured with pulsed field gradient spin–echo NMR), indicating that the protons are transported as undissociated H[NTf2]. The Stokes radius of H[NTf2] is estimated to be 3.24 Å from the slope of a Stokes–Einstein plot, in agreement with the literature. Proton transport in propylene carbonate follows the same Stokesian relationship, implying that H[NTf2] also is not dissociated in this molecular solvent. Finally, proton transport in water follows the well-established Grotthuss mechanism, as expected. Although we have shown that there is no Grotthuss-like proton conduction mechanism operating in the investigated ILs, this work lays the foundation for further studies on proton reduction, activity, and transport in this class of solvent. Ultimately, the goal is to develop an IL formulation which facilitates facile anhydrous proton conduction over a wide temperature range.

Brønsted acidic hydrogensulfate ionic liquid immobilized SBA-15: [MPIm][HSO4]@SBA-15 as an environmentally friendly, metal- and halogen-free recyclable catalyst for Knoevenagel–Michael-cyclization processes

The Brønsted acidic imidazolium-based metal-free and halogen-free ionic liquid hydrogen sulfate was immobilized on nanoporous silica SBA-15. The structures of synthesized catalysts were investigated using different characterization techniques, including FT-IR, small angle XRD, SEM, TEM and TGA. The [MPIm][HSO4]@SBA-15 is used as an alternative to conventional catalysts in the Knoevenagel–Michael-cyclization processes for the synthesis of tetrahydrochromenes and hexahydroquinoline carboxylates via a multicomponent procedure. The reaction time is reduced drastically and the reaction is progressed in an environmentally friendly way. The immobilized catalyst can be recycled without substantial loss of activity after seven runs.

Electrochemical Fluorination Using Halogen Mediators in Ionic Liquid Hydrogen Fluoride Salt

In order to utilize ammomium halides (Et4NX, X = Cl, Br, I) as halogen mediator for electrocatalytic fluorination, cyclic voltammetry measurements of the halides were investigated. The catalytic current of the halides in the presence of a dithioacatal compound was observed and the macro-scale electrolysis of dithioacetals using the halogen mediator was also carried out in ionic liquid hydrogen fluoride (HF) salt to give the corresponding fluorinated products in excellent yields. The recycle use of the halogen mediator in the electrochemical fluorination was successfully demonstrated. More inexpensive halides such as potassium bromide and potassium iodide could be soluble in HF salt and worked well as halogen mediator for the electrocatalytic fluorination.

Acceleration of the imine base/isocyanate (IBI)-mediated polymerization of MMA caused by ionic liquid traces

The brutto rate of the imine base/isocyanate (IBI)-mediated radical polymerization of methyl methacrylate (MMA) can be significantly increased by use of ionic liquid (IL) traces. At least, catalytic amounts of IL influence both the value of the brutto polymerization rate νBr,0 and the necessary reaction temperature of the used IBI mixture. Combinations of 2-phenyl-2-oxazoline (POX) or 1-methyl pyrazole (1MP) with isocyanates are IBI systems that usually do not initiate MMA at room temperature. By adding traces of 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([Emim]FAP), polymethyl methacrylate (PMMA) with high average molecular weight can be obtained whereas the initiator mixture (imine base/isocyanate) concentration can be decreased by a factor of 10. The polymerization kinetics of several IBI combinations in the presence of ILs has been determined and a comparison to non-IL containing initiator mixtures is given. Additionally, the temperature dependence of the IL-containing polymerizations was measured. The interaction of the IL with MMA and the individual IBI initiator components is studied by means of attenuated total reflection Fourier transformation middle infrared spectroscopy (ATR FT MIR). Furthermore, the IBI brutto polymerization rate constants kBr,0 were brought into relation to the IL hydrogen bond donating ability α. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

Electrochemical Behaviour of Hydrogen in Low-Viscosity Phosphonium Ionic Liquids

The electrochemical and diffusive properties of hydrogen in low-viscosity phosphonium ionic liquids were investigated by the electrochemical methods such as cyclic voltammetry and chronoamperometry. The hydrogen redox reactions were concluded to be a quasi-reversible system in phosphonium-based ionic liquids. The diffusion coefficients of hydrogen in these ionic liquids were of the order of 10-10 m2 s-1 at 25 ° C. Additionally, the obtained activation energy of the diffusion process for hydrogen was 11.2 - 15:9 kJ mol-1 estimated from the temperature dependence of the diffusion coefficients. A new type of proton conducting medium such as triethylphosphonium bis(trifluoromethylsulfonyl) amide was synthesized by the neutralization reaction, because the trialkylphosphine-based ionic liquids with good stability at higher temperature and high conductivity were appropriate candidates. This proton conducting membrane containing the ionic liquids with trialkylphosphine-based cations and the polyvinylidenefluoride-co-hexafluoropropylene has been fabricated in the present study. The proton conducting membrane exhibits relatively high ionic conductivity along with good mechanical stability.

Use of Task-Specific Ionic Liquid for Selective Electrocatalytic Fluorination

Highly selective indirect anodic fluorination of organic compounds was successfully carried out for the first time by using a task-specific ionic liquid of iodoarene as a mediator in ionic liquid hydrogen fluoride salts.

ChemInform Abstract: Prins Cyclization in Ionic Liquid Hydrogen Fluoride Salts: Facile and Highly Efficient Synthesis of 4‐Fluorinated Tetrahydropyrans, Thiacyclohexanes, and Piperidines.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Electrochemical polymer reaction: selective fluorination of a poly(fluorene) derivative

Anodic fluorodesulfurization of a poly(fluorene) derivative coated on a Pt electrode was successfully carried out in an ionic liquid hydrogen fluoride salt, yielding a alternating copolymer containing a difluorofluorene moiety.

Prins Cyclization in Ionic Liquid Hydrogen Fluoride Salts: Facile and Highly Efficient Synthesis of 4‐Fluorinated Tetrahydropyrans, Thiacyclohexanes, and Piperidines

AbstractPrins cyclization of homoallylic alcohols with various aldehydes was investigated in ionic liquid hydrogen fluoride (HF) salts, which played roles as a reaction medium, a catalyst, and a fluorine source. The reaction afforded the corresponding 4‐fluorinated tetrahydropyrans in excellent yields with a high stereoselectivity (cis form exclusively). When benzaldehydes having a strongly electron‐donating group at the para position were used, the stereoselectivity was lost in this system. In order to apply this method to the synthesis of other 4‐fluorinated heterocyclic compounds, we also carried out thia‐Prins and aza‐Prins cyclization in HF salt and successfully obtained 4‐fluorinated thiacyclohexanes and piperidines, respectively.(© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2009)

ChemInform Abstract: Facile and Highly Efficient Synthesis of Fluorinated Heterocycles via Prins Cyclization in Ionic Liquid Hydrogen Fluoride Salts

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Anodic Fluorination and Fluorodesulfurization in Ionic Liquid Hydrogen Fluoride Salts with Polyether Additives

In order to avoid an anodic passivation, which sometimes occurs during anodic fluorination in organic solvent, we carried out anodic fluorination and fluorodesulfurization of sulfur-containing compounds in neat ionic liquid hydrogen fluoride salts (, , ). The addition of polyether additives into the reaction system highly improved the yields of the desired fluorinated products due to their anodic stability and coordination ability to counter cations of fluoride ions. Furthermore, HF salts allow the electrolysis in a large current density and exhibited a good result, especially in the presence of polyether additives.

Effects of additives on anodic fluorination in ionic liquid hydrogen fluoride salts

Anodic fluorination of ethyl α-(2-pyrimidylthio)acetate in neat ionic liquid hydrogen fluoride salts (Et 3N–3HF, Et 4NF–4HF, Et 4NF–5HF) was investigated to avoid an anode passivation, which sometimes occurs during anodic fluorination in organic solvent. In order to improve the yield of fluorinated product, polyether having coordination ability to cation and anodic stability was introduced to the reaction system as additives (∼3%). Furthermore, such additives were found to be also effective for anodic fluorodesulfurization of 4-phenylthio-1,3-dioxolan-2-one in neat ionic liquid system.

Facile and highly efficient synthesis of fluorinated heterocycles via Prins cyclization in ionic liquid hydrogen fluoride salts

Prins cyclization of homoallylic alcohols, thiols, and amines with various aldehydes in an ionic liquid HF salt (Et(4)NF.5HF) afforded the corresponding 4-fluorinated heterocycles in excellent yields.