INTL. SYMP. ON SUSTAINABLE MOLTEN SALT AND IONIC LIQUID PROCESSING

A computational model for simulating the production of metallic rare earth by reduction process of molten salts within an electrowinning cell is discussed. The model was formulated based on the multiphase and multicomponent Navier-Stokes and k-epsilon turbulence transport equations, coupled with Maxwell's relations to account for the magneto hydrodynamic phenomena. The multiphase transport equations are solved using the finite volume formulation. The SIMPLE algorithm is used to couple the momentum and pressure equations, and the algebraic coefficients are calculated using the power law scheme. The set of the discretized algebraic equations are iteratively solved using the line by line procedure based on the tridiagonal matrix. The model equations were implemented in a computational code, and the parametric geometry and operational data used were based on the actual operation of the electrowinning cell specially designed for rare earth production. Results based on the simulation cases were discussed and shown feasibility and accordance with actual operation units. Simulated scenarios indicated that optimal conditions could be achieved with lower emissions and high energy consumption efficiency. The model is useful for predicting optimal parameters of processing, such as cell geometry, current density, gas and particulate emissions, and cell stability.

Ionic liquids are liquids composed entirely of ions. These ions are in constant motion. Ionic liquids have found use in a wide range of electrochemical applications, such as batteries, fuel cells and solar cells. In these applications ionic liquids are exposed to electric fields. It is, therefore, surprising that the dynamics of ions in ionic liquids has been hardly studied.
This paper reports our results on the diffusion of solutes in ionic liquids using Fluorescence Correlation Spectroscopy. We show that the diffusion of these ions slow on the application of an electric field. Further to this, we show that the relaxation of this motion after discharge of the cell is remarkably slow on the timescale of tens of minutes. We also report a study of the rotation of molecular rotors by Fluorescence Lifetime Spectroscopy, which can be correlated with the viscosity of the solvent in the cybotactic region of the probe rotor. These results show that the slower motion of ions is associated with an increase in this viscosity.
We have also been studying these systems with molecular dynamics simulations. These are giving an insight into how the ionic liquid ions behave in electric fields.

Ionic liquids (IL) are drawing increasing and considerable attention in the field of catalysis as perfect, non-volatile, thermally stable solvents and media for liquid phase selective reactions [1]. We represent here examples from the catalytic chemistry, where ILs has been successfully used for improving two industrially important reactions.
Well-known commercial synthesis of terephthalic acid (TPA) is based on aerobic oxidation of p-xylene in acetic acid solution of the Co/Mn/Br catalyst, that followed by the cost and energy-consuming hydropurification of the crude TPA product from p-carboxybenzaldehyde (4-CBA) [2]. We showed that addition of ILs (dialkylimidazolium acetate and bromide) and ammonium acetate changes properties of the conventional solvent to improve solubility and accelerate oxidation of 4-CBA to TPA. Efficient combinations of the additives and appropriate reaction conditions have been selected to obtain the target product with 4-CBA content below 25 ppm [3]. Positive effect is caused by excellent solvating ability of ILs for TPA and 4-CBA. The designed catalytic systems can be applied to obtain high-quality TPA just after oxidation stage, without the hydropurification.
The next example is related to the alkylation of benzene with dodecene-1 for production of linear alkylbenzene catalyzed with binary 1-butyl-3-methylimidazolium chloride-aluminum chloride system. This catalyst showed high performance in the synthetic detergent not only from neat dodecene-1, but from the feedstock containing a mixture of C10-C13 alkanes and C10-C13 alkenes. The best results have been obtained when the mole fraction of [BMIM]Cl ionic liquid is around 40%. Furthermore, the optimal reaction conditions, such as benzene/alkene ratio (1.6-3) and temperature (30-40°C), have been found. In this case, a very high 98-99% yield of detergent is achieved [4].

Analytical chemistry is very actively searching for the possibilities of taking into use ionic liquids (ILs), which are completely different from conventional molecular solvents. More and more specific ILs have appeared with the aim to fill the task of a certain application task specific ionic liquids (TSIL) - and this has been a growing trend in analytical applications as well. The design and optimisation of TSILs is becoming a part of good practice in the development of ionic liquids.
Ionic liquids in gas-liquid chromatography have already stepped into the commercialization stage, as listed in catalogues [1]. The great potential of ILs for expanding opportunities of almost all of the separation technologies has been clearly expressed in many publications. In case of micro-extraction, the use of ILs increases the performance and speed of a method and makes it greener in terms of reagents consumption [2]. Even in analytical methods like liquid chromatography and electrophoresis, where ILs are used mostly as ordinary salt additives, the structural novelty of these compounds is supplying a wider range of interaction modalities [3].
In liquid chromatography there are examples of the use of pure ILs as eluents, which were considered impossible in the past [4]. With unique elution pattern, they are showing a new potential of ILs application. In this case, the use of ILs increases the performance of a method and makes it greener in terms speed and reagents consumption. Here, the design of functional ILs with suitable physico-chemical properties is also the key issue.
A rapidly emerging field in analytical research is the development of sensors and diagnostic devices, where use of ILs as alternatives to molecular solvents and conventional materials are increasing sensitivity, selectivity, and limits of analysis detections [5].
However, there are some areas in analytical chemistry, like mass spectrometry, which have experienced loss of inflated expectations. It means only slowing down the development to look at things from other angles, and working towards a second generation of methods and materials.

Several studies on the toxicity and environmental impact of ILs have raised questions about their real "greenness". However, despite that, ILs have a great potential for green chemistry solutions that needs to be realized. Moreover, since relevant physico-chemical and biological properties, including toxicity and biodegradability, can be modified and optimized through a rational design, ILs should represent a continuous stimulus and an endless challenge to chemists.

This presentation highlights two recent developments of our group using ionic liquids as bulk liquid phase in industrially relevant, new process concepts. The first part of the presentation is dedicated to the role of an IL sorbent during the catalytic hydrogenation of CO₂ to methanol. This reaction is limited under stoichiometric conditions to around 20 % methanol yield by the equilibrium (75 bar total pressure, 250 °C). However, in the presence of an IL that absorbs both methanol and water under reaction conditions, significantly higher overall MeOH yields can be realized. This new application of IL sorbents has been demonstrated on a 5 L reactor scale with a continuous methanol production rate of more than 50 g per hour.
The second part of the presentation deals with a novel liquid-phase technology to convert lactic acid from fermentation to bio-acrylic acid. Acrylic acid is a major industrial chemical that is so far exclusively produced by a two-step oxidation process from propene. Selective conversion from biomass via lactic acid promises a strong reduction of the CO2 footprint, but also higher productivity under much milder conditions. The new process applies a bromide ionic liquid reaction medium to realize a nucleophile assisted dehydration process in hitherto unreached selectivity and yield.[2, 3]

Carbon Capture in Molten Salts (CCMS) is a method for extracting CO₂ from a variety of flue gases related to power generation and industrial processes [1-3]. It is based on a well known principle called calcium looping, where CaO reacts with CO₂, forming CaCO₃ in a reactor chamber at temperatures well below 900°C. By moving the formed carbonate to another chamber and raising the temperature above 900°C, CaCO₃ decomposes - driving CO₂ off in a controlled manner reforming CaO. Solid sorbents may be moved between chambers by applying fluidized bed principles. In CCMS, the active chemicals are present as dissolved or partly dissolved in an inorganic molten salt. The salt is frequently based on CaCl₂, with additions such as CaF₂ or NaF to suit specific needs with regards to capture efficiency, handling, and costs. In this paper we report on the most recent developments in CCMS technology as well as the economical aspects of using this method for capturing carbon from industrial flue gases. By dissolving and suspending the CaO and CaCO₃ in a molten salt, very rapid reaction kinetics are experienced due to catalytic properties exhibited by the molten salts. This is evidenced by activity coefficients for CaO and CaCO₃ being substantially above unity. This enables more efficient absorption than in systems based on sorption in the solid state.

There are a very small number of molten halides, which have negative temperature coefficients of electrical conductivity, starting from the salt melting point [1]. We have established [2] that among them are the melts of ZrCl4 and HfCl4, existing only in the narrow (a few tens of degrees) temperature range at high (22-58 atm) pressures of saturated vapors.
According to the only publication on this subject [3], the electrical conductivity of molten InCl₃ also decreases as the temperature increases. This substance melts at 5820 under the vapor pressure of 12 atm, and there is no published data on the critical point of the melt. It is assumed [4] that the structure of molten indium trichloride is intermediate between the molecular configurations of InCl₃, In₂Cl₆, and the network structure of molten YCl₃-type.
Our experimental data on the electrical conductivity of molten InCl₃, obtained in a wider temperature range (589-736 °C) than in [3] in a special capillary-type quartz cell with tungsten electrodes, confirm the Klemm's information [3] on the negative temperature coefficient conductivity of the melt, but deviate by 2-7% to the higher values. With a good approximation (R2 > 0.998) our experimental data are represented by the equation:
k = 0.89545 - 3.3764*10-4*T - 2.3178*10-7*T₂ , S/cm; T, K.
The density, molar conductivity, and activation energy of molten InCl₃ were calculated. The reasons for the appearance of negative temperature coefficients of conductivity polytherms of molten salts are discussed.

The aim of this work is to provide the experimental basis for the development and verification of the model of electrical conductivity of complex molten mixtures based on LiCl-KCl. This communication is a continuation of our work [1]. Such mixtures are formed at the anodic dissolution of spent nuclear fuel into the molten LiCl-KCl eutectic. To achieve this goal, we measured the electrical conductivity of molten mixtures of LiCl-KCl eutectic with CeCl₃, NdCl₃ and CeCl₃ + NdCl₃ (1:1). The measurements were carried out over the entire concentration and in wide temperature (up to 800-950°C) ranges. The lower temperature of the measurements was 5-10 degrees below the liquidus temperature of all compositions in order to fix the onset of the crystallization temperature.
The electrical conductivity of all melts increases with temperature and decreases as the concentration of trichlorides increases. The specific electrical conductivity (S/cm) of a number of molten mixtures of LiCl-KCl eutectic with CeCl₃ and NdCl₃ is exemplified below:
k = -3.8121 + 8.5652*10-3T - 2.8313*10-6T2, (752-1076 K) 10mol.% CeCl₃ + 10mol.% NdCl₃; k = -3.7858 + 6.8563*10-3*T - 1.7911*10-6*T2, (890-1122 K) 50.8 mol.% CeCl₃ ; k = -2.8669 + 4.5885*10-3*T - 8.2555*10-7*T2, (981-1102 K) 80 mol.% NdCl₃.
For the mixtures under study, the density was estimated and the molar conductivity was calculated. In all molten (LiCl-KCl)eut. - LnCl₃ mixtures studied, the significant negative deviations (up to -40% in maximum) of molar conductivity from additive values were observed over the whole concentration range, indicating a strong complexation in the systems.

Carbamide melts have found applications as electrolytes for electrochemical treatment of metals [1]. The possibility of electrodeposition of refractory metals from carbamide melts at 1350°С has been examined for molybdenum as an example. When studying the electrochemical behaviour of molybdenum oxide and its compounds (MoO₃, Li₂MoO₄, Na₂MoO₄, K₂MoO₄ or CaMoO₄) in molten carbamide, it can be concluded that maximum limiting currents are typical of the system (NH₂)2CO-Na₂MoO₄. Micron Mo coatings on nickel cathodes and metallic Mo powder have been obtained by the electrolysis of the molten system (NH₂)₂CO-Na₂MoO at current densities of 10-20 mA/cm².

Molten salt technology [1] has very diverse applications. Interest in the use of molten salts in industrial processes is continually increasing, and these media are gradually becoming accepted as a normal field of chemical engineering. Applications include extraction of metals, as well as heat and surface treatment of metals and alloys. In the field of energy, molten salts are commonly used as a medium for high-temperature batteries, fuel cells as well as for nuclear and solar energy systems. They play a crucial role for heat transfer and energy storage in nuclear and solar energy systems.
Molten salt reactors might spell a nuclear energy revolution. A molten salt reactor (MSR) is a type of nuclear reactor that uses liquid fuel instead of the solid fuel rods used in conventional nuclear reactors. Using liquid fuel provides many advantages in safety and simplicity of design.MSRs are a huge departure from the conventional reactors most people are familiar with. Key features include: unparalleled safety, a solution to nuclear waste and stockpiles of plutonium, abundant energy cheaper than energy from coal, load following solar and wind power, abundant energy for hundreds of years, replacement of fossil fuels where wind and solar are problematic (CO₂ -free liquid fuels).
Molten salts are also excellent materials for thermal energy storage for high-efficiency solar power facilities. Among the different types of thermal energy storage, one can be realized through two different phenomena associated with materials that produce storage. This is known as storage by sensible heat and latent heat storage. Sensible heat of molten salts is also used for storing solar energy at a high temperature. Molten salts can be employed as a thermal energy storage method to retain thermal energy. Presently, this is a commercially used technology to store the heat collected by concentrated solar power (e.g., from a solar tower or solar trough). The heat can later be converted into super-heated steam to power conventional steam turbines and generate electricity in bad weather or at night. Various eutectic mixtures of different salts are used (e.g., sodium nitrate, potassium nitrate and calcium nitrate).

The transformation of biofeedstock into higher value bulk and fine chemicals is of paramount importance to become fully independent of fossil fuels. Using homogeneous catalysis for such valorization processes allows for highly selective transformation to be carried out under mild conditions.
Here, we demonstrate the use of homogeneous PNP transition metal complexes for catalyzing a range of biofeedstock valorization processes. In addition, we show how this catalyst type may be used for hydrogen storage in organic compounds.
For example (bio)ethanol may be transformed to to sodium acetate, ethyl acetate, or butanol. Likewise, potassium lactate is produced from glycerol and gamma-valerolactone is made from levulinates.
Furthermore, we show how methanol, (bio)ethanol, isopropanol, glycerol, sugar alcohols, and carbohydrates all are well tolerated substrates for extruding hydrogen molecules.

Ionic liquids are complex Coulombic fluids with many interesting physico-chemical properties. However, experimental results are often difficult to interpret in terms of cationic and anionic contributions. In addition, the impact of particular functional groups, of the chain length of the cations or of different compositions of ionic liquid mixtures, is unclear. Consequently, fundamental knowledge on the modes of interaction between the ions is appreciated for the design of more efficient ionic liquid combinations for a particular application [1].
Here, simulations on quantum-mechanical as well as on molecular dynamics level may help to decompose the overall behavior of the ionic liquid mixtures into contributions of interest, e.g. cationic/anionic/co-solvent, translational/rotational/vibrational, permanent and induced dipoles, hydrogen bonded networks, ionic clusters, etc. [2,3]. Furthermore, hypotheses on corresponding mechanisms can be tested individually for their validity [4].
In this talk we will discuss the advantages and limits of several computational methods to predict and interpret various physico-chemical properties with an emphasis on equilibrium and non-equilibrium molecular dynamics simulations [5].

Hydrogen is an attractive energy vector for future renewable energy systems [1]. Using novel Liquid Organic Hydrogen Carrier (LOHC) systems, hydrogen can be chemically bound/released through catalytic hydro-genation/dehydrogenation, and thus be stored and transported efficiently under ambient conditions [2]. This simplifies handling and enables transport and storage using already existing infrastructure for liquid fuels, resulting in reduced investment cost for implementation [3]. However, due to high dehydrogenation enthalpies, reactions are often performed above 300 °C, which possess a challenge for heat integration with state-of-the-art PEM fuels for clean energy production [4].
In this work, reversible catalytic hydrogenation/dehydrogenation of N-functionalized heterocycles are demonstrated as efficient LOHC systems operating as low as 120 °C. Catalytic dehydrogenation with a homogeneous hydrogenation iridium catalyst in biphasic reaction mode using a molten salt as catalyst immobilization phase has been investigated. This approach facilitated easy catalyst separation and required only a small amount of catalyst phase to store large amounts of hydrogen, which is beneficial for future large-scale continuous hydrogen storage and release.

The metal product of the electrolytic reduction of oxide spent nuclear fuel in molten LiCl-Li₂O mixtures retains about 8-30 wt% of the residual LiCl-Li₂O salt. The salt occluded in the uranium metal should be removed by vacuum distillation.
The purpose of this work is to study the distillation of the LiCl-Li₂O mixture (without uranium).
We have tested different distillation regimes. The distillation of LiCl-Li₂O melts (3 wt.%) was carried out in quartz tubes at 750-800°C and the pressure of (1-3)*10-2 mm Hg for 30-70 min. Herewith, the initial mixture was kept in the MgO crucible. The crucible was weighed before and after the experiment. The salt remaining in the crucible and the sublimates were analyzed for Li₂O content. The amount of Li₂O was determined by titration of the aqueous solutions of the salts with a pH meter, and also by ICP-AES.
The results of our studies do not confirm the conclusions of ref. [1] on the significant co-evaporation of hardly volatile lithium oxide together with more volatile LiCl during distillation.
In our experiments, the fraction of evaporated lithium oxide remained insignificant (less than 1-3%), regardless of the fraction of evaporated LiCl (25-95%).
The loss of large amounts of Li₂O from the initial mixture of LiCl-Li₂O is possible either with spattering of the melt in the case of rapid evaporation of LiCl, or as a result of a side reaction of the uranium metal oxidation with Li₂O in residual salts: U + 2Li₂O * UO₂ + 4Li. This reaction becomes probable at temperatures above 850-900°C due to the evaporation of metallic lithium at such temperatures.

Ureas are important compounds found in the structures of a large number of biologically active compounds and widely used as agrochemicals, dyes, antioxidants, and HIV inhibitors, as well as key intermediates in organic synthesis [1]. Ureas can be prepared via the oxidative carbonylation of amines in the presence of a Pd-complex catalyst, usually at high pressure and temperature and under an explosive CO/O₂ gas mixture making the overall system unsafe [2]. Accordingly, it is desirable to develop an active catalytic system applicable for the oxidative carbonylation of amines under milder reaction conditions.
Ionic liquids (ILs) can have beneficial effects in many homogeneously catalyzed reactions [3]. Furthermore, the use of ILs in liquid-liquid biphasic reactions makes processes in many cases greener than when using traditional organic solvents, due to associated advantages such as low vapor pressure, as well as good thermal stability, tunable solubility, and coordination properties [4]. In addition, such systems provide good separation of reaction products and catalyst recovery.
In this work, we present a new efficient, robust, and versatile Pd-complex/IL catalytic biphasic system for the oxidative carbonylation of aromatic amines under mild reaction conditions [5]. Reaction parameters, including oxidant agent, pressure, temperature, catalyst and IL loading were optimized, resulting in a catalytic system which operates under mild conditions, is fully recyclable, is 100% selective and has activity two orders of magnitude higher than previously reported systems [6].

Energy consumption is one of the most challenging issues that humankind is facing. Approximately 20% of the world's energy is used for lighting. It is therefore important to reduce the energy consumption of lighting devices and increase their efficiency. For that reason, the old incandescent lamp which has been used for illumination for over 130 years is being phased out in most countries. The most common replacement are CFLs (compact fluorescent lamps), which have certain drawbacks related to the mercury content. LEDs (light emitting diodes) have become competitive for illumination as energy efficient lighting sources. However, it is now realized that both CFLs and LEDs rely on materials like rare earths, gallium and indium that bear a severe supply risk. Thus, there is a significant driving force to look for alternative lighting sources. The discovery of OLEDs (organic light-emitting diodes) marks a significant progress in this direction. However, one of the major drawbacks of OLEDs for lighting applications is their complex device architecture and air-sensitivity which makes them expensive to manufacture and prone to de-composition. The alternative, LECs (light emitting electrochemical cells) can be as simple as being only composed of a light emitting material sandwiched between two electrodes (one reflective electrode: widely the cathode and a second transparent electrode: usually the anode to allow light to exit the device) and LECs are promising as a low cost large area future lighting technology which allows overcoming the problems of OLEDs. Ionic liquids play a key role to enable this still young technology. One of the key challenges is to develop ionic, ionic liquid-based, efficient emitter materials that have a significant lifetime need to be provided for this technology to enter the market. Ionic Ir(III) complexes are the most promising emitters in light emitting electrochemical cells (LECs), especially in the high energy emission range for which it is difficult to find emitters with sufficient efficiencies and lifetimes. To overcome this challenge, the concept of intramolecular π-π-stacking of an ancillary ligand (6-phenyl-2,2'-bipyridine, pbpy) is introduced in the design of a new green emitting iridium ionic transition metal complex with a fluoro-substituted cyclometallated ligand, 2-(4-fluorophenyl)pyridinato (4Fppy). [Ir(4Fppy)2(pbpy)][PF6] has been synthesized, characterized and its photophysical and electrochemical properties have been studied. The complex emits green light with maxima at 561 and 556 nm under UV excitation from powder and thin film, respectively, and displays a high photoluminescence quantum yield (PLQY) of 78.5%. [Ir(4Fppy)2(pbpy)][PF6] based LECs driven under pulsed current conditions showed under an average current density of 100 A m-2 (at 50% duty cycle) a maximum luminance of 1443 cd m-2, resulting in 14.4 cd A-1 and 7.4 lm W-1 current and power efficiencies, respectively. A remarkable long device lifetime of 214 hours was observed. Reducing the average current density to 18.5 A m-2 (at 75% duty cycle) led to an exceptional device performance of 19.3 cd A-1 and 14.4 lm W-1 for current and power efficiencies, an initial maximum luminance of 352 cd m-2 and a lifetime of 617 hours.

The conventional synthesis of functional materials relies heavily on water and organic solvents. Alternatively, the synthesis of functional materials using or in the presence of ionic liquids represents a burgeoning direction in materials chemistry [1]. Ionic liquids are a family of non-conventional molten salts that can act as both templates and precursors to functional materials, as well as solvents. They offer many advantages, such as negligible vapor pressures, wide liquidus ranges, good thermal stability, tunable solubility of both organic and inorganic molecules, and much synthesis flexibility. The unique solvation environment of these ionic liquids provides new reaction media for controlling the formation of porous materials and tailoring morphologies of advanced materials. Challenges and opportunities in using ionic liquids for synthesizing functional materials in energy-related applications will be discussed.

Fluorides of metals with low neutron capture cross-section are usually considered as a basis for the fuel compositions of the molten salts nuclear reactor of IV generation. The advantages of chloride systems can be attributed to less aggressiveness towards the reactor material and lower melting temperatures. However, the chloride systems, compared to the fluoride systems, have higher vapour pressure and a low thermodynamic stability at high temperatures. Therefore, in order to ensure a more reliable operation of new generation reactors, it is advisable to consider the features of the reciprocal chloride-fluoride systems. Some additional problems exist in the manipulation with the multicomponent reciprocal systems: recalculation of the concentrations and dividing of the polyhedral complexes into the simplexes. Relation between the mass-centric coordinates in multicomponent salt systems have been considered in [1]. Tetrahedration of the quaternary reciprocal systems with the inner diagonals were discussed in [2-3]. Later, an algorithm for topological correction of lists of simplexes of different dimensions for polyhedration of multicomponent systems was formulated [4], and has been used to correct the published data on the quaternary reciprocal systems with the inner diagonals and with some variants of tetrahedration [5]. In this paper, this technique is used to divide the complex Li,Na,U||F,Cl with the 2 congruently melting binary compounds R1=3NaFa*UF₄ and R2=7NaFa*6UF₄ into the simplexes. First variant of tetrahedration with the inner diagonal LiF-UCl₃ and 3 diagonals from the top NaCl produces 5 simplexes: LiF-NaF-NaCl-R1, LiF-UF₄-NaCl-UCl₃, LiF-UF₄-NaCl-R2, LiF-LiCl-NaCl-UCl₃, LiF-NaCl-R1-R2. Second variant with the same inner diagonal and 3 diagonals from the top UCl₃ produces 5 simplexes too: LiF-LiCl-NaCl-UCl₃, LiF-UCl₃-R1-R2, LiF-NaF-NaCl-UCl₃, LiF-NaF-UCl₃-R1, LiF-UF₄-UCl₃-R2. To search the low-temperature solvents parameters, the nonplanar tie-lines method are used [6].

Dissolution reactions of transition metal oxides (e.g. V₂O₅, Nb₂O₅, MoO₃, WO₃) in molten pyrosulfate, and formation of the corresponding molten metal oxosulfato complexes [1-4] have expanded our knowledge on coordination chemistry of the pertinent transition metals, and provided a very useful family of coordination complexes as reference compounds for understanding the molecular structure of supported metal oxides, commonly used as catalysts [5]. Herein, we show that the oxide of a heptavalent transition metal, Re₂O₇ (m.p. 297°C), undergoes likewise a reaction-induced dissolution in molten potassium pyrosulfate. Large amounts of Re₂O₇ can be dissolved in molten K₂S₂O₇ (i.e. a mixture with X(Re₂O₇) = 0.5 fuses readily at 260°C). The structural and vibrational properties of molten Re(VII)I oxosulfato complexes formed in binary Re₂O₇-K₂S₂O₇ (as well as ternary Re₂O₇-K₂S₂O₇-K₂SO₄) molten mixtures under O₂ atmosphere and static equilibrium conditions are studied by Raman spectroscopy at temperatures of 260-470°C. The corresponding composition effects are explored in the X(Re₂O₇) = 0 - 1 range. A quantitative exploitation of the relative Raman band intensities, due to the species present at static equilibrium, allows to determine the stoichiometry of the reaction taking place in the binary system [Re₂O₇ + nS₂O₇(2-) = C(2n-)] pointing to n = 1. Temperature and composition dependent evolutions of molecular structures and configurations are discussed and consistent band assignments are proposed.

The palladium-catalysed reaction between aryl halides or vinyl halides and alkenes in the presence of a base — referred to as the Heck reaction — facilitates the carbon-carbon coupling with preservation of double bond. Next to the common VOC solvents, ionic liquids (ILs) have shown great potential for Heck reaction under homogeneous conditions.[1,2] However, for the recycling of expensive metal heterogenization, this system becomes a necessity. One of the potential methods includes supporting Pd complexes and an ionic liquid in a form of Supported Ionic Liquid Catalyst (SILCA) while avoiding the use of toxic and expensive ligands.
In a present study, we designed new silica supported catalyst with the nitrogen-rich ionic liquid layer that can ligate active palladium. Through the multiple anchoring points, leaching of the metal was suppressed, and catalyst activity was preserved. Optimization was done by changing the support, metal sources, and varying anion-cation parts of ILs. Remarkable activity in different Heck reactions was demonstrated. In order to get a full understanding of the catalyst structure and behaviour, it was characterised by means of nitrogen physisorption, TGA, XRD, FT-IR, solid-state NMR, XPS, SEM and ICP-MS.

It was almost 50 years ago, during my study of Chemical Engineering (Civil Engineer) at the Technical University of Denmark (DTU), that I was "baptised" in molten alkali chloroaluminates in the group of Prof. Niels Bjerrum. Since then, I have stayed faithful to molten media for nearly the entirety of my scientific career.
Firstly, my PhD degree (Licentiatus Technices at that time...) concerned unusual oxidation states of the chalcogenes in molten chloroaluminates. Selected experimental results covering rare oxidation states like +1/2, + 1/4 and +1/8 of pure Sulfur, Selenium, and Tellurium species will be highlighted here.
At the end of the 1970's I turned to catalysis in molten salts, with a special focus on the chemistry of the sulfuric acid catalyst, the key material for the production of the most important chemical at the tonnage scale in the world - at that time as well as now. For the following 35 years, more than 60 journal publications and a large number of reports described the efforts of me and my numerous collaborators and students. The most important results will be shown, including the discovery of the complex and compound chemistry Vanadium in molten alkali pyrosulfate melts, and the state-of-the-art reaction mechanism modelling the working sulfuric acid catalyst. In addition, our in-situ and operando investigations of commercial industrial catalysts have been essential to link our ex-situ results to the "real world", and our efforts to achieve the global goal of the catalyst producers - the low temperature sulfuric acid catalyst- allowing more economic and sustainable sulfuric acid production, will also be highlighted.
My educational background as a chemical engineer that focused on organic chemistry during my Master's and on inorganic chemistry during the PhD, combined with my Master thesis on "Hydroformylation by Rh-phosphine Catalysis" (modified Shell Process) was probably essential to me joining the early efforts of research and application of ionic liquids from year 2000. Shortly after, our first results on Supported Ionic Liquid Phase (SILP) continuous flow catalysis were published, regarding Rh-phosphine complexes dissolved in ionic liquids and subsequent impregnated in meso porous inorganic supports. This concept – parallel to the sulfuric acid catalyst also being a Supported Liquid Phase (SLP) catalyst during operation- allowed continuous conversion of gas phase olefins with H₂ and CO to gas phase aldehydes, since no evaporation of solvent or catalyst took place. Thus, an attractive design of the otherwise batch operated Oxo process was provided– a concept that whose commercialization is currently being attempted by, among others, our group and an European industrial partner. Subsequently, we have also applied the SILP concept to other important catalytic industrial processes, like carbonylation of methanol to acetic acid (our patent acquired by an European chemical company), in addition to alkoxycarbonylation of alkenes (important for e.g. MMA production), and also in the Water-Gas-Shift (WGS) process through collaboration with FAU (Erlangen, DE) and the European industry . Selected results of our SILP catalyst research and applications will also be shown at this occasion. In addition, we have recently extended the SILP concept to continuous gas separation and encircled appropriate ionic liquids and porous supports for the selective reversible absorption of gasses like CO₂, NO_x, SO₂ and H₂S. Our fundamental results and the possible application of these selective SILP filters to e.g. CO₂ capture, flue gas cleaning, biogas and natural gas sweetening – pursued industrially together with a Nordic partner – will be described as well.
In conclusion, the importance of the concept "From Molecular Understanding to Industrial Application" – the motto of our research center at DTU (Centre for Catalysis and Sustainable Chemistry) - should be obvious from our achievements so far and undoubtedly also in the future.

Nitrogen oxides (NO_x) are formed in combustion processes and are known to cause acid rain and to promote the formation of smog [1]. NO_x emissions are under increasing legislative control, and improved technologies for preventing NO_x emissions are needed. In particular, the areas of biomass fired boilers and mobile sources of NO_x emission have proven challenging for the traditional vanadia-based catalyst, and low-temperature DeNOx technologies are attractive.
Selective Catalytic Reduction of NO_x by NH₃ (SCR) can be utilized to minimize the emission of NO_x. The catalysts used for SCR are mainly vanadia, copper, or iron based. The formation of N₂ and H₂O can be obtained at a much higher rate, when NO₂ is present during the SCR process [2]. This is known as fast SCR and can be an important step in implementing more efficient SCR technologies, including low-temperature processes for tail-end application. During the investigation of Supported Ionic Liquid Phase (SILP) based catalysts to oxidize NO, it was discovered that the addition of alcohol could promote the NO oxidation to NO₂ [3]. A silica-based 1-butyl-3-methylimidazolium nitrate, [BMIM][NO₃], SILP material was prepared and tested under various conditions, including various temperatures (0-120°C), varying NO concentration and the addition of methanol. Preliminary results show significant conversion of NO to NO₂ can be obtained in continuous flow at ambient temperatures and high water content. The dependence on setup and optimum flow conditions are currently being investigated.

Application of functional elements and nanostructures on flexible substrates is a promising trend in electronics. Textiles represent material with great potential, whose mechanical properties (high strength, large surface area, lightness, flexibility, easy integrability into clothing) make it unique even in comparison with other flexible substrates [1,2]. Polymerized ionic liquids (PILs) was first reported in 1998, and a brief overview of their properties can be found in [3]. Their electrotransport properties are unique (when compared with other organic substances), as they are purely ionic conductors. Moreover, a majority of them can be considered to be single-ion conductors. PILs are characterized by a large capacity to absorb gases (analytes) with small molecules, especially CO₂ and water. On such absorption, the internal volume of the polymer is modified, and hence mobility of ions changes [4]. In the field of sensing, PILs are often employed in electrochemical sensors [5], but much rarely for sorbents in QCM sensors [6]
This work deals with textile chemiresistors with sensitive layers based on two types of cationic PILs / poly(tetrabutylphosphonium 3-sulfopropylacrylate) and poly(tributylhexylphosphonium 3-sulfopropyl acrylate). It includes: (i) investigation of sensitive layer - electrode contact phenomena by measuring current voltage characteristics; (ii) general characterization of these PILs by impedance spectroscopy; (iii) overview and analysis of DC- and AC- responses of PILs sensors to 10 ppm of methanol (MeOH), nitrogen dioxide (NO₂), 4-bromoacetophenone (4-BAP), diethylmalonate (DEM) and yperite; and (iv) FTIR spectra of PILs— exposed and unexposed— to analyte vapours [7].
Under these circumstances, the DC- responses (SDC) varied from 0.48 to 1.36, and maximum AC- responses (Spa) from 8 to 26 deg. It was shown that sensor dynamics depend mainly on molecular weight of the analyte. Moreover, the magnitude of AC-responses correlates both qualitatively and quantitatively with the dipole moment of the analysed molecule.

The demand for end-of-pipe deNO_x technologies has driven the research for activation and conversion of nitric oxide, NO, at low temperatures compared to the traditional selective catalytic reduction of NO with ammonia.
This study describes the progress made in the absorption and catalytic conversion of NO by ionic liquids. Nitrate based ionic liquids such as BMIM (butyl-methyl-imidazolium) nitrate has proven surprisingly efficient for conversion of NO_x to nitric acid using air as the oxidant.[1,2] The nitric acid is absorbed into the ionic liquid. Desorption can occur in a successive separation step forming commercial grade concentrated nitric acid and a fully regenerated absorber. Using the SILP (Supported Ionic Liquid Phase) technology the ionic liquid is impregnated onto a porous support.
Alternatively, the SILP material can be extruded as monoliths and loaded into a catalyst bed for continuous NO oxidation at low temperature (< 100°C) and high humidity.[3] The technology facilitates the conversion of NO into a mixture of higher oxygenates (NO₂, HNO₂, and HNO₃) for further downstream processing or absorption. Recently[3], we have discovered that small amounts of alcohols injected into the flue gas upstream the SILP material enhances the low temperature oxidation of NO considerably, increasing the effectiveness of the catalyst.
Currently we pursue the invention for gas cleaning application in collaboration with industry.

Carbon dioxide (CO₂) capture is the key to global warming. Advances in CO₂ capture technology are being sought by industries in an attempt to revolutionize the energy sector and divert some of the CO₂ being released from industrial emissions onto greener paths. Among the endless capture technologies, the use of ionic liquids has gained tremendous popularity as a novel environmentally and energy efficient solution. Three different ionic liquids were investigated for their ability to capture CO₂. With the aid of a gravimetric microbalance, their capacity to absorb carbon dioxide was determined experimentally. The ionic liquids explored in this study were a dicyanamide [DCN]-based solvent, and two bis (trifluoro methylsulfonyl)imide [TF₂N] based solvents. Solubilities were examined at readings of 313.15, 323.15 and 333.15K and over a pressure range up to 20 bar. Experimental densities were also measured, and the Henry's law constants, entropy and the enthalpy values were calculated and reported. Three thermodynamic models were used to correlate the data. The Non-Random Two-Liquid (NRTL) model and the Peng-Robinson and Soave-Redlich-Kwong equations of state correlated the data quite accurately. The best ionic liquid in his study, [TDC][TF₂N], was found to be akin to some popular ionic liquids such as [hmim][TF₂N], which makes it an attractive physical solvent for CO₂ removal processes.

Ionic Liquids (ILs, salts that melt below 100 °C) loaded on silica have been studied for gas phase reactions, but they have not been used in solution due to the leaching properties of the ILs and the deactivation of the catalyst. One area where the "Supported Ionic Liquid Phase" (SILP) strategy would be a tremendous advantage would be in the loading of ILs that are intended and necessarily leached in order to carry out their functions, as is the case of ILs of Active Pharmaceutical Ingredients (APIs). We have found that IL-APIs are readily loaded and leached from silica, giving to the material a few advantages, including the ability to deliver these liquid salt drugs in solid form as free flowing powders. This presentation will discuss the loading, leaching, and favorable physical and chemical properties exhibited by these IL-APIs in solid form.

Spectroscopy is an enabling tool to understand structure-reactivity relationships, that can be applied from predicting toxicity of nanomaterials to engineer better catalytic processes. Operando methodology analyzes both, the catalyst structure and its activity/selectivity simultaneously in a cell that is fit for in situ spectroscopy and performs like a catalytic reactor; correlating structure changes with catalytic performance. Some representative works illustrate this. 1-3 We will present a study on the role of additives, support, coverage, hydration and reaction conditions on the states of supported vanadium and its relevance for catalytic reaction and reducibility. This is applied to assess the molecular basis for activation/deactivation and the nature of the catalyst active site for oxide reduction, alkane oxidative dehydrogenation, ammoxidation and for environmental selective catalytic reduction of NOx. We will also illustrate the capacity of real time spectroscopy to understand reaction mechanism for liquid phase reactions,4 like the role of Brønsted Acid Sites (BAS) vs. that of Lewis Acid Sites (LAS) for the acetalization of glycerol into solketal. Mesoporous cellular foams modified to contain exclusively BAS, LAS and combinations thereof illustrate the role of BAS.4 This relevance led us to use novel Brønsted acid ionic liquids (BAILs).5 The transversal nature of the operando approach places it at the junction between fundamental catalytic chemistry and applied chemical engineering. This work is supported by European Commission BIORIMA GA 760928 and Spanish Ministry RIEN2O, CTM2017-82335-R.

Carbon dioxide (CO₂) concentration in the atmosphere surpassed the 400 ppm milestone in 2016 [1], approximately 120 ppm higher compared to the pre-industrial era. Along with the significant increase in the CO₂ level during the past decades, the human race has witnessed unprecedented climate change [2]. Therefore, it is necessary to find an efficient solution for capturing CO₂ from flue gases, in order to cut down anthropogenic CO₂ emissions. There is an increasing interest in polyamines, because they possess multiple reactive sites for high CO₂ uptake capacity, high thermal stability, as well as lower toxicity compared to the today's alternatives. Polyamines have the potential to improve the CO₂ loading, CO₂ absorption rate, and has a lower energy penalty [3, 4].
A reversible CO₂ uptake study was performed in neat pentaethylenehexamine (PEHA) and its aqueous solutions, and the performance was compared with industrially applied aqueous solution of monoethanolamine (MEA). Simultaneously, the relative amount of CO₂ chemisorbed chemical species, such as carbamates/(bi)-carbonates forming, was studied using NMR analysis and a calculation method introduced by Holmes et al. [5]. Furthermore, the CO₂ capture capacity of the solvents, correlated with their respective Kamlet-Taft polarity parameters, and the system were modelled with Linear Solvation Energy Relationship (LSER) approach.
It was observed that CO₂ capture capacity, as well as the nature of chemical species were influenced by water. The LSER calculations represented that amongst the studied Kamlet-Taft parameters, the CO₂ capture capacity merely depends on hydrogen bond acceptor ability (beta) and polarizability (pi). Upon the thermal regeneration study, the pure PEHA was obtained from CO₂ saturated reaction mixture at 120°C. Considering the high CO₂ absorption capacity and very low evaporation rate during regeneration compared to aqueous solution of MEA, PEHA can be used as a sustainable solvent for CO₂ capture in large-scale flue gas cleaning processes.

Despite remarkable developments in ionic liquid technologies with a diverse range of applications, considerably less progress has been made in their preparation. Until today, most hydrophobic prepared in a two-step batch process involves the initial alkylation of an amine or phosphine followed by subsequent metathesis to exchange the anion, a strategy which has already been described in seminal books and reviews on ionic liquids in synthesis in the late 1990s, and has since then remained almost unaltered [1]. Yet a number of critical aspects limits its utility for the large-scale production of hydrophobic ionic liquids in this classical batch process. In parallel to their classical synthesis, the majority of applications of ionic liquids in catalysis is dedicated to batch processes, despite the clear advantages and benefits of a continuous flow set-up.
In here, we present novel strategies for the continuous flow production of ionic liquids, aiming for a fast and halide-free approach that eliminates the need of anion metathesis [2]. Critical aspects of an atom efficient continuous-flow synthesis of ionic liquids, but also of their application in catalysis will be discussed. Eventually, advantages and limitations of continuous flow processes will be highlighted, with a number of processes varying from ionic liquid synthesis to their application as reaction media or catalysts in hydrogen or carboxylation reactions either with bulk or supported ionic liquids [3,4].

Interest in systems with fluoride metals is due to the fact that they have been considered as a potential component for nuclear reactor fuel in molten salts. Three ternary systems of Li,Na,Rb||F, Li,Rb,La||F and Na,Rb,La||F on the boundary of quaternary system Li,Na,Rb,La||F have been analyzed. Model for the 4th boundary Na,Li,La||F was built earlier [1].
Li,Na,Rb||F has the simplest structure. Its eutectic type is complicated by the compound R=LiRbF₂, decaying in the solid phase, and is characterized by two invariant equilibria: eutectic one and decomposing of R (dot Y). Space model includes 3 liquidus surfaces, 3 - solidus, 10 - solvus, 22 - ruled ones, and 2 horizontal complexes at temperatures of E and Y, and has 4 monophase regions (А, В, С, R), 9 - 2-phase (L+A, L+В, L+С, A+B, A+C, B+C, A+R, B+R, C+R) and 7 - 3-phase ones (L+A+В, L+A+C, L+B+C, A+B+C, A+C+R, A+B+R, B+C+R).
System Li,Rb,La||F is complicated by 5 binary compounds: R₁=LiRbF₂ - with the exotermic decaying, and 4 incongruently melting R₂=Rb₃LaF₆, R₃=Rb₂LaF₅, R₄=RbLaF₃, R₅=RbLa₂F₇. Compounds R3, R5 have endothermic decay and exist in the short temperature interval. Space model consists of 7 liquidus surfaces, 31 ruled surfaces, 6 horizontal complexes and includes 10 2-phase regions (L+A, L+B, L+C, L+R2, L+R3, L+R4, L+R5, R1+R2, A+R2, A+R4) and 16 3-phase regions (L+A+B, L+A+C, L+A+R2, L+A+R4, L+B+R2, L+C+R4, L+C+R5, L+R2+R3, L+R2+R4, L+R3+R4, L+R4+R5, A+R1+R2, A+B+R2, A+R2+R4, A+C+R4, B+R1+R2). 2-phase regions R1+R2, A+R2, A+R4 have a degenerated structure in the form of vertical planes.
System Li,Rb,La||F has a similar structure, but is sophisticated by the additional liquidus surface of R1=NaLaF₄. As a result, there are 3 invariant equilibria, 8 liquidus surfaces, 35 - rules ones and 6 horizontal complexes on the boundary of 28 phase regions (L+A, L+B, L+C, L+R1, L+R2, L+R3, L+R4, L+R5, A+R2, A+R4, R1+R4, L+A+B, L+A+R1, L+A+R2, L+A+R4, L+B+R2, L+C+R1, L+C+R4, L+C+R5, L+R1+R4, L+R2+R3, L+R2+R4, L+R3+R4, L+R4+R5, A+R1+R2, A+R2+R4, A+R1+R4, R1+R4+C). Concentration fields in the 4 ternary systems with the different trajectories of phases have been analyzed [2-3].
4 ternary systems are used to forecast a topological structure of T-x-y-z diagram Li,Na,Rb,La||F [4] with 6 binary compounds: R₁=LiRbF₂, R₂=NaLaF₄, R₃=Rb₃LaF₆, R₄=Rb₂LaF₅, R₅=RbLaF₄, R₆=RbLa₂F₇ (R1 decays in solid, R2-R6 - with incongruently melting, and R3, R5 with endothermic decaying). In the ternary systems there are 14 invariant equilibria. For T-x-y-z diagram Li,Na,Rb,La||F it is forecasted 4 invariant 5-phase equilibria with 9 liquidus hypersurfaces.

Ionic liquids (ILs) are composed entirely of ions; however, unlike molten salts, the ions are larger and more complex. Typical ILs include organic cations and mineral, inorganic, or biological anions. The large ions experience reduced Coulombic interactions, frustrated crystal packing, and enhanced entropic contributions that also help to lower the melting point— ILs are liquid at or just above room temperature. ILs are promising solvents and electrolytes with a number of appealing physical and chemical properties. ILs are of particular interest as advanced functional materials and engineering fluids (additives, storage media, fuels, and lubricants) and as electrolytes in electrochemical applications (Li-batteries, supercapacitors, fuel/solar-cells, industrial electrochemistry).

A key feature and advantage of ionic liquids is the potential ability to tailor physico-chemical properties by varying the constituent ions. However, advances in the development and use of ILs are being hampered by an inability to predict, or even rationalise, IL properties. Computational studies can help by establishing a link between the chemical make-up of constituent ions and the resultant properties of an IL. However, ILs also present some difficult aspects in modeling and simulation.
Interactions within ILs are dominated by Coulombic forces; the size and distribution of partial atomic charges is particularly relevant. However, very different charge distributions are generated by different methods. [1] MK and CHelpG charges are based on fitting to the electrostatic potential (ESP); however, the charges produced do not necessarily correlate with the underlying bonding and electronic interactions. NPA and QTAIM charges are based on the electronic density; however, the produced charges generate a poor fit to the ESP. In addition, the quality of the representation provided by each method can be evaluated by comparison to experimentally derived data (NEXAFS, XPS).[2,3] Our goal has been to better understand the dichotomy raised by these apparently opposing "charge" distributions and to establish if there is any common ground between the methods.

Upgrading of biogas requires the removal of both CO₂ and H₂S. Amino Acid based ionic liquids (AA-ILs) are known to efficiently remove CO2 by binding to the carboxylate group and DFT studies suggest that H₂S can bind to both the carboxylate and the amine group of the amino acid anion. This study has demonstrated that that indeed two moles of H₂S can bind to one mole of [P4444][Pro] even when a highly dilute stream (750 ppm) is used. Adsorption to the stronger sites (amine groups) is possible even in the presence of a vast excess of CO₂. There is reason to believe that H₂S removal levels of > 90 % could be maintained for several days at a space velocity of 100 h-1 with an H₂S inlet concentration of 750 ppm. Potential pressure drop problems were solved by impregnating the ionic liquid onto mesoporous pellets prepared by a simple and scalable technique. H₂S removal under relatively mild conditions (60 °C, 50 mbar) was unsuccessful and raises concerns about the ability to regenerate [P4444][Pro]. This might also mean that pure CO₂ removal using [P4444][Pro] requires gas streams practically free of H₂S.

Room-Temperature ionic liquids (IL) have been widely studied over the past several years for metal ion extraction, as their unique physico-chemical properties can be adjusted by selecting their ionic components for a specific need. For the extraction of metal ions like actinides (An) and lanthanides (Ln), IL can be used in several ways: as a solvent in the replacement of conventional molecular solvents [1], as an extracting molecule by using task-specific ionic liquid synthesised from a well-known extracting pattern, or as a synergistic agent in a traditional extractant/molecular solvent system [2].
This presentation will be focused on the extraction of actinides and lanthanides, to illustrate how the use of IL can result in higher efficiency and/or selectivity. With the support of spectroscopic techniques, UV-Vis and EXAFS, to identify the nature of extracted complexes and a modelling of the extraction data, we also demonstrate the mechanisms involved in the ion extraction, and compare them with those occurring in conventional extracting systems using molecular solvents. The advantages and drawbacks of the IL use will be discussed.
Typical examples on the use of IL for the An and Ln separation will be presented. First, we will focus on how the extraction of uranium(VI) proceeds in a hydrophobic IL used in replacement of the usual organic solvent. Two extracting systems were investigated, using either TBP or a malonamide extractant. Then, we will present the An(III)/Ln(III) separation using a task-specific ionic liquid based on the CMPO pattern. We show that it allows a sequential separation of U(VI) and Eu(III)/Am(III), just by changing this ligand concentration in the organic phase. Finally, we will show how the extraction of uranium(VI) from nitric acid solutions with TODGA into the molecular solvent dichloroethane can be strongly enhanced by addition of a small amount of the ionic liquid C₄mimTf₂N in the organic phase, by the mean of a synergistic effect [3,4].

X-ray Photoelectron Spectroscopy (XPS) is widely accepted to be a powerful tool to study electrochemically induced changes of the electrode/electrolyte interface as it is very surface sensitive, allows for quantitative analysis and assignment of oxidation states or chemical environment of the detected species. As electrochemical experiments are commonly performed under atmospheric pressure using liquid electrolytes that are not ultrahigh vacuum (UHV) compatible, XPS can usually not be applied directly in the analyser chamber of the spectrometer and one may distinguish three experimental approaches, that are (i) transfer of the electrode into the UHV system via air contact, also referred to ex situ analysis, (ii) transfer of the electrode under inert conditions, also referred to as quasi in situ approach, and (iii) performing electrochemistry directly in the analyser chamber of the spectrometer, also referred to as in situ EC XPS [1]. The in situ approach may be realized using ambient pressure XPS or UHV compatible electrolytes such as ionic liquids (IL). Ionic liquids are also known to provide large electrochemical stability windows making them attractive for electrochemical applications such as electrochemical double layer capacitors (EDLC) [2].
In order to elucidate the electrochemical stability windows of carbon/IL systems in detail, quasi in situ [3] and in situ [4] EC XPS setups were realized. The setups and results as well as recently performed XPS half-cell measurements of IL [5] will be presented and discussed with respect to their opportunities and limits, interfacial processes and interpretation of XPS data.