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This study establishes a preparative route towards a model system for supported catalytically active liquid metal solutions (SCALMS) on nanostructured substrates. This model is characterized by a uniquely precise geometrical control of the gallium particle size distribution. In a SCALMS system, the Ga serves as a matrix material which can be decorated with a catalytically active material subsequently. The corresponding Ga containing precursor is spin-coated on aluminum based substrates, previously nanostructured by electrochemical anodization. The highly ordered substrates are functionalized with distinct oxide coatings by atomic layer deposition (ALD) independently from the morphology. After preparation of the metal particles on the oxide interface, the characterization of our model system in terms of its geometry parameters (droplet diameter, size distribution and population density) points to SiO2 as the best suited surface for a highly controlled geometry. This flexible model system can be functionalized with a dissolved noble metal catalyst for the application chosen.

A new two-stage production route for methanol from biomass is proposed, including hydrogenolysis of methyl formate to methanol. The Cu0.9Al2O4 spinel catalyst is shown to be highly active for this reaction and stable against corrosion by formic acid.

The oxygen functionalized LOHC system benzophenone/dicyclohexylmethanol reveals new possibilities in the field of hydrogen transport and storage.

Isopropanol fuel cells offer an attractive way to provide electric energy from a liquid, easily transportable fuel without producing significant amounts of CO2. The oxidation product acetone can be easily hydrogenated back to isopropanol to close the storage cycle, thereby avoiding the sophisticated handling of fugitive molecular hydrogen. Until now, Direct-Isopropanol Fuel Cells (DIFC) usually rely on various perfluorosulfonic acid ionomers, like Nafion, which are costly and have an unfavorable high fluorine content. Additionally, the dissolution of Nafion in isopropanol/acetone/water solutions within respective applications has prevented the long time operation of DIFCs so far. The swelling of those ionomers during operation promotes fuel crossover and reduces the system's overall energy efficiency. This study uses ionic cross-linking of polymer blends to manufacture chemically stable membranes and introduces a new click-like covalent cross-linking strategy for ion exchange polymers. Compared to Nafion XL, the manufactured membranes increase the maximum power density by up to 10 %, resist a dissolution stress test up to 84 w-% and reduce the detected isopropanol/acetone crossover up to 75/100 % during fuel cell operation. Consequently, the material can be considered a major step toward the technical implementation of isopropanol fuel cell technologies.

Non-precious metal supported catalytically active liquid metal solutions exhibit attractive performance in ethylene oligomerization. It is found for the Ga–Ni system on silica that the performance depends strongly on the applied Ga/Ni ratio. Ga-rich systems forming liquid alloys exhibit a far higher Ni-based catalytic activity than solid intermetallic compounds or Ni nanoparticles., Non-precious metal supported catalytically active liquid metal solutions exhibit attractive performance in ethylene oligomerization.

Lubricant-infused repellent coatings provide efficient repellency against contamination as the lubricant avoids direct contact between the surface and any contaminant to be repelled. Here, we address two mechanisms that potentially cause failure of the coating by loss of the liquid lubricant, and present a strategy for long-lasting coatings. We use ionic liquids as lubricants with extremely low vapor pressure. These are confined to the underlying substrate by means of functionalized polymeric gel that matches the chemical structure of the ionic liquids and thereby maximizes their molecular interactions. We use pentafluorophenol-based active ester polymers to provide a versatile platform that allows a convenient post-synthetic functionalization of the polymer network. The matching functional groups to efficiently bind a desired ionic liquid can thus be introduced via their amine-functionalized analogues, which we demonstrate for imidazole- and phosphonium-based molecules. We copolymerize benzophenone methacrylate for surface attachment and gel formation in one step. At 85 °C the surface and repellency properties remained constant for several months, outperforming thick, swollen PDMS films as the gold standard of lubricant-infused coatings.

This review deals with the chemical storage of green hydrogen in the form of Liquid Organic Hydrogen Carrier (LOHC) systems. LOHC systems store hydrogen by an exothermal catalytic hydrogenation reaction that converts the hydrogen-lean compounds of the LOHC system to their hydrogen-rich counterparts. All compounds of a technically suitable LOHC system are liquids and this offers the advantage of simple logistics of chemically bound hydrogen in the existing infrastructure for fuels. On demand, hydrogen can be released from the hydrogen-rich LOHC molecule in an endothermal catalytic dehydrogenation at low hydrogen pressure (typically below 5 bar). Our contribution deals first with available sources of green hydrogen for a future hydrogen economy and then describes established technical processes to produce clean hydrogen from technically hydrogen-rich gas mixtures. Subsequently, the review focuses on the hydrogenation of aromatic and heteroaromatic compounds as the key step of the LOHC-based hydrogen storage cycle. Special emphasis is given to the hydrogen-charging of hydrogen-lean LOHC compounds with various gas mixtures demonstrating that such a Mixed Gas Hydrogenation (MGH) process offers the technical potential to selectively extract hydrogen in a chemically bound form that enables very efficient hydrogen logistics. In this way, low cost hydrogen sources can be connected to high value hydrogen application, e.g. hydrogen filling stations for clean mobility applications, to enable a future hydrogen economy.

Formic acid decomposition (FAD) generates H2 at low temperatures. However, many known catalyst systems suffer from deactivation due to competing side reactions during FAD. In this work, we focus on the origins of the deactivation of Pd catalysts but also on protocols which allow for reactivation of this precious metal catalyst. We combined batch experiments with results from in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). We find that CO adsorbates block catalytic sites and deactivate the Pd catalyst. Oxidative treatment lifts this inhibition. Additionally, our results show that oxidative pretreatment activates the Pd catalyst, whereas reduction leads to a catalyst which is essentially inactive for FAD.

The kinetics of the acid catalyzed reactions of acetaldehyde ammonia trimer (AAT) and paraldehyde (para) to 2-methyl-5-ethyl pyridine (MEP) in the presence of an acid catalyst were investigated systematically. A reaction model has been developed based on experimental data. With full characterisation of side products it is possible to describe the reaction as a polymerisation and to understand the different reactivity of AAT and para, respectively. A kinetic model to describe the formation of MEP and the side products was developed using operando Raman spectroscopy. The model, involving four main reactions, is able to describe the formation of MEP and side products and incorporates the effects of reactant concentration, temperature and promoter concentration. This model is an important step that allows for further process intensification and evaluation of each of the two reaction routes.

The need to supply significant amounts of heat at the high temperature level required thermodynamically for cycloalkane dehydrogenation has so far been seen as the main hurdle to bring the otherwise highly attractive Liquid Organic Hydrogen Carrier (LOHC) technology to broad technical use. The LOHC technology promises infrastructure-compatible storage and transport of hydrogen in chemically bound form, e.g. for long-term energy storage, global energy logistics and heavy-duty mobility. Our contribution shows that hydrogen release from the hetero-atom free, pure hydrocarbon LOHC compound perhydro-benzyl toluene is possible at temperatures down to 200 °C, if the operation is carried out in a reactive distillation column under reduced pressure. Such low temperature dehydrogenation of hydrocarbon-based LOHC systems facilitates heat integration with waste heat sources and the energetic use of the released hydrogen considerably, and this will greatly enhance the attractiveness of LOHC-based hydrogen storage for many applications.

In this study, the performance of an In2O3/ZrO2 catalyst for hydrogenation of CO2 to methanol is reported in the presence of typical impurities of industrial CO2 feed gas streams. Experiments were performed with defined amounts of SO2, H2S, NO2, NH3 and hydrocarbons purposely added to the reaction mixture under industrially relevant conditions (225–275 °C, 50 bar total pressure, H2 : CO2 = 3 : 1). Comparative studies – with and without added impurities – further relate the observed effects to the behaviour of the commercial Cu/ZnO/Al2O3 methanol catalyst under identical treatments. Elemental analysis was used to determine the amount of sulphur, nitrogen and carbon residing on the catalyst after poisoning and after methanol synthesis. Moreover, temperature programmed desorption (TPD), temperature programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS) allowed identifying potential catalyst poisons formed on the catalyst surface. This work discloses that H2S and SO2 impurities led to drastic deactivation of the In2O3/ZrO2 catalyst (due to indium sulfide and -sulphate formation), while NH3, NO2 and hydrocarbon impurities have no major effect on the methanol production.

We report the highly remarkable discovery that glucose oxidation catalysed by polyoxometalates (POMs) in methanolic solution enables formation of formic acid and methyl formate in close to 100% combined selectivity, thus with only negligible sugar oxidation to CO2. In detail, we report oxidation of a methanolic glucose solution using H8[PV5Mo7O40] (HPA-5) as catalyst at 90 °C and 20 bar O2 pressure. Experiments with 13C-labelled glucose confirm unambiguously that glucose is the only source of the observed formic acid and methyl formate formation under the applied oxidation conditions. Our results demonstrate a very astonishing solvent effect for the POM-catalysed glucose oxidation. In comparison to earlier work, a step-change in product yield and selectivity is achieved by applying an alcoholic reaction medium. The extremely high combined yields of formic acid and methyl formate greatly facilitate product isolation as low-boiling methyl formate (bp = 32 °C) can simply be isolated from the reaction mixture by distillation.

Ir-Complex catalysed hydrogen release/storage using a 2-methylindole/2-methylindoline Liquid Organic Hydrogen Carrier (LOHC) system is shown to be effective in a temperature range of 120 to 140 °C. In the form of a liquid-liquid biphasic reaction system with molten [PPh4][NTf2] as catalyst immobilisation phase, the applied cationic Ir-complex can be easily separated and recycled enabling a small amount of ionic catalyst solution to store/release a large amount of hydrogen.

Renewable energy sources such as wind and solar power generate fluctuating electric energy. To bridge energy-lean times and to utilize the temporal surplus of electricity production large amounts of energy must be stored. One promising approach is the chemical storage in methanol that is formed from renewable H2 from water electrolysis and CO2. In our contribution we demonstrate a way to increase the methanol yields in CO2 hydrogenation significantly by in situ sorption of methanol and water in alkali salt-doped ionic liquids (ILs). The reaction and product sorption take place in a single reactor vessel which shifts the methanol yield from the thermodynamic equilibrium of 25.3% at 75 bar (H2 : CO2 = 3 : 1) and 250 °C up to 60%.

Homogeneous Cr–PNP tri- and tetramerization catalysts were dissolved together with the co-catalyst MAO in the high-boiling, non-polar, aliphatic hydrocarbon perhydro-dibenzyltoluene (H18-DBT). The solution was then dispersed onto different high surface area supports. The resulting solid materials were tested in the gas-phase selective oligomerization of ethylene at 43 °C and pressures between 1 and 14 bar. Low activities were observed at ambient pressure. At ethylene pressures of higher than 3 bar the formed 1-hexene and 1-octene condensed inside the porous system, thereby facilitating the dissolution and redistribution of the Cr–PNP catalyst. Further studies were conducted at pressures up to 35 bar at which a change in the primary reaction selectivity from 1-hexene to 1-octene could be observed. Such a selectivity switch is in accordance with previously reported mechanistic and kinetic studies.

Ru-based supported ionic liquid phase (SILP) systems efficiently catalyze the low- temperature water-gas shift reaction (WGSR). While previous studies suggest that Ru-carbonyl species play an important role in the mechanism, detailed knowledge on the catalytically active species is still missing. To identify these carbonyl complexes, we apply in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) in combination with density functional theory (DFT). Investigations of an as-prepared [RuIJCO)3Cl2]2/ [C4C1C1Im]Cl/Al2O3 catalyst indicate splitting of the dimer induced by Cl−. Subsequently, an equilibrium between several [RuIJCO)xCly]n species is established, in which the IL serves as an effectively infinite Cl− reservoir. We find that the major species in the system freshly-prepared from [RuIJCO)3Cl2]2 is indeed [RuIJCO)3Cl3]−. A smaller amount of [RuIJCO)2Cl3]− and chloride-rich species [RuIJCO)2Cl4]2− or [RuCOCl4]2− are also found in the SILP. Similar Ru-carbonyl species are observed during carbonylation of RuCl3/ [C4C1C1Im]Cl/Al2O3, another potential WGSR catalyst. The response of [RuIJCO)3Cl2]2/[C4C1C1Im]Cl/Al2O3 to heating and/or CO dosing was probed in situ and the results confirm the presence of the equilibrium proposed above.

The pH dependency of the reaction of acetaldehyde and ammonia to form the acetaldehyde-ammonia trimer has been studied in detail. The acetaldehyde-ammonia trimer is a molecule of interest in organic synthesis, since it can be used as a substrate in many reactions involving acetaldehyde or ammonia. This trimer is well known in the literature but no references are present so far to describe its formation from ammonia sources other than ammonium hydroxide. The focus of this study is on describing the course of reaction after addition of acetaldehyde to solutions of ammonia and various acids. Products have been analysed by means of 1H-NMR and IR spectroscopy and the complete range of pH values has been covered. Depending on the pH, two reaction regimes can be distinguished. At high pH, only the trimer is formed. In contrast, at low pH, only low quantities of the trimer are produced and the nature of the applied acid has a distinct effect on the reaction outcome. Inorganic acids result in low trimer concentration and high quantity of unreacted ammonia. Polymer formation dominates with simple carboxylic acids. Complex organic acids, such as e.g. maleic or nicotinic acid, lead to comparable quantities of the trimer and acetaldehyde. Based on our results, we propose some adjustments to the traditional reaction scheme developed for acetaldehyde-ammonia trimer formation at high pH.

In this work, a novel synthesis route to produce 2-methyl-5-ethylpyridine (MEP) from the cyclic acetaldehyde ammonia trimer (AAT) is explored. The reaction was studied in a semi-batch reactor in the presence of different promoters to adjust the pH of the reaction solution. Among various ammonium salts tested as promoters, ammonium acetate was identified as the most suitable promoter for the reaction. By using a Design of Experiments (DoE) approach, the temperature and concentration of reactants and the promoter were identified as the most important/decisive parameters influencing the course of the reaction. Additional mechanistic investigations were carried out to assess the effect of these parameters in detail and to clarify the by-product formation via oligomer formation.

New solid catalysts with ionic liquid layer (SCILLs) were prepared by the coating of heterogeneous Pd/C catalysts with a thin film of acidic liquid: a known chloroaluminate ionic liquid (IL), [BMIM]Cl/AlCl3, and a recently developed liquid coordination complex (LCC), urea/AlCl3. Both coatings improved the activity of Pd/C catalyst against toluene hydrogenation; at lower temperatures (40 °C) the IL-SCILL performed better, whereas at 80 °C the LCC-SCILL gave higher conversion. A thin film of ionic liquid proved to be sufficient to increase activity, while larger volumes of ionic liquid resulted in a decrease in activity due to pore blocking and hence mass transport limitations. Kinetic investigations in batch mode revealed a zero order with respect to toluene concentration, a first order in hydrogen pressure, and activation energy of 64.7 kJ mol−1 for the Pd/C catalyst. The SCILL catalysts had slightly lower values of 53.1 kJ mol−1 for [BMIM]Cl/AlCl3 and 61.4 kJ mol−1 for urea/AlCl3, respectively.

The catalytic hydrogenation of the LOHC compound dibenzyltoluene (H0-DBT) was investigated by 1H NMR spectroscopy in order to elucidate the reaction pathway of its charging process with hydrogen in the context of future hydrogen storage applications. Five different reaction pathways during H0-DBT hydrogenation were considered including middle-ring preference (middle-side-side, MSS), side-middle-side order of hydrogenation (SMS), side-ring preference (SSM), simultaneous hydrogenation of all three rings without intermediate formation and statistical hydrogenation without any ring preference. Detailed analysis of the 1H NMR spectra of the H0-DBT hydrogenation over time revealed that the reaction proceeds with a very high preference for the SSM order at temperatures between 120 °C and 200 °C and 50 bar in the presence of a Ru/Al2O3-catalyst. HPLC analysis supported this interpretation by confirming an accumulation of H12-DBT species prior to full hydrogenation to H18-DBT with middle ring hydrogenation as the final step.

We show that both tetraphenylphosphonium bis(trifluoromethylsulfonyl)imide ([PPh4][NTf2]) and Cs[NTf2] are low melting salts of exceptionally high and also very similar thermal stability. This similarity indicates that the thermal stability is dominated by the anion. Moreover, eutectic mixtures of [PPh4][NTf2] and Cs[NTf2] with melting points below 100 °C are presented. Surface analysis of the latter in the liquid state reveals a surprising depletion of [PPh4]+ ions from the surface.

The selective oxidation of complex, water-insoluble and wet biomass from second and third generation to formic acid including effective catalyst recycling is reported. Additionally, the relevance and limits of potential contaminants are illustrated by different experimental approaches. By using a very robust homogeneous polyoxometalate catalyst in aqueous solution, molecular oxygen as an oxidant and an acid as a solubilizer, it is possible to convert different lignocellulosic and algae feedstock into formic acid and pure carbon dioxide. The applied green oxidation system benefits from its low reaction temperature (below 100 °C) and its very selective nature. Furthermore, catalyst recycling over three batches has been successfully carried out.

Liquid Organic Hydrogen Carrier (LOHC) systems offer a very attractive way to store and transport hydrogen, a technical feature that is highly desirable to link unsteady energy production from renewables with the vision of a sustainable, CO2-free, hydrogen-based energy system. LOHCs can be charged and discharged with considerable amounts of hydrogen in cyclic, catalytic hydrogenation and dehydrogenation processes. As their physico-chemical properties are very similar to diesel, today's infrastructure for liquid fuels can be used for their handling thus greatly facilitating the step-wise transition from today's fossil system to a CO2 emission free energy supply for both, stationary and mobile applications. However, for a broader application of these liquids it is mandatory to study in addition to their technical performance also their potential impact on the environment and human health. This paper presents the first account on the toxicological profile of some potential LOHC structures. Moreover, it documents the importance of an early integration of hazard assessment in technology development and reveals for the specific case of LOHC structures the need for additional research in order to overcome some challenges in the hazard assessment for these liquids.

A particularly suitable reactor concept for the continuous dehydrogenation of perhydro-N-ethylcarbazole in the context of hydrogen and energy storage applications is described. The concept addresses the fact that dehydrogenation is a highly endothermic gas evolution reaction. Thus, for efficient dehydrogenation a significant amount of reaction heat has to be provided to a reactor that is essentially full of gas. This particular challenge is addressed in our study by the use of a catalyst-coated (Pt on alumina), structured metal reactor obtained by selective electron beam melting. The so-obtained reactor was tested both as a single tube set-up and as a Hydrogen Release Unit (HRU) with ten parallel reactors. In stationary operation, the HRU realized a hydrogen release capacity of 1.75 kWtherm (960 Wel in a subsequent fuel cell) with up to 1.12 gH2 min−1 gPt−1 and a power density of 4.32 kWel L−1 of HRU reactor.

The complexes [(mall)Ni(dppanis)][SbF6] (mall = methallyl, dppanis = (2-methoxyphenyl)diphenylphosphine) 1, [(mall)Ni(PPh3OC10)][SbF6] (PPh3OC10 = (2-decyloxyphenyl)diphenylphosphine) 2, and [(mall)Ni(PPh3OdiMePh)][SbF6] (PPh3OdiMePh = (2-(2,6-dimethylphenoxy)phenyl)diphenylphosphine) 3 were immobilized as Supported Ionic Liquid Phase (SILP) catalysts and applied for the tandem dimerization/isomerization of ethylene to 2-butene in a fluidized bed reactor. The better heat removal in the fluidized bed improves the catalyst stability and allows for a more detailed investigation of the deactivation mechanism. Based on kinetic studies, a second order deactivation mechanism is proposed, in which two nickel complexes dimerize if the supply of ethene is insufficient.

Different Keggin-type polyoxometalates have been synthesized and characterized in order to identify optimized homogeneous catalysts for the selective oxidation of biomass to formic acid (FA) using oxygen as an oxidant and p-toluenesulfonic acid as an additive. Applying the optimized polyoxometalate catalyst system H8[PV5Mo7O40] (HPA-5), a total FA-yield (with respect to carbon in the biogenic feedstock) of 60% for glucose within 8 h reaction time and 28% for cellulose within 24 h reaction time could be achieved. The transformation is characterized by its mild reaction temperature, its excellent selectivity to FA in the liquid product phase and its applicability to a very wide range of biogenic raw materials including non-edible biopolymers and complex biogenic mixtures.

Nickel(II) complexes with double alkyl chain functionalized N-heterocyclic carbene (NHC) ligands, [NiCl2(C12MIM)2] and [NiCl2(C12C12IM)2], where C12MIM = 1-dodecyl-3-methylimidazolin-2-ylidene (1) and C12C12IM = 1,3-didodecylimidazolin-2-ylidene (2), have been prepared and fully characterized by 1H NMR, 13C NMR, and CHN elemental analyses. Furthermore, we have developed a system, in which double long alkyl chain derivatized Ni–NHC complexes are dissolved in the related ionic liquid crystalline 1,3-didodecylimidazolium tetrafluoroborate, [C12C12IM][BF4], to form pre-organized structures for enhanced reactivity. Remarkably, differential scanning calorimetry, polarized optical microscopy, and temperature-programmed IR reflection absorption spectroscopy performed on a mixture of 10 wt% Ni complexes in [C12C12IM][BF4] demonstrate that this system retains an ionic liquid crystalline phase; even after immobilization onto a silica-100 support with pore filling α = 1.

A new environmentally friendly method to synthesize long-chain and functionalized alkylsulfate ionic liquids is reported. The two-step synthesis comprises the synthesis of a methylsulfate or ethylsulfate ionic liquid by direct alkylation in the first step. In the second step, this intermediate is transformed in a transesterification reaction, using different functionalized and non-functionalized alcohols, to the corresponding new alkylsulfate melts. The entire reaction sequence is halide-free and liberates methanol or ethanol as the only by-products. Moreover, it is carried out in a solvent-free manner and scale-up is straight forward.

Extraction of S- and N-compounds from gasoline and diesel oil by ionic liquids (ILs) indicates that such a process could be an alternative to common hydrodesulfurization (HDS) for deep desulfurization down to values of 10 ppm S or even lower. The results show the selective extraction properties of ILs, especially with regard to those S-compounds which are hard to remove by HDS, e.g. dibenzothiophene derivatives present in middle distillates like diesel oil. The application of mild process conditions (ambient pressure and temperature) and the fact that no hydrogen is needed, are additional advantages compared to HDS. Very promising ILs are [BMIM][OcSO4] and [EMIM][EtSO4], as they are halogen-free and available from relatively cheap starting materials. Extraction with ILs is not limited to diesel oil, but probably even more attractive for FCC-gasoline. Although HDS of S-species present in this gasoline constituent – mainly thiophenes – is relatively straightforward, a major drawback is the loss in octane number by olefin saturation, which favours extraction with ILs.

The activity and stability of cationic palladium complexes [Pd(PBu3)2S2]2+ used for the selective tail-to-tail dimerisation of methyl acrylate are significantly improved with the utilisation of ionic liquids like [BMIM][BF4] or the protonated N-butyl-imidazole, [HBIM][BF4]. Problems related to product inhibition and catalyst recycling are overcome by running the reaction in a two-phase mode, toluene being used as extractant. Catalyst stabilisation is further improved by trapping the ancillary ligand into the ionic liquid with an ionic tail: with the use of 1-dibutylphosphino-2-dimethylaminoethane, the catalyst is stable for more than 100 h, therefore demonstrating the feasibility of a continuous process for methyl acrylate dimerisation.

Ionic liquid 1-n-butyl-3-methylimidazolium tetrafluoroborate and supercritical CO2 have been used for the biphasic palladium-catalysed dimerisation of methyl acrylate. Substrate and product distribution between the two phases and extraction capability of scCO2 are evaluated. The effect of the biphasic medium on the catalyst performance is also addressed. The selectivity for the tail-to-tail dimers is >98%, as high as under monophasic conditions. The same trend stands for turnover number and frequency although there is a lower substrate to palladium ratio in the IL phase. The CO2-rich phase acts as a substrate and product reservoir, a suitable case for studying the reaction under continuous feed and extraction regime.

Ionic liquids of the 1,3-dialkylimidazolium-type reveal great potential for the innovative application of microwaves for synthesis as well as for separations. Ionic liquids efficiently absorb microwave energy and thus are employed as solvents and co-solvents. In this context, microwaves assist in carrying out syntheses or unit operations.

Hydrogensulfate and tetrakis(hydrogensulfato)borate ionic liquids have been synthesised and characterised. These ionic liquids are halogen-free, available from cheap raw materials and easy to prepare. They have been used as additives to sulfuric acid in the Friedel–Crafts-alkylation of benzene with 1-decene. The results clearly demonstrate an interplay of acidity and solubility effects caused by the ionic liquid additive. In some cases, low amounts of ionic liquid additive result in a dramatic improvement of product yield.

Ionic liquids are considered as green solvents mainly due to their lack of vapour pressure. In fact, environmental and safety problems arising through the volatility of organic solvents can be avoided by the use of these innovative liquids. However, typical ionic liquids consist of halogen containing anions (such as [AlCl4]−, [PF6]−, [BF4]−, [CF3SO3]− or [(CF3SO2)2N]−) which in some regard limit their ‘greenness’. The presence of halogen atoms may cause serious concerns if the hydrolysis stability of the anion is poor (e.g. for [AlCl4]− and [PF6]−) or if a thermal treatment of spent ionic liquids is desired. In both cases additional effort is needed to avoid the liberation of toxic and corrosive HF or HCl into the environment. In this context, we present here the synthesis and application of 1-n-butyl-3-methylimidazolium ([bmim]) [n-C8H17OSO3] which represents a halogen-free and relatively hydrolysis-stable ionic liquid. Moreover, the technical availability and the well documented toxicology of the octylsulfate anion make this ionic liquid a highly interesting candidate for industrial application.

In this review, we introduce photonic crystal fibre as a novel optofluidic microdevice that can be employed as both a versatile chemical sensor and a highly efficient microreactor. We demonstrate that it provides an excellent platform in which light and chemical samples can strongly interact for quantitative spectroscopic analysis or photoactivation purposes. The use of photonic crystal fibre in photochemistry and sensing is discussed and recent results on gas and liquid sensing as well as on photochemical and catalytic reactions are reviewed. These developments demonstrate that the tight light confinement, enhanced light-matter interaction and reduced sample volume offered by photonic crystal fibre make it useful in a wide range of chemical applications.

Cr(III) complexes of tridentate PNP ligands have been prepared and evaluated as catalysts for ethylene trimerisation, with several giving high activity and excellent selectivity towards 1-hexene when activated with methylaluminoxane.

We describe for the first time an alternative and far more efficient method to synthesise functionalised ionic liquids in a simple, straightforward, two-step synthesis.

The oxidation of complex, water-insoluble biomass to formic acid is reported using a Keggin-type polyoxometalate (H5PV2Mo10O40) as the homogeneous catalyst, oxygen as the oxidant, water as the solvent and p-toluenesulfonic acid as the best additive. The reaction proceeds at 90 °C and 30 bar O2 and transforms feedstock like wood, waste paper, or even cyanobacteria to formic acid and CO2 as the sole products. The reaction obtains up to 53% yield in formic acid for xylan as the feedstock within 24 h. Besides the role of the additive as a reaction promoter, the formic acid isolation and the recycling of catalyst and additive are demonstrated.

In order to expand the temperature limits of Supported Ionic Liquid Phase (SILP) or Solid Catalyst with Ionic Liquid Layer (SCILL) systems to higher operation temperatures, the mixture of lithium acetate, potassium acetate, and caesium acetate (molar ratio of 0.2/0.275/0.525) has been studied in detail. Physico-chemical properties of the bulk melt are reported together with stability data of the modern salt on various solid support materials showing attractive properties for many potential high temperature applications.

New Brønsted acidic ionic liquids (BAILs) are prepared by treating zwitterions, which are composed of an imidazolium cation and a sulfonate anion, with an alkanedisulfonic acid. Acidification of the zwitterions produces the cation and deprotonation of the alkanedisulfonic acid forms the anion of the new BAILs. Direct laser desorption/ionisation (LDI), matrix-assisted LDI (MALDI) and electrospray ionisation (ESI) are employed to transfer ions into the gas-phase for detection by mass spectrometry and for dissociation studies by tandem mass spectrometry. The components of the BAILs are confirmed by LDI and MALDI by the detection of the respective cation and anion and by ESI by the observation of the cation and the dianion. A prominent feature of ESI is the formation of aggregates (cluster ions). Positively charged cluster ions are formally composed of multiple zwitterions plus one additional proton. In the negative-ion mode the clusters also incorporate the zwitterions which are, however, linked with the alkanedisulfonate dianion. In collision-induced dissociations (CID), the cationic aggregates show the evaporation of zwitterions until the protonated zwitterion is reached. Similarly, the cluster dianions release zwitterions until the free alkane disulfonate dianion is reached. However, the 1:1 adduct of dianion and zwitterion also displays proton transfer and Coulomb explosion into the mono-protonated disulfonic mono-anion and an imidazole-based carbene with sulfonate mono-anion.

New chiral ionic liquids have been synthesised which are directly derived from the ‘chiral pool’ and therefore readily available in kg scale; NMR-measurements indicate that these liquids may be interesting solvents for enantioselective reactions and useful in chiral separation techniques.

A new concept for storage and superregional transport of solar energy from the earth's desert belt is proposed. The concept is based on solid alkaline earth metal compounds, showing an energy-rich and an energy-lean state which are used in an energy distribution cycle. The concept is evaluated with regard to overall solar-to-electricity efficiency and benchmarked by the overall efficiency of the DESERTEC concept. For a scenario assuming that the current share of electricity production from lignite coal in Germany is replaced by the here proposed concept, the CO2 mitigation potential is calculated. The assessment shows that the proposed concept can compete with the benchmark and even shows high potential for optimization.

Exploitation of hydrogen as an energy carrier requires the development of systems for its storage and delivery. Formic acid has been proposed as valuable hydrogen carrier compound, due to its relatively high hydrogen content (53 g L−1), the latter being easily and cleanly released in catalytic reactions under mild conditions (HCOOH → H2 + CO2). Ionic liquids are interesting solvents for homogeneous catalyzed formic acid decomposition systems as their extremely low volatility avoids solvent contamination of the produced hydrogen stream. In this paper an outstandingly simple, robust and active catalyst system is presented, namely RuCl3 dissolved in 1-ethyl-2,3-dimethylimidazolium acetate (RuCl3/[EMMIM][OAc]). This system proved to be fully recyclable over 10 times. Turnover frequencies (TOF) of 150 h−1 and 850 h−1 were obtained at 80 °C and 120 °C, respectively.

A new and straightforward method to transform carbohydrate-based biomass to formic acid (FA) by oxidation with molecular oxygen in aqueous solution using a Keggin-type H5PV2Mo10O40 polyoxometalate as catalyst is presented. Several water-soluble carbohydrates were fully and selectively converted to formic acid and CO2 under very mild conditions. It is worth noting, even complex biomass mixtures, such as poplar wood sawdust, were transformed to formic acid, giving 19 wt% yield (11% based on the carbon atoms in the feedstock) under non-optimized conditions.

This contribution describes a concept for the establishment of a competitive energy distribution network based on Liquid Organic Hydrogen Carrier (LOHC) compounds. These compounds are characterized by the fact that they can be loaded and un-loaded with considerable amounts of hydrogen in a cyclic process. This concept links the technical challenge of storing temporary and local energy over-production from regenerative sources with the vision of a sustainable, hydrogen-based mobility. The proposed LOHC compounds have many physico-chemical similarities to diesel. Thus, LOHCs could make use of the existing energy infrastructure (e.g. tank ships, storage tanks or fueling stations) and enable a slow and step-wise replacement of the existing hydrocarbon fuels by alternative LOHC fuels. We consider LOHCs as an attractive way to provide wind and solar energy for mobility applications in the form of liquid energy carrying molecules of similar energy storage densities and manageability as today's fossil fuels.

The underlying principle of the chirality transfer in imidazolium-based camphorsulfonate ionic liquids is rationalized by linking catalytic results from the hydrogenation of [N-(3'-oxobutyl)-N-methylimidazolium] [(+)-camphorsulfonate] to [N-(3'-hydroxybutyl)-N-methylimidazolium] [(+)-camphorsulfonate] in tetrahydrofuran with electrolyte theory by the help of dielectric relaxation spectroscopy. Using this approach we are able to explain why the maximum of the enantiomeric excess of the hydrogenation reaction in tetrahydrofuran is found at a medium concentration of 0.15 mol L(-1), whereas it declines at both, lower and higher concentrations. Dielectric spectra in the concentration range between 0.05 and 1.0 mol L(-1) reveal a solute mode due to dipolar ion pairs and larger dipolar ion clusters. They verify that at very low concentrations the ionic liquid ions are fully solvated with an increasing tendency to form neutral ion pairs with increasing concentration. Already at 0.025 mol L(-1) the degree of dissociation reaches a minimum reflecting a maximum of neutral ion pair formation. With increasing ionic liquid concentration ordered ion clusters are formed by two and more ion pairs. At high concentrations these clusters collapse by dilution in the excess ionic liquid and the defined ion contact necessary for the chirality transfer is lost to a great extent.

A new approach for the deep desulfurization of diesel fuels by extraction with ionic liquids is described.

Ethylene oligomerisation in ionic liquids gives predominately alk-1-ene products with better reactivity and selectivity than in conventional solvents; turnover frequencies are correlated with polarity data obtained using solvatochromic dyes.

Lipases show good activity and, in some cases, improved enantioselectivity when employed in pure ionic liquids for dynamic kinetic resolution of 1-phenylethanol by transesterification.

New guanidinium-modified diphosphine ligands with a xanthene backbone show high overall activity and high regioselectivity in the biphasic hydroformylation of oct-1-ene using hexafluorophosphate ionic liquids.