This contribution proposes the usage of Liquid Organic Hydrogen Carriers (LOHC) for the storage and subsequently the transport of renewable energy. It is expected that a significant share of future ...energy consumption will be satisfied with the import of energy coming from regions with high potential for renewable generation, e.g. the import of solar power from Northern Africa to Europe. In this context the transport of energy in form of chemical carriers is proposed supplementary to electrical transmission. Because of their high storage density and good manageability under ambient conditions Diesel-like LOHC substances could be transported within the infrastructure that already exists for the handling of liquid fossil fuels (e.g. oil tankers, tank trucks, pipelines, etc.). A detailed assessment of energy consumption as well as of transport costs is conducted that confirms the feasibility of the concept.
► Storage and transport of renewable energy via Liquid Organic Hydrogen Carriers (LOHC). ► LOHC substances could be distributed via the existing infrastructure for liquid fossil fuels. ► Hydrogen transport via LOHC shows very favorable economics. ► Renewable energy imported as hydrogen could be cost-competitive compared to on-site production.
Reducing CO2 emissions is an urgent global priority. The enforcement of a CO2 tax, stringent regulations, and investment in renewables are some of the mitigation strategies currently in place. For a ...smooth transition to renewable energy, the energy storage issue must be addressed decisively. Hydrogen is regarded as a clean energy carrier; however, its low density at ambient conditions makes its storage challenging. The storage of hydrogen in liquid organic hydrogen carriers (LOHC) systems has numerous advantages over conventional storage systems. Most importantly, hydrogen storage and transport in the form of LOHC systems enables the use of the existing infrastructure for fuel. From a thermodynamic point of view, hydrogen storage in LOHC systems requires an exothermic hydrogenation step and an endothermic dehydrogenation step. Interestingly, hydrogenation and dehydrogenation can be carried out at the same temperature level. Under high hydrogen pressures (typically above 20 bar as provided from electrolysis or methane reforming), LOHC charging occurs and catalytic hydrogenation takes place. Under low hydrogen pressures (typically below 5 bar), hydrogen release from the LOHC system takes place. Hydrogen release from charged LOHC systems is always in conflict between highly power-dense hydrogen production and LOHC stability over many charging/discharging cycles. We therefore discuss the role of different catalyst materials on hydrogen productivity and LOHC stability. The use of density functional theory techniques to determine adsorption energies and to identify rate-determining steps in the LOHC conversion processes is also described. Furthermore, the performance of a LOHC dehydrogenation unit is strongly dependent on the applied reactor configuration. Industrial implementation of the LOHC technology has started but is still in an early stage. Related to this, we have identified promising application scenarios for the South African energy market.
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•Vapor-feed DIFC enabling the direct energy generation out of LOHC-bound hydrogen.•Record-high power densities of a direct isopropanol fuel cell with 254 mW/cm2 at 0.55 V.•High ...temperature lead to enhanced reaction kinetics and fast desorption of acetone.
Liquid Organic Hydrogen Carrier (LOHC) systems offer a very interesting option for hydrogen storage in the existing infrastructure for common fuels. Technically most attractive is the direct use of LOHC-bound hydrogen in a low-temperature PEM fuel cell. Here, the isopropanol/acetone LOHC system is suggested to produce electricity from a condensable liquid without CO2 emissions. A high-performance direct isopropanol fuel cell using a vaporizer and a commercial fuel cell test system is demonstrated. For the first time backpressure is used to enhance the performance. The self-fabricated GDEs combined with a Nafion composite membrane achieved a power density of 203 mW cm−2 for Isopropanol/Air operation at 300 kPa absolute and 85 °C. By increasing the operation temperature to 100 °C a peak power density of 254 mW cm−2 is achieved, exceeding the highest reported values for isopropanol fuel cells operated with air by over 80%. The observed increase in performance can be attributed to the higher reaction rate of the electrooxidation of isopropanol at the anode side during pressurized conditions and to the reduced acetone-poisoning of the Pt-Ru catalyst at elevated temperatures.
Herein, we report a remarkable finding that biomass oxidation to formic acid (FA) in water-organic biphasic reaction systems is far more selective than the same reaction in a monophasic aqueous ...media. While literature claims that the yield of FA from carbohydrates and biomass is limited to less than 68%, even for simple substrates such as glucose or glycerol, we demonstrate in this study that FA yields of up to 85% can be obtained from glucose. Using our biphasic reaction protocol, even raw lignocellulosic biomass, such as beech wood, leads to FA yields of 61%. This is realized by applying polyoxometalate H sub(8)PV sub(5)Mo sub(7)O sub(40) as a homogeneous catalyst, oxygen as the oxidant and water as the solvent in the presence of a long-chain primary alcohol as an in-situ extracting agent. The new, liquid-liquid biphasic operation opens a highly effective way to produce pure FA, a liquid syngas equivalent, from wood in a robust, integrated, and low-temperature process.
This review describes the development of supported ionic liquid phase (SILP) materials as novel hydroformylation catalysts. Ligand-modified rhodium catalysts can be immobilized in a thin film of ...ionic liquid, which itself is dispersed on a porous material. The solid SILP catalysts have been improved with respect to activity, selectivity, and stability. In addition, their applicability in continuous gas-phase processes opens new opportunities for improved chemical production routes.
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 CO
2
. In detail, we report oxidation of a methanolic glucose solution using H
8
PV
5
Mo
7
O
40
(HPA-5) as catalyst at 90 °C and 20 bar O
2
pressure. Experiments with
13
C-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.
We report the highly remarkable discovery that glucose oxidation catalysed by polyoxometalates in methanolic solution enables formation of formic acid and methyl formate in close to 100% combined selectivity, thus with only negligible sugar oxidation to CO
2
.
The oxidation of complex, water-insoluble biomass to formic acid is reported using a Keggin-type polyoxometalate (H sub(5)PV sub(2)Mo sub(10 )O sub(40)) 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 degree C and 30 bar O sub(2) and transforms feedstock like wood, waste paper, or even cyanobacteria to formic acid and CO sub(2) 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.
Beech lignin was oxidatively cleaved in ionic liquids to give phenols, unsaturated propylaromatics, and aromatic aldehydes. A multiparallel batch reactor system was used to screen different ionic ...liquids and metal catalysts. Mn(NO3)2 in 1‐ethyl‐3‐methylimidazolium trifluoromethanesulfonate EMIMCF3SO3 proved to be the most effective reaction system. A larger scale batch reaction with this system in a 300 mL autoclave (11 g lignin starting material) resulted in a maximum conversion of 66.3 % (24 h at 100 °C, 84×105 Pa air). By adjusting the reaction conditions and catalyst loading, the selectivity of the process could be shifted from syringaldehyde as the predominant product to 2,6‐dimethoxy‐1,4‐benzoquinone (DMBQ). Surprisingly, the latter could be isolated as a pure substance in 11.5 wt % overall yield by a simple extraction/crystallization process.
Beech lignin is oxidatively cleaved in ionic liquids to give phenols, unsaturated propylaromatics, and aromatic aldehydes. By adjusting the reaction conditions and catalyst loading, the selectivity of the process can be shifted from syringaldehyde as the predominant product to 2,6‐dimethoxy‐1,4‐benzoquinone (DMBQ).
Ionic liquids in chemical engineering Werner, Sebastian; Haumann, Marco; Wasserscheid, Peter
Annual review of chemical and biomolecular engineering,
01/2010, Letnik:
1
Journal Article
Recenzirano
The development of engineering applications with ionic liquids stretches back to the mid-1990s when the first examples of continuous catalytic processes using ionic liquids and the first studies of ...ionic liquid-based extractions were published. Ever since, the use of ionic liquids has seen tremendous progress in many fields of chemistry and engineering, and the first commercial applications have been reported. The main driver for ionic liquid engineering applications is to make practical use of their unique property profiles, which are the result of a complex interplay of coulombic, hydrogen bonding and van der Waals interactions. Remarkably, many ionic liquid properties can be tuned in a wide range by structural modifications at their cation and anion. This review highlights specific examples of ionic liquid applications in catalysis and in separation technologies. Additionally, the application of ionic liquids as working fluids in process machines is introduced.
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