Potential Liquid Organic Hydrogen Carrier Research Articles

The production of a liquid organic hydrogen carrier (LOHC) and jet fuel fractions by hydroprocessing of pyrolysis fuel oil (PFO)

The scheme of combined processing of pyrolysis fuel oil (PFO) to obtain the components of synthetic jet fuel and liquid organic hydrogen carrier (LOHC) was proposed and experimentally evaluated. The PFO processing scheme includes primary distillation, two-stage hydrogenation and finishing distillation. The product was naphthene-rich fraction (PFO–H1) with a boiling range of T10%/T90% = 200/246 °C, the main components of which were bicyclic naphthenes (decalin, bicyclohexyl) according to GCxGC/MS. This fraction was studied as a potential LOHC. Its dehydrogenation produced a gas with an average H2 content of 98.0 vol %. The average hydrogen capacity of the PFO-H1 fraction amounted to ≈6.63 wt %. The isomers of decalins of alkylhydrindane-like type underwent dehydroisomerization reaction with formation of alkylnaphthalenes upon dehydrogenation. The dehydrogenated PFO-H0 fraction had density of 1005 kg m−3, boiling range T10%/T90% = 200/246 °C, flash point of 80 °C and pour point of −4 °C.Both the PFO-H1 and its isomerization product PFO-Hi were additionally characterized as potential components of high-energy-density jet fuels with relatively high specific gravities (d20 = 871/885 kg m−3) and calorific values (36.7/37.3 MJ L−1).

Novel Liquid Organic Hydrogen Carriers with High Hydrogen Performance: NPhCZ/18H-NPhCZ

Exploring the potential liquid organic hydrogen carriers (LOHCs) with high efficiency can promote the advancement of hydrogen storage technology. In this work, a new LOHC member of the carbazole family, perhydro-N-phenylcarbazole (18H-NPhCZ), was first proposed for its high theoretical hydrogen storage capacity (6.9 wt %) and available dehydrogenation reaction enthalpy (ΔrHm(d)⊖ = 51.68 kJ/molH2) based on theoretical calculations. The hydrogenation and dehydrogenation performances were evaluated and exhibited high efficiency in the optimized reaction conditions. The results indicated that 4.74 wt % of H2 was released from 18H-NPhCZ dehydrogenation within 15 min. The combination of experiments and density functional theory (DFT) calculations was employed to investigate the possible intermediates and H2 uptake and release mechanisms. It was found that the elementary reaction from 6H-NPhCZ to NPhCZ was regarded as the rate-limiting step. Furthermore, to balance the storage hydrogen capacity and liquid state at room temperature, a brand-new MIX-LOHC hydrogen storage system (18H-M-B2P1, 6.44 wt %) containing both 18H-NPhCZ and perhydro-dibenzyltoluene (18H-DBT) was successfully proposed as well. It achieved an almost 100% of H2 uptake for 4–6 h and a practical H2 release amount of 6.08 wt % for 10 h. The efficient cycle cohydrogenation and codehydrogenation measurements after 160 h also suggested the stability and reliability of the applications in the hydrogen storage field.

Systematic evaluation of physicochemical properties for the selection of alternative liquid organic hydrogen carriers

Chemical hydrogen storage is a key step for establishing hydrogen as a main energy vector. For this purpose, liquid organic hydrogen carriers (LOHCs) present the outstanding advantage of allowing a safe, efficient, and high-density hydrogen storage, being also highly compatible with existing transport infrastructures. Typical LOHCs are organic compounds able to be hydrogenated and dehydrogenated at mild conditions, enabling the hydrogen storage and release, respectively. In addition, the physical properties of these chemicals are also critical for practical implementation.In this work, key properties of potential LOHCs of three different chemical families (homoaromatics, and N- and O-heteroaromatics) are estimated using molecular simulations. Thus, density, viscosity, vapour pressure, octanol-water coefficient, melting point, flash point dehydrogenation enthalpy and hydrogen content are estimated using the programs COSMO-RS and HYSYS. In addition, we have also evaluated the performance of several binary mixtures as LOHCs using these methodologies.Considering the hydrogen content, characteristic temperatures, and previous experimental results of the cyclic process; our simulation results suggest that 1-methylnaphthalene/1-methyldecahydronaftalene and methylbenzylpyridine/perhydromethylbenzylpyridine pairs are appropriate candidates for chemical hydrogen storage. Binary mixtures of LOHCs are also relevant alternatives since substances with a great potential can be used as LOHCS when dissolved. That is the case of naphthalene and 1-methyl-naphthalene mixtures or indoles dissolved in benzene or benzylbenzene. Concerning O-compounds, although several pairs could be used as LOHCs, thermodynamic and kinetic feasibility of the hydrogenation/dehydrogenation cycles must be better studied.

The production and the properties of the liquid organic hydrogen carrier (LOHC) obtained from the light cycle oil (LCO)

A technological concept of production of a hydrocarbon LOHC prototype from the light cycle oil (LCO) has been proposed with the estimate of the key features through an experimental study. It has been shown that an alkylnaphthalene-rich LCO could be converted into a narrow alkyldecalin fraction (T5%/T95% = 206/231 °C) via a combined distillation‑hydrogenation approach. The obtained product has been characterized as a potential LOHC. Upon the dehydrogenation over a commercial Pd/C catalyst in a flow reactor at 320–400 °C the release of pure H2 (99.3–99.8 vol%) was observed; the estimated H2 yield did not exceed 26% due to a severe catalyst deactivation. A multistep dehydrogenation in a batch reactor (T = 380 °C, Pd/C) allowed a conversion of 87.9% be obtained. Both the starting and the dehydrogenated carriers were found to be diesel fuel-like liquids with high flash points (87 and 101 °C), low viscosities (2.63 and 2.89 mm2 s−1) and excellent low-temperature properties (freezing points < −60/−26 °C; melting points < −60/−36 °C). The GCxGC/MS technique was applied to characterize the chemical composition of the LOHC; the calculation of the hydrogen capacity by means of the “virtual (de)hydrogenation” protocol has been shown. The hydrogen capacity for the LCO-derived LOHC prototype was found to be 5.97 wt% or 66.9 nl H2 per 1 kg of the LOHC, and the hydrogen content in the H2-rich and H2-lean carriers amounted to 13.27 and 7.77 wt%, respectively.

N-Heterocyclic Molecules as Potential Liquid Organic Hydrogen Carriers: Reaction Routes and Dehydrogenation Efficacy

This study is focused on the development of liquid organic hydrogen carriers (LOHC) based on N-heterocyclic compounds. These LOHC-substrates are attractive for their lower hydrogen extraction temperature compared to cycloalkanes, which is caused by the low enthalpy of the dehydrogenation reaction of the N-heterocyclic compounds. The low hydrogen extraction temperature, as well as the low volatility of the heterocycles, provide high purity hydrogen from the reaction. Under similar reaction conditions, the comparison of the efficacy of three promising heterocycles (1-methyl-octahydroindole (8HMI), tetradecahydrophenazine and decahydroquinoline) was carried out in the presence of palladium-containing catalysts. As a result, the advantages of using catalysts supported by alumina, and the high perspectivity of the 8MHI application as a LOHC-substrate, were shown. The dehydrogenation of 8HMI in the presence of 1 wt.% Pd/Al2O3 allowed for reaching a 100% yield in hydrogen under the conditions of the standard catalytic test (1 h, 240 °C). In order to study the high reactivity of 8HMI, thermodynamic dehydrogenation reaction profiles were computationally evaluated, which showed that 8HMI was the most energetically preferred in the field of hydrogen storage from the studied heterocyclic compounds.

Comprehensive thermodynamic study of substituted indoles/perhydro indoles as potential liquid organic hydrogen carrier system

Indole has been proposed as a Liquid Organic Hydrogen Carrier (LOHC) component. Its hydrogenation leads to octahydro indole, which can subsequently release hydrogen again in an endothermic, catalytic dehydrogenation reaction. This reaction requires high temperatures due to limitations by the reaction equilibrium. It is therefore interesting to find derivatives of the carrier molecules with lower enthalpies of reaction, which corresponds to a higher equilibrium constant. In this study, methyl and phenyl substituted derivatives of indole have been examined. Vapor pressures and enthalpies of vaporisation/sublimation have been measured. The standard molar enthalpies of formation in the gas phase have been calculated using quantum chemistry. The liquid phase standard molar enthalpies of formation were derived and used for calculating reaction enthalpies. The results show that methylation lowers the enthalpy of reaction for dehydrogenation. The reduction is not very pronounced in case of single methylation (up to 3.1 kJ mol−1/H2), but can be increased by manifold methylation (e.g. 4.6 kJ mol−1/H2 in case of 2,3-dimethyl-H8-indole). Substitution of indole with a phenyl group leads to a corresponding hydrogenated counterpart, that can only be dehydrogenated partially under mild conditions. This is due to the fact that the reducing effect of the nitrogen atom on enthalpy of reaction is only effective in the indole system itself, while the cyclohexyl ring has similar dehydrogenation properties to homocyclic LOHCs.

Analysis of Liquid Organic Hydrogen Carrier Systems

Liquid organic hydrogen carriers (LOHCs) provide attractive opportunities for hydrogen storage and transportation. In this study, a detailed examination of the most prominent LOHCs is performed, with a focus on their properties and scope for successful process implementation, as well as catalytic materials used for the hydrogenation and dehydrogenation steps. Different properties of each potential LOHC offer significant flexibility within the technology, allowing bespoke hydrogen storage and transportation solutions to be provided. Among different LOHC systems, dibenzyltoluene/perhydro-dibenzyltoluene has been identified as one of the most promising candidates for future deployment in commercial LOHC-based hydrogen storage and transport settings, based on its physical and toxicological properties, process conditions requirements, availability and its moderate cost. Platinum group metal (pgm)-based catalysts have been proven to catalyse both the hydrogenation and dehydrogenation steps for various LOHC systems, though base metal catalysts might have a potential for the technology.

Statistical and stochastic feasibility studies of potential liquid organic hydrogen carriers in a membrane reactor for simultaneous hydrogen storage and production: Technical, economic, and environmental aspects

With a global trend of transition to the hydrogen-based energy system, the importance of improved systems of hydrogen production and transportation is emphasized. Especially, liquid organic hydrogen carrier is introduced due to its significant advantages when it is employed as a hydrogen energy carrier. In this study, the comprehensive preliminary feasibility study in technical, economic, and environmental aspects for hydrogen production systems using several promising systems of dodecahydro-N-ethycarbazole, Perhydro-dibenzyltoluene, methylcyclohexane, and methanol in a membrane reactor is conducted to investigate its potential to be alternative hydrogen production and transportation. With process simulation using Aspen Plus® based on detailed reaction kinetics for dehydrogenation of each dehydrogenation system and steam reforming of methanol, technical performance in terms of production rate is revealed. In addition, unit hydrogen production costs and key economic parameters for each system at various scales are estimated and compared by itemized cost estimation. Furthermore, realistic uncertainty analysis reflecting detailed distributions of each economic parameter obtained by various regression types of triangular, Epsilon skew normal, Birnbaum-Saunders, and Rayleigh and environmental assessment using SimaPro® are conducted revealing possible ranges of unit hydrogen production cost and carbon dioxide emission rate.

Reversible storage and release of hydrogen with LOHC: Evaluation of thermochemical data for methyl-quinolines with complementary experimental and computational methods

The liquid organic hydrogen carriers (LOHC) are aromatic molecules, which can be considered as an attractive option for the storage and transport of hydrogen. A considerable amount of hydrogen can be loaded and unloaded with a reversible chemical reaction. Methyl-substituted quinolines are available from petroleum, coal processing, wood preservation or they can be synthesized from aniline. Quinolines can be considered as potential LOHC systems, provided they have favorable thermodynamic properties, which were the focus of this current study. The absolute vapor pressures of methyl-quinolines were measured using the transpiration method. The standard molar enthalpies of vaporization of methyl-quinolines were derived from the vapor pressure temperature dependences. Thermodynamic data on vaporization and formation enthalpies available in the literature were collected, evaluated, and combined with own experimental results. The theoretical standard molar gas-phase enthalpies of formation of methyl-quinolines, calculated using the quantum chemical G3MP2 and G4 methods, agreed well with the evaluated experimental data. The hydrogenation/dehydrogenation reaction enthalpies of methyl-quinolines were calculated and compared with the data for other potential liquid organic hydrogen carriers. The comparatively low enthalpies of reaction make these heteroaromatics a seminal LOHC systems.

Hydrogen Storage: Thermodynamic Analysis of Alkyl-Quinolines and Alkyl-Pyridines as Potential Liquid Organic Hydrogen Carriers (LOHC)

The liquid organic hydrogen carriers (LOHC) are aromatic molecules, which can be considered as an attractive option for the storage and transport of hydrogen. A considerable amount of hydrogen up to 7–8% wt. can be loaded and unloaded with a reversible chemical reaction. Substituted quinolines and pyridines are available from petroleum, coal processing, and wood preservation, or they can be synthesized from aniline. Quinolines and pyridines can be considered as potential LOHC systems, provided they have favorable thermodynamic properties, which were the focus of this current study. The absolute vapor pressures of methyl-quinolines were measured using the transpiration method. The standard molar enthalpies of vaporization of alkyl-substituted quinolines and pyridines were derived from the vapor pressure temperature dependencies. Thermodynamic data on vaporization and formation enthalpies available in the literature were collected, evaluated, and combined with our own experimental results. The theoretical standard molar gas-phase enthalpies of formation of quinolines and pyridines, calculated using the quantum-chemical G4 methods, agreed well with the evaluated experimental data. Reliable standard molar enthalpies of formation in the liquid phase were derived by combining high-level quantum chemistry values of gas-phase enthalpies of formation with experimentally determined enthalpies of vaporization. The liquid-phase hydrogenation/dehydrogenation reaction enthalpies of alkyl-substituted pyridines and quinolines were calculated and compared with the data for other potential liquid organic hydrogen carriers. The comparatively low enthalpies of reaction make these heteroaromatics a seminal LOHC system.

Recent Advances in Homogeneous/Heterogeneous Catalytic Hydrogenation and Dehydrogenation for Potential Liquid Organic Hydrogen Carrier (LOHC) Systems

Here, we review liquid organic hydrogen carriers (LOHCs) as a potential solution to the global warming problem due to the increased use of fossil fuels. Recently, hydrogen molecules have attracted attention as a sustainable energy carrier from renewable energy-rich regions to energy-deficient regions. The LOHC system is one a particularly promising hydrogen storage system in the “hydrogen economy”, and efficient hydrogen mass production that generates only benign byproducts can be applied in the industry. Therefore, this article presents hydrogenation and dehydrogenation, using homogeneous or heterogeneous catalysts, for several types of LOHCs, including formic acid/formaldehyde/ammonia, homocyclic compounds, nitrogen- and oxygen-containing compounds. In addition, it introduces LOHC system reactor types.

Advances in Nonprecious Metal Homogeneously Catalyzed Formic Acid Dehydrogenation

Formic acid (FA) possesses a high volumetric concentration of H2 (53 g L−1). Moreover, it can be easily prepared, stored, and transported. Therefore, FA stands out as a potential liquid organic hydrogen carrier (LOHC), which allows storage and transportation of hydrogen in a safe way. The dehydrogenation to produce H2 and CO2 competes with its dehydration to give CO and H2O. For this reason, research on selective catalytic FA dehydrogenation has gained attention in recent years. Several examples of highly active homogenous catalysts based on precious metals effective for the selective dehydrogenation of FA have been reported. Among them are the binuclear iridium-bipyridine catalysts described by Fujita and Himeda et al. (TOF = 228,000 h−1) and the cationic species [IrClCp*(2,2′-bi-2-imidazoline)]Cl (TOF = 487,500 h−1). However, examples of catalytic systems effective for the solventless dehydrogenation of FA, which is of great interest since it allows to reduce the reaction volume and avoids the use of organic solvents that could damage the fuel cell, are scarce. In this context, the development of transition metal catalysts based on cheap and easily available nonprecious metals is a subject of great interest. This work contains a summary on the state of the art of catalytic dehydrogenation of FA in homogeneous phase, together with an account of the catalytic systems based on non-precious metals so far reported.

Experimental Measurement and Correlations of High Pressure Density Data for potential Liquid Organic Hydrogen Carriers

The high pressure density data of six substances which are potential liquid organic hydrogen carrier systems (LOHCs) (toluene and methylcyclohexane, N-ethylcarbazole and dodecahydro-N-ethylcarbazole, dibenzyltoluene and octadecahydro-dibenzyltoluene) have been measured within pressure range of (1 to 25) MPa within wide range of temperature varying from 293.15 K to 523.15 K. The experimental data were correlated as a function of temperature and pressure using Tait equation. The experimental data were compared with correlated data, resulting in absolute average deviation (AAD = 0.10 %), maximum deviation (MD = 0.30 %), and standard deviation (σ = 1.12 × 10−4 g·cm−3).

Novel Catalysts for Dibenzyltoluene as a Potential Liquid Organic Hydrogen Carrier Use—A Mini-review

The utilization of pure and valuable energy carriers such as hydrogen is becoming important in various applications, especially in the automotive fuel cell industry. However, as a result of the pro...

Thermodynamic analysis of hydrogen storage: Biphenyl as affordable liquid organic hydrogen carrier (LOHC)

One of the promising directions for accumulating hydrogen is its binding into a liquid organic hydrogen carrier (LOHC). In this concept, a LOHC is loaded with hydrogen (hydrogenation) during production and then discharged again (dehydrogenation) when the hydrogen is needed. Biphenyl is an interesting option as potential LOHC due to its reasonable storage capacity. This paper deals with the experimental chemical equilibrium study and a detailed analysis of the biphenyl hydrogenation reactions. We evaluated the consistent set of vapour pressures and standard molar thermodynamic properties of biphenyl derivatives with help of complementary vapour pressure measurements, and empirical and quantum-chemical calculations. The chemical equilibrium constants of hydrogenation-dehydrogenation and thermodynamic characteristics for the biphenyl system were determined.

Statistical and Stochastic Feasibility Studies of Potential Liquid Organic Hydrogen Carriers in a Membrane Reactor for Simultaneous Hydrogen Storage and Production: Techcnial, Economic, and Environmental Aspects

Statistical and Stochastic Feasibility Studies of Potential Liquid Organic Hydrogen Carriers in a Membrane Reactor for Simultaneous Hydrogen Storage and Production: Techcnial, Economic, and Environmental Aspects

Dehydrogenation of ethylene diamine monoborane adducts and their cyclic products (monomers, dimers, and trimers): Potential liquid organic hydrogen carriers

The dehydrogenation mechanisms of ethylene diamine monoborane (EDMB) adducts and its derivatives having CH3, Cl, F, NH2, OCH3, CN, and H substituents at two sites on the ethylene backbone were investigated to explore their potential as liquid organic hydrogen carriers (LOHCs). Using density functional theory calculations, the thermodynamic parameters of the EDMB adducts and dehydrogenation reactions to form cyclic monomers, dimers, and trimers were calculated. In particular, we focused on the free energy barriers of EDMB adducts substituted with Cl/CN, Cl/OCH3, F/CN, F/OCH3, F/F, and NH2/H for cyclic monomer formation, H/CH3, H/CN, Cl/H, and NH2/H for cyclic dimer formation, and H/Cl, H/F, and NH2/H for cyclic trimer formation, which are promising candidates for chemical hydrogen storage. We also explored the formation of cyclic trimers from the selected cyclic monomers with CH3/CH3, H/CH3, and NH2/H substituents. As a result, the dehydrogenation pathways and transition states of the various adducts for the formation for the various cycles were identified, and electrostatic potential surfaces and frontier molecular orbitals calculations were calculated to understand the reaction further. The results obtained indicate the potential of these materials for hydrogen storage, and we hope that this work will encourage the experimental investigation of these materials.

Potential Liquid-Organic Hydrogen Carrier (LOHC) Systems: A Review on Recent Progress

The depletion of fossil fuels and rising global warming challenges encourage to find safe and viable energy storage and delivery technologies. Hydrogen is a clean, efficient energy carrier in various mobile fuel-cell applications and owned no adverse effects on the environment and human health. However, hydrogen storage is considered a bottleneck problem for the progress of the hydrogen economy. Liquid-organic hydrogen carriers (LOHCs) are organic substances in liquid or semi-solid states that store hydrogen by catalytic hydrogenation and dehydrogenation processes over multiple cycles and may support a future hydrogen economy. Remarkably, hydrogen storage in LOHC systems has attracted dramatically more attention than conventional storage systems, such as high-pressure compression, liquefaction, and absorption/adsorption techniques. Potential LOHC media must provide fully reversible hydrogen storage via catalytic processes, thermal stability, low melting points, favorable hydrogenation thermodynamics and kinetics, large-scale availability, and compatibility with current fuel energy infrastructure to practically employ these molecules in various applications. In this review, we present various considerable aspects for the development of ideal LOHC systems. We highlight the recent progress of LOHC candidates and their catalytic approach, as well as briefly discuss the theoretical insights for understanding the reaction mechanism.

Engineering PdCu and PdNi bimetallic catalysts with adjustable alloying degree for the dehydrogenation reaction of dodecahydro-N-ethylcarbazole

The NECZ/12H-NECZ (N-ethylcarbazole/dodecahydro-N-ethylcarbazole) system is regarded as the most potential liquid organic hydrogen carrier. However, the low activity, selectivity of NECZ and high cost of catalysts for the dehydrogenation reaction restrict its efficiency and commercial applications. In this work, a series of bimetallic Pd-M(M = Cu, Ni)/SiO2 catalysts were prepared and employed to enhance catalytic activity and selectivity of NECZ for the 12H-NECZ dehydrogenation reaction. Pd3Ni1/SiO2 exhibited high catalytic performance with 100% conversion, 91.1% selectivity of NECZ and 5.63 wt% hydrogen release amount at 453 K, 101.325 kPa for 8 h. The TOF (turnover frequency) of Pd3Ni1/SiO2 is enhanced by 42.4% compared with Pd/SiO2. Combined with the characterization analysis, it was found that adjusting the alloying degree or the alloy phase in the PdCu and PdNi bimetallic catalysts could significantly enhance the dehydrogenation activity and selectivity, which were dependent on the component of bimetallic catalysts. This work may provide theoretical guidance for designing the efficient and low-cost bimetallic catalysts for the dehydrogenation of 12H-NECZ, which could boost the commercial applications of liquid organic hydrogen carriers.

Furfuryl alcohol as a potential liquid organic hydrogen carrier (LOHC): Thermochemical and computational study

The liquid organic hydrogen carriers (LOHCs) are considered as a promising materials for hydrogen storage. The liquid phase standard molar enthalpies of formation of furfuryl alcohol and tetrahydrofurfuryl alcohol were obtained from high-precision combustion calorimetry. Their standard molar enthalpies of vaporisation were derived from the vapor pressure temperature dependences measured by the transpiration method. Gas phase molar enthalpies of formation of furfuryl alcohol and tetrahydrofurfuryl alcohol calculated by the high-level quantum-chemical method G4, were in an excellent agreement with the experimental results. Reaction enthalpies and equilibrium temperature of the hydrogenation/dehydrogenation reactions of furfuryl alcohol were calculated and compared with the data for furan and other potential liquid organic hydrogen carriers.