Liquid Organic Carriers Research Articles

Process simulation and optimization of methanol production and utilization for electricity generation

The utilisation of liquid organic carriers for hydrogen storage has demonstrated to be a highly effective method for storing hydrogen under ambient temperature and pressure conditions. Methanol has a hydrogen (H2) content of 12.6% by weight and can be synthesised by the process of carbon dioxide (CO2) hydrogenation. The main goal of the study is to demonstrate methanol’s role as a hydrogen carrier and its application in a direct methanol fuel cell for energy generation. The suggested system synthesises methanol by utilizing green hydrogen with CO2 recovered from industrial sources. The Aspen Plus simulation of the DMFC showed a 58% methanol conversion and a 61% energy efficiency (Methanol-to-power).

The product of hydrogenation of a model mixture of alkyl-substituted C7—C12 benzene compounds as a new liquid organic carrier of hydrogen

The product of hydrogenation of a model mixture of alkyl-substituted C7—C12 benzene compounds as a new liquid organic carrier of hydrogen

GBL/BDO pair as a bio-based liquid organic carrier: Kinetic modeling of liquid phase hydrogenation and dehydrogenation over copper-based catalyst

The use of liquid organic hydrogen carriers (LOHC) for hydrogen storage has technical, economical, and environmental advantages. The γ-butyrolactone (GBL)/1,4-butanediol (BDO) pair is used in this work as a bio-based LOHC. Reaction kinetics of liquid phase GBL hydrogenation and BDO dehydrogenation have been studied using a semi-batch reactor filled with a copper based methanol catalyst with the experiments have been performed in the temperature range of 458–503 K with a constant pressure of 50 and 3 bar for hydrogenation and dehydrogenation respectively. Based on analytical results, a reaction pathway including the formation of side products was proposed. This pathway includes the formation of two side-products: 4-hydroxybutyl 4-hydroxybutanoate (4-HHB) is produced from the transesterification of GBL by BDO in both reactions; and dibutyleneglycol (DG) from the etherification of BDO in dehydrogenation. Based on experimental results, kinetic models were established for hydrogenation and dehydrogenation reactions. In these models, balanced reactions with a first order were used. Estimation of kinetic parameters for both reactions allows a good prediction of the experimental data and results in a temperature extrapolation by an Arrhenius law. Activation energies for GBL hydrogenation and BDO dehydrogenation were determined to be respectively 104 kJ/molLOHC and 98.3 kJ/molLOHC. Furthermore, models are valid at short (up to 5 h) and long (up to 20 h) reaction times and the estimation results display acceptable uncertainties for all the reaction temperatures.

Carbonized Melamine Cyanurate as a Palladium Catalyst Support for the Dehydrogenation of N-heterocyclic Compounds in LOHC Technology

In this work, the use of graphite-like carbon nitride (g-C3N4) with improved texture characteristics for the synthesis of supported palladium catalysts of dehydrogenation of nitrogen-containing heterocycles was studied. This process is key to the creation of liquid organic carrier technology (LOHC) using N-heterocycles as reversibly hydrogenated/dehydrogenated substrates. For the preparation of graphite-like carbon nitride supports with advanced textural characteristics, well-established technology of the melamine cyanurate complex carbonization and standard techniques of adsorption precipitation together with wet impregnation were used for the synthesis of Pd-containing systems. The activity of the synthesized catalysts was studied in decahydroquinoline dehydrogenation. The high weight content of extractable hydrogen (7.2 wt%) and the high extraction rate, respectively, make it possible to consider these substances as the most promising N-heterocyclic compounds for this technology. It was shown that an increase in the specific surface area of g-C3N4 allows for achieving a slightly lower but comparable fineness of palladium particles for the 1 wt% Pd/MCA-500 sample, compared to the standard 1 wt% Pd/C. In this case, the catalytic activity of 1 wt% Pd/MCA-500 in the dehydrogenation of both substrates exceeded the analogous parameter for catalysts supported by nitrogen-free supports. This regularity is presumably associated with the electron-donor effect of surface nitrogen, which favorably affects the dehydrogenation rate as well as the stability of catalytic systems.

The Potential Role of Ammonia for Hydrogen Storage and Transport: A Critical Review of Challenges and Opportunities

Hydrogen is being included in several decarbonization strategies as a potential contributor in some hard-to-abate applications. Among other challenges, hydrogen storage represents a critical aspect to be addressed, either for stationary storage or for transporting hydrogen over long distances. Ammonia is being proposed as a potential solution for hydrogen storage, as it allows storing hydrogen as a liquid chemical component at mild conditions. Nevertheless, the use of ammonia instead of pure hydrogen faces some challenges, including the health and environmental issues of handling ammonia and the competition with other markets, such as the fertilizer market. In addition, the technical and economic efficiency of single steps, such as ammonia production by means of the Haber–Bosch process, ammonia distribution and storage, and possibly the ammonia cracking process to hydrogen, affects the overall supply chain. The main purpose of this review paper is to shed light on the main aspects related to the use of ammonia as a hydrogen energy carrier, discussing technical, economic and environmental perspectives, with the aim of supporting the international debate on the potential role of ammonia in supporting the development of hydrogen pathways. The analysis also compares ammonia with alternative solutions for the long-distance transport of hydrogen, including liquefied hydrogen and other liquid organic carriers such as methanol.

Formic Acid Dehydrogenation over a Monometallic Pd and Bimetallic Pd:Co Catalyst Supported on Activated Carbon

In this study, palladium is proposed as an active site for formic acid dehydrogenation reaction. Pd activity was modulated with Co metal with the final aim of finding a synergistic effect that makes possible efficient hydrogen production for a low noble metal content. For the monometallic catalysts, the metal loadings were optimized, and the increase in the reaction temperature and presence of additives were carefully considered. The present study aimed, to a great extent, to enlighten the possible routes for decreasing noble metal loading in view of the better sustainability of hydrogen production from liquid organic carrier molecules, such as formic acid.

Positive influence of minute Pt addition on the activity of Ni supported on defective graphene for hydrogenation/dehydrogenation of N-ethylcarbazole as liquid organic carrier

Positive influence of minute Pt addition on the activity of Ni supported on defective graphene for hydrogenation/dehydrogenation of N-ethylcarbazole as liquid organic carrier

Active site imprinting on Ti oxocluster metal–organic frameworks for photocatalytic hydrogen release from formic acid

MOFs offer great potential in the photocatalytic hydrogen release from liquid organic carriers: towards the use of on-board H2as a transportation fuel.

Continuous Room-Temperature Hydrogen Release from Liquid Organic Carriers in a Photocatalytic Packed-Bed Flow Reactor.

Invited for this month's cover is the group of Prof. Dr. Milad Abolhasani at North Carolina State University. The image shows an energy-efficient strategy for on-site and room-temperature hydrogen release from liquid organic hydrogen carriers. The Research Article itself is available at 10.1002/cssc.202200733.

Continuous Room-Temperature Hydrogen Release from Liquid Organic Carriers in a Photocatalytic Packed-Bed Flow Reactor.

Despite the potential of hydrogen (H2) storage in liquid organic carriers to achieve carbon neutrality, the energy required for H2 release and the cost of catalyst recycling have hindered its large‐scale adoption. In response, a photo flow reactor packed with rhodium (Rh)/titania (TiO2) photocatalyst was reported for the continuous and selective acceptorless dehydrogenation of 1,2,3,4‐tetrahydroquinoline to H2 gas and quinoline under visible light irradiation at room temperature. The tradeoff between the reactor pressure drop and its photocatalytic surface area was resolved by selective in‐situ photodeposition of Rh in the photo flow reactor post‐packing on the outer surface of the TiO2 microparticles available to photon flux, thereby reducing the optimal Rh loading by 10 times compared to a batch reactor, while facilitating catalyst reuse and regeneration. An example of using quinoline as a hydrogen acceptor to lower the energy of the hydrogen production step was demonstrated via the water‐gas shift reaction.

A quantitative review of slurries for hydrogen storage – Slush hydrogen, and metal and chemical hydrides in carrier liquids

Methods of storing hydrogen for energy applications have been widely discussed, both across time and by people from various organisations and backgrounds. Recently, interest in hydrogen storage has developed for space exploration, for both terrestrial and extra-terrestrial applications, and more recently by politicians and business leaders for displacing carbon-intensive fuels. Hydrogen storage options range from solid to gas phases, with several detailed reviews focussing on metal hydrides such as alkali-earth alloys, chemical hydrides such as ammonia, and liquid organic carriers available. An overlooked part of the literature has been hydrogen storage in slurries, where each method of storage has unique advantages, challenges, and stages of research and development. Here, we focus on reviewing the literature on slush hydrogen and slurries of metal and chemical hydrides.

(Invited) Development and Understanding of Advanced Materials for Hydrogen Storage and Delivery

Continued efforts to advance hydrogen storage and delivery require development and validation of efficient materials platforms coupled with mechanistic understanding of storage and conversion of hydrogen or its carriers. The Hydrogen Materials Advanced Research Consortium (HyMARC) is working with the research community to provide cutting-edge materials development advanced characterization, and theoretical modeling in support of these efforts, leveraging multiple U.S. Department of Energy national labs and their user facilities. Within this program, Berkeley Lab is developing stable and efficient solutions to hydrogen storage involving nanoscale encapsulation, and boosts to the conversion efficiency for liquid organic carriers through the development of single-atom catalyst platforms. The Molecular Foundry and The Advanced Light Source at Berkeley Lab provide deep insight into our materials advances through first-principles modeling of atomic and electronic structure, and X-ray spectroscopy of evolving materials systems at high temperatures and pressures.

Hydrogenation/Dehydrogenation Catalysts for Hydrogen Storage Systems Based on Liquid Organic Carriers (A Review)

Hydrogenation/Dehydrogenation Catalysts for Hydrogen Storage Systems Based on Liquid Organic Carriers (A Review)

Hydrogen economy, energy, and liquid organic carriers for its mobility

The World hydrogen economy refers to the structure of hydrogen production and its utilization as a primary energy carrier. One of the major keys for the development of hydrogen economy is safe, economical, and compact hydrogen storage. The traditional liquid state hydrogen storage poses several challenges such as safety and cost for on-board energy carrier. Hence, they failed to meet future energy challenges. Liquid organic hydrogen carriers (LOHCs) provide a pliable route to storage and transportation of hydrogen energy. This transport relies on two steps i.e. hydrogenation and dehydrogenation. In hydrogen storage chemistry, hydrogen undergoes covalent bonding with respective LOHC. LOHCs at ambient conditions are very much similar to the traditional fuels like diesel and gasoline, hence it can be easily transported and stored. Following the same, systems like Dodecahydro-N-ethylcarbazole and 1,2-dihydro-1,2-azaborine represents potential properties with capacities of 5.8 and 7.1 wt% hydrogen uptake. Apart from this, circular hydrogen carrier like methanol i.e. synthesized from atmospheric carbon dioxide (CO2) is also a potential candidate for hydrogen storage. The present review highlights the above-mentioned systems based on their operating temperature, economical aspects, toxicity, and other factors that are highly considerate for their mobile applications.

Hydrogen storage using liquid organic carriers: Equilibrium simulation and dehydrogenation reactor design

Liquid organic hydrogen carriers (LOHC) are unsaturated organic compounds used for chemical hydrogen storage. Using an equilibrium model of the LOHC N-ethylcarbazole, we discuss potential efficiency increases of hydrogen storage systems based on N-ethylcarbazole by the integration of low-temperature waste heat. N-ethylcarbazole is well suited for pressure swing operation with heat exchange between hydrogenation and dehydrogenation. We present and discuss kinetic data of the dehydrogenation reaction gathered in a tubular reactor that was mounted in different orientations and flow configurations. Similar maximum values of power density are reached in vertical and in horizontal orientation. Vertical orientation allows the favorable operation with counter-flow of the liquid carrier and the evolved hydrogen gas and radial heat transfer is significantly better than in horizontal orientation. In vertical reactor configurations, catalyst efficiency and operational stability are impaired at high void fractions. This issue can be reduced by dehydrogenation at elevated pressure and intermediate gas separation from the catalyst bed.

Structure-reactivity relationship in catalytic hydrogenation of heterocyclic compounds over ruthenium black; Part B: Effect of carbon substitution by heteroatom

The effect of the type of heteroatom in the structure on the recyclability of possible candidate compounds for application as LOC (liquid organic carriers) was studied by comparing the rate and selectivity obtained in hydrogenation of carbazole, dibenzothiophene, dibenzofuran and fluorene. The effect of a partial saturation of the compound on its hydrogenation yield and reaction pathway was also considered by studying hydrogenation of 1,2,3,4-tetrahydrocarbazole. Using Ru black catalyst, the rate of hydrogenation was found to decrease in order; dibenzofuran>1,2,3,4-tetrahydrocarbazole>carbazole>>fluorene. No reaction was observed in the hydrogenation of dibenzothiophene under the conditions studied which was attributed to the immediate poisoning of ruthenium metal by sulphur compounds. The rate of hydrogenation of fluorene was around 3 times lower as compared to carbazole and over 8 times lower as compared to that of dibenzofuran under the same reaction conditions. With the exeption of S containing dibenzothiophene, the presence of the heteroatom in the structure was found to be beneficial in terms of increasing the rate of hydrogen loading step. Additionally, a higher reaction rate was obtained in the hydrogenation of the partially saturated 1,2,3,4-tetrahydrocarbazole as compared to the substrate carbazole. The structure and stability of intermediates was found to be significantly influenced by the type and presence of a heteroatom in the structure. A stable octahydro-intermediate was observed only with N-heterocycles, whereas a stable hexahydro-intermediate was produced in the polyaromatic hydrocarbon-fluorene. Additionally, the theoretically obtained lowest total enthalpies using DFT calculations agreed well with the stable intermediates observed experimentally in the hydrogenation of fluorene. Theoretical DFT differences in enthalpies also indicated the products of hydrogenolysis of perhydro-dibenzofuran to be the most favourable products of its hydrogenation, which agreed well with the experimental observations. Overall, taking into account the recyclability of LOC, substitution of carbon with a N heteroatom was demonstrated to be one of the promising approaches to improve the kinetics of the hydrogen loading step.

Structure-reactivity relationship in catalytic hydrogenation of heterocyclic compounds over ruthenium black-Part A: Effect of substitution of pyrrole ring and side chain in N-heterocycles

The catalytic hydrogenations of carbazole, 9-carbazole-9H-ethanol and acridine over Ru black were studied and compared with the results obtained from 9-ethylcarbazole with the aim to elucidate the influence of the molecules structures on their ability to store hydrogen. The reactions were modelled with the rate constants derived for each of the elementary reactions observed. The specific catalytic activity and selectivity were found to be strongly dependent on variation in the structure of substrate due to both thermodynamic and kinetic reasons. The hydrogenation activity was found to increase in order: acridine>9-H-carbazole-9H-ethanol>carbazole>9-ethylcarbazole. The hydrogenation pathway of the molecule consisting of six-membered ring (acridine) was found to be more complex than that of a corresponding five-membered ring structure. The type of intermediates also appeared to depend on the basicity and steric environment of the nitrogen heteroatom, which influenced the geometry of the adsorption on the ruthenium surface. It is believed that this work can provide some general guidelines for the design of superior liquid organic carriers (LOCs).

Hydrogen Storage in Liquid Organic Hydride: Producing Hydrogen Catalytically from Methylcyclohexane

Hydrogen storage for stationary and mobile applications is an expanding research topic. One of the more promising hydrogen storage techniques relies on the reversibility and high selectivity of liquid organic hydrides, in particular, methylcyclohexane (MCH). The use of liquid organic hydrides in hydrogen storage also provides high gravimetric and volumetric hydrogen density, low potential risk, and low capital investment because it is largely compatible with the current transport infrastructure. Despite its technical, economical, and environmental advantages, the concept of hydrogen storage in liquid organic carriers has not been commercially established because of technical limitations related to the amount of energy required to extract the hydrogen from liquid organic hydride and the insufficient stability of the dehydrogenation catalyst. This paper provides a review for the effort that has been directed toward the development of this concept over the past few decades and mainly focuses on the catalytic...