High-Purity Hydrogen Generation via Dehydrogenation of Organic Carriers: A Review on the Catalytic Process

Abstract

High-purity hydrogen delivery for stationary and mobile applications using fuel cells is a subject of rapidly growing interest. As a consequence, the development of efficient storage technologies and processes for hydrogen supply is of primary importance. Promising hydrogen storage techniques rely on the reversibility and high selectivity of liquid organic hydrogen carriers (LOHCs), for example, methylcyclohexane, decalin, dibenzyltoluene, or dodecahydrocabazole. LOCHs have high gravimetric and volumetric hydrogen density, and they involve low risk and capital investment because they are largely compatible with the current transport infrastructure used for fossil fuels. A further advantage comes from the high purity (close to 100%) of the hydrogen generated by dehydrogenation, suitable to directly feed fuel cells without the need for bulky purification modules. Partial dehydrogenation (PDH) of liquid fuels has recently emerged as a transition technology for hydrogen delivery purposes. The principle is to extract from fossil fuels a small fraction of the available hydrogen, which can be used for fuel cell applications, while the dehydrogenated hydrocarbon mixture maintains suitable properties for its use as fuel. With this technology, the large energy demand of dehydrogenation processes can be satisfied by implementing a heat exchanger between the engine and the dehydrogenation reactor, overcoming one of the main constraints associated with the use of organic liquids as hydrogen carriers. This method qualifies itself as a transition technology toward more electrified transportations, in which the main propulsion is still obtained by fuel combustion, although the electrical utilities or auxiliary propulsion are powered by fuel cells. This paper provides a review of the effort that has been directed toward the utilization of organic liquids as hydrogen carriers, with particular focus on the design of the catalytic dehydrogenation process and on the recent approach of fuel partial dehydrogenation.

Construction of a Nanoporous Highly Crystalline Hexagonal Boron Nitride from an Amorphous Precursor for Catalytic Dehydrogenation

“…[32][33][34] But the realization of this future economy relies on the development of ah ighly efficient catalytic system for the reversibility and high selectivity of LOHC, [35] especially the N-ethylcarbazole (NEC) and dodecahydro-N-ethylcarbazole (12H-NEC) cycle systems. [32][33][34] But the realization of this future economy relies on the development of ah ighly efficient catalytic system for the reversibility and high selectivity of LOHC, [35] especially the N-ethylcarbazole (NEC) and dodecahydro-N-ethylcarbazole (12H-NEC) cycle systems.…”

“…Handling hydrogen in chemically bound form as liquid organic hydrogen carriers (LOHCs) supports concept that af uture hydrogen economy may work without the need to handle large amounts of elemental hydrogen. [32][33][34] But the realization of this future economy relies on the development of ah ighly efficient catalytic system for the reversibility and high selectivity of LOHC, [35] especially the N-ethylcarbazole (NEC) and dodecahydro-N-ethylcarbazole (12H-NEC) cycle systems. [36] However,e ven after decades of research, the unsatisfactory performance obtained using high doses of precious-metal dehydrogenation catalysts and the required high reaction temperatures has proven to be ab ottleneck (Table S1).…”

Enhancing Multicomponent Metal–Organic Frameworks for Low Pressure Liquid Organic Hydrogen Carrier Separations

“…Cycloalkanes, such as cyclohexane and methylcyclohexane, are essential components of the chemical and petrochemical industries . Of significant importance is their application as liquid organic hydrogen carriers (LOHCs) to safely store and transport hydrogen . These LOHCs are hydrogenated for hydrogen storage, and then dehydrogenated upon demand to release hydrogen .…”

“…Of significant importance is their application as liquid organic hydrogen carriers (LOHCs) to safely store and transport hydrogen . These LOHCs are hydrogenated for hydrogen storage, and then dehydrogenated upon demand to release hydrogen . The cyclohexane–benzene–hydrogen and the methylcyclohexane–toluene–hydrogen cycles are the most conventional examples, although the former is not as industrially relevant due to the carcinogenic properties of benzene .…”

Highly Selective Hydrogenation of Tetralin to cis‐Decalin Using Ru Catalyst

“…And cyclic saturated hydrocarbons such as decalin and cyclohexane are proposed as new mobile hydrogen storage media, named liquid organic hydrogen carriers (LOHCs), because they are more stable, safer, cheaper and greener than other storage methods. [1,2] Decalin with high hydrogen contents of 7.3 wt.% and 64.8 kg H 2 /m 3 is considered to be an excellent mobile storage medium of hydrogen. [3] In addition, cis-decalin is more preferable, because the dehydrogenation rate of cis-decalin is faster than that of trans-decalin.…”