Advances in Catalytic Hydrogenation of Liquid Organic Hydrogen Carriers (LOHCs) Using High-Purity and Low-Purity Hydrogen

Liquid organic hydrogen carriers (LOHCs) are emerging as a promising solution for global hydrogen logistics. The LOHC process involves two primary chemical reactions: hydrogenation for hydrogen storage and dehydrogenation for hydrogen reconversion. In the exothermic hydrogenation reaction, hydrogen-lean compounds are converted to hydrogen-rich compounds, storing hydrogen from various sources such as water electrolysis, fossil fuel reforming, biomass processing, and industrial by-products. Conversely, hydrogen is extracted from hydrogen-rich compounds through an endothermic dehydrogenation reaction and supplied to several hydrogenation utilization offtakers. This review article discusses the development trends in catalytic hydrogenation processes for various LOHC materials, including benzene, toluene, naphthalene, biphenyl-diphenylmethane, benzyltoluene, dibenzyltoluene, and N-ethylcarbazole. It introduces references for catalytic hydrogenation processes utilizing both high-purity and low-purity (alternatively, mixed) hydrogen feedstocks, with particular emphasis on low-purity hydrogen applications. The direct storage of hydrogen with minimal purification, using by-product hydrogen and mixed hydrogen from hydrocarbon and biomass reforming, is crucial for the economic viability of this hydrogen carrier system.