Modelling and scaleup of the kinetics with deactivation of methylcyclohexane dehydrogenation for hydrogen energy storage

Liquid Organic Hydrogen Carriers or Organic Liquid Hydrides: 40 Years of History

The term LOHC stands for Liquid Organic Hydrogen Carriers. The term has been so well accepted by the scientific community that the studies published before the existence of this name are not very visible. In this mini-review, we have tried to rehabilitate various studies that deserve to be put back in the spotlight in the present context. Studies indeed began in the early 1980s and many publications have compared the use of various organic carriers, various catalysts and reactors. Recent reviews also include the economic aspects of this concept.

Catalytic Hydrogenation and Dehydrogenation Reactions of N-alkyl-bis(carbazole)-Based Hydrogen Storage Materials

Recently, there have been numerous efforts to develop hydrogen-rich organic materials because hydrogen energy is emerging as a renewable energy source. In this regard, we designed and prepared four new materials based on N-alkyl-bis(carbazole), 9,9′-(2-methylpropane-1,3-diyl)bis(9H-carbazole) (MBC), 9,9′-(2-ethylpropane-1,3-diyl)bis(9H-carbazole) (EBC), 9,9′-(2-propylpropane-1,3-diyl)bis(9H-carbazole) (PBC), and 9,9′-(2-butylpropane-1,3-diyl)bis(9H-carbazole) (BBC), to investigate their hydrogen adsorption/hydrogen desorption reactivity depending on the length of the alkyl chain. The gravimetric densities of MBC, EBC, PBC, and BBC were 5.86, 5.76, 5.49, and 5.31 H2 wt %, respectively, again depending on the alkyl chain length. All materials showed complete hydrogenation reactions under ruthenium on an alumina catalyst at 190 °C, and complete reverse reactions and dehydrogenation reactions were observed under palladium on an alumina catalyst at <280 °C. At this temperature, all the prepared compounds were thermally stable, and no decomposition was observed.

Low-temperature selective catalytic dehydrogenation of methylcyclohexane by surface protonics

The methylcyclohexane (MCH)–toluene cycle is a promising liquid organic hydride system as a hydrogen carrier. Generally, MCH dehydrogenation has been conducted over Pt-supported catalysts, for which it requires temperatures higher than 623 K because of its endothermic nature. For this study, an electric field was applied to Pt/TiO₂ catalyst to promote MCH dehydrogenation at low temperatures. Selective dehydrogenation was achieved with the electric field application exceeding thermodynamic equilibrium, even at 423 K. With the electric field, “inverse” kinetic isotope effect (KIE) was observed by accelerated proton collision with MCH on the Pt/TiO₂ catalyst. Moreover, Pt/TiO₂ catalyst showed no methane by-production and less coke formation during MCH dehydrogenation. DRIFTS and XPS measurements revealed that electron donation from TiO₂ to Pt weakened the interaction between catalyst surface and π-coordination of toluene. Results show that the electric field facilitated MCH dehydrogenation without methane and coke by-production over Pt/TiO₂ catalyst.

Electric field facilitated MCH dehydrogenation at 423 K without methane and coke by-production over Pt/TiO₂ catalyst by surface protonics.

Irreversible catalytic methylcyclohexane dehydrogenation by surface protonics at low temperature

Surface protonics by applying electric field promotes low temperature methylcyclohexane dehydrogenation for effective hydrogen production.

Associative Adsorption Kinetics: A Novel Kinetic Model for the Dehydrogenation of Methylcyclohexane

Methylcyclohexane (MCH) dehydrogenation is an important reforming reaction and is considered as a model naphthene dehydrogenation reaction. An increase in the rate of this reaction with the addition of hydrogen at low pressures has been observed by various researchers in the field. This enhancement in rate is described, in the present study, using the concept of associative adsorption of MCH with hydrogen in Langmuir–Hinshelwood–Hougen–Watson single-site and dual-site surface reaction mechanisms. The various rate equations developed on these bases are tested against the experimental data of Usman over Pt/Al2O3 and the best-fit rate model is presented. An activation energy of 52.0 kJ mol−1 is obtained for the best-fit rate model.