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

Safronov SP, Vostrikov SV, Samarov AA, Wasserscheid P, Müller K, Verevkin SP (2023)

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Publication Type: Journal article

Publication year: 2023

Journal

Book Volume: 331

Article Number: 125764

DOI: 10.1016/j.fuel.2022.125764

Abstract

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.

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How to cite

APA:

Safronov, S.P., Vostrikov, S.V., Samarov, A.A., Wasserscheid, P., Müller, K., & Verevkin, S.P. (2023). Comprehensive thermodynamic study of substituted indoles/perhydro indoles as potential liquid organic hydrogen carrier system. Fuel, 331. https://doi.org/10.1016/j.fuel.2022.125764

MLA:

Safronov, Sergey P., et al. "Comprehensive thermodynamic study of substituted indoles/perhydro indoles as potential liquid organic hydrogen carrier system." Fuel 331 (2023).

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