2023
DOI: 10.3390/hydrogen4010004
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Comprehensive Thermodynamic Study of Alkyl-Cyclohexanes as Liquid Organic Hydrogen Carriers Motifs

Abstract: Alkyl-cyclohexanes can be considered as suitable model compounds to understand the thermochemistry of aromatic compounds and their hydrogenated counterparts discussed as Liquid Organic Hydrogen Carrier systems. Thermochemical measurements on these hydrogen-rich compounds are thwarted by complications due to the 99.9 % purity limitation and sample size specific to these methods. However, the data on vaporisation and formation enthalpies are necessary to optimize the hydrogenation/dehydrogenation processes. In t… Show more

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Cited by 9 publications
(7 citation statements)
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“…In these units the hydrogenation enthalpies of the alkyl benzoates are very similar at −67 kJ•mol −1 / H2 (see Table 12), and the dependence on chain length is hardly noticeable. For comparison, these reaction enthalpies are very similar to those of benzene (−68.5 kJ•mol −1 / H2 ), 69 toluene (−67.5 kJ• mol −1 / H2 ), 69 biphenyl (−65.4 kJ•mol −1 / H2 ), 70 and commercially available thermofluid benzyltoluenes (Marlothem LH) and dibenzyltoluenes (Marlotherm SH) (−63.5 and −65.4 kJ• mol −1 / H2 , respectively 71 ).…”
Section: Energetics Of Hydrogenation and Transfer Hydrogenation React...mentioning
confidence: 71%
“…In these units the hydrogenation enthalpies of the alkyl benzoates are very similar at −67 kJ•mol −1 / H2 (see Table 12), and the dependence on chain length is hardly noticeable. For comparison, these reaction enthalpies are very similar to those of benzene (−68.5 kJ•mol −1 / H2 ), 69 toluene (−67.5 kJ• mol −1 / H2 ), 69 biphenyl (−65.4 kJ•mol −1 / H2 ), 70 and commercially available thermofluid benzyltoluenes (Marlothem LH) and dibenzyltoluenes (Marlotherm SH) (−63.5 and −65.4 kJ• mol −1 / H2 , respectively 71 ).…”
Section: Energetics Of Hydrogenation and Transfer Hydrogenation React...mentioning
confidence: 71%
“…An alternative chemical modification, instead of integrating something into the ring itself, could be the introduction of substitutions at the ring. For example, there are indications that alkylation on the ring leads to a reduction in enthalpy of reaction for dehydrogenation [3].…”
Section: Introductionmentioning
confidence: 99%
“…The enthalpies of the hydrogenation/dehydrogenation reactions are desired to be as low as possible to decrease the energy demand of hydrogen release (without compromising the stable interaction of hydrogen with the organic carrier) [5]. In our recent work [6], the influence of structure on the magnitude of hydrogenation/dehydrogenation enthalpies in the LOHC system based on alkylbenzene/alkyl-cyclohexane component pairs has been analyzed. It has been found that in the case of the sterically hindered ortho-substituted species (e.g., 1,2dimethyl-benzene and 1-methyl-2-ethyl-benzene, or alkylbenzenes) with branched tertbutyl substituents, the heats of reaction are significantly lower than the usual level for aromatic homocycles (see Figure 1).…”
Section: Introductionmentioning
confidence: 99%
“…From a practical point of view, the di-and tri-substituted iso-propyl-and tert-butylbenzenes can be prepared using known synthetic routes [7,8], and both the hydrogen-lean and hydrogen-rich counterparts have acceptably low vapour pressures [6], which is one of the criteria for LOHC applications. Thus, if specific structural motifs that allow for a reduction in reaction enthalpy could be revealed, this could support the development of improved LOHC systems.…”
Section: Introductionmentioning
confidence: 99%
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