Density functional theory study on the dehydrogenation of 1,2-dimethyl cyclohexane and 2-methyl piperidine on Pd and Pt catalysts

Yook, Hyunwoo; Kim, Kyeounghak; Park, Ji Hoon; Suh, Young Woong; Han, Jeong Woo

doi:10.1016/j.cattod.2019.09.039

Cited by 33 publications

(11 citation statements)

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“…The deviation of these different methods was within 5%. Although the detailed reaction mechanism consisting of possible elementary steps for this reaction was not elucidated yet, it was recently demonstrated that the heterocyclic piperidine ring exhibited faster dehydrogenation kinetics than the homocyclic cyclohexane ring according to the theoretical calculations for the dehydrogenation of two separate cyclic compounds (i.e., 2-methylpiperidine and 1,2-dimethylcyclohexane) . Therefore, the dehydrogenation can occur first on H 12 -MBP to produce H 6 -MBP as an intermediate that can successively be dehydrogenated to H 0 -MBP as the final desired product.…”

Section: Resultsmentioning

confidence: 99%

Catalytic Consequences of Supported Pd Catalysts on Dehydrogenative H₂ Evolution from 2-[(n-Methylcyclohexyl)methyl]piperidine as the Liquid Organic Hydrogen Carrier

Kim

Song

Choi

et al. 2020

ACS Sustainable Chem. Eng.

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Herein, nanoporous Al2O3, CeO2, TiO2, ZrO2, and SnO2 were used as the supports for Pd nanoparticles, and effects of surface characteristics on catalytic performances for dehydrogenation of 2-[(n-methylcyclohexyl)methyl]piperidine (H12-MBP) as the H2-rich liquid organic hydrogen carrier were investigated. The H2 yield, dehydrogenation rate, product selectivity, and recyclability of the supported Pd catalysts depended on the metal oxide support and Pd loading. The H2 yield and reaction rate of the Al2O3 supporting 5 wt % Pd with a mean size of 5.76 nm were the highest (75.8%) and the fastest (k 1 = 0.076 min–1), respectively, of all the catalysts. CeO2 exhibited the highest reducibility and the best supporting ability for Pd nanoparticles, which thus dispersed Pd with the smallest mean size of 3.45 nm. Although this catalyst exhibited a lower H2 yield (67.1%) and a slower reaction rate (k 1 = 0.030 min–1) than Al2O3, it showed the best recyclability without a significant loss of activity during four consecutive runs, which could be attributed to the strong metal–support interaction of Pd to the surface of CeO2. The H2 yield and the dehydrogenation rate were systematically correlated with the surface characteristics of the metal oxides, such as acidity, adsorption affinity (adsorption energy), and charge transfer value of H12-MBP, which were determined via combined experimental and theoretical studies.

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Section: Resultsmentioning

confidence: 99%

Catalytic Consequences of Supported Pd Catalysts on Dehydrogenative H₂ Evolution from 2-[(n-Methylcyclohexyl)methyl]piperidine as the Liquid Organic Hydrogen Carrier

Kim

Song

Choi

et al. 2020

ACS Sustainable Chem. Eng.

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“…From DFT calculations, Pd was also found to have a higher catalytic activity than Pt with a lower activation energy barrier by 10.6 kJ mol −1 . 131 3.1.3.2. Tetrahydroquinoline.…”

Section: Catalysis In Liquid Organic Hydrogen Carriersmentioning

confidence: 99%

Catalysis in Liquid Organic Hydrogen Storage: Recent Advances, Challenges, and Perspectives

Salman

Rambhujun

Pratthana

et al. 2022

Ind. Eng. Chem. Res.

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With the renewed interest for hydrogen as an energy carrier, means to produce, but most importantly store, transport, and distribute, "green" hydrogen over long distances has become important. In this context, liquid organic molecules that can be hydrogenated and dehydrogenated under mild conditions of temperature and pressure continue to attract significant attention. These liquid organic molecules referred as "liquid organic hydrides" in the early 1980s include molecules such as cyclohexane, methylcyclohexane, decalin, N-heterocycles, methanol, ethanol, and formic acid. However, current liquid organic hydrides still suffer from limitations along with the emergence of more effective catalysts to meet the requirement of competing (de)hydrogenation reactions, as well as new chemistry to enable their (de)hydrogenation reactions under milder conditions and extended cycle lives. Herein, we critically review common state-ofthe-art catalyst designs, which remain one of the main barriers to the effective emergence of liquid organic hydrogen carriers enabling the widespread transport and distribution of hydrogen. Many of the most effective current catalysts are based on noble metals. Transitioning away from these rare critical elements to enable hydrogen uptake/release from organic compounds under economically viable chemical routes is a necessity.

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“…Both dehydrogenation steps follow the first-order kinetics. However, the dehydrogenation rates and rate constants ( k 1 and k 2 in Scheme ) for piperidine and cyclohexane rings are significantly different due to the different reactivities of the homocycle and heterocycle. ,, In general, the homocyclic cyclohexane ring is dehydrogenated at a slower rate than the heterocyclic piperidine ring (typically, k 1 ≫ k 2 ). ,,, Therefore, the overall dehydrogenation rate corresponding to the maximum H 2 yield is strongly dependent on the rate and extent of H 2 discharge from the cyclohexane moiety of H 6 -MBP, which is formed as the intermediate species. − , …”

Section: Introductionmentioning

confidence: 99%

“…16,24,25 In general, the homocyclic cyclohexane ring is dehydrogenated at a slower rate than the heterocyclic piperidine ring (typically, k 1 ≫ k 2 ). 16,17,26,27 Therefore, the overall dehydrogenation rate corresponding to the maximum H 2 yield is strongly dependent on the rate and extent of H 2 discharge from the cyclohexane moiety of H 6 -MBP, which is formed as the intermediate species. [16][17][18]26 For complete dehydrogenation of H 12 -MBP to H 0 -MBP, the partially dehydrogenated intermediate, H 6 -MBP bearing a pyridine ring should be bound to the catalyst surface with sufficient residence time to surmount the second activation barrier for dehydrogenation of the cyclohexane ring.…”

Section: ■ Introductionmentioning

confidence: 99%

“…16,17,26,27 Therefore, the overall dehydrogenation rate corresponding to the maximum H 2 yield is strongly dependent on the rate and extent of H 2 discharge from the cyclohexane moiety of H 6 -MBP, which is formed as the intermediate species. [16][17][18]26 For complete dehydrogenation of H 12 -MBP to H 0 -MBP, the partially dehydrogenated intermediate, H 6 -MBP bearing a pyridine ring should be bound to the catalyst surface with sufficient residence time to surmount the second activation barrier for dehydrogenation of the cyclohexane ring. However, the pK b value of pyridine being 8.7, it is a weaker base than piperidine which has a lower pK b value of 2.7.…”

Section: ■ Introductionmentioning

confidence: 99%

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Enhanced Dehydrogenative H₂ Release from N-Containing Amphicyclic LOHC Boosted by Pd-Supported Nanosheet MFI Zeolites Having Strong Acidity and Large Mesoporosity

Lim

Song

Jeong

et al. 2022

ACS Sustainable Chem. Eng.

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The amount and rate of H 2 discharge from 2-[(nmethylcyclohexyl)methyl]piperidine (H 12 -MBP), an amphicyclic liquid organic hydrogen carrier (LOHC) having two cycle moieties (cyclohexane and piperidine) with different reactivities, are determined by dehydrogenation of a cyclohexane ring with less reactivity. To realize high H 2 yields with rapid kinetics, the cyclohexane ring in the partially dehydrogenated 2-[nmethylcyclohexyl]methyl)pyridine (H 6 -MBP) that is generated as the intermediate species should be fully dehydrogenated to 2-(nmethylbenzyl)pyridine (H 0 -MBP). This is approached using Pdsupported nanosheet zeolites having mesoporous structures bearing high concentrations of strongly acidic sites on external surfaces, which can not only enhance the diffusion of bulky H 12 -MBP but also strongly bind the basic piperidine ring in H 12 -MBP and H 6 -MBP. The H 2 yields and rate constants are correlated with the acidity, mesoporosity, and adsorption behaviors of the LOHCs. As these factors are strengthened, H 2 yield and rate constants increased dramatically within the ranges of 16.0−64.7% and 0.0001−0.0013 min −1 , respectively. The results prove that mesoporous zeolites can be used for constructing supported Pd catalysts achieving high H 2 yields with rapid kinetics from N-containing amphicyclic LOHCs.

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Density functional theory study on the dehydrogenation of 1,2-dimethyl cyclohexane and 2-methyl piperidine on Pd and Pt catalysts

Cited by 33 publications

References 50 publications

Catalytic Consequences of Supported Pd Catalysts on Dehydrogenative H₂ Evolution from 2-[(n-Methylcyclohexyl)methyl]piperidine as the Liquid Organic Hydrogen Carrier

Catalytic Consequences of Supported Pd Catalysts on Dehydrogenative H₂ Evolution from 2-[(n-Methylcyclohexyl)methyl]piperidine as the Liquid Organic Hydrogen Carrier

Catalysis in Liquid Organic Hydrogen Storage: Recent Advances, Challenges, and Perspectives

Enhanced Dehydrogenative H₂ Release from N-Containing Amphicyclic LOHC Boosted by Pd-Supported Nanosheet MFI Zeolites Having Strong Acidity and Large Mesoporosity

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Density functional theory study on the dehydrogenation of 1,2-dimethyl cyclohexane and 2-methyl piperidine on Pd and Pt catalysts

Cited by 33 publications

References 50 publications

Catalytic Consequences of Supported Pd Catalysts on Dehydrogenative H2 Evolution from 2-[(n-Methylcyclohexyl)methyl]piperidine as the Liquid Organic Hydrogen Carrier

Catalytic Consequences of Supported Pd Catalysts on Dehydrogenative H2 Evolution from 2-[(n-Methylcyclohexyl)methyl]piperidine as the Liquid Organic Hydrogen Carrier

Catalysis in Liquid Organic Hydrogen Storage: Recent Advances, Challenges, and Perspectives

Enhanced Dehydrogenative H2 Release from N-Containing Amphicyclic LOHC Boosted by Pd-Supported Nanosheet MFI Zeolites Having Strong Acidity and Large Mesoporosity

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Catalytic Consequences of Supported Pd Catalysts on Dehydrogenative H₂ Evolution from 2-[(n-Methylcyclohexyl)methyl]piperidine as the Liquid Organic Hydrogen Carrier

Catalytic Consequences of Supported Pd Catalysts on Dehydrogenative H₂ Evolution from 2-[(n-Methylcyclohexyl)methyl]piperidine as the Liquid Organic Hydrogen Carrier

Enhanced Dehydrogenative H₂ Release from N-Containing Amphicyclic LOHC Boosted by Pd-Supported Nanosheet MFI Zeolites Having Strong Acidity and Large Mesoporosity