Reforming of ethanol to hydrogen and acetic acid catalyzed by pincer-ruthenium complexes

Arora, Vinay; Dhole, Sunil; Kumar, Akshai

doi:10.1039/d3cy01107k

Cited by 8 publications

(3 citation statements)

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“…A comparison of the individual RDSs of the segments related to the transformation of methanol/ 1 → formaldehyde/ 1′ (Scheme ), 16 → 22 (Scheme ) and 22 → 3 (Scheme ) suggests that the overall RDS is the dehydrogenolysis step ( TS-15a ; Δ G 140 ⧧ = 24.06 kcal/mol) that lies in the methanol → formaldehyde dehydrogenation segment (Scheme ). This is in line with the observed secondary KIE of 1.56 (eqs 9, Scheme ). Not surprisingly, none of the intermediates involved in the cycles 1 → 1′ (Scheme ), 16 → 22 (Scheme ), and 22 → 3 (Scheme ) are observed in the HRMS analysis.…”

Section: Resultssupporting

confidence: 90%

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Pincer–Ruthenium-Catalyzed β-Methylation of Alcohols

Nandi,

Jasra,

Kumar

2023

Organometallics

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The synthesis and characterization of three NNN pincer−Ru complexes based on bis(imino)pyridine ligands have been reported. These complexes along with other previously reported pincer−Ru catalysts based on bis(imino)pyridine and 2,6-bis(benzimidazol-2-yl)pyridine ligands have been employed to accomplish the β-methylation of 2-phenylethanol and the selective β-dimethylation of 1-phenylethanol using methanol as an alkylating agent. In general, the pincer−ruthenium complex [( MeBim 2 NNN)RuCl(PPh 3 ) 2 ]Cl based on the dimethyl-substituted 2,6-bis(benzimidazol-2-yl)pyridine ligand was found to be the most efficient among the considered catalysts. Under the best conditions, in the [( MeBim 2 NNN)RuCl(PPh 3 ) 2 ]Cl (0.5 mol %)-catalyzed reactions in the presence of 0.75 equiv of KOH using 7.5 equiv of methanol, up to 92% yield of βmethylated 2-phenylethanol was obtained at 140 °C. On the other hand, selective β-dimethylation of 1-phenylethanol could be achieved in the [( MeBim 2 NNN)-RuCl(PPh 3 ) 2 ]Cl (0.5 mol %)-catalyzed reactions in the presence of 2 equiv of Na using 24.8 equiv of methanol. The developed synthetic protocol is generic in nature and could be applied to accomplish β-methylation and selective β-dimethylation of about 35 substrates. The reaction has also been probed from a mechanistic point of view. While mercury poisoning experiments revealed the reaction to be catalyzed by well-defined molecular catalysts, kinetic experiments indicated that the rate of product formation has a linear dependence on the concentrations of both the pincer−ruthenium catalyst and 2-phenylethanol. DFT studies complement the observed secondary kinetic isotope effect (KIE) of 1.56 and suggest that dehydrogenolysis involving σ-bond metathesis of methanol with the Ru−H species leading to the evolution of hydrogen is the rate-determining step with a barrier of 24.06 kcal/mol. The Ru− H and Ru−OMe species, being the lowest-energy intermediates of the catalytic cycle, are likely to be the resting state of the cycle and have been detected by NMR and HRMS analysis.

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Section: Resultssupporting

confidence: 90%

“…Competitive deuterium labeling studies reveal a secondary kinetic isotope effect (KIE) of 1.56 (eq 10, Scheme ). It is hence unlikely that C–H activation is a part of the rate-determining step (RDS), though it is involved in the catalytic cycle.…”

Section: Resultsmentioning

confidence: 99%

Pincer–Ruthenium-Catalyzed β-Methylation of Alcohols

Nandi,

Jasra,

Kumar

2023

Organometallics

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“…This observation of a stable pincer backbone is very similar to our earlier reports on related dehydrogenation reactions catalysed by bis(imino)pyridine pincer–M (M = Ru, Ni, Co, Mn and Cr) complexes. 55…”

Section: Resultsmentioning

confidence: 99%

Efficient net transfer-dehydrogenation of glycerol: NNN pincer–Mn and manganese chloride as a catalyst unlocks the effortless production of lactic acid and isopropanol

Bisarya,

Dhole,

Kumar

2024

Dalton Trans.

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Bimetallic Ni‐Co Supported on Nitrogen‐Doped Carbon Nanotubes For Prox Reaction

de Souza,

Toniolo,

Schmal

2024

ChemCatChem

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Hydrogen is a key component for a successful energy transition on a large scale since it boasts a remarkable energy efficiency. Currently, H2 is mainly obtained through steam reforming of natural gas or hydrocarbons and low‐carbon alcohols but contains approximately 2% of CO, a contaminant detrimental to H2 fuel cells. Herein, an N‐doped carbon nanotube was prepared via the soft nitriding method to support nickel and cobalt for the PROX‐CO as the main reaction for hydrogen purification. The most efficient condition was achieved when the reaction temperature reached 250°C and the Ni and Co loading rate was 7.5%. In this situation, the CO2 selectivity reached almost 33% and CO conversion was 61%. Regarding CO conversion among bimetallic catalysts at 250°C a minimal variation occurred and the catalyst 10Ni/N‐CNTs slightly out performed (64.4%). The effect of N‐doping on the carbon nanotube’s structure was also revealed. Nitrogen atoms incorporated into the lattice of carbon nanotubes impart an electron‐donor character. Consequently, Co oxide reduction to the metallic phase occurred at significantly lower temperatures compared to other supports such as SiO2, Al2O3, and graphene. For the bimetallic catalysts, the strong metal‐support interaction facilitated obtaining different oxide and metallic phases at milder temperatures

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Reforming of ethanol to hydrogen and acetic acid catalyzed by pincer-ruthenium complexes

Abstract: Ethanol is feed-agnostic and is hence currently one of the most preferred renewable resources for manufacturing essential industrial commodities globally. Herein, we present the catalytic aqueous–phase reforming of ethanol employing...

Cited by 8 publications

References 84 publications

Pincer–Ruthenium-Catalyzed β-Methylation of Alcohols

Pincer–Ruthenium-Catalyzed β-Methylation of Alcohols

Efficient net transfer-dehydrogenation of glycerol: NNN pincer–Mn and manganese chloride as a catalyst unlocks the effortless production of lactic acid and isopropanol

Bimetallic Ni‐Co Supported on Nitrogen‐Doped Carbon Nanotubes For Prox Reaction

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