Production of hydrogen from alcohols via homogeneous catalytic transformations mediated by molecular transition-metal complexes

Chemical Communications, Journal Year: 2024, Volume and Issue: 60(31), P. 4148 - 4169

Published: Jan. 1, 2024

An overview of the state-of-the-art advancements is provided on use transition-metal based molecular catalysts to produce hydrogen from liquid organic carriers (LOHCs) derived renewable sources such as alcohols.

Language: Английский

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

Dalton Transactions, Journal Year: 2024, Volume and Issue: 53(30), P. 12698 - 12709

Published: Jan. 1, 2024

Herein, a series of pincer-Mn complexes based on bis(imino)pyridine ligands the type

Language: Английский

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Production of Lactic Acid via Catalytic Transfer Dehydrogenation of Glycerol Catalyzed by Base Metal Salt Ferrous Chloride and Its NNN Pincer-Iron Complexes

Inorganic Chemistry, Journal Year: 2024, Volume and Issue: 63(33), P. 15294 - 15310

Published: Aug. 7, 2024

NNN-Bis(imino) pyridine-based pincer-Fe(II) complexes with an expected trigonal bipyramidal (TBP) geometry equilibrated to a rearranged ion pair of octahedral dicationic Fe complex containing two bis(imino)pyridine ligands that are neutralized by tetrahedral dianionic-[FeCl4]2–. Single-crystal X-ray diffraction (SCXRD), high-resolution mass spectrometry (HRMS), and UV–visible (UV–vis) studies suggested the equilibrium was dictated sterics R group on imine N, less-crowded groups tilting bulky ones favoring TBP geometry. Electron paramagnetic resonance (EPR) Evan's magnetic moment measurements indicated were Fe(II) in high-spin state. In solution, over period 7 days, these oxidized mixture low-spin Fe(III) species. These found be highly active toward transformation biodiesel waste glycerol value-added lactic acid (LA). Particularly, (Ph2NNN)FeCl2 (0.1 mol %) gave 91% LA 99% selectivity at 140 °C using 1.2 equiv NaOH. With 0.0001 % (Ph2NNN)FeCl2, very high turnovers (74% LA, 98% selectivity, 740 000 turnover number (TON) 4405 per hour (TOs/h)) obtained after days. EPR species catalyst, few which detected HRMS. Experiments Hg suggestive mostly homogeneous molecular nature catalyst minor contribution from heterogeneous nanoparticles.

Language: Английский

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Pincer–Ruthenium-Catalyzed β-Methylation of Alcohols

Organometallics, Journal Year: 2023, Volume and Issue: 42(21), P. 3138 - 3152

Published: Oct. 30, 2023

The synthesis and characterization of three NNN pincer–Ru complexes based on bis(imino)pyridine ligands have been reported. These along with other previously reported catalysts 2,6-bis(benzimidazol-2-yl)pyridine employed to accomplish the β-methylation 2-phenylethanol selective β-dimethylation 1-phenylethanol using methanol as an alkylating agent. In general, pincer–ruthenium complex [(MeBim2NNN)RuCl(PPh3)2]Cl dimethyl-substituted ligand was found be most efficient among considered catalysts. Under best conditions, in (0.5 mol %)-catalyzed reactions presence 0.75 equiv KOH 7.5 methanol, up 92% yield β-methylated obtained at 140 °C. On hand, could achieved 2 Na 24.8 methanol. developed synthetic protocol is generic nature applied about 35 substrates. reaction has also probed from a mechanistic point view. While mercury poisoning experiments revealed catalyzed by well-defined molecular catalysts, kinetic indicated that rate product formation linear dependence concentrations both catalyst 2-phenylethanol. DFT studies complement observed secondary isotope effect (KIE) 1.56 suggest dehydrogenolysis involving σ-bond metathesis Ru–H species leading evolution hydrogen rate-determining step barrier 24.06 kcal/mol. Ru–OMe species, being lowest-energy intermediates catalytic cycle, are likely resting state cycle detected NMR HRMS analysis.

Language: Английский

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BIMETALLIC Ni‐Co SUPPORTED ON NITROGEN‐DOPED CARBON NANOTUBES FOR PROX REACTION

ChemCatChem, Journal Year: 2024, Volume and Issue: 16(21)

Published: July 29, 2024

Abstract Hydrogen is a key component for successful energy transition on large scale since it boasts remarkable efficiency. Currently, H 2 mainly obtained through steam reforming of natural gas or hydrocarbons and low‐carbon alcohols but contains approximately % CO, contaminant detrimental to fuel cells. Herein, an N‐doped carbon nanotube was prepared via the soft nitriding method support nickel cobalt PROX‐CO as main reaction hydrogen purification. The most efficient condition achieved when temperature reached 250 °C Ni Co loading rate 7.5 %. In this situation, CO selectivity almost 33 %, conversion 61 Regarding among bimetallic catalysts at minimal variation occurred catalyst 10Ni/N‐CNTs slightly outperformed (64.4 %). effect N‐doping nanotube's structure also revealed. Nitrogen atoms incorporated into lattice nanotubes impart electron‐donor character. Consequently, oxide reduction metallic phase significantly lower temperatures compared other supports such SiO , Al O 3 graphene. For catalysts, strong metal‐support interaction facilitated obtaining different phases milder temperatures.

Language: Английский

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Phosphine-free Ru(II)-CNC pincer complexes with mixed protic- and classical-NHCs in the same molecule for hydrogen production via oxidant-free benzyl alcohol dehydrogenation to benzoic acids

New Journal of Chemistry, Journal Year: 2024, Volume and Issue: unknown

Published: Jan. 1, 2024

New phosphine-free complexes with mixed protic- and classical-NHCs in the same molecule are reported. These shown to be effective catalysts for hydrogen production via oxidant-free benzyl alcohol dehydrogenation benzoic acids.

Language: Английский

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Supported Ruthenium Catalysts for Transformation of Aqueous Glycerol to Hydrogen Gas and Lactic Acid

Energy Advances, Journal Year: 2024, Volume and Issue: unknown

Published: Jan. 1, 2024

We report the transformation of aqueous glycerol (GLY) to selectively produce high-purity H 2 gas (productivity ∼12 L /g Ru /h) and lactic acid (LA, yield 86%) over a supported catalyst at 130 °C.

Language: Английский

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Pincer-Ruthenium-Catalyzed Direct Formation of Fuel-Grade Alkanes via a Net-Decarboxylative Coupling of Alcohols

ACS Catalysis, Journal Year: 2024, Volume and Issue: 15(1), P. 543 - 556

Published: Dec. 20, 2024

The net-decarboxylative coupling of low-molecular weight alcohols to high-molecular alkanes has been investigated using a series NNN pincer-Ru catalysts based on bis(imino)pyridine and 2,6-bis(benzimidazole-2-yl)pyridine ligands. Notably, majority the considered complexes, including Ru precursors, were either not very active or unselective giving alkene/alkane mixtures. However, in presence 0.5 equiv NaOH toluene at 140 °C, complex (MeBim2NNN)RuCl2(PPh3)2 ligand demonstrated high activity up 91% yield with 100% selectivity toward alkane (1,3-diphenyl propane) starting from 2-phenyl ethanol after 24 h reaction. On other hand, (iPr2NNN)RuCl2(PPh3) was found be least gave 14% 1,3-diphenyl propane 25% selectivity. Experimental mechanistic studies point evolution hydrogen (detected by GC) formic acid 1H NMR) during reaction along involvement organic intermediates such as α,β-unsaturated aldehydes. [(MeBim2NNN)RuCl(PPh3)2]Cl catalyzed transformation first-order dependence initial rate concentration both catalyst base. While poisoning experiments Hg revealed homogeneous well-defined molecular nature catalyst, few these species, resting state (MeBim2NNN)RuHCl (experimentally trapped its PPh3 adduct), have identified HRMS analysis NMR studies. DFT complement experimental findings indicate that more favorable hydrogenolysis path, dehydrogenolysis step is rate-determining (ΔG140‡ = 22.81 kcal/mol), it leads formation acetaldehyde (MeBim2NNN)RuHCl. corresponding cycle involved insertion propene into Ru–H bond RDS had relatively unfavorable barrier 27.81 kcal/mol. This work provides direct access jet-fuel-grade single-step, one-pot strategy offers great promise open exciting opportunities this important field study.

Language: Английский

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