Platinum Metal Catalysts

Rylander, Paul N.

doi:10.1016/b978-0-12-395532-6.50004-0

Cited by 12 publications

(8 citation statements)

References 108 publications

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“…To further study the degree of isotope exchange and implications on data analysis of deuterium incorporation, hydrogenation of tetra(ethylene glycol) diacrylate (TEGDA) was carried out. TEGDA was utilized for its water-solubility and to observe deuterium incorporation in a mechanistically simpler reduction, known to occur over Pt sites alone Scheme shows expected deuterium incorporation into the alkene after hydrogenation with permutation A .…”

Section: Resultsmentioning

confidence: 99%

A Mechanistic Study of Polyol Hydrodeoxygenation over a Bifunctional Pt-WO_x/TiO₂ Catalyst

et al. 2020

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In recent years, metal−metal oxide catalysts have proven to be robust catalysts for hydrodeoxygenation (HDO) of oxygenated compounds derived from biorenewable feedstocks to value-added products. Herein, the conversion of 1,2,6-hexanetriol (1,2,6-HT) to 1,6-hexanediol (1,6-HD) in aqueous media over a Pt-WO x /TiO 2 catalyst is examined via isotope incorporation in HDO of a model compound, 1,2-pentanediol (1,2-PD). Absence of a primary kinetic isotope effect (k H /k D = 0.84 ± 0.11) disproves a potential direct C−O bond scission mechanism. The observation of nearly complete deuterium incorporation in both the α-C and the β-C is inconsistent with the reverse Mars−van Krevelen mechanism and suggests an enol formation pathway. Evidence consistent with the intermediacy of an oxocarbenium ion as a minor contributor has also been observed. In drawing the conclusions, it was necessary to characterize the facile isotope exchange between surface activated hydrogen and the water solvent. Hydrogenation of a water-soluble olefin, tetra(ethylene glycol) diacrylate (TEGDA) in H 2 /D 2 O revealed predominant incorporation of deuterium instead of hydrogen in the reduced product, confirming the rapid exchange of surface activated hydrogen. The methods used in this study provide clarification about a reaction mechanism currently under debate, and these findings can be applied to other systems involving HDO of linear polyols over metal−metal oxide catalysts, improving catalyst design and utilization of sustainable feedstocks.

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Section: Resultsmentioning

confidence: 99%

A Mechanistic Study of Polyol Hydrodeoxygenation over a Bifunctional Pt-WO_x/TiO₂ Catalyst

et al. 2020

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“…Both the lower overall reaction rate and the enhanced secondary cracking can be attributed to the partial poisoning of the (de)hydrogenation metallic function by CO, which is known to adsorb strongly on Pt 0 , decreasing the number of surface metal sites available for hydrogen abstraction . While enhanced CO tolerances have been reported for alternative metals such as Pd, or bimetallic combinations (e.g., PtPd, PtFe, etc.…”

Section: Resultsmentioning

confidence: 99%

In Situ Hydrocracking of Fischer–Tropsch Hydrocarbons: CO-Prompted Diverging Reaction Pathways for Paraffin and α-Olefin Primary Products

et al. 2016

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The single-step production of wax-free liquid hydrocarbons from syngas (H₂ + CO) via integration of Fischer–Trospch (FT) and hydrocracking catalysts represents an attractive approach toward process intensification in compact gas-to-liquid technologies. Despite current, intensive efforts on the development of hybrid (multifunctional) catalysts to this end, not much is known about the reactivity of different FT primary products on hydrocracking catalysts under syngas. Using model compounds, the individual and collective reactivities of n-paraffin and α-olefin FT primary products were systematically studied on a Pt/nano-H-ZSM-5 hydrocracking catalyst under H₂ (standard hydrocracking) and syngas (in situ hydroprocessing) atmospheres. Under H₂, both reactants show indistinguishable reactivity as rapid olefin hydrogenation precedes hydrocracking. Under syngas, however, inhibition of (de)hydrogenation functionalities by CO poisoning of metal sites leads to a notable divergence of the reaction pathways for n-paraffins and α-olefins. Under these conditions, α-olefins showed enhanced reactivity, as an initial dehydrogenative activation step is not required, and contributed to moderate secondary cracking, likely via enhanced competitive adsorption on the acid sites. Besides, CO poisoning restored the intrinsic activity of the zeolite for the oligomerization of short-chain (α-)olefins, providing an additional net chain-growth pathway, which contributes to reducing the overall yield to undesired gas (C_4–) hydrocarbons. These findings emphasize the key role of not only the chain-length distribution, but also the olefinic content of the FT primary hydrocarbons for the ultimate product distribution, and suggest guidelines for the design of multifunctional catalysts for the single-step synthesis of liquid hydrocarbons from syngas

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“…The chemoselective hydrogenation of α,β-unsaturated carbonyl compounds to their corresponding unsaturated alcohols is an important class of organic reactions because the resulting allylic alcohols are important intermediates in the synthesis of numerous fine chemicals and pharmaceutical agents, agrochemicals, and perfumes. − The chemoselective hydrogenation of a carbonyl group of the α,β-unsaturated carbonyl compounds is challenging because reduction of the olefin group is kinetically faster than that of the carbonyl group. Additionally, hydrogenation of the CC group relative the CO group is thermodynamically preferred by a factor of 35 kJ mol –1 .…”

Section: Introductionmentioning

confidence: 99%

“…In this context, numerous heterogeneous and homogeneous catalysts have been studied for chemoselective reduction of the carbonyl group of the α,β-unsaturated carbonyl compounds. − ,− ,− Here, the homogeneous catalysts show admirable reactivity for the chemoselective hydrogenation of carbonyl compounds. Alternatively, the heterogeneous catalysts exhibit noticeable benefits, including multiple-recycling ability, facile separation of products and catalysts, and easy handling, that underline the demand for developing highly efficient heterogeneous catalysts for the chemoselective reduction of α,β-unsaturated carbonyl compounds.…”

Section: Introductionmentioning

confidence: 99%

Direct Heterogenization of the Ru-Macho Catalyst for the Chemoselective Hydrogenation of α,β-Unsaturated Carbonyl Compounds

2021

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In this study, a commercially available homogeneous pincer-type complex, Ru-Macho, was directly heterogenized via the Lewis acid-catalyzed Friedel–Crafts reaction using dichloromethane as the cross-linker to obtain a heterogeneous, pincer-type Ru porous organometallic polymer (Ru-Macho-POMP) with a high surface area. Notably, Ru-Macho-POMP was demonstrated to be an efficient heterogeneous catalyst for the chemoselective hydrogenation of α,β-unsaturated carbonyl compounds to their corresponding allylic alcohols using cinnamaldehyde as a model compound. The Ru-Macho-POMP catalyst showed a high turnover frequency (TOF = 920 h–1) and a high turnover number (TON = 2750), with high chemoselectivity (99%) and recyclability during the selective hydrogenation of α,β-unsaturated carbonyl compounds.

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Platinum Metal Catalysts

Cited by 12 publications

References 108 publications

A Mechanistic Study of Polyol Hydrodeoxygenation over a Bifunctional Pt-WO_x/TiO₂ Catalyst

A Mechanistic Study of Polyol Hydrodeoxygenation over a Bifunctional Pt-WO_x/TiO₂ Catalyst

In Situ Hydrocracking of Fischer–Tropsch Hydrocarbons: CO-Prompted Diverging Reaction Pathways for Paraffin and α-Olefin Primary Products

Direct Heterogenization of the Ru-Macho Catalyst for the Chemoselective Hydrogenation of α,β-Unsaturated Carbonyl Compounds

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Platinum Metal Catalysts

Cited by 12 publications

References 108 publications

A Mechanistic Study of Polyol Hydrodeoxygenation over a Bifunctional Pt-WOx/TiO2 Catalyst

A Mechanistic Study of Polyol Hydrodeoxygenation over a Bifunctional Pt-WOx/TiO2 Catalyst

In Situ Hydrocracking of Fischer–Tropsch Hydrocarbons: CO-Prompted Diverging Reaction Pathways for Paraffin and α-Olefin Primary Products

Direct Heterogenization of the Ru-Macho Catalyst for the Chemoselective Hydrogenation of α,β-Unsaturated Carbonyl Compounds

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A Mechanistic Study of Polyol Hydrodeoxygenation over a Bifunctional Pt-WO_x/TiO₂ Catalyst

A Mechanistic Study of Polyol Hydrodeoxygenation over a Bifunctional Pt-WO_x/TiO₂ Catalyst