Modelling the Hydrodenitrogenation of Aromatic N-Heterocycles in the Homogeneous Phase

Bianchini, Claudio; Meli, Andrea; Vizza, Francesco

doi:10.1002/1099-0682(20011)2001:1<43::aid-ejic43>3.0.co;2-9

Cited by 68 publications

(13 citation statements)

References 143 publications

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“…According to Laine [21], C-N hydrogenolysis is initiated by insertion of the catalyst into the a-C-H bond to form a r-complexed or a; b adsorbed intermediate, i.e., one metallic site is involved. Later, various homogeneous models were proposed for HDN catalysis [22,23,24] and several examples of metal-mediated C-N scissions were reported. g 2 (N-C) coordination modes for pyridine and quinoline transition metal complexes were proposed to be the most active mode for a subsequent nucleophilic attack.…”

Section: Reactivity Of Pt Supported Catalystsmentioning

confidence: 99%

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Mechanism of carbon?nitrogen bond scission in the presence of H2S on Pt Supported catalysts

et al. 2005

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The reactivity of a series of amines with various structures and different numbers of hydrogen atoms on the carbon atoms in the a and b position was used to evidence the C-N bond scission mechanism in the presence of H 2 S on Pt based catalysts (deposited on alumina, zirconia and silica-alumina) and compare it with the mechanism on a NiMoP on alumina sulfide catalyst. The effect of the H 2 S partial pressure was also checked. Catalytic activities (amine overall conversion, C 5 hydrocarbon formation, and amine disproportionation) deeply depend on the structure of the N-containing molecule. Tert-pentylamine is the most reactive molecule for sulfide catalysts whereas, in the case of n-pentylamine, Pt on zirconia was found to be the most efficient for C-N bond breaking. Such properties cannot be related to the acidic properties of the support but to a unique support-metal interaction, since alumina or silica-alumina supported platinum catalysts do not present this behaviour.

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Section: Reactivity Of Pt Supported Catalystsmentioning

confidence: 99%

“…g 2 (N-C) coordination modes for pyridine and quinoline transition metal complexes were proposed to be the most active mode for a subsequent nucleophilic attack. But ultimate denitrogenation apparently requires the cooperation of two metal centers [23].…”

Section: Reactivity Of Pt Supported Catalystsmentioning

confidence: 99%

Mechanism of carbon?nitrogen bond scission in the presence of H2S on Pt Supported catalysts

et al. 2005

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“…The principal reaction pathways [1] [3] [4] proposed for the HDN of Q are shown in Scheme 1. The most efficient reaction would proceed via the step sequence a) 3 b) 3 c), which does not involve the hydrogenation of the carbocyclic ring and, therefore, consumes less H 2 than any other path, and yields fuels with a higher octane rating due the residual aromaticity in the denitrogenated products.…”

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“…Since then, various transition metals (Mn, Fe, Co, Rh, Ru, Os) have been found capable of forming catalysts for the selective conversion of Q to THQ in different phase-variation systems that range from being truly homogeneous [4] [7a,i,k,l] [9a ± e,g], to aqueous-biphasic [4] [17] to heterogeneous single-site [4] [18] (Scheme 2). In contrast to the relative abundance of catalysts, very few mechanistic and kinetic studies of the selective hydrogenation of Q have been reported so far [4] [7a,i] [9c,e]. Accordingly, the relative kinetic relevance of each catalytic step and the optimal catalyst composition to give high productivity and selectivity are issues that need further investigation.…”

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“…No reaction was observed between the 16e À Rh III fragment [Rh(H) 2 [25] can readily be achieved by reaction with a Brùnsted acid. High-pressure NMR (HP-NMR) spectroscopy showed 3 to be thermally unstable in THF, where it is transformed into the binuclear compound [{Rh(H)} 2 (triphos-k 3 P) 2 (m-H) 2 ](PF 6 ) 2 (4) [23] [25] and, to a much lesser extent, into a new hydride-containing triphos-Rh complex (5), whose structure is still obscure. In view of the propensity of Rh to form, in combination with triphos, various binuclear polyhydride complexes [23] [25], it is very likely that 5 is also a binuclear species.…”

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Hydrogenation of Quinoline by Rhodium Catalysts Modified with the Tripodal Polyphosphine Ligand MeC(CH2PPh2)3

Bianchini

Barbaro

Macchi

et al. 2001

HCA

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Dedicated to the late Professor Luigi M. Venanzi, a friend, a master, and a pioneer in the organometallic chemistry of polydentate ligands As part of our modelling studies of the hydrodenitrogenation of N-heterocycles contained in raw oil materials, we investigated the selective hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline by rhodium catalysts modified with the tripodal polyphosphane ligand MeC(CH 2 PPh 2 ) 3 . Experiments in standard autoclaves and in high-pressure sapphire NMR tubes, kinetic and isotope labelling studies, and independent reactions with isolated compounds have contributed to the elucidation of the catalytic mechanism as well as identification of the electronic requisites of the metal catalyst for selective and efficient hydrogenation.

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Hydrodesulfurization & Hydrodenitrogenation

Angelici

2005

Encyclopedia of Inorganic Chemistry

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Hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) are large‐scale commercial processes that occur when petroleum feedstocks are treated with hydrogen (H 2 ) at moderately high pressures and temperatures. During the reactions, the organosulfur and organonitrogen molecules liberate H 2 S and NH 3 . The process results in the production of hydrocarbon fuels with low levels of sulfur and nitrogen. Such fuels are necessary in order to prevent pollution of the atmosphere by sulfur and nitrogen oxides. The HDS and HDN processes are catalyzed by heterogeneous catalysts consisting of molybdenum and cobalt sulfides supported on alumina. Because it is experimentally impossible to determine details of the HDS and HDN processes as they occur on catalyst surfaces, detailed transformations that may occur on the catalyst are modeled by reactions that occur in transition metal complexes that can be fully characterized. As models for the adsorption of thiophenes, benzothiophenes, indoles, and quinolines on metal sites of the catalyst surface, these organosulfur and organonitrogen compounds are coordinated to metals in a variety of complexes. This coordination occurs through the sulfur or nitrogen atom or through π‐bonds in the hydrocarbon portion of the molecules and depends on the electronic state of the metal center. Once coordinated to a metal center, the organosulfur or organonitrogen compound is activated in ways that lead to the cleavage of CS and CN bonds, which are also reactions that occur in the heterogeneous HDS and HDN reactions. Patterns of reactivity of organosulfur and organonitrogen compounds in their metal complexes are used to propose detailed mechanisms for the steps that lead to the formation of H 2 S and NH 3 in the catalytic processes. The validity of these mechanisms has been tested in a range of isotopic labeling, spectroscopic, and reactivity investigations on the heterogeneous catalysts. Not only have the studies of organosulfur and organonitrogen complexes provided a basis for understanding and potentially improving the HDS and HDN processes, they have led to new approaches to the removal of sulfur and nitrogen and to new transformations of organosulfur and organonitrogen compounds.

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Modelling the Hydrodenitrogenation of Aromatic N-Heterocycles in the Homogeneous Phase

Cited by 68 publications

References 143 publications

Mechanism of carbon?nitrogen bond scission in the presence of H2S on Pt Supported catalysts

Mechanism of carbon?nitrogen bond scission in the presence of H2S on Pt Supported catalysts

Hydrogenation of Quinoline by Rhodium Catalysts Modified with the Tripodal Polyphosphine Ligand MeC(CH2PPh2)3

Hydrodesulfurization & Hydrodenitrogenation

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