Author
Keith J. Weller
Bio: Keith J. Weller is an academic researcher from University of Arizona. The author has contributed to research in topics: Hydrodenitrogenation & Bond length. The author has an hindex of 5, co-authored 5 publications receiving 299 citations.
Papers
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TL;DR: In this paper, a model system delineates one process by which heterocyclic C-N bonds are cleaved and offer new insight as to how nitrogen heterocycles may be further degraded after C -N bond cleavage in hydrodenitrogenation catalysis.
Abstract: The reaction of the {eta}{sup 2}(N,C)-pyridine complex with LiBEt{sub 3}H affords the C-N bond scission product (2). The reactions of (1) with carbon nucleophiles RLi or RMgX provide the alkyl derivatives [R = Me (3), Et (4), {sup n}Pr (5), {sup n}Bu (6), and CH{sub 2}SiMe{sub 3} (7)]. Kinetic and mechanistic studies of the 3 {yields} 8 rearrangement reveal that methyl migration is strictly intramolecular. The reactions of this model system delineate one process by which heterocyclic C-N bonds are cleaved and offer new insight as to how nitrogen heterocycles may be further degraded after C-N bond cleavage in hydrodenitrogenation catalysis. 74 refs., 7 figs., 5 tabs.
104 citations
TL;DR: In this article, a stable metallapyridine complex of tantalum was obtained in the course of model studies of hydrodenitrogenation (HDN) reactions, and the structure and reactions of the complex were described.
74 citations
TL;DR: In this paper, the authors provide an overview of the heterogeneous HDN process and outline various homogeneous models for hydrodenitrogenation catalysis including binding modes of HDN substrates, catalytic hydrogenation processes and recent CN bond cleavage reactions of nitrogen heterocycles.
68 citations
TL;DR: In this paper, a two-electron reduction of these complexes, an η 1 (N ) → η 2 (N,C ) bonding rearrangement is effected and the thermally sensitive, d 2 species [η 2( N,C) )-QUIN]Ta(OAr) 3 Cl 2 (OEt 2 ) and 6MQ = 6-methylquinoline (6MQ) are prepared from pentane.
39 citations
TL;DR: In this article, a stable metallapyridine complex of tantalum was obtained by thermolyzing the η2(N,C)-pyridine compound in THF.
24 citations
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TL;DR: Ni2P/SiO2 catalysts with varying Ni/P ratios have been shown to have better performance in hydroprocessing than a commercial Ni-Mo-S/Al2O3 (HDS 98% vs 78% and HDN 80% vs 43%), based on equal sites loaded in the reactor.
715 citations
TL;DR: This paper presents the results of aalysis experiments conducted at the BNLMS and Nankai University with real-time measurements of the response of the H2O-O2/O2 mixture to E2O/O3 mixture.
Abstract: Kunbing Ouyang,†,‡ Wei Hao,† Wen-Xiong Zhang,*,†,§ and Zhenfeng Xi† †Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of the Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China ‡Institute of Chemistry, Chinese Academy of Sciences (CAS), Beijing 100190, China State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China
477 citations
TL;DR: In this article, it was shown that at least four different catalytic sites are required to interpret experimental observations in contrast with a dual site site concept, which only considered two sites.
Abstract: A high level of hydrodenitrogenation (HDN) is required to achieve a desirable conversion of other hydroprocessing reactions. This results from a strong adsorption of nitrogen‐containing compounds on catalytic sites that slows down the hydrogen activation process and hinders the adsorption of other reactants. Studies on model compounds and real feeds indicate that less than 50 ppm of nitrogen in the feed can poison catalytic sites. Kinetic studies determined adsorption constants of various nitrogen‐containing compounds and concluded that at least four different catalytic sites are required to interpret experimental observations in contrast with a dual site site≅concept, which only considered two sites. The advancements in experimental techniques allowed identification of products formed during very early stages of hydrodenitrogenation. These results confirmed that the removal of the amino group from saturated amines, as the last step in hydrodenitrogenation, is governed by the type of carbon to which the a...
233 citations
TL;DR: In this paper, electrospray ionization was found to ionize selectively basic pyridine homologues, responsible for deactivation of hydrotreatment catalysts and instability of fuels during storage.
Abstract: High-resolution (100 000 < m/Δm50% < 250 000, in which Δm50% denotes mass spectral peak full width at half-maximum height) electrospray ionization Fourier transform ion cyclotron resonance positive-ion mass spectra of unprocessed (and processed) diesel fuels resolves approximately 500 (and 200) chemically different constituents over a mass range from 200 to 452 Da, with as many as 6 resolved elemental compositions at a given nominal mass. Molecular formulas were assigned from accurate mass measurement to within ±1 ppm. Compound types were identified by Kendrick mass analysis. On the basis of the experimental behavior of model compounds, electrospray ionization was found to ionize selectively basic pyridine homologuescompounds responsible for deactivation of hydrotreatment catalysts and instability of fuels during storage. Compound classes identified in the unprocessed diesel fuel include those containing N, N2, NS, NO, N2O, O2, and SO and, in the processed diesel, N, N2, NO2, and SO. Comparison of unproce...
175 citations
TL;DR: The results of a number of theoretical studies that provide important insights into the nature and reactivity of metallabenzenes are discussed and in the concluding section some of the immediate goals and challenges in this field are identified.
Abstract: Metallabenzenes are analogues of benzene in which one of the benzene CH groups has been formally replaced by a transition metal and its ancillary ligands. This article summarises some of the important recent highlights of metallabenzene chemistry including the synthesis of the first platinabenzene, the synthesis of the first metallanaphthalene (an iridanaphthalene) and the development of new synthetic routes to metallabenzenes. The results of a number of theoretical studies that provide important insights into the nature and reactivity of metallabenzenes are discussed and in the concluding section some of the immediate goals and challenges in this field are identified.
169 citations