“…In this regard, the work of Finiels et al (91) seems to be the only one of its kind. In this regard, the work of Finiels et al (91) seems to be the only one of its kind.…”
Section: Hydrodenitrogenation Of Petroleummentioning
confidence: 99%
“…Attempts to measure the rate of HDN of CHamine and diCHamine were made by Finiels et al (91) at 623 K and 6.0 MPa over sulfided NiW/Al 2 O 3 catalyst. However, the rate was so high that it could not be measured.…”
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 ffi 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 amino group is attached rather than the number of hydrogen atoms attached to carbon in a and b position to nitrogen Performance of conventional Co(Ni)Mo(W)/Al 2 O 3 catalysts during hydrodenitrogenation was enhanced by combination with various additives and by replacing the traditionally used g-Al 2 O 3 support with novel supports. Catalytic functionalities could be modified by using different precursors of active metals and varying conditions during preparation. Progress has been made in the development of catalysts possessing a high selectivity for hydrodenitrogenation. In this case, the nonconventional catalysts based on the carbides and nitrides of transition metals exhibited high activity and selectivity. Noble metal sulfides alone or supported on different supports were active for HDN as well. Feedstocks used for catalyst evaluation included model compounds and mixtures of model compounds as well as real feeds. The challenges in the development of catalysts for hydrodenitrogenation of heavy feeds containing asphaltenes and metals have been identified.In general, compared to Q, conversions were little affected by a methyl (Me) on the aromatic ring, while being lower for Me on the N-ring, except for 2-MeQ. It is evident that Me substitution in the 2-position had little effect on HDN over the NiMoP/Al 2 O 3 catalyst, whereas it actually enhanced the HDN rate over the CoMo/Al 2 O 3 catalyst. For both catalysts the HDN rate was suppressed in 6-MeQ and particularly in 3-MeQ and 4-MeQ. The distribution of N-containing intermediates was influenced by the ring substitution and the type of catalyst. This suggests that several factors influence the overall HDN mechanism of Qs. This should be kept in mind while analyzing differences in the networks proposed by different authors.The preceding discussion on the HDN of Q mostly referred to conventional catalysts. A number of studies on the HDN of Q were conducted over unconventional catalysts. For example, 3-and 4-MeQs were more reactive than Q over the unsupported Zr,...
“…In this regard, the work of Finiels et al (91) seems to be the only one of its kind. In this regard, the work of Finiels et al (91) seems to be the only one of its kind.…”
Section: Hydrodenitrogenation Of Petroleummentioning
confidence: 99%
“…Attempts to measure the rate of HDN of CHamine and diCHamine were made by Finiels et al (91) at 623 K and 6.0 MPa over sulfided NiW/Al 2 O 3 catalyst. However, the rate was so high that it could not be measured.…”
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 ffi 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 amino group is attached rather than the number of hydrogen atoms attached to carbon in a and b position to nitrogen Performance of conventional Co(Ni)Mo(W)/Al 2 O 3 catalysts during hydrodenitrogenation was enhanced by combination with various additives and by replacing the traditionally used g-Al 2 O 3 support with novel supports. Catalytic functionalities could be modified by using different precursors of active metals and varying conditions during preparation. Progress has been made in the development of catalysts possessing a high selectivity for hydrodenitrogenation. In this case, the nonconventional catalysts based on the carbides and nitrides of transition metals exhibited high activity and selectivity. Noble metal sulfides alone or supported on different supports were active for HDN as well. Feedstocks used for catalyst evaluation included model compounds and mixtures of model compounds as well as real feeds. The challenges in the development of catalysts for hydrodenitrogenation of heavy feeds containing asphaltenes and metals have been identified.In general, compared to Q, conversions were little affected by a methyl (Me) on the aromatic ring, while being lower for Me on the N-ring, except for 2-MeQ. It is evident that Me substitution in the 2-position had little effect on HDN over the NiMoP/Al 2 O 3 catalyst, whereas it actually enhanced the HDN rate over the CoMo/Al 2 O 3 catalyst. For both catalysts the HDN rate was suppressed in 6-MeQ and particularly in 3-MeQ and 4-MeQ. The distribution of N-containing intermediates was influenced by the ring substitution and the type of catalyst. This suggests that several factors influence the overall HDN mechanism of Qs. This should be kept in mind while analyzing differences in the networks proposed by different authors.The preceding discussion on the HDN of Q mostly referred to conventional catalysts. A number of studies on the HDN of Q were conducted over unconventional catalysts. For example, 3-and 4-MeQs were more reactive than Q over the unsupported Zr,...
“…Different conclusions were reached, however, by Finiels et al (1986), who examined the HDN of several aniline derivatives and secondary amines (Table XVI). In their experiments with diphenylamine, the following products were formed: aniline, benzene, cyclohexene, IV-phenylcyclohexylamine, and cyclohexane, with the latter formed in substantial amounts.…”
“…The presence of the second aromatic ring (e.g., dibenzothiophene) and subsequent alkyl substitution at the 4 and 6 positions appears to be necessary to provide adequate steric shielding of the sulfur atom so as to prevent or inhibit desulfurization, whereas the O-homologues seem to require only the presence of the second aromatic ring. The lack of reactivity of the N- and O-containing compounds has previously been attributed to the requirement of hydrogenation of the aromatic ring prior to heteroatom−carbon bond cleavage ,, but is also composition-dependent. 9 Mass scale-expanded segments from the fractionated processed diesel fraction, identifying the nitrogen-containing quinoline series (with similar degrees of alkyl substitution) previously seen in the dibenzothiophenes in the raw diesel fuel sample.…”
Elemental compositional analysis of processed and unprocessed diesel fuels is obtained with a 5.6-T Fourier
transform ion cyclotron resonance (FT-ICR) mass spectrometer coupled to an all-glass heated inlet system
(AGHIS). High-resolution mass spectra of electron-ionized diesel fuel samples are obtained from as little as a
500-nL septum injection into the AGHIS, to yield ∼500
peaks over a range 90 < m/z < 300, with as many as
seven peaks present at the same nominal mass. Molecular formulas (elemental compositions) are assigned from
accurate mass measurement with an average error less
than ±0.5 ppm. Comparison of the raw and processed
diesel spectra shows complete removal of the sulfur-containing species except for dimethyldibenzothiophene
and higher alkyl-substituted dibenzothiophenes. These
results confirm prior reports of the resistance of these
species to hydrotreatment due to steric hindrance of
catalytic desulfurization arising from 4,6 dimethyl substitution. A simple liquid chromatographic separation to
isolate N-, O-, and S-containing aromatics from processed
diesel fuel simplifies the mass spectrum and extends the
dynamic range of the analysis, making it possible to
identify many nitrogen and oxygen homologues of the
sulfur-containing species, as well as to confirm the presence of sulfur-containing species initially detected in the
unfractionated processed diesel fuel.
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