Effect of fluoride on the structure and activity of NiW/Al2O3 catalysts for HDS of thiophene and HDN of pyridine

Benitez, A.; Ramı́rez, Jorge; Fierro, J.L.G.; Agudo, Antonio

doi:10.1016/0926-860x(96)00121-4

Cited by 51 publications

(22 citation statements)

References 42 publications

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“…This was demonstrated by Ozkan et al (162,163), who reported high yields of OEAN and EBz for the HDN of IN using a H 2 S/ H 2 ratio of 1.6 Â 10 22 . Such groups may have the character of weak Bronsted acid sites (254,255). For the HDN of OEAN alone, the same change in the ratio increased the rate of HDN by promoting HYD of the aromatic ring.…”

Section: Hydrodenitrogenation Of Petroleummentioning

confidence: 99%

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Hydrodenitrogenation of Petroleum

Furimsky¹,

2005

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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,...

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Section: Hydrodenitrogenation Of Petroleummentioning

confidence: 99%

“…For example, Benitez et al (254) observed the increase in k HDN on the addition of fluoride ion to sulfided NiMo/Al 2 O 3 catalysts. For example, Benitez et al (254) observed the increase in k HDN on the addition of fluoride ion to sulfided NiMo/Al 2 O 3 catalysts.…”

Section: Vi15 Effect Of Fluoridationmentioning

confidence: 99%

Hydrodenitrogenation of Petroleum

Furimsky¹,

2005

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“…One way to obtain that could be to modify the surface properties of the alumina in order to decrease the tungsten-alumina interaction, since easier sulfidable species could be synthesized. Studies by FT-IR(NO) [14], TPS, XPS [15], quick extended X-ray absorption fine structure (QEXAFS), Xray absorption near-edge structure spectroscopy (XANES) [16] and nuclear magnetic resonance (NMR) [17] have shown that fluorination of alumina modified the interaction of tungsten with the support increasing the sulfidation of this metal. Also, it has been published that, at low concentrations, gallium decreased the interaction of Ni [18] with ␥-Al 2 O 3 , due to the high affinity of Ga 3+ to the tetrahedral sites of alumina, modifying the ratio of Ni 2+ tet /Ni 2+ oct species.…”

Section: Introductionmentioning

confidence: 99%

Hydrodesulfurization of sulfur refractory compounds: Effect of gallium as an additive in NiWS/γ-Al2O3 catalysts

León¹,

Picquart²,

Massin³

et al. 2012

Journal of Molecular Catalysis A: Chemical

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“…For both series of catalysts, a main broad band around 200-350 nm is observed, which is the sum of two peaks at around 230 and 280 nm [31] assigned to isolated tetrahedral W and polymeric octahedral W species, respectively [32]. This band shifts toward higher wavelength after adding ZrO 2 , indicating the decrease in tetrahedrally coordinated W and the increase in octahedrally coordinated W [20,33]. An evident shoulder around 350-450 nm assigned to the octahedral W in bulk WO 3 [32,34] only appears in the IM-prepared catalysts, in line with the XRD results.…”

Section: Drsmentioning

confidence: 82%