HDN Activities Research Articles

Synthesis and Characterization of NiMo Catalysts Supported on Fine Carbon Particles for Hydrotreating: Effects of Metal Loadings in Catalyst Formulation

The by-products collected during the synthesis of carbon nanohorns via the arc discharge synthesis method is comprised of other carbon particles (OCP). At a hydrotreating operating temperature of 370°C, preliminary investigations using a bimetallic catalyst with support originating from the fine fractions of other carbon particles (OCPf) and containing 13 wt% Mo and 2.5 wt% Ni resulted in an HDS and HDN conversion of 78 and 25%, respectively. Variation of metal compositions in catalyst formulation and its impact on hydrotreating activity was therefore considered in this study to enhance the hydrotreating activity of OCPf–supported catalyst, and to determine if the best NiMo/OCPf catalyst achieved from this study could be a viable catalyst for hydrotreating applications. The co-incipient wetness impregnation was used in preparing series of hydrotreating catalysts with Ni and Mo loadings within the range of (2.5–5.0 wt%) and (13–26 wt%) respectively. Overall, the catalyst samples with maximum Ni loading of 5.0 wt% and Mo loadings of either 13 or 19 wt% showed higher dispersion and the ability to form a Type II Ni-Mo-S phase with enhanced activity. The effects of metal compositions on both HDS and HDN activities were correlated with their physicochemical properties.

Effect of Gallium and Vanadium in NiMoV/Al2O3-Ga2O3 Catalysts on Indole Hydrodenitrogenation

The effect of Ga as support modifier and V as second promoter on the NiMoV/Al2O3-Ga2O3 catalyst varying the synthesis method (SG: sol–gel synthesis vs I: impregnation synthesis) was studied. The catalysts were characterized by elemental analysis, textural properties, XRD, XPS, 27Al NMR, Raman, EDX elemental mapping and HRTEM. The chemical analyses by XRF showed coincidence between experimental and theoretical values according to stoichiometric values proposed to Mo/Ni = 6 and (V + Ni)/(V + Ni + Mo) = 0.35. The sol–gel synthesis method increased the surface area by incorporation of Ga3+ ions into the Al2O3 forming Ga–O–Al bonding; whereas the impregnation synthesis leads to decrease by blocking of alumina pores, as follows NiMoV/Al2O3-Ga2O3(I) < NiMoV/Al2O3-Ga2O3(SG) < Al2O3-Ga2O3(I) < NiMo/Al2O3 < Al2O3-Ga2O3(SG) < Al2O3. The values of BJH mesopores mean size between 6.13 and 7.68 nm. XRD and XPS confirmed a bulk structure typical of (NH4)4[NiMo6O24H6]·5H2O and the presence at the surface of Mo4+, Mo6+, NixSy, NiMoS, Ni2+, Ga3+ and V5+ species, respectively. Raman showed that the sol–gel synthesis method reduces the interactions Ni-Mo sulfide-support and improvement the sulfidation degree NiMoV/Al2O3-Ga2O3(SG) as showed sulfur analysis CHONS. The largest proportion of AlO4 content using the impregnation method to add Ga was verified by 27Al solid-state MAS NMR. The EDS elemental mapping confirmed that Ni, Mo, Al, Ga, V and S are well-distributed on support. The HRTEM analysis shows that the length and stacking distribution of MoS2 crystallites varied from 5.67 to 6.01 nm and 2.46 to 2.74 when using the sol–gel and impregnation synthesis method, respectively. The catalytic results revealed that the synthesis method induced the presence of gallium on the surface influencing the dispersion V5+ species, whose effect could have some relation with strength and density of acid sites that in turn influence the dispersion of the MoS2 phase, which correlates well with the indole HDN activities. The activities as indole HDN pseudo-first-order rate constants’ values (kHDN) from 0.29 to 2.78 mol/(m2·h): NiMoV/Al2O3 < NiMoV/Al2O3-Ga2O3(I) < NiMo/Al2O3 < NiMoV/Al2O3-Ga2O3(SG). Nevertheless, the nature of the active site can be related with reaction pathways, that is, NiMoV/Al2O3-Ga2O3(SG) and NiMoV/Al2O3-Ga2O3(I) catalysts produce ECH through HIND, while NiMoV/Al2O3 and NiMo/Al2O3 produce EB by hydrogenolysis of HIND to OEA. In the regard, the Ga and V act as structural promoters in the NiMo catalysts, allowing the largest generation of NiMoS M-edge-like and BRIM sites for HDN. The synthesis method influences the reaction pathways for indole HDN, suggesting that NiMoV/Al2O3-Ga2O3(SG) and NiMoV/Al2O3-Ga2O3(I) had the highest production of OEA suggesting that ECH derive from HIND, whereas NiMo/Al2O3 shows that OEA concentration is very low at short times, indicating that ECH derives of OEA

New methods for the preparation of nanoscale nickel phosphide catalysts for heteroatom removal reactions

Recent advances in the preparation of nickel phosphide (Ni2P) catalysts from hypophosphite-based precursors have resulted in high HDS and HDN activities.

Synthesis of aluminum-modified 3D mesoporous TUD-1 materials and their hydrotreating performance of FCC diesel

In this paper, alumina modified TUD-1 were synthesized. The related catalysts exhibited higher HDS and HDN activities than the catalyst over Al2O3. Therefore, TUD-1 is a promising candidate of catalyst additives for the industrial application.

Hydrotreating of Heavy Gas Oil on Mesoporous Mixed Metal Oxides (M–Al2O3, M = TiO2, ZrO2, SnO2) Supported NiMo Catalysts: Influence of Surface Acidity

Mesoporous mixed metal oxides, TiO2–Al2O3, ZrO2–Al2O3, and SnO2–Al2O3, were synthesized using a novel method and were used as a support material for the NiMo hydrotreating catalyst. The catalyst was prepared via the incipient wetness sequential impregnation method. All catalysts were characterized using N2 adsorption–desorption isotherms (BET), X-ray diffraction, FTIR, pyridine-FTIR, acridine-FTIR, CO-chemisorption, ICP-MS, TPD, and TPR. The HDS and HDN activities of the catalysts were determined using Athabasca bitumen derived heavy gas oil at industrial reaction conditions. The catalytic activity of synthesized NiMo/γ-Al2O3 catalyst was also determined for comparative studies. Low angle XRD and BET analysis has confirmed that the method developed for synthesis is suitable for the preparation of a mesoporous mixed oxide based NiMo hydrotreating catalyst. H2-TPR analysis has confirmed that the introduction of metal oxides such as ZrO2, TiO2, and SnO2 in alumina increases the active metal (Mo) and support ...

Hydrotreating of heavy gas oil on mesoporous zirconia supported NiMo catalyst with EDTA

Large pore, high surface area mesoporous zirconia was synthesized using P123 as structure directing agent and was used as support material for hydrotreating of heavy gas oil. The mesoporous zirconia supported NiMo hydrotreating catalyst was prepared with and without EDTA via incipient wetness impregnation method. The structural characteristics of catalysts were measured by X-ray diffraction (XRD), FT-IR, RAMAN, TPD (Temperature Programmed Desorption), TPR (Temperature Programmed Reduction), HRTEM, XANES and N2-adsorption desorption isotherms (BET). The hydrotreating activities of the catalysts were measured using Athabasca bitumen derived heavy gas oil at industrial reaction conditions. Catalytic activity of NiMo/γ-Al2O3 and NiMo SBA-15 catalysts was also determined for comparative studies. Low angle XRD and BET results support the formation of ordered mesoporous structure in the catalyst. Wide angle XRD, FT-IR and RAMAN analyses confirm the presence of mixture of monoclinic and tetragonal phase of zirconia in the catalyst. Surface acidity and type of acidic sites present were measured using NH3-TPD and Pyridine-FTIR. The extent of active metal dispersion in NiMo/Meso-Zr, Ni(NO3)2–Mo/Meso-Zr and NiMo/Meso-Zr(EDTA) catalyst is shown by CO chemisorption and HRTEM analysis. It has been confirmed from physio-chemical characterization that addition of EDTA increases the catalytic activity by (i) increasing the active metal dispersion as indicated by HRTEM and CO chemisorption, (ii) increase in Ni sulfidation temperatures and (iii) decreasing the metal support interaction as shown by XANES analysis. XANES analysis revealed that molybdenum oxide is present predominantly in tetrahedral form in NiMo/Meso-Zr catalyst whereas its present predominantly in octahedral form in NiMo/Meso-Zr (EDTA) catalyst. The catalytic activity was investigated and corelated systematically with the textural and structural properties of the catalysts. The HDS and HDN activities follows the order: NiMo/Meso-Zr(EDTA)⩾NiMo/γ-Al2O3>NiMo/Meso-Zr>Ni(NO3)2–Mo/Meso-Zr>NiMo/SBA-15.

On the structure and hydrotreating performance of carbon-supported CoMo- and NiMo-sulfides

The sulfiding behaviour and hydrotreating performance of CoMo and NiMo on carbon catalysts were investigated, with a view to establishing the suitability of an active-carbon carrier for industrial hydrotreatment purposes. The sulfidation process (H2/H2S at 0.1 and 4MPa) was followed with 57Co Mössbauer emission spectroscopy, and X-ray absorption spectroscopy (Mo- and Co-edge). It turns out that the structural evolution of the CoMo/C catalyst is in broad terms very similar to that of a CoMo/Al2O3 one, including the type I→II phase transition at increased sulfiding pressure, albeit that some sintering takes place concomitantly. In the hydrotreating part a NiMo/C catalyst was employed, sulfided at 1 or 4MPa, in trickle-flow conditions at 3.5 (HDS) and 6 (HDN) MPa. It transpires that the adsorption properties of NiMo/C are quite different from those of a NiMo/alumina, in that dibenzthiophene, quinoline, and polyaromatics are much stronger adsorbed on the carbon-supported catalyst. This leads to very high dibenzothiophene HDS and quinoline HDN activities, but to a disappointing performance in the hydrotreatment of a heavy gasoil, where the polyaromatics can compete effectively for adsorption on the active HDS/N sites.

V–Ni–Mo sulfide supported on Al2O3: Preparation, characterization and LCO hydrotreating

The effect of vanadium incorporation on the HDS, HDN, and HDA activities of LCO hydrotreating was investigated on NiMo supported hydrotreating catalysts. The catalysts were characterized by XRD, BET, XPS, NO-chemisorption and evaluated in fixed bed reactor using real LCO as feed. The vanadium promoted NiMo catalyst presented higher HDS and HDN activities, and surprisingly a relatively low activity toward the HDA. This behavior is probably due to a vanadium-mixed active phase, this has superior conversion as compared to NiMo catalyst.

Hydrotreating of coker light gas oil on SBA-15 supported nickel phosphide catalysts

SBA-15-supported nickel phosphides with a Ni/P atomic ratio of 2 and 0.5 were prepared by temperature programmed reduction method (TPR). The phase purity and structural/surface properties were studied by X-ray diffraction and N2 sorption measurements respectively. X-ray diffraction (XRD) analysis of the passivated catalysts confirmed the presence of Ni12P5 and Ni2P phases in catalysts prepared from oxidic precursors. Supports and catalysts were thoroughly characterized using other techniques such as SEM, EDAX, and TEM. Results from low angle XRD measurements confirmed the presence of hexagonally ordered mesoporous structure in SBA-15 material. Hydrotreating experiments were conducted under industrial conditions using coker light gas oil (CLGO) as feed which contains 2439ppm nitrogen 23,420ppm sulfur respectively. The activity results show that SBA-15 supported NixPy catalysts show higher catalytic activities compared to reference NiMo/SBA-15 and NiMo/γ-Al2O3 catalysts under similar reaction conditions. This higher catalytic activity of NixPy/SBA-15 is due to the structure and surface chemical properties of this phase which is resistant to sulfur poisoning. It was also found that the Ni/P ratio had a profound effect on the active structure and hydroprocessing behavior of the NixPy/SBA-15 catalysts. The HDS and HDN conversions was found in the following order NixPy/SBA-15 (0.5)>NixPy/SBA-15 (2.0)>NiMo/SBA-15>NiMo/γ-Al2O3. The NixPy/SBA-15 (0.5) catalyst showed higher HDS and HDN activities compared with NixPy/SBA-15 (2.0) catalyst which has lower P content. The higher amount of P content in NixPy/SBA-15 (0.5) catalyst modifies the nature of the nickel in that catalyst and increased the amount of octahedral nickel species and causes higher hydrotreating activity.

Hydrotreating activities of alumina-supported bimetallic catalysts derived from noble metal containing molecular sulfide clusters Mo 3S 4M′ (M′ = Ru, Rh, Ir, Pd, Pt)

Molecular sulfide clusters with bimetallic Mo 3S 4M′ cluster cores (M′ = Ru, Rh, Ir, Pd, Pt) were impregnated on γ-alumina as the compounds [(Cp′) 3Mo 3S 4M′(L) x ][pts] y (Cp′ = methylcyclopentadienyl; L = ligand; pts = para-toluenesulfonate). These catalyst precursors were sulfided at 350 °C leading to decomposition of the molecular clusters and the formation of MoS 2-like phases with optimal chances for noble metal atoms to be in close contact with MoS 2. The hydrotreating activities of the catalysts obtained were measured by using a feed containing dibenzothiophene, indole and naphthalene. The HDS, HDN and HYD activities followed the order Mo 3Ir > Mo 3Rh > Mo 3Ru > Mo 3Pt > Mo 3Pd. Comparison with the sum of activities of a monometallic Mo and a monometallic noble metal reference catalyst revealed strong synergies for the Mo 3Ir and Mo 3Rh catalysts, whose HDS and HDN activities had increased by factors of 2.7–3.9 and 1.8–4.3, respectively. A comparison with the hydrotreating activities of a Mo 3Ni catalyst prepared from [(Cp′) 3Mo 3S 4NiL][pts] showed, however, that the performances of the Mo 3Rh and Mo 3Ir catalysts generally were inferior by a factor of 2 to a Mo 3Ni catalyst. An inhibiting effect on the catalyst activity was observed for the Mo 3Pd catalyst. The sulfided Mo 3Rh, Mo 3Ir and Mo 3Pd catalysts were studied by TEM. The Mo 3Rh and Mo 3Ir catalysts showed a homogeneous and very high dispersion of both metals, the MoS 2 dispersion being higher than in the monometallic Mo reference catalyst. The Mo 3Pd catalyst showed a strong inhomogeneity due to the presence of 10 nm large Pd 4S particles fully encapsulated by layers of MoS 2.

Investigation of hydrodearomatization of gas oils on noble metal/support catalysts

Due to the more and stricter requirements of diesel fuels, one of the most important key factors of production of modern diesel fuel blending components is the two-stage deep hydrodesulphurization and hydrodearomatization, where in the second step noble metal catalysts are used for the deep hydrodearomatization of prehydrogenated feeds. In this paper, the results of hydrodearomatization of different sulphur- and nitrogen containing real gas oil fractions on PtPd/USY zeolite, PtPd/amorphous SiO 2–Al 2O 3 and PtPd/γ–Al 2O 3 catalysts are presented. In case of PtPd/USY catalyst, the effect of Pd/Pt atomic ratio on the sulphur tolerance was also investigated, additionally, the effect of sulphur and nitrogen content of the feeds and the process conditions on HDA, HDN and HDS activities were studied. The main goal of our experiments was to find a bimetallic PtPd/USY catalyst possessing Pd/Pt mass ratio of 2:1 (Pd/Pt atomic ratio of 3.7:1), which was suitable for the deep hydrodearomatization of relatively high sulphur (up to 300 mg S/kg) and nitrogen (up to 200 mg N/kg) containing feeds. In case of optimal process parameters ( T = 310 °C, P = 60 bar, LHSV = 1.0–1.5 h −1, H 2/hydrocarbon volume ratio = 600 N m 3/m 3), low total aromatic (<10%), practically sulphur and nitrogen free products (≤10 mg S/kg and ≤1 mg N/kg) having high cetane number (56–58) could be produced, which are less pollutant diesel fuel blending components. The relatively high activity for hydrodesulphurization and hydrodearomatization, and the low hydrocracking activity of this catalyst provides flexibility for the two-step deep hydrodesulphurization and deep hydrodearomatization processes. It means that applying this catalyst, the deep hydrodearomatization and further deep heteroatom removal of different feeds can be performed with high gas oil yield. Therefore, it is not necessary to apply deep hydrodesulphurization to max. 50 or 10 mg S/kg in the first stage on transition metal/support catalysts.

Effect of anodic alumina pore diameter variation on template-initiated synthesis of carbon nanotube catalyst supports

Multi-walled carbon nanotubes (MWCNTs) are a potential alternative to commonly used heterogeneous catalyst supports due to their high surface area, structural integrity, and controllable dimensional characteristics. Synthesis of MWCNTs with specific pore diameters can be achieved by chemical vapor deposition (CVD) of a carbon source onto an anodic aluminum oxide (AAO) template. AAO films consist of pore channels in a uniform hexagonal arrangement that run parallel to the surface of the film. These films are created by the passivation of an aluminum anode within an electrolysis cell consisting of certain weak acid electrolytes. A two-step anodization method has been developed to produce these templates. Changing the concentration of the oxalic acid electrolyte and the electrical potential of the electrolysis cell altered the structural characteristics of these AAO films, specifically the diameter of their pore channels. The AAO characteristics were examined by SEM analysis. Controlling the pore diameter of these templates enabled the pore diameter of MWCNTs synthesized by CVD to be controlled as well. After considering their thermal and structural stability, the produced MWCNTs were characterized by SEM, TEM, TGA–DTA, BET N2 adsorption analysis, and DRIFT spectroscopy. Anodizing conditions of 0.40M oxalic acid concentration and 40.0V maximum anodizing potential were found to produce AAO films that resulted in MWCNTs with optimum surface characteristics for a catalyst support application. These MWCNTs with optimum pore diameters were synthesized for the purpose of being used as a support for NiMoS hydrotreating catalyst. This optimum grade of MWCNTs was found to produce the highest HDS and HDN activities when applied in the packed-bed processing of coker light gas oil.

LCO hydrotreating with Mo-Ni and W-Ni supported on nano- and micro-sized zeolite beta

The effect of zeolite beta particle size on the HDS, HDN, and HDA activities of LCO hydrotreating was investigated on Mo-Ni and W-Ni supported on nano- and micro-sized zeolite beta hydrotreating catalysts. The catalysts were characterized by XRD, BET, TEM, and XPS, and evaluated with an autoclave using real LCO as feed. It was concluded that, with the Mo-Ni catalysts, the catalyst containing nano-sized zeolite beta particles had similar hydrogenation activity as the one containing micro-sized (conventional) particles; with the W-Ni catalyst, the nano-sized zeolite catalyst presented higher HDS, HDN, and HDA activities as expected. Higher liquid yields could be achieved by using the W-Ni and Mo-Ni nano-sized zeolite catalysts.

Tetraalkylthiomolybdates-derived Co(Ni)Mo/γ-Al 2O 3 sulfide catalysts for gas oil hydrotreating

Bimetallic γ-Al 2O 3-supported CoMo and NiMo sulfide catalysts were prepared using ammonium thiomolybdate (ATM), tetramethylammonium thiomolybdate (TMATM), tetrabutylammonium thiomolybdate (TBATM), cetyltrimethylammonium thiomolybdate (CTMATM) as precursors for MoS 2. The CO chemisorption study showed better dispersion of MoS 2 on γ-Al 2O 3 support in the catalysts prepared from the thiosalts precursor than the catalysts obtained from the oxides precursor. Among the catalysts derived from tetraalkylammonium thiomolybdates, Co(Ni)Mo/γ-Al 2O 3 catalysts derived from CTMATM precursor showed higher CO uptake. The presence of molybdenum carbide phase in the Co(Ni)MoS 2 catalysts formed from the tetraalkylammonium thiomolybdates is evidenced by NEXAFS study. DRIFT spectra showed lesser amount of partially sulfided molybdenum species in thiosalts-derived catalysts compared to those catalysts prepared by the conventional oxide precursors. The HDN and HDS activities of Co(Ni)Mo/γ-Al 2O 3 sulfide catalysts with coker light gas oil (KLGO) feed at temperature, pressure and LHSV of 350 °C, 8.8 MPa and 1.5 h −1 were studied. The activity of thiosalts-derived catalysts is significantly higher than the respective oxides precursor catalysts. The presence of carbo-sulfide phases promotes the HDN and HDS activities of tetraalkylammonium thiomolybdates derived NiMo and CoMo catalysts. In both NiMo and CoMo series, catalyst prepared by in situ decomposition CTMATM showed a maximum HDN and HDS activities as result of better dispersion of active phase on the support via microemulsion.

HDS, HDN and HDA activities of nickel–molybdenum catalysts supported on alumina

In this work, NiMo–Al 2O 3 catalysts were prepared by using different alumina precursors. The supports were impregnated by means of the spray at incipient wetness technique in both basic and acid media. Both the supports and fresh catalysts were characterized by the adsorption–desorption isotherms, Temperature-Programmed Reduction (TPR), Thermal Pyridine Adsorption–Desorption (TPD) and X-Ray Diffraction analyses (XRD). After sulfidation, the NiMoS metallic particles were characterized by Transmission Electron Microscopy (TEM). The initial analyses were performed in a trickle-bed reactor by using a real feedstock (Mexican heavy gas oil) and performing hydrotreating reactions (HDS, HDN and HDA) at three different temperatures: 613, 633 and 653 K; and 54 kg cm − 2 . The catalytic activities are discussed in relation to the physicochemical properties of the NiMo catalysts, alumina phase and pH of the impregnating solution. The catalytic results show an increase in the conversion profiles with temperature. The sulfur conversion was increased from 89 to 99.25%, 91–99%, 90.8–97%, 83–95% and 78–96% when the crystal size of the support varied from 3 to 20 nm, respectively. The nitrogen and aromatic conversions were also increased in the range of 23–45 wt.%. It was found that the γ phase reached a higher catalytic performance than the η phase. The NiMo catalysts synthesized in a basic medium showed a better catalytic performance than that obtained with those prepared in acid solutions. The significance of the kinetic data to compare the catalysts is discussed. The maximum value of the catalytic activity was reached with the catalysts with the smallest particle sizes.

Hydrodenitrogenation on Pt/silica–alumina catalysts in the presence of H 2S: Role of acidity

The effect of the support acidity on the HDN activity of a series of Pt/silica–alumina catalysts was investigated. Catalyst containing 1 wt.% of Pt supported on silica–aluminas with silica content varying between 10 and 50 wt.% were prepared by incipient wetness impregnation. The acidity was characterized by IR spectroscopy of adsorbed pyridine and isooctane hydrocracking and a good correlation with the silica content of the supports was observed. All the catalysts presented similar metal dispersion as measured by hydrogen chemisorption. The conversion pathway of 1,4-tetrahydroquinoline (1,4-THQ), used as model molecule for HDN study, on Pt/silica–alumina catalysts was similar to the one previously reported for sulfided catalysts, having as main steps the complete saturation of this molecule followed then by C–N bond scission to form completely denitrogenated products. Hydrogenation and HDN activities increased with the Brønsted acidity of the catalysts. As the thiotolerance of these catalysts does not seem to be affected by the support acidity, it is proposed that the 1,4-THQ activity increase would be related to a bifunctional mechanism involving neighboring Pt sites and Brønsted sites of the silica–alumina support.

Application of multi-walled carbon nanotubes as efficient support to NiMo hydrotreating catalyst

The feasibility of multi-walled carbon nanotubes (MWCNTs) as support to NiMo catalysts for hydrotreating of gas oil derived from Athabasca bitumen was tested in a trickle bed reactor at industrial conditions. High quality MWCNTs were prepared by CVD method using ferrocene as catalyst and toluene as carbon source. The produced MWCNTs were characterized by XRD, TEM, TGA and Raman spectroscopy in order to reveal the morphological and structural characteristics. Using functionalized MWCNTs as support, NiMo catalysts were prepared with varying Ni and Mo content by pore filling impregnation method. The calcined NiMo/MWCNTs catalysts were characterized by ICP-MS, N2 adsorption, XRD and TPR and the sulfide form of the catalysts was examined by DRIFT spectroscopy of adsorbed CO. The XRD patterns confirm the enhanced dispersion of MoO3 particles when increasing the Ni content from 0 to 4.5 wt.% over 12 wt.% Mo/MWCNTs. The TPR profiles indicate the two step reduction characteristics of Mo6+ to Mo in lower oxidation state such as Mo4+ and Mo0. The promoted and unpromoted MoS2 sites were clearly differentiated with the help of DRIFT of adsorbed CO over sulfided catalysts. The number of Ni promoted MoS2 (NiMoS phase) sites is increased significantly with increasing Ni addition up to 3 wt.% over 12 wt.% Mo/MWCNTs. The HDN and HDS activities of sulfided NiMo/MWCNTs using bitumen derived light gas oil were carried out at different temperatures under industrial condition. The HDN and HDS activities of the catalysts increased with increasing Ni content up to 3 wt.% and Mo content up to 12 wt.%. Based on weight of the catalyst, the HDN and HDS activities of 3 wt% Ni–12 wt.% Mo/MWCNTs are significantly higher than those over conventional Al2O3-based catalyst under the experimental conditions studied. The introduction of 2.5 wt.% P to MWCNTs-based catalyst found to show a fall in hydrotreating activity.

Hydrotreating of gas oil on SBA-15 supported NiMo catalysts

The siliceous and the metal substituted (B or Al)-SBA-15 molecular sieves were used as a support for NiMo hydrotreating catalysts (12 wt.% Mo and 2.4 wt.% Ni). The supports were characterized by X-ray diffraction (XRD), scanning electron microscopy and N 2 adsorption–desorption isotherms. The SBA-15 supported NiMo catalysts in oxide state were characterized by BET surface area analysis and XRD. The sulfided NiMo/SBA-15 catalysts were examined by DRIFT of CO adsorption and TPD of NH 3. The HDN and HDS activities with bitumen derived light gas oil at industrial conditions showed that Al substituted SBA-15 (Al-SBA-15) is the best among the supports studied for NiMo catalyst. A series of NiMo catalysts containing 7–22 wt.% Mo with Ni/Mo weight ratio of 0.2 was prepared using Al-SBA-15 support and characterized by BET surface area analysis, XRD and temperature programmed reduction and DRIFT spectroscopy of adsorbed CO. The DRIFT spectra of adsorbed CO showed the presence of both unpromoted and Ni promoted MoS 2 sites in all the catalysts, and maximum “NiMoS” sites concentration with 17 wt.% of Mo loading. The HDN and HDS activities of NiMo/Al-SBA-15 catalysts were studied using light gas oil at temperature, pressure and WHSV of 370 °C, 1300 psig and 4.5 h −1, respectively. The NiMo/Al-SBA-15 catalyst with 17 wt.% Mo and 3.4 wt.% of Ni is found to be the best catalyst. The HDN and HDS activities of this catalyst are comparable with the conventional Al 2O 3 supported NiMo catalyst in real feed at industrial conditions.

HDN and HDS of different gas oils derived from Athabasca bitumen over phosphorus-doped NiMo/γ-Al2O3 carbides

A series of phosphorous-doped γ-Al2O3 supported Ni–Mo bimetallic carbide catalysts (PNiMo2C/Al2O3) with 0–4.5wt.% Ni, 13wt.% Mo and 2.5wt.% P were synthesized and characterized by elemental analysis, pulsed CO chemisorption, surface area measurement, X-ray diffraction (XRD), near-edge X-ray absorption fine structure (NEXAFS), DRIFT spectroscopy of CO adsorption and H2 temperature programmed reduction. XRD indicated the formation of pure β-Mo2C phase in these catalysts, whereas the near edge X-ray absorption fine structure of C K-edge confirmed the formation of carbidic carbons. DRIFT spectra of adsorbed CO revealed that Ni or P addition to Mo2C/Al2O3 catalyst not only increases the number of surface Mo sites, but also promotes the reducibility of Mo. The partial sulfidation of Mo2C phase in the presence of H2S/H2 gas mixture at 370°C was evidenced by DRIFTS of adsorbed CO. The HDN and HDS activities of these PNiMo2C/Al2O3 catalysts were performed in a trickle bed reactor using light gas oil (LGO) and heavy gas oil (HGO) derived from Athabasca bitumen at 8.8MPa and compared with the unpromoted Mo carbide (Mo2C/Al2O3), P doped Mo carbide (PMo2C/Al2O3) and Ni promoted Mo carbide (NiMo2C/Al2O3). The P doped Ni–Mo bimetallic carbide catalysts showed enhanced HDN activity compared to the Mo2C/Al2O3, NiMo2C/Al2O3 and PMo2C/Al2O3 catalysts. The maximum N and S conversions, respectively, were obtained over PNiMo2C/Al2O3 and NiMo2C/Al2O3 catalysts containing 2.5wt.% Ni.

Effect of the preparation of Re/γ-Al 2O 3 catalysts on the HDS and HDN of gas oil

The effects of Re content and catalyst preparation on the surface structure of two series of Re/γ-Al 2O 3 catalysts, prepared by one-step (Re( x)-I) and successive-step impregnation (Re( x)-II) methods, and their catalytic behaviour in the HDS and HDN of gas oil were studied. Characterization data by XRD, Raman spectroscopy and XPS revealed that the structure of Re on Re( x)-I and Re( x)-II catalysts in their oxidic state was very similar; Re in oxided state was present as two slightly different isolated ReO 4 − monomeric species coordinated to the alumina surface in all the range of Re content studied, but the Re coverage was slightly lower on Re( x)-I than on Re( x)-II catalysts. Upon sulfidation, the dispersion of Re decreased significantly and left to be monomolecularly dispersed above 0.5 Re at. nm −2, especially for the Re( x)-I catalysts, causing therefore that the HDS and HDN activities of the two catalyst series reached maximum values at a Re content of about 0.5 at. nm −2 and then decreased. The higher activity for both HDS and HDN reactions observed for the Re( x)-II catalysts are consistent with their higher dispersion of the Re sulfided phase. Both Re( x)-I and Re( x)-II catalysts showed exceptionally high HDN/HDS selectivity values, which were slightly higher for the Re( x)-II catalysts due to their slightly higher concentration of acid sites in the oxidic state.