HDN Activity Research Articles

Modification of HDT catalysts of FCC feedstock by adding silica to the kneading paste of alumina support: Advantages and disadvantages

The effect of Si incorporation at the stage of alumina preparation on physico-chemical properties and catalytic performance of NiMo/Al2O3 catalysts for FCC feedstock pretreatment has been studied. Silicon was added to alumina support by kneading. Si/Al molar ratio was 0–0.16. Supports and catalysts were characterized by XRD, MAS NMR spectroscopy, Raman and IR spectroscopies, nitrogen adsorption-desorption, HRTEM, UV-Vis DRS, XPS. Introduction of Si changes textural characteristics of supports and leads to the decrease in acidity of parent alumina caused by blocking of a part of surface OH groups by deposits of silicon compounds. Silicon addition promotes the formation of small amount of strong LAS and strong BAS. Incorporation of Si facilitates segregation of Ni from the NiMoS phase. Testing of catalysts in VGO hydrotreating shows that addition of silicon to alumina support by kneading improves hydrodesulfurization activity of catalysts. However, an improvement in HDN activity was not achieved.

Synthesis and characterization of lanthanum-modified pseudoboehmite - The precursor of alumina supports and catalysts

The present work shows that the introduction of 0.25–1.25 wt% lanthanum to the composition of aluminum hydroxide at the stage of its hydrothermal synthesis allows increasing the content of the pseudoboehmite phase in the product up to 95 wt% and, as a consequence, reduces the content of the “amorphous” component. Lanthanum uniformly distributes over the surface of aluminum hydroxide as isolated cations with a surface density of 10–15 cations per 10 nm 2 . During plasticizing of lanthanum-modified pseudoboehmite followed by granulation and heat treatment, the formation of the oxide form of La is not observed, and the cations retain their isolated state. The specific surface area of La-modified alumina increases by 18–26 m 2 /g compared to the unmodified sample, while the pore volume remains the same and the average pore diameter slightly reduces. It was found that when the content of La in pseudoboehmite was 1 wt%, the temperature of reaching a residual sulfur content of 10 ppm in the hydrotreated diesel fuel was 5 °C lower comparing to the unmodified sample. • The effect of La addition at the stage of pseudoboehmite preparation was studied. • La promotes the formation of pseudoboehmite phase. • La is present as isolated cations on the surface of pseudoboehmite and alumina. • Catalyst with 1 wt% La shows the highest HDS and HDN activity.

Synthesis of Nimo Catalyst Supported on the Tailoring Alumina: Effect of the Mos2 Morphology on the Adsorption Capacity and Hdn Activity of Quinoline

Synthesis of Nimo Catalyst Supported on the Tailoring Alumina: Effect of the Mos2 Morphology on the Adsorption Capacity and Hdn Activity of Quinoline

The Application of Mesoporous ZSM-5 Zeolite in the ULSD Catalysts

The mesoporous ZSM-5 zeolite containing MoCoP/Al2O3 catalyst (C12-ZSM5) with the mixture of Al2O3 and mesoporous ZSM- 5 zeolite as carrier was synthesized. The catalytic performance of C12-ZSM5 catalyst was evaluated by the hydrodesulfurization (HDS) of different diesel feedstock. The carriers and catalysts were characterized by N2 adsorption-desorption, pyridine-FTIR, X-ray diffraction (XRD) and CO in-situ FTIR (CO-FTIR) techniques. Results showed that mesoporous ZSM-5 can improve the acidity of the catalyst and increase the number of MoCoS active phases. The C12-ZSM5 catalyst had low HDS and HDN activity, because the acidic sites of mesoporous ZSM-5 were easily occupied by nitrogen compounds. The HDS activity of C12-ZSM5 catalyst was fully exploited by using graded packing technology, the sulfur content of product oil was 5.9 ng/μL. The relative HDS activity of C12-ZSM5 catalyst is 1.47 times that of FHUDS-8 catalyst.

Nickel sulfide crystals in Ni-Mo and Ni-W catalysts: Eye-catching inactive feature or an active phase in its own right?

Ni sulfide (NiSx) crystals dominate the TEM images and STEM-EDX elemental maps of used Ni-Mo and Ni-W hydrotreating catalysts. Crystal sizes ranging from about 5 to over 100nm in diameter are observed not only in severely deactivated catalysts after use in commercial reactors, but also in highly active catalysts obtained after relatively short testing regimes. Depending on Ni-S stoichiometry and reaction conditions, NiSx crystals have different dimensions, shapes and crystal structures. Many of the NiSx crystals are decorated by multiple layers of MoS2/WS2. Although the activity of bulk Ni sulfide is generally deemed to be negligible, this does raise the question if these crystals play a role in catalysis after all.The number and percentage of accessible Ni sites in different catalysts can be estimated by combining the results of (i) the dispersion measurements on the MoS2/WS2 phase, (ii) the dispersion measurements on the visualized NiSx crystals and (iii) the composition of the catalyst matrix surrounding the NiSx crystals as derived from the phase analysis. The calculations based on the apparent Ni to Mo/W ratio of the catalyst matrix show that the catalyst matrix contains much more Ni than what can be accommodated on the MoS2/WS2 edges. We assume that this excess Ni is present as small non-visualized NiSx crystals mixed in the catalyst matrix. The fraction of Ni atoms on the surface of NiSx crystals can be calculated using the parameters of the millerite structure.The calculations carried out for NiMo/Al2O3 and NiW bulk catalysts show that the NiSx crystals could account for 19% and 48% of the active Ni sites, respectively. Despite this relatively high number of accessible Ni sites on the surface of NiSx crystals, no positive effect of a Ni/W ratio higher than 0.25 on the catalyst HDS and HDN activity was observed for a series of NiW bulk catalysts with variable Ni/W ratio. This suggests that, despite their spectacular presence in the TEM micrographs, the NiSx crystals do not significantly contribute to the HDS and HDN activity.

Product compositions from catalytic hydroprocessing of low temperature coal tar distillate over three commercial catalysts

Catalytic hydroprocessing of low temperature coal tar (LTCT) <360 °C distillate was performed over commercial Ni–W/γ-Al2O3, Ni–Mo/γ-Al2O3 and Co–Mo/γ-Al2O3 catalysts in a fixed-bed reactor to produce clean liquid fuel. Experimental feedstock and liquid products were divided into twelve groups based on converted material with the molecules and saturation levels to investigate the effect of catalysts on reaction network of the main compounds in feedstock by GC/MS analysis. Meanwhile, the influence of catalyst component on the product composition like group composition, distribution of carbon number, heteroatom removal, gaseous and oil properties was also investigated. The experimental results showed that phenols were mainly transformed into cycloalkanes and alkylbenzene, while alkyl-naphthalenes were converted to phenyl cycloalkanes and phenyl olefins. In addition, total carbon number in a slightly decreasing tendency. The Ni–W/γ-Al2O3 catalysts showed a higher hydrogenation activity and intermediate carbon number (C9–C16) selectivity, whereas the higher HDN and ring open activity was observed using Ni-Mo/γ-Al2O3 catalyst. The highest percentage of sulfur removal (about 97.8 %) was reached over the Co-Mo/γ-Al2O3 catalyst. Besides, methane was the predominant constituent in the light hydrocarbon gaseous product. And the properties of raw LTCT could be considerably upgraded after hydrotreatment.

Role of Citric Acid Modification on Hydrodesulfurization of DBT and 4,6 DMDBT in the Presence of Pyridine Over CoMo/Al2O3

In this study, the effect of pyridine as a basic nitrogen compound on HDS activity of DBT and 4,6 DMDBT in treated diesel over modified CoMo/Al2O3 by citric acid has been investigated. It has been obviously found that the modification of CoMo/Al2O3 catalyst by citric acid can inhibit the influence of pyridine on HDS activity of DBT and 4,6 DMDBT. This can be explained that when citric acid was applied in the catalyst preparation, the increasing of total amount of acid sites and the enhancement of HDN activity play an important role in the tolerance of pyridine.

Preparation of NiMoS nanoparticles for hydrotreating

NiMo sulfide nanoparticles were prepared by precipitation using water in oil (w/o) microemulsions, and were characterized by X-ray diffraction (XRD), Dynamic Light Scattering (DLS), X Ray Photoelectron Spectroscopy (XPS) and nitrogen adsorption (BET). They were also tested in the HDS of vacuum gas oil (VGO). Nanoparticles of 3-5nm which produced 50% HDS conversion of a Vacuum Gas Oil (VGO), as well as an enhanced HDN activity (when compared to a NiMo/Al2O3 catalyst), were obtained. After sulfidation of the solids the Ni, at the surface, is mainly decorating the edges of the MoS2 slabs (90at.%), however, an important proportion of the Ni segregates out of this position during the reaction (39%).

Combined Effects of EDTA and Heteroatoms (Ti, Zr, and Al) on Catalytic Activity of SBA-15 Supported NiMo Catalyst for Hydrotreating of Heavy Gas Oil

M-SBA-15 (M = Ti, Al, and Zr) materials with a Si/M ratio of 20 were synthesized using a direct synthesis method. M-SBA-15 supported NiMo hydrotreating catalysts with and without EDTA was prepared by an incipient wetness impregnation method. A EDTA/Ni molar ratio of 2 was used for catalysts with EDTA. The hydrotreating activities of these catalysts were measured using Athabasca bitumen derived heavy gas oil, and comparison was done with the performance of NiMo/SBA-15 and NiMo/γ-Al2O3 catalysts. All catalysts were thoroughly characterized by BET, TPR, TPD, CO-chemisorption, XRD, XANES, HRTEM, ICP-MS, and 13C NMR. Incorporation of Ti, Al, and Zr in SBA-15 framework results in an increase in the surface acidity and metal support interactions in otherwise neutral SBA-15 material. This increases the dispersion, and HDS, HDN and HDA activity of a NiMo/SBA-15 catalyst increases by 12%, 70%, and 22%, respectively, as in the case of a NiMo/Ti-SBA-15 (Cat-Ti) catalyst. EDTA addition helps in better redispersion of ...

Beneficial influence of EDTA on the structure and catalytic properties of sulfided NiMo/SBA-15 catalysts for hydrotreating of light gas oil

SBA-15 supported NiMo hydrotreating catalysts with different EDTA/Ni molar ratio were prepared by incipient wetness impregnation method. Hydrotreating activities of these catalysts were studied with Athabasca bitumen derived light gas oil and comparison was done with NiMo/SBA-15 and NiMo/γ-Al2O3 catalysts. A beneficial effect of chelating ligand was seen in hydrotreating activity and 28% increase in HDS of LGO was found as compared to NiMo/γ-Al2O3 in the case of EDTA/Ni molar ratio 4. Detailed mechanistic aspect of interaction between support – EDTA (ethylene diamine tetraacetic acid), EDTA-metallic species, support – metal, metallic species – metallic species at different reaction conditions is studied at different process parameters by using different characterization techniques such as X-ray absorption near-edge structure (XANES), Fourier transform infrared spectroscopy (FTIR), HRTEM, XRD, Raman, temperature programmed reduction (TPR), ICP-MS, CO chemisorption and N2 adsorption. A detailed scheme has been developed to explain the behavior of chelating agent in mesoporous SBA-15 supported catalysts. HRTEM results explain the high dispersion of Ni and MoS2 active phases in sulfided state even though big crystallite of MoO3 was seen in oxide state characterized by XRD and Raman spectra which explains role of EDTA in redistribution of active phases during sulfidation. XANES technique is used as predominant method for atomic level study of various structural changes in sulfided and oxide catalysts to find out the appropriate mechanism of the reaction. Characterization by XANES reveals that the presence of chelating agent delayed Ni2+ sulfidation which is main cause of improvement in HDS and HDN activity of the catalysts prepared in presence of organic chelates. Nickel sulfidation starts only when the EDTA–Ni complex decomposes and released nickel atoms move to the reactive edges of the MoS2 to form a finely dispersed sulfide NiMoS type II active phase.

Effect of Ti loading on the HDS and HDN activity of KLGO on NiMo/TiSBA-15 catalysts

TiSBA-15 with high surface area and large pore diameter with variable Si/Ti molar ratios of 20, 40, and 80 were synthesized and used as supports for NiMo catalysts. TiSBA-15 supports and NiMo/TiSBA-15 catalysts were extensively characterized by using XRD, N 2 adsorption analysis, FT-IR, Py-FTIR, Raman, TPR, SEM and TEM techniques. Results from XRD and IR measurements confirm the hexagonally ordered mesoporous structure and incorporation of Ti into the framework of SBA-15 support, respectively. TPR analysis confirmed that Ti incorporation resulted in better dispersion and more homogeneous distribution of octahedral Ni and Mo species on the support compared to NiMo/SBA-15. Hydrotreating experiments were conducted using coker light gas oil (KLGO) under industrial conditions of temperature, pressure, LHSV, and gas to oil ratio of 330–370 °C, 8.8 MPa, 2 h −1, and 600 mL/mL, respectively. NiMo/TiSBA-15 catalysts showed very high catalytic activities of hydrodesulfurization and hydrodenitrogenation of KLGO than the NiMo catalysts prepared by using SBA-15 and γ-Al 2O 3 as support.

HDS and HDN activity of (Ni,Co)Mo binary and ternary nitrides prepared by decomposition of hexamethylenetetramine complexes

Highly dispersed pure phases of binary and ternary nitrides (Co,Ni)Mo were prepared using decomposition of hexamethylenetetramine (HMTA) complexes. Their catalytic activity was evaluated in the HDS of thiophene and HDN of quinoline. Three different pre-treatment modes were applied, including direct in situ preparation of nitrides in the catalytic reactor; pre-sulfidation with hydrogen sulfide and soft oxidation in air followed by sulfidation. Pure bimetallic nitrides are highly active HDN catalysts in the absence of sulfur and show substantial synergy effect between Ni or Co and Mo. By contrast, no synergy was observed for thiophene HDS, specific surface rates for binary and ternary nitrides being similar to that of unsupported MoS 2. Transmission microscopy, XRD and XPS studies showed that MoS 2 segregation on the surface occurs during HDS reaction or sulfidation with H 2S. As a result bimetallic catalysts contained nitride particles covered with MoS 2 layers and VIII group metal sulfide crystalline particles in the subsurface layer. The introduction in the preparation sequence of an additional step of oxidation–sulfidation led to a considerable increase of HDS catalytic activity of bimetallic catalysts. Pre-sulfidation of nitrides with H 2S/H 2 mixture resulted in a drastic decrease of specific surface area (Ssp) and very low HDS activity. Soft sulfidation with thiophene under reaction conditions led to high Ssp and high HDS activity per unit of mass.

Phosphorus promoted trimetallic NiMoW/γ-Al 2O 3 sulfide catalysts in gas oil hydrotreating

A series of phosphorus promoted γ-Al 2O 3-supported NiMoW sulfide catalysts consisting of 6 wt.% Mo, 7 wt.% W, 2.5 wt.% Ni and 0–2.5 wt.% P was synthesized by a co-impregnation method. The catalysts were characterized by N 2 adsorption, carbon monoxide chemisorption, X-ray diffraction, Raman spectroscopy, diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, X-ray absorption near edge structure (XANES) and DRIFT spectroscopy of adsorbed CO. The CO uptake measurement and Raman spectroscopy showed that P addition to NiMoW improves the dispersion of Mo and W species on the γ-Al 2O 3 surface. DRIFT spectra of adsorbed CO evidenced that the number of active sites on the surface of NiMoW/γ-Al 2O 3 sulfide increases with increasing phosphorus concentration and reaches an optimum at 1.6 wt.% of phosphorus. DRIFT spectroscopy evidenced the aluminum phosphates on the surface and also new Brønsted acid groups in P-doped catalysts. XANES study revealed that P doping in γ-Al 2O 3 does not affect the bulk electronic structure of γ-Al 2O 3. The HDS and HDN of coker light gas oil derived from Athabasca bitumen in a trickle bed reactor at industrial conditions showed that phosphorus doping has a stronger promotional effect for HDN than the HDS. The enhancement in HDN activity with phosphorus addition could be attributed more to the effect of acidity than to the improvement in dispersion. The PNiMoW/γ-Al 2O 3 catalyst with P loading of 1.6 wt.% showed superior hydrotreating activity than the bimetallic PNiMo/γ-Al 2O 3, PNiW/γ-Al 2O 3 and commercial catalysts.

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.

Hydrotreating of light cycle oil using WNi catalysts containing hydrothermally and chemically treated zeolite Y

One W–Ni catalyst supported on hydrothermally treated zeolite Y and two W–Ni catalysts supported on chemically treated zeolite Y were prepared. The catalysts were characterized by NH 3-TPD, pyridine-IR, TEM, BET, and XPS. Their performance of hydrodesulfurization, hydrodenitrogenation, and hydrodearomatization were compared using light cycle oil (LCO) as the feed. The results showed that the hydrothermal treatment promotes HDS activity whereas the chemical approach favours the HDA activity. The HDN activity of the three catalysts was similar. Addition of zeolite Y with high proportion of Brønsted acidity in the catalysts helps to enhance the hydrodearomatization activity.

Bimetallic PtPd on zirconia catalysts for hydrotreating purposes

Abstract In the framework of a two stage process for the hydrotreatment of gas oil, the use of noble metal catalysts in the second stage, where the H 2 S partial pressure is considerably decreased, was proposed. Thus, the catalytic properties of a series of Pt x Pd 100− x ( x corresponding to at.% in the alloy) particles supported on zirconia were investigated in tetralin hydrogenation and decahydroquinoline hydrodenitrogenation. TEM micrographs and EDS analysis evidenced the high dispersion of the monometallic and bimetallic composition of the nanoparticles. Whereas a promoting effect is observed in the case of hydrogenation reaction, the introduction of Pd suppressed the catalytic activity in C–N bond scission reaction. This poisoning effect can be simply understood as a linear effect of the segregation of Pd at the surface of PdPt particles. The effect of H 2 S partial pressure on the HDN activity was investigated and showed that for this reaction thioresistance is not improved by alloying.

HDS and HDN activity of molybdenum and nickel–molybdenum catalysts supported on alumina–titania carriers

Alumina–titania supports containing 5–50 wt.% of TiO 2 were prepared by coprecipitation method using inorganic precursors (sodium aluminate and titanium chloride). DTA-TGA, XRD, SEM, TPD NH3, and IR spectroscopy were used to characterise these materials. The study shows that the promoting effect of nickel on the HDS activity of molybdenum catalysts supported on Al 2O 3TiO 2 is significantly lower than that for molybdenum catalyst supported on Al 2O 3, and depends on the TiO 2 content. The SEM results show that in the case of rich Al support (20 wt.% of TiO 2) molybdenum was aggregated on the external surface of the catalyst, whereas it was uniformly dispersed on the external surface of alumina. Results also show that molybdenum is preferably supported on aluminum oxide. Application of Al 2O 3TiO 2 oxides enhances the HDN activity of nickel–molybdenum catalysts. The highest HDN efficiency was obtained for the NiMo/Al 2O 3TiO 2 catalyst containing 50 wt.% of TiO 2. HDN activity was found to depend on protonic acidity and anatase content.

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.

INFLUENCE OF CATALYST ACIDITY AND FEEDSTOCK QUALITY ON HYDROTREATING CATALYST DEACTIVATION BY COKE DEPOSITION

Influence of catalyst acidity and feedstock quality on the extent of initial coke formation and its role in hydrotreating catalyst deactivation were investigated. A series of Ni–Mo/Al2O3 catalysts with varying acidities were prepared by using sodium and fluoride ions as acidity modifying additives. Acidities of the catalysts decreased in the sequence: Ni-Mo-F(5%) > Ni-Mo-F(2%) > Ni-Mo > Ni-Mo-Na(1%) > Ni-Mo-Na (5%). The amount of coke formed on the catalyst did not show any direct relation to catalyst's acidity but was found to depend strongly on the type of additive used for modifying acidity. In the case of sodium addition, although, the catalyst's strong acidity decreased, coke deposition increased probably due to the suppression of catalyst's hydrogenation function by interaction between sodium and molybdenum. Fluoride addition at low concentration levels (e.g. 2wt%) increased both HDS and HDN activities of the catalyst, but at high concentration levels of fluoride (e.g. 5 wt%), the catalyst showed a sharp decrease in HDS and HDN activity. Sodium addition at all levels decreased catalysts activity for both HDS and HDN. In the feed quality effect studies, a feedstock with a higher concentration of nitrogen and asphaltenes led to rapid coke build up during the initial period. Solid state carbon-13 NMR analysis of the coke on various spent catalyst samples showed that the coke formed from residual oil feed was more aromatic in character than that from VGO, and the initial coke changed its aromatic character with processing time.

Characterization and catalytic properties of supported nickel molybdenum nitrides for hydrodenitrogenation

The characterization and hydrodenitrogenation activity of 3-methyl pyridine have been obtained. The results from the characterization techniques (X-ray diffraction (XRD), temperature-programmed reaction (TPR) and XPS) were used to illustrate the structure, surface reduction properties and the role of Ni metal in the reaction. The NiMoN x /γ-Al 2O 3 catalyst is more active than a Mo 2N/γ-Al 2O 3 catalyst with the same MoO 3 loading. Mo 2N, Ni 3Mo 3N and Ni metal are formed in the NiMoN x /γ-Al 2O 3 catalyst; moreover, the synergy among them is probably responsible for the high activity of NiMoN x /γ-Al 2O 3 catalyst. The addition of Ni metal enhances the reducibility of Mo 2N/γ-Al 2O 3 phase and also promotes the HDN activity. The reasons for reduction before reaction and the surface ion state changes during reduction are illustrated by XPS techniques.