Hydrodesulfurization Activity Research Articles

Catalytic Activities of Noble Metal Phosphides for Hydrogenation and Hydrodesulfurization Reactions

In this work, the development of a highly active noble metal phosphide (NMXPY)-based hydrodesulfurization (HDS) catalyst with a high hydrogenating ability for heavy oils was studied. NMXPY catalysts were obtained by reduction of P-added noble metals (NM-P, NM: Rh, Pd, Ru) supported on SiO2. The order of activities for the hydrogenation of biphenyl was Rh-P > NiMoS > Pd-P > Ru-P. This order was almost the same as that of the catalytic activities for the HDS of dibenzothiophene. In the HDS of 4,6-dimethyldibenzothiophene (4,6-DMDBT), the HDS activity of the Rh-P catalyst increased with increasing reaction temperature, but the maximum HDS activity for the NiMoS catalyst was observed at 270 °C. The Rh-P catalyst yielded fully hydrogenated products with high selectivity compared with the NiMoS catalyst. Furthermore, XRD analysis of the spent Rh-P catalysts revealed that the Rh2P phase possessed high sulfur tolerance and resistance to sintering.

Synthesis of hierarchically structured alumina support with adjustable nanocrystalline aggregation towards efficient hydrodesulfurization

The development of highly active hydrodesulfurization (HDS) catalysts is still of great importance in hydroprocessing of the heavy residue oils in industry. Herein, hierarchically structured alumina hollow microspheres with high specific surface area were successfully prepared via a citric-acid-modulated hydrothermal method. With different dosages of citric acid applied, alumina microspheres were assembled with different specific surface areas, pore volumes and acidity. After the loading of the MoNi active components, a series of HDS catalysts were characterized systematically by various relevant techniques; and their catalytic activity and selectivity towards hydrodesulfurization of dibenzothiophene (DBT) were evaluated and compared. It is revealed that, the catalytic efficiency of the catalyst highly depends on the factors including the specific surface area and the acidity, the sulfidity and the dispersion of the active metal components. On this basis, we have established a facile method for preparation of hierarchically structured alumina supports with desirable physicochemical properties and high HDS catalytic efficiency. This work could also provide theoretical guidance for rational design of highly active HDS catalysts.

Synthesis of an Ni2P catalyst supported on Na-MCM-41 with highly activity for dibenzothiophene HDS under mild conditions

A novel and simple method to synthesize supported Ni2P/Na(x)-MCM-41 catalysts (where x is the mass fraction of Na-to-MCM-41 in terms of percentage) at a lower reduction temperature by incorporation of Na was described. The catalysts were characterized by H2 temperature-programmed reduction (H2-TPR), X-ray diffraction (XRD), N2 adsorption–desorption, CO uptake, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The effect of Na on the structure of catalysts and catalytic properties for the dibenzothiophene (DBT) hydrodesulfurization (HDS) was investigated, which confirmed that a suitable amount of Na can promote highly dispersed Ni2P particles. The Na preferentially interacts with phosphate to generate the sodium phosphate and therefore suppresses the formation of stronger P–O–P bonds, which enables the phosphide catalyst to be easily formed at a lower reduction temperature. Compared with conventional phosphate (973–1273 K), the reduction temperature of Ni2P/Na(x)-MCM-41 catalyst was relatively low (773 K). The Ni2P/Na(x)-MCM-41 catalyst with x = 1.0 showed the maximum DBT conversion of 91.6%, which is higher than that of Ni2P/M41 without Na (80.3%).

Comparable investigation of unsupported MoS2 hydrodesulfurization catalysts prepared by different techniques: Advantages of support leaching method

Unsupported molybdenum disulfide catalysts were synthesized from ammonium tetrathiomolybdate with chitosan, hexadecylammonium and Triton X100 as structural agents by leaching of MoS2/Al2O3 and MoS2/C/Al2O3 catalyst supports with HF acid and covering of “FeS” seeds by the MoS2 shell. Activation of the solids was performed under the H2S/H2 flow or by the decomposition of precursors in the presence of a hydrocarbon solvent in an autoclave reactor with varied H2 pressure. X-ray diffraction, N2 adsorption, temperature-programmed reduction, X-ray photoelectron spectroscopy and transmission electron microscopy techniques were used to characterize their structure and morphology. The nature of organic additives and activation conditions affect the surface area, pore size distribution, and morphological characteristics of MoS2 particles. Hydrodesulfurization of dibenzothiophene was performed in an autoclave reactor over unsupported MoS2based catalysts. The catalytic behavior of bulk MoS2 catalysts showed that the hydrogenation pathway prevailed over the direct desulfurization pathway. Higher HYD/DDS selectivity for dibenzothiophene hydrogenation was observed with the bulk molybdenum disulfide catalyst formed by etching of the MoS2/Al2O3 catalyst support. Unsupported Mo sulfide catalysts exhibited high hydrogenation activity in dibenzothiophene hydrodesulfurization and, therefore, might find wide applications in hydroprocessing of heavy feed and co-hydrotreating of petroleum fractions and plant oils.

Essential role of promoter Co on the MoS2 catalyst in selective hydrodesulfurization of FCC gasoline

The essential role of Co on the MoS2 catalyst in selective hydrodesulfurization (HDS) of FCC gasoline was investigated with ammonium tetrathiomolybdate supported on alumina modified with various amount of Co sulfide. According to the data obtained by XRD, HRTEM, XPS, H2-TPR and Py-FTIR analysis, the Co species could significantly affect the microstructure and composition proportion of the active phase, and thus induced the enormous differences in catalytic properties. The evaluation results demonstrated that the Co atoms tending to form the CoMoS phase as Co/Mo (atomic ratio)<0.2 could greatly improve the HDS activity, but slightly improve the hydrogenation (HYD) activity of olefins. The spillover hydrogen produced by the formation of Co9S8 phase as 0.2<Co/Mo (atomic ratio)<0.6 greatly improved the HDS activity, but showed almost no effect on the HYD of olefins. The excess Co could inevitably form some large size Co9S8 phase as Co/Mo (atomic ratio)>0.6, which would hinder the mutual contact of the reactants and the active sites, and thus lead to the decrease of the HDS activity and selectivity. The obtained results were useful for developing highly effective hydrotreating catalyst.

A New Approach to Deep Desulfurization of Light Cycle Oil over Ni2P Catalysts: Combined Selective Oxidation and Hydrotreating

Amphiphilic phosphotungstic acid (A-PTA) and Ni2P/SBA-15 catalysts were prepared to apply for selective oxidation of refractory sulfur compounds in light cycle oils and hydrotreating of the oxidized S compounds, respectively. Physical properties of the catalyst samples were analyzed by BET, CO uptake chemisorption, and TEM. Structural properties for the supported Ni2P catalysts were analyzed by X-ray diffraction (XRD) and extended X-ray absorption fine structure (XAFS) spectroscopy. The selective oxidation of S compounds in the LCO feed was conducted in a batch reactor at H2O2/S ratio of 10, atmospheric pressure and 353 K and then the products were fed to a continuous flow fixed-bed reactor for hydrotreating at 623 K, 3.0 MPa, and LHSV’s of 0.5–2.0 h−1. A-PTA catalyst showed a high oxidation conversion of 95% for a real LCO feed. The following hydrotreating led to a hydrodesulfurization (HDS) conversion of 99.6% and a hydrodenitrogenation (HDN) conversion of 94.7% over Ni2P/SBA-15, which were much higher than those of direct hydrotreating results which gave an HDS conversion of 63.5% and an HDN conversion of 17.5% based on the same LHSV of 2.0 h−1. It was revealed that the reduction in refractory nitrogen compounds after oxidative treatment contributed to the increase of the following HDS activity.

The Effects of Chelating Agents on CoMo/TiO2–Al2O3 Hydrodesulfurization Catalysts

A series of CoMo/TiO2–Al2O3 catalysts with different chelating agents were prepared by co-impregnation method. The influence of chelating agents on dispersions of active phase, textural properties, and hydrodesulfurization (HDS) activity for CoMo/TiO2–Al2O3 catalysts was studied. XRD characterization demonstrates that the addition of chelating agents can promote the dispersion degree of active components. TPR experiments exhibit an important effect of chelating agents on the catalysts. CoMo/TiO2–Al2O3 catalysts prepared with different chelating agents shows different HDS activity, and the addition of EDTA results in a remarkable improvement in both thiophene and DBT HDS conversions compared with others.

Preparation of Fe2P/Al2O3 and FeP/Al2O3 catalysts for the hydrotreating reactions

Abstract A 60%Fe/Al2O3 catalyst was prepared by the co-precipitation method. It was reduced by H2 to produce metallic Fe, which was then sulfided by CS2 to Fe0.96S and Fe3S4 or phosphided by triphenylphosphine (PPh3) in liquid phases to Fe2P and FeP. It was found that the iron sulfides (Fe0.96S and Fe3S4) exhibited the low activity for the hydrodesulfurization (HDS) reactions. The HDS activity was also low on the Fe(metal)/Al2O3 and Fe2P/Al2O3 catalysts since they were converted into Fe0.96S and Fe3S4 during the HDS reactions. In contrast, the FeP/Al2O3 was found to be stable and active for the HDS reactions. In particular, FeP/Al2O3 possessed significantly smaller FeP particles than FeP/C, leading to the significant higher HDS activity of FeP/Al2O3 than FeP/C.

A novel route for synthesis of NiCoP/SiO2 hydrodesulfurization catalysts with active S species

We report a new route for synthesis of NiCoP/SiO2 with active S species using NiS and CoS as precursors. The as‐prepared catalysts were characterized using X‐ray powder diffraction, N2‐adsorption specific surface area measurements, inductively coupled plasma atomic emission spectroscopy, transmission electron microscopy, and X‐ray photoelectron spectroscopy (XPS). The catalyst was highly active during the dibenzothiophene hydrodesulfurization (HDS) of NiCoP/SiO2. The XPS spectra of the as‐obtained samples show that the surface of NiCoP contains a small amount of S species, which may be responsible for the higher HDS activity.

Effect of trimesic acid as chelating agent in sulfided CoMoP/γ-Al2O3 catalyst for hydrodesulfurization of straight-run gas oil

The effect of trimesic acid (TA) on the surface of γ-Al2O3 for CoMoP catalysts has been investigated in the hydrodesulfurization (HDS) of straight-run gas oil. The γ-Al2O3 support was modified by surface impregnation of a solution of TA to afford TA/Co molar ratios (0.5, 1.0 and 2.0) in the final composition. The CoMoP material with atomic ratio of TA/Co = 1.0 displayed the highest HDS activity. FT-IR results suggest that the carboxylic acid moieties (AA) of the TA deposited on the γ-Al2O3 interact with the Mo and Co species. The DRS UV vis revealed the presence of Co species in distorted octahedral symmetry. The MoOh/MoTh ratio varied depending on the amount of the organic additive. TGA results indicated that the TA on the catalyst with TA/Co ratio = 1.0 often decomposes at lower temperature in comparison with the other samples. Thus, a lower temperature decomposition favors the surface concentration of metals species for the sulfurization degree. The interaction of the TA induces moderate metal-support interaction. Raman spectroscopy showed that the presence of TA influenced significantly on the ratio MoO/(MoO + MoOMo + MoO) on the catalyst surface. Raman results also evidenced the highest ratio MoO/(MoO + MoOMo + MoO) for the CoMoP (1.0) sample. Apparently, the augment of the MoO species is related to a major availability of Mo species for the formation of MoS2 for HDS reaction. The XPS and HRTEM results showed higher formation and more dispersed MoS2 and CoMoS species for the catalysts modified by TA compared to that of the reference sample. The CoMoP (1.0) showed higher Moe/Mot ratio in comparison with CoMoP (0.0), which resulted in a higher gas oil HDS activity.

Active phase transformation in industrial CoMo/Al2O3 hydrotreating catalyst during its deactivation and rejuvenation with organic chemicals treatment

Reactivation of industrial CoMo/Al2O3 hydrotreating (HDT) catalysts was studied. A spent catalyst was used in the ULSD production for about 2.5 years. It was oxidatively regenerated and rejuvenated by organic acids (citric and thioglycolic), glycols (ethylene and triethylene), and dimethylsulfoxide solutions. All solids were characterized by the elemental analysis, N2 physisorption, X-ray powder diffraction, thermogravimetric analysis, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Changes in the active phase composition and morphology during the CoMo/Al2O3 HDT catalyst operation, regeneration and rejuvenation were shown. The rejuvenated catalysts were tested in hydrodesulfurization (HDS) of dibenzothiophene and hydrogenation (HYD) of naphthalene. It was found that oxidative regeneration allowed restoring about 70–85% rel. of initial activity. Rejuvenation with organic chemicals resulted in the complete restoration of HDS and HYD activities. Resulting catalytic activity of the reactivated catalysts depended on the properties of the formed active phase species. These correlations are discussed in the study.

CoMo catalyst on zeolite TS-1 nanorod assemblies with high activity in the hydrodesulfurization of 4,6-dimethyldibenzothiophene

Crystalline TS-1 zeolite nanorod (NTS-1) assemblies were successfully synthesized. NTS-1 possesses a hierarchically porous structure and a large nanoporous surface area. Following impregnation with Co and Mo species and sulfidation, the obtained catalyst (CoMoS2/NTS-1) shows higher activity in the hydrodesulfurization of refractory 4,6-dimethyldibenzothiophene than the γ-Al2O3, mesoporous zeolite ZSM-5, and Silicalite-1 (MZSM-5 and M-Silicalite-1), as well as binary SiO2–TiO2 supported catalysts. In the absence of mass transfer, the reaction rate constant on CoMoS2/NTS-1 (9.5 × 10−2 μmol∙g−1∙s−1) is much higher than those on CoMoS2/γ-Al2O3, CoMoS2/M-Silicalite-1, CoMoS2/MZSM-5, and CoMoS2/SiO2-TiO2 catalysts (4.2 × 10−2, 7.9 × 10−2, 8.7 × 10−2, and 7.0 × 10−2 μmol∙g−1∙s−1). Characterization results show that the framework Ti species in NTS-1 intensify the interaction of the Mo species with NTS-1, resulting in a sulfided catalyst with a less stacked and shorter MoS2 phase. This exposes more brim sites for hydrogenation, improving the hydrodesulfurization activity of the catalyst.

Effect of TiO2 Coating on Morphology of Active Phase on Sulfided CoMo/Al2O3 Hydrotreating Catalysts

A series of CoMo catalysts supported on various Al2O3 supports added with TiO2 were prepared to investigate the addition effect of TiO2 on formation of an active phase on sulfided CoMo/Al2O3 catalyst. The catalytic activity tests were carried out with hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene, hydrodenitrogenation (HDN) of acridine, and hydrodearomatization (HDA) of o-xylene, 1-methylnaphthalene (1-MN), and phenanthrene. A 20 wt % TiO2 added CoMoAlTi20 catalyst showed the lowest hydrogenation activity in HDA of 1-MN and phenanthrene and highest HDS and HDN activities. The property of a support and/or the interaction between active metal and the support significantly affect the formation of active sites for HDS and HDA. The active sites for HDS on sulfided CoMo catalysts were different from those for HDA and/or hydrogenation. The addition of TiO2 enhanced the reduction, the formation, and stacking number of CoMoS active slabs. The finding that desulfurization via the hydrogenation pathway ...

MOR nanosheet assemblies supported NiW catalysts in the hydrodesulfurization of the 4,6-DMDBT: Effect of Ni/W ratio on the catalytic performance

The preparation of highly active hydrodesulfurization (HDS) catalyst is of vital importance for the production of ultra-clean fuel. Herein, nanosheet assemblies MOR were employed as support to prepare series of NiW catalyst with different Ni/W ratio (NiW/NS-MOR). After impregnation of Ni and W species and sulfidation, the obtained NiW/NS-MOR catalyst showed an increasing activity in the HDS of the refractory 4,6-dimethyldibenzothiophene with the rise of the Ni content in the prepared NiW catalysts, and reached the maximum HDS activity at the Ni/W ratio of 0.55. Also, the reaction rate constant and TOF on NiW/NS-MOR-0.55 (11.1 × 10−4 mol g−1 h−1 and 3.3 h−1) were much higher than those on NiW/γ-alumina catalyst (8.1 × 10−4 mol g−1 h−1 and 2.2 h−1). All the prepared supported-NiW catalysts were characterized by N2 physisorption, X-ray powder diffraction, Ultraviolet visible spectroscopy, Raman spectroscopy, temperature-programmed reduction by H2, X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. Characterization results show that the increase in Ni/W for the prepared catalyst weakened the interaction of the tungstate oxide species with NS-MOR, and then more tungstate oxide species were transformed into stacked and highly active Type II NiWS active phase, improving the HDS activity of the catalyst.

Tuning of the active phase structure and hydrofining performance of alumina-supported tri-metallic WMoNi catalysts via phosphorus incorporation

The effects of phosphorus on the structure and hydrofining performance of tri-metallic WMoNi/Al2O3 catalysts prepared with W/Mo-based hybrid precursor nanocrystals were investigated. The incorporation of phosphorus weakened the metal-support interactions (MSIs) and facilitated the formation of more synergetic NiWMoS phases with higher stacks. Catalytic tests using a fluid catalytic cracking diesel fuel showed that the changes in the MSIs and the morphology of the active phases had a more positive effect on the hydrodenitrogenation activity than on the hydrodesulfurization activity. In contrast, when phosphorus was incorporated into a tri-metallic WMoNiP/ Al2O3 catalyst prepared by a conventional incipient impregnation method, the MSIs decreased causing aggregation of the metal species which resulted in poorer hydrofining performance of the catalyst. These results show that incorporating phosphorus into a WMoNi/Al2O3 catalyst can finely tune the structure of the active phase to enhance the hydrogenation and hydrodenitrogenation activity of the resulting tri-metallic catalyst.

Efficient hydrodesulfurization catalysts derived from Strandberg P[sbnd]Mo[sbnd]Ni polyoxometalates

Highly active hydrodesulfurization (HDS) catalysts have been prepared successfully through a molecular approach using well-defined Strandberg PMoNi polyoxometalates (POMs) as superior precursors. The hand-picked POMs significantly facilitated not only the formation of highly dispersed NiMo species but also the formation of abundant and accessible NiMoS active sites at lower sulfidation temperatures, thereby resulting in a remarkable activity improvement in comparison with reference catalysts prepared with conventional precursors. Characterization results revealed the multidirecting effects of the POMs component and structure on the morphology and composition of the species in the NiMoS active phase and the evolution of precursors during the catalyst preparation simultaneously. The bottom-up POMs-based preparation methodology provides a better understanding of HDS catalyst structure and performance, thus further shedding light on the rational design and controllable fabrication of efficient HDS catalysts.

Catalyst used in fluid catalytic cracking (FCC) unit as a support of NiMoP catalyst for light cycle oil hydroprocessing

The behavior of the NiMoP catalysts prepared by means of impregnation of different supports (MCM-41, SBA-15, catalyst used in FCC unit) has been studied, using them in the hydroprocessing of Light Cycle Oil (LCO) with the aim of maximizing the sulfur removal and reduce polyaromatics content; so the hydroprocessed LCO can be hydrocracked in another unit with metal noble catalysts.Catalysts have been characterized through several techniques: N2 adsorption–desorption, elemental analysis (ICP-AES), X-ray diffraction (XRD), acidity measurement by temperature programmed desorption (TPD) of tert-butylamine, temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), UV–Vis spectroscopy, transmission electron microscopy (TEM), and temperature programmed oxidation (TPO) (spent catalysts). The hydroprocessing runs have been carried out in a fixed bed reactor working in trickle bed regime at 320–400 °C; 80 bar; H2:LCO ratio, 1000mLNH2mL−1LCO; space time, 0.2 h, and time on stream (TOS), 8 h.The catalyst NiMoP/HY-Al2O3 (spent FCC catalyst) stands out due to its high hydrodesulfurization activity attributable to the ease of impregnation of metals over FCC catalyst and the accessibility of the components of the LCO to the hierarchical porous structure. Its activity for reducing polyaromatics compounds of LCO is also remarkable, without diminishing the diesel fraction content by overcracking. Besides, the deposition of coke over this catalyst is scarce, since the retention of the high molecular weight molecules of LCO in its porous structure is minimized.

Effect of Vanadium Introduction on the Activity of NiMo/Al2O3 Catalysts in the Hydrotreating of Diesel Fractions

The influence of the introduction of V2O5 into NiMo/Al2O3 catalysts on their activity in hydrodesulfurization (HDS) and hydrogenation reactions of the components of petroleum fractions has been studied. The activity of the synthesized catalysts has been determined in the straight-run diesel and light coker gas oil hydrotreating processes in a flow-through unit under hydrogen pressure. The most active catalyst for HDS and hydrogenation of polycyclic aromatic hydrocarbons has been synthesized using VMo12 heteropoly compounds: the activity increases by 6–10 and 11–13 wt % in HDS and PAH hydrogenation, respectively, at different temperatures. It has been shown that the activity of the regenerated catalyst further impregnated with the vanadium compound in HDS and PAH hydrogenation increases by 2–5 rel. %, as compared to the regenerated catalyst.

Hydrotreating of Vacuum Gas Oil on NiW/Al2O3 Catalysts Prepared with the Use of Chelating Agents

Alumina-based NiW catalysts have been prepared from 12-phosphotungstic heteropoly acid (PW12HPA), ammonium metatungstate (NH4)6H2[W12O40], and nickel hydroxide carbonate or nickel nitrate using citric acid (CA) or ethylenediaminetetraacetic acid (EDTA) as a chelating agent. The obtained samples have been studied by N2 adsorption, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy techniques. The catalysts obtained using the PW12HPA and CA have been characterized by the greatest dispersion of active-phase particles, and the use of EDTA has provided the maximum proportion of NiWS. The hydrodesulfurizing activity of catalysts in the hydrotreating of vacuum gas oil has been found to decrease in the following order: Ni-CAPW/Al2O3 > Ni-CAW/Al2O3 > Ni-EDTA-W/Al2O3 > Ni-W/Al2O3, which in general correlates with the particle size of the active phase and the concentration of promoted active sites.

The particular characteristics of the active sites of MoS2, WS2 catalysts in thiophene hydrodesulfurization

It was reported in earlier studies that a linear correlation existed between the total sulfur exchange capacity and thiophene hydrodesulfurization activity of different, alumina- or silica-supported molybdenum- or tungsten-sulfide based porous catalysts promoted with different metals: Co, Ni, Pt and Pd. The aim of this study was to clear up how general the linear correlation is, whether that correlation is generally applicable, whether it shows a particular character of the active sites in thiophene hydrodesulfurization (HDS). Industrial catalysts are more complex than typical model catalysts so the extents of thiophene HDS were determined on six industrially manufactured catalysts available today (combinations of Mo, W and Ni supported on alumina and of one NiW on silica-alumina) and compared to their sulfur uptake, and radiosulfur exchange capacity at 623 K. The majority of these catalyst samples also contained some phosphorus in different amounts. The results of the cyclohexane dehydrogenation as a model reaction indicated the absence of metallic nickel on the surface of the catalysts. A linear correlation was observed between the sulfur exchange capacity and HDS activity of these catalysts (with the exception of the sample supported on silica-alumina) similar to that observed previously.