Hydrodesulfurization Activity Research Articles

Hierarchically Structured Porous Silica Spheres by Microemulsion/Vesicle Templating for Hydrodesulfurization of Fluid Catalytic Cracking Diesel

A series of hierarchically structured porous silica sphere (HSPSS) materials are successfully fabricated by a facile, one‐step microemulsion/vesicle bimodal method in a multicomponent microemulsion system of P123/n‐butanol/1,3,5‐trimethylbenzene/KCl/H2O (surfactant/cosurfactant/oil/salt/water). The pore structures of the obtained HSPSS products consist of mesocellular foam and mesostructured vesicles. In contrast to the traditional porous silica materials the new structures combine two separate, distinct mesophases with different‐sized mesovoids in a single porous sphere. Moreover, the proportion of every mesophase in obtained HSPSS can be easily adjusted by tuning the initially added amount of n‐butanol or KCl in this multicomponent microemulsion system. When the molar ratio of KCl/tetraethoxysilane is 2.15, the obtained HSPSS material is turned into uniform mesostructured vesicle silica spheres, which consist of many small diameter vesicle particles. The hydrodesulfurization (HDS) activity of fluid catalytic cracking diesel over the HSPSS was tested. HSPSS‐0.75‐1.43 catalyst support with multiple mesoporous structures shows the highest HDS efficiency (98.5%) among all the studied catalysts.

Facile Preparation of Ni2P with a Sulfur‐Containing Surface Layer by Low‐Temperature Reduction of Ni2P2S6

Preparation of Ni2P by temperature-programmed reduction (TPR) of a phosphate precursor is challenging because the P-O bond is strong. An alternative approach to synthesizing Ni2P, by reduction of nickel hexathiodiphosphate (Ni2P2S6), is presented. Conversion of Ni2P2S6 into Ni2P occurs at 200-220 °C, a temperature much lower than that required by the conventional TPR method (typically 500 °C). A sulfur-containing layer with a thickness of about 4.7 nm, composed of tiny crystallites, was observed at the surface of the obtained Ni2 P catalyst (Ni2P-S). This is a direct observation of the sulfur-containing layer of Ni2P, or the so-called nickel phosphosulfide phase. Both the hydrodesulfurization activity and the selective hydrogenation performance of Ni2P-S were superior to that of the catalyst prepared by the TPR method, suggesting a positive role of sulfur on the surface of Ni2P-S. These features render Ni2P-S a legitimate alternative non-precious metal catalyst for hydrogenation reactions.

Influence of sulfidation conditions on morphology and hydrotreating performance of unsupported Ni–Mo–W catalysts

Oxidic unsupported Ni–Mo–W catalysts were prepared from a precipitate by high-temperature hydrothermal synthesis. The catalysts were sulfided in-situ by CS2 and H2 under different sulfiding conditions. The catalytic activity and selectivity were studied in the model reactions of naphthalene hydrogenation (HYD), quinoline hydrodenitrogenation (HDN), and dibenzothiophene (DBT) hydrodesulfurization (HDS). The sulfided catalysts were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and energy dispersive spectrum (EDS) mapping. Sulfided unsupported Ni–Mo–W catalysts showed visible diffraction peaks of Ni3S2 and MoS2/WS2. As the sulfiding temperature or time increased, the Ni3S2 and MoS2/WS2 nanoparticles agglomerated, with MoS2/WS2 lamella curved to some extent. Specifically, the stacking of the MoS2/WS2 slabs increased with increasing sulfidation time. Meanwhile, the catalysts showed higher HDS, HDN, and HDAr activities when the sulfiding temperature was 320°C. However, the hydrogenation activity decreased above 340°C.

Hydrodesulfurization activities of NiMo catalysts supported on mechanochemically prepared Al-Ce mixed oxides

Al2O3-CeO2 supports containing 1-10 wt% Ce were prepared mechanochemically by milling aluminum and/or cerium nitrates with NH4HCO3. Heteropolymolybdate, (NH4)4NiMo6O24, was used as the precursor of the Ni and Mo to prepare NiMo6/Al2O3-CeO2 components in catalysts by impregnation method. The physicochemical properties of the catalysts were determined using chemical analysis, X-ray diffraction, temperature-programmed H2 reduction, temperature-programmed NH3 desorption, X-ray photoelectron spectroscopy (XPS), and the Brunauer-Emmett-Teller method. The catalyst acidity decreased with increasing Ce concentration in the support. XPS showed that the NiS/MoS ratio decreased two-fold for the Ce-modified alumina support. NiMo6/Al2O3, which had the highest acidity, showed the highest activity in hydrodesulfurization of 1-benzothiophene (normalized per weight of catalyst). The concentration of surface MoOxSy species (which is equal to the concentration of Mo5+) gradually decreased to zero for catalysts with Ce concentrations ( 10 wt%. However, the activities of all the catalysts prepared mechanochemically from Al2O3 and Al2O3-CeO2 supports significantly exceeded that of a reference NiMo6/Al2O3 catalyst prepared by impregnation method using the same precursor and with the same composition.

Highly-active nickel phosphide hydrotreating catalysts prepared in situ using nickel hypophosphite precursors

An in situ method for the preparation of nickel phosphide (Ni2P) on silica, alumina, and amorphous silica-alumina (ASA) supports is described. The synthesis avoids the use of nickel and phosphorus salts by employing the reaction between nickel hydroxide (Ni(OH)2) and hypophosphorus acid (H3PO2), allowing the impregnation of nickel hypophosphite (Ni(H2PO2)2) onto the oxide supports in the absence of salt by-products. Temperature-programmed reduction (TPR) in flowing hydrogen at 573–773K yields phase pure Ni2P on the supports with small average particle sizes (3–4nm) as measured using transmission electron microscopy. The conversion of Ni(H2PO2)2 to Ni2P and related reactions were probed using TPR with on-line mass spectral analysis of the gas effluent. Unsupported Ni(H2PO2)2 reacts in flowing hydrogen to produce PH3 and H2O at 468 and 482K, respectively; the reaction is shifted to increasingly higher temperatures for Ni(H2PO2)2 supported on SiO2, Al2O3 and ASA. The hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) properties of the Ni2P catalysts were probed using a mixed feed containing carbazole and benzothiophene. While Ni2P/SiO2 catalysts prepared by the different methods exhibited similar HDN and HDS activities, the in situ prepared Ni2P/Al2O3 and Ni2P/ASA catalysts were substantially more active than their ex situ counterparts prepared from hypophosphite- and phosphate-based precursors.

Facile hydrothermal synthesis of flower-like Co–Mo–S catalysts and their high activities in the hydrodeoxygenation of p-cresol and hydrodesulfurization of benzothiophene

Co–Mo–S catalysts were synthesized by a facile hydrothermal synthesis and their activities were tested in the hydrodeoxygenation (HDO) of p-cresol, hydrodesulfurization (HDS) of benzothiophene, and simultaneous HDO of p-cresol and HDS of benzothiophene. When Co/Mo mole ratio in Co–Mo–S was adjusted to 0.3, the catalyst presented a flower-like morphology and exhibited high HDO and HDS activity, which was attributed to its specific structure and the maximum synergy between CoS2 and MoS2. In the HDO of p-cresol, direct deoxygenation (DDO) was the main reaction route and toluene selectivity reached to 97.5%. The hydrogen consumption was markedly cut down. By adding small amount of benzothiophene, p-cresol conversion was enhanced because the produced H2S from the HDS of benzothiophene slowed down the catalyst deactivation. In simultaneous HDO of p-cresol and HDS of benzothiophene, because of the competitive adsorption of reactants on the active sites, both the toluene selectivity and desulfurization degree were lowered compared with the single component reactions.

Low-temperature synthesis of rhodium phosphide on alumina and investigation of its catalytic activity toward the hydrodesulfurization of thiophene

In this study, the low-temperature synthesis of rhodium phosphide (Rh2P) on alumina (Al2O3) using triphenylphosphine (TPP) as a phosphorus (P) source and its catalytic activity toward hydrodesulfurization (HDS) were investigated to prepare a highly active HDS catalyst. TPP was more easily reduced than phosphate, and Rh2P was formed in the P(T)/Rh/Al2O3 catalyst prepared from TTP at lower temperature as compared with the temperature required by Rh-P(A)/Al2O3 catalyst prepared from a phosphate precursor. However, after reduction at a low temperature (450°C), excess P covered the surface of Rh2P. The optimal reduction temperature for HDS rate of the P(T)/Rh/Al2O3 catalyst (650°C) was lower than that of the Rh-P(A)/Al2O3 catalyst (800°C). Furthermore, this temperature was slightly higher than the optimal reduction temperature for CO uptake (600°C). These results are explained as follows: HDS rate is increased by both elimination of excess P on the active sites at higher reduction temperatures and enhancement of the crystallinity of Rh2P. Furthermore, because the particle size of the P(T)/Rh/Al2O3 catalyst (ca. 1.2nm) was substantially smaller than that of the Rh-P(A)/Al2O3 catalyst, the P(T)/Rh/Al2O3 catalyst exhibited greater HDS rate compared with the Rh-P(A)/Al2O3 catalyst.

Morphology tuning of CoMo catalysts: Effect of La and Fe as an additive

Three catalysts CoMo/γ-Al 2 O 3 , CoMo-La/γ-Al 2 O 3 , CoMo-Fe/γ-Al 2 O 3 with different morphologies were prepared for study the effect of introduction of La and Fe on morphology properties and hydrodesulfurization (HDS) activity. The morphology properties of catalysts were characterized by BET, XPS and HRTEM. In addition, the catalytic performances of catalysts were investigated. The results indicated that the introduction of La and Fe promoted the sulfidation of Mo species and made the average length and stacking layer numbers of MoS2 slabs longer and higher. These effects could improve the activity of catalysts for HDS. The present results indicated that the catalyst modified by Fe had the best HDS activity with the optimal morphology among three catalysts

Effect of Particle Size on the HDS Activity of Molybdenum Sulfide

More than half of the total world oil reserves are heavy oil, extra heavy oil, and bitumen; however their catalytic conversion to more valuable products is challenging. The use of submicronic particles or nanoparticles of catalysts suspended in the feedstock may be a viable alternative to the conversion of heavy oils at refinery level or downhole (in situ upgrading). In the present work, molybdenum sulfide (MoS2) particles with varying diameters (10000–10 nm) were prepared using polyvinylpyrrolidone as capping agent. The prepared particles were characterized by DLS, TEM, XRD, and XPS and tested in the hydrodesulfurization (HDS) of a vacuum gas oil (VGO). A correlation between particle size and activity is presented. It was found that particles with diameters around 13 nm show double the HDS activity compared with the material with micrometric particle sizes (diameter ≈ 10,000 nm).

A Novel Self-Assembled Hierarchical-Structured Catalyst for the Diffusion of Macromolecules

A novel self-assembled catalyst, FA-Z30, possessing a mesoporous/macroporous structure is prepared and applied to FCC diesel hydrodesulfurization (HDS). The catalyst has 54 % of the total pore volume lying within 30–60 nm pores, greater than 26 % of the continuous phase. This indicates interconnected pores. N2 adsorption data show a bimodal structure with pores ranging between 30–60 nm and <10 nm. Textural properties of the catalyst show that the pore volume is 0.78 cm g–1 having a specific surface area of 181 m2 g–1 with a most probable pore diameter of 20 nm. The catalyst possesses a low active metal concentration of ~154.9 g L–1 per unit volume and a low bulk density of ~0.50 g cm–3. X-Ray diffraction, high resolution transmission electron microscopy, and X-ray photoelectron spectroscopy show improved active metal dispersion with an average MoS2 layered slab number of 3–7, having lengths ranging from 5 to 10 nm. Molybdenum sulfide sulfidity at 75 % is higher than the commercial catalyst, FCB, at 62 %. The activity and stability of HDS and hydrodenitrification (HDN) are improved, as is aromatics saturation (HDAr) reflected by limited coke formation. Average conversion rates of HDS, HDN, and HDAr are 95, 97, and 67 % at 100 h on stream for FA-Z30, respectively, and their respective rates of 6.1, 6.3, and 4.3 % per unit volume of active metal is twice that of the commercial catalyst. The low bulk density of FA-Z30 improves the utilization rate and relative activity of the active metals. FA-Z30 is a promising catalyst for FCC diesel hydrogenation.

Potential of templated mesoporous aluminas as supports for HDS CoMo catalysts

Activities in thiophene hydrodesulfurization were increased by a factor three when using aluminas, as support for CoMo catalysts, prepared using an optimized sol–gel method.

A NiMoS flower-like structure with self-assembled nanosheets as high-performance hydrodesulfurization catalysts.

Uniform 3D NiMoS nanoflowers with self-assembled nanosheets were successfully synthesized via a simple hydrothermal growth method using cheap and nontoxic elemental sulfur as sulfur sources. The structure and morphology of the nanomaterials were characterized by SEM, TEM, XRD, Raman and XPS analyses, revealing that the NiMoS nanoflowers were composed of ultrathin nanosheets with a thickness of approximately 6-12 nm. The HRTEM results indicate that the curve/short MoS2 slabs on the nanosheets possess the characteristics of dislocations, distortions and discontinuity, which suggests a defect-rich structure, resulting in the exposure of additional Ni-Mo-S edge sites. The obtained NiMoS nanoflowers exhibited an excellent activity for thiophene hydrodesulfurization (HDS) and 4,6-dimethyldibenzothiophene deep HDS due to their high density of active sites. The outstanding HDS performance suggests that these NiMoS composites with a unique flower-like nanostructure could be useful as promising catalysts for deep desulfurization of fuel oils.

The Pore Confinement Effect of FDU-12 Mesochannels on MoS2Active Phases and Their Hydrodesulfurization Performance

FDU-12 silica with highly ordered face-centered cubic mesoporous structure is developed as support to prepare Mo/FDU-12 catalysts for hydrodesulfurization (HDS) of dibenzothiophene (DBT). A series of Mo/FDU-12 catalysts are synthesized by using incipient wetness impregnation method with different MoO3loadings (6, 8, 10, 12, and 15 wt.%). The objective of this work is to explore the pore confinement effect of FDU-12 mesochannels on the MoS2morphology with various metal loadings. It is found that, as increasing MoO3loadings from 6 to 15 wt.%, the MoS2nanocrystallites transform from monolayer to multilayer and the morphology changes from straight layered to curved and then to ring-like and finally to spherical-like morphology due to the restriction of cage-like pore channels of FDU-12 support. The HDS results show that the catalytic activity increases first and then decreases with the best HDS performance at the MoO3loading of 10 wt.%. In addition, we compared the HDS activity of Mo catalyst supported on FDU-12 with that on the commercialγ-Al2O3and SBA-15; the result exhibits that FDU-12 is superior to the other two supports due to its large pore size and ordered three-dimensional open pore channels.

Effect of Chitosan on the Performance of NiMoP-Supported Catalysts for the Hydrodesulfurization of Dibenzothiophene

Chitosan-added NiMoP catalysts supported on alumina and alumina-titania were studied in the hydrodesulfurization (HDS) of dibenzothiophene (DBT). The preparation of catalysts containing Mo (12 wt%), Ni (3 wt%), P (1.6 wt%), and chitosan/nickel = 2 (mol ratio) was accomplished by sequential pore-filling impregnation varying the order of chitosan integration. Materials were characterized by DRIFTS, TPR, TG-DTA, and XPS techniques. The TG-DTA study showed that the nature of the support influences the degradation of chitosan onto the catalytic materials and also influences the HDS of DBT and the product distribution as well. The series of catalysts supported on alumina presented the most remarkable effect of chitosan, in which the OH and NH groups of the organic molecule interact with acid sites of the support weakening the interaction between alumina and deposited metal phases. In all cases, DBT was converted mainly through direct sulfur removal. The catalysts ChP3/A (alumina support impregnated with chitosan in phosphoric acid solution, prior to NiMoP deposition) and ChP4/AT (alumina-titania support impregnated with NiMoP solution, prior to contacting with a solution comprising chitosan and phosphorus) exhibited the best performance in HDS reactions and also showed the highest selectivity in biphenyl formation. Presence of carbonaceous residua on the catalyst’s surface, as shown by XPS, could enhance the HDS activity over the ChP4/AT sample.

Structure Investigation and Dibenzothiophene Hydrodesulfurization Properties of Fe-Substituted Ni–Si Intermetallics

Development of highly active and sulfur-tolerant catalysts for deep hydrodesulfurization (HDS) is of great importance in petroleum refining. Here, the discovery of Fe-substituted Ni–Si intermetallic catalysts (Ni1–xFexSi2) that efficiently removes dibenzothiophene (DBT) by HDS is reported. The structure of the catalyst was identified through X-ray diffraction, Mossbauer spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results showed that Fe atoms substituted Ni atoms in Ni1–xFexSi2 catalysts, which preferentially bond with Ni to form alloy and combine with Si to form silicide. The DBT activity for the Ni1–xFexSi2 has the following order: Ni0.75Fe0.25Si2 > NiSi2 > Ni0.50Fe0.50Si2 ≈ Ni0.25Fe0.75Si2 ≈ Fe–Si. The positive synergistic effect on HDS activity can be correlated to that the formation of Ni–Fe and Fe–Si bonds makes the metal site to have high d-electron density, which promotes the hydrogenation activity. Comparison with the fresh and spent catalysts revealed...

Size-dependent activity of unsupported Co–Mo sulfide catalysts for the hydrodesulfurization of dibenzothiophene

A series of CoMoO4 hydrates composed of nanorods have been synthesized with different alcohol–water solvent systems, and the corresponding Co–Mo sulfides are obtained after sequential calcination and sulfurization. The characterization results show the change in solvent system can efficiently adjust the particle size of the Co–Mo precursors, while cannot affect their components and morphologies. Because of the different particle size, the specific surface areas (SSA) of the final Co–Mo sulfides are different. The particles with small size can lead to a high SSA that benefits the exposure and dispersion of active components, and further promote the incorporation of MoS2 slabs with Co atoms to form “Co–Mo–S” structures on the surface of the sulfides. More “Co–Mo–S” structures would create more coordinative unsaturated sites with high activity in situ during hydrodesulfurization (HDS) reaction, resulting in a higher HDS activity. Among the Co–Mo sulfides, since S-m/w derived from methanol–water system possesses the smallest particle size and the most active sites, it naturally exhibits the highest HDS activity toward dibenzothiophene.

Role of the Si/Al molar ratio and pH in NIW/MCM41-Al2O3 catalysts for HDS of DBT

This research presents a series of catalytic supports of MCM41 modified with γ-Al2O3 with a Si/Al molar ratio of 10, 25 and 50. These materials were impregnated with Ni+W solutions at pH 7 and pH 9, respectively and were evaluated in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) reaction. In order to modify the low acidity of MCM41, its surface acidity was modified by incorporation of alumina content in the supports.The sol–gel incorporation method of Al2O3 to the structure of the MCM41 did produce changes in the characteristic of hexagonal arrangement of mesoporous materials.The symmetries of the materials were determined through UV–vis where the octahedral and tetrahedral nickel species were found. By Raman, monotungstate (WO4) and polytunsgtate (W12O408−) species were observed. The HDS of DBT showed that in the NiW/AMS50 catalyst impregnated at pH 9 presents the highest reaction rate. And in the case of the catalysts impregnated at pH 7 the highest reaction rate was achieved by the NiW/AMS10 catalyst. The selectivity was mainly oriented to the production of biphenyl (BP). The low catalytic activity was attributable to low formation NiWS species responsible for the HDS activity.

A Novel NiWS-TiO2(w) Catalyst Using NiWO4 Nanoparticles as Precursor with Enhanced Hydrodesulfurization Activity

In this work, NiWO4 nanoparticles were prepared by a novel simple method and loading on the mesoporous TiO2 whiskers (TiO2(w)) carrier as the precursor of NiWS. In addition, the NiWS-TiO2(w) catalysts showing high hydrodesulfurization (HDS) activity is described. The structure and chemical composition of the as-prepared samples were characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, temperature-programmed reduction, NH3-temperature programmed desorption and transmission electron microscopy, respectively. Results indicate that smaller crystallite size and better dispersion of active NiWO4 particles could be achieved by using TiO2(w) as the support to disperse NiWO4 nanoparticles. TiO2(w) can also decrease the reduction temperature of Ni–W metal oxide and promote a highly sulfidation degree of Ni and W active sites. The obtained NiWS-TiO2(w) catalysts show much higher dibenzothiop HDS activity than the unsupported NiWS catalyst, and the sulphur content of desulfurated oil can reach 20 ppm at the mild condition of 260 °C and 2 Mpa.

Deep HDS of FCC gasoline over alumina supported CoMoS catalyst: Inhibiting effects of carbon monoxide and water

The selective hydrodesulfurization (HDS) of FCC gasoline is a key catalytic process for reducing sulfur content in gasoline. In the present work, we focus on the effect of H2O amount alone or in mixture with CO on the transformation of a model FCC gasoline composed of 2-methylthiophene (2MT) and 2,3-dimethylbut-2-ene (23DMB2N) molecules, over an alumina supported CoMoS catalyst. A negative impact of water and CO on the conversion of 2MT and 23DMB2N is found. However the effect in the presence of CO is much stronger. The comparison of Density Functional Theory (DFT) calculations of CO and water adsorption on the S- and M-edge sites of the CoMoS slabs shows a significantly stronger CO adsorption energy than water adsorption energy. When CO and water were introduced simultaneously, the negative impact observed in the transformation of the model feed is mainly due only to the presence of CO. However whatever the oxygenated molecules used and their amount, no impact in the selectivity measured by the ratio between the activity in hydrodesulfurization and in hydrogenation is observed.

Preparation of a highly dispersed Ni2P/Al2O3 catalyst using Ni–Al–CO32 − layered double hydroxide as a nickel precursor

We now report a novel method for the synthesis of a Ni2P/Al2O3-LW catalyst using Ni–Al–CO32− layered double hydroxide (Ni–Al–CO32−-LDH) as a nickel precursor and ammonium dihydrogen phosphate as a phosphorous precursor under microwave–hydrothermal (MWH) treatment for 20min at 363K. The catalysts were characterized by XRD, TPR, BET, CO uptake and XPS. MWH treatment can promote the formation of smaller and highly dispersed Ni2P particles and a higher surface area of the catalyst. The Ni2P/Al2O3-LW shows hydrodesulfurization activity of 99.3%, which was much higher than that found for the Ni2P/Al2O3 catalyst obtained via an impregnation method.