Hydrodesulfurization Activity Research Articles

Enhanced hydrotreating performance of hierarchical NiMo-S/Al2O3 catalysts through ZrO2 incorporation and template-driven structural modulation

A dual template-assisted approach for optimizing support structures to enhance catalytic efficiency in hydrotreating reactions is presented. Catalysts synthesized using activated carbon (AC) templates exhibited significantly higher activity in both hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) compared to those prepared with starch (ST) templates. The unique porous architecture, characterized by well-distributed meso- and macropores, facilitated efficient access of bulky molecules to the active sites. On the other hand, while the reactivity in the selective opening of the naphthenic ring (SONR), which is indicative of hydrocracking functionality, was similar across all catalysts, those modified with Zr exhibited a slight improvement. The catalysts displayed bifunctional characteristics, and their performance was influenced by the amphoteric nature of the support and the specific ratios of active species on the surface. A clear correlation between catalytic activity, selectivity, and the distribution of active sites was established.

Microporosity and Catalytic Activity for Hydrodesulfurization of Pharmacosiderite Mo4P3O16 Synthesized at a Moderate Temperature.

Pharmacosiderite Mo4P3O16 (Pharma-MoPO) consists of [Mo4O4] cubane unit and [PO4] tetrahedral to form an open framework with a microporous structure similar to that of LTA-type zeolite. Although attractive applications are expected due to its microporous structure and redox-active components, its physicochemical properties have been poorly investigated due to the specificity of its synthesis, which requires a high hydrothermal synthesis temperature of 360 °C. In this study, we succeeded in synthesizing Pharma-MoPO by hydrothermal synthesis at 230 °C, which can be applied using a commercially available autoclave by changing the metal source. Through the study of the solids and liquids obtained after hydrothermal syntheses, the formation process of Pharma-MoPO under our studied synthesis conditions was proposed. Advanced characterizations provided detailed structural information on Pharma-MoPO, including the location site of a countercation NH4+. Pharma-MoPO could adsorb CO2 with the amount close to the number of cages without removing NH4+. Pharma-MoPO exhibited stable catalytic activity for the hydrodesulfurization of thiophene while maintaining its crystal structure, except for the introduction of sulfide by replacing lattice oxygens. Pharmacosiderite Mo4P3O16 was successfully obtained by hydrothermal synthesis at a moderate temperature, and its microporosity for CO2 adsorption and catalytic properties for hydrodesulfurization were discovered.

Enhanced hydrodesulfurization activity of thiophene over hollow tubular CoMo unsupported catalysts

Enhanced hydrodesulfurization activity of thiophene over hollow tubular CoMo unsupported catalysts

Elucidating Local Structure and Positional Effect of Dopants in Colloidal Transition Metal Dichalcogenide Nanosheets for Catalytic Hydrogenolysis.

Tailoring nanoscale catalysts to targeted applications is a vital component in reducing the carbon footprint of industrial processes; however, understanding and controlling the nanostructure influence on catalysts is challenging. Molybdenum disulfide (MoS2), a transition metal dichalcogenide (TMD) material, is a popular example of a nonplatinum-group-metal catalyst with tunable nanoscale properties. Doping with transition metal atoms, such as cobalt, is one method of enhancing its catalytic properties. However, the location and influence of dopant atoms on catalyst behavior are poorly understood. To investigate this knowledge gap, we studied the influence of Co dopants in MoS2 nanosheets on catalytic hydrodesulfurization (HDS) through a well-controlled, ligand-directed, tunable colloidal doping approach. X-ray absorption spectroscopy and density functional theory calculations revealed the nonmonotonous relationship between dopant concentration, location, and activity in HDS. Catalyst activity peaked at 21% Co:Mo as Co saturates the edge sites and begins basal plane doping. While Co prefers to dope the edges over basal sites, basal Co atoms are demonstrably more catalytically active than edge Co. These findings provide insight into the hydrogenolysis behavior of doped TMDs and can be extended to other TMD materials.

Synergistic effect between CoSx and MoS2 at the micrometer scale: Considerable promotion of the hydrodesulfurization of DBT

The future implementation of ultralow sulfur fuel regulations requires researchers to have an excellent understanding of the mechanism of the synergistic effect between the Co(Ni) and (Mo)W sulfides in supported Co(Ni)Mo(W)S hydrodesulfurization (HDS) catalysts. This synergistic effect occurs when the distance between two metals is on the mm or nm scale. To investigate the promotion of HDS on the µm scale, a series of Co and Mo multilayer flake catalysts with a thickness of 1 mm were prepared by laminate molding. The distance between CoSx and MoS2 in these specially structured catalysts was adjustable on the µm scale by controlling the order and quality of the catalyst powder. The results for the HDS of dibenzothiophene (DBT) demonstrate that there is an obvious synergistic effect between CoSx and MoS2 on the µm scale. The results of pyridine IR spectroscopy indicate that this synergy is due to CoSx and MoS2 synergistically generating more coordinatively unsaturated sites (CUSs) and -SH active sites at the μm scale, thus increasing the HDS activity. Moreover, the catalyst activity increases as the distance between CoSx and MoS2 decreases, and the fact that the feed comes into contact with CoSx first greatly improves the activity.

Controlled construction of Co3S4@CoMoS yolk-shell sphere for efficient hydrodesulfurization promoted by hydrogen spillover effect

A yolk-shell structured Co3S4@CoMoS catalyst was prepared through Oswald ripening method and subsequently used for hydrodesulfurization (HDS) reaction. The shells, constructed from Co-promoted MoS2 nanosheets, possess abundant active sites and facilitate the adsorption of reactants through the development of pore channels. The MoS2 sheets are arranged in a staggered and convoluted manner, creating numerous defect sites. The shorter MoS2 slabs provide a wide distribution of reactive sites, ensuring efficient reactions. The Co3S4 species within the inner core acts as an auxiliary active phase, inducing the hydrogen spillover effect in the HDS system. This facilitates the transfer of active hydrogen species to the CoMoS shell, where both CoMoS and Co3S4 phases synergistically enhance the HDS reaction. The Co3S4@CoMoS catalyst achieved up to 99.2% dibenzothiophene (DBT) conversion and 94.9% 4,6-dimethyldibenzothiophene conversion at the lower dosage (30 mg). The structure-activity relationships between active phase and HDS activity were investigated via in-situ infrared spectroscopy and other characterizations as well as density functional theory calculations.

One–pot solvothermal preparation of the porous NiS2//MoS2 composite catalyst with enhanced low-temperature hydrodesulfurization activity

The simple preparation of mesoporous NiS2//MoS2 composite catalyst through a one-pot solvothermal method is presented. The improvement of the specific surface area (220 m2/g) and the construction of the porous structure are realized by this method in the case of no support. The organics acts as a microscopic binder contribute to uniform stacking of MoS2 with NiS2 clusters. The composite structure including NiS2 and MoS2 was obtained (proved by XRD, XPS, TEM, IR, UV–vis and RAMAN) and changed the microelectronic environment of the active metal surface (DFT calculation). The mesoporous NiS2//MoS2 catalyst (Ni1Mo1-200) showed an excellent hydrodesulfurization performance of dibenzothiophene (DBT conversion: 78 % at 260 °C) and a high ratio of direct desulfurization pathway (SDDS/HYD = 16.6) at a low reaction temperature. By combining the characterization and theoretical calculation results, the advantages of this NiS2//MoS2 composite structure in synergistic catalysis was further confirmed.

Hierarchically porous ZSM-5/SBA-15 composite: Tuning pore structure and acidity for hydrodesulfurization of dibenzothiophene

Series ZSM-5/SBA-15 (ZS15-x) composites with different pore structure and acidity were synthesized, and the corresponding NiMo/ZS15-x catalysts were prepared for dibenzothiophene (DBT) hydrodesulfurization (HDS). The controlled introduction of ZSM-5 nanocrystal imparts more acid sites to the NiMo/ZS15 catalyst without altering its fundamental morphology. Furthermore, the increased presence of acid sites enhances the HDS effect of NiMo/ZS15-x catalysts. Simultaneously, the introduction of ZSM-5 nanocrystal modulates the interactions between metal and support (MSI), thereby promoting the dispersion of the active sites. The optimized NiMo/ZS15-50 exhibited superior HDS activities of 98.9 % for DBT, with the optimal reaction rate constant of 3.0 × 10−7 mol/g s−1 and turnover frequency of 2.0 × 10−4 s−1. This can be attributed to its two-dimensional open channels, suitable acidic sites and highly dispersed MoS2. The increased proportion of the ZSM-5 framework and enhanced acidity are advantageous for DBT HDS.

Nickel-embedded zeolite subcrystal catalyst: rapid enhancement of activity and metal impurity resistance in the hydrodesulfurization of 4,6-dimethyldibenzothiophene

Ni nanoparticles embedded in an Al-containing MFI zeolite subcrystal (<7 nm) lead to superior hydrodesulfurization activity and exceptional resistance to Ni/V metal impurities.

Probing the Effect of Environments on the Stability of Ni2P Nanoparticle Electrocatalysts

Ni2P has been shown to be an effective catalyst for the hydrogen evolution reaction (HER), making it a promising replacement for Pt which is the current state of the art HER catalyst.1,2 H2 is a clean-energy critical fuel and chemical highlighted by the US Department of Energy’s “Hydrogen Shot,” which seeks to reduce “the cost of carbon-neutral hydrogen by 80% to $1 per 1 kg in 1 decade, highlighting the key role of hydrogen in implementing carbon-neutral solutions.”3 Ni2P is also a good or promising catalyst for other reactions, such as alcohol oxidation, hydrodesulfurization,4,5 nitrate reduction, and oxygen evolution reaction.6 However, Ni2P and other TMPs are susceptible to oxidation, which can lead to catalyst degradation and loss in certain conditions.7,8 Stability is an important part of catalysis, especially for achieving the goals of the Hydrogen Shot. Therefore, it is important to understand complex degradation mechanisms in order to better understand structure-activity relationships in these materials. In the present work, in situ Ni K-edge X-ray absorption spectroscopy (XAS) and ex situ P Kα and Kβ X-ray emission spectroscopy (XES) couple together to understand the degradation of Ni2P and show the effects of electrolyte pH, ligands, and air on Ni2P nanoparticles.5 nm Ni2P nanoparticles were synthesized by heating NiCl2 and tris(diethylamino)phosphine in oleylamine. The nanoparticles were drop cast onto carbon fiber paper electrodes and Si wafers or Au-coated wafers for P Kα and Kβ XES. Oleylamine ligands are removed by thermal annealing. Electrochemical experiments were conducted with a three-electrode cell using carbon fiber paper or Au-coated wafers deposited with Ni2P nanoparticles as working electrode, Ag/AgCl calibrated to the H2 redox couple as reference electrode, and graphite rod as counter electrode. P Kα and Kβ XES experiments were conducted inside a N2 glovebox to prevent unintentional air oxidation. Transmission-mode Ni K-edge XAS was conducted on a benchtop spectrometer.Upon exposure to air, as-synthesized Ni2P nanoparticles were studied via P Kα and Kβ XES. Results showed that the phosphide species converted to phosphate with analysis of intermediates well fit by a simple two-phase mixture. Phosphide:phosphate ratios were quantified using linear combination analysis, providing a powerful tool to analyze P speciation on various samples in an inert environment and with minimal loss of material, both advantages of this system over 31P magic angle spinning solid state nuclear magnetic resonance spectroscopy and X-ray photoelectron spectroscopy. Continued work looks at analyzing the effects of the ligand environment on the stability of nanoparticles in electrolytes spanning from acidic to basic pH. We hypothesize that ligands will significantly stabilize the nanoparticles against corrosion and that without ligands Ni2P readily converts to a nickel phosphate species upon exposure to electrolyte.References(1) Popczun, E. J.; McKone, J. R.; Read, C. G.; Biacchi, A. J.; Wiltrout, A. M.; Lewis, N. S.; Schaak, R. E. Nanostructured Nickel Phosphide as an Electrocatalyst for the Hydrogen Evolution Reaction. J. Am. Chem. Soc. 2013, 135 (25), 9267–9270. https://doi.org/10.1021/ja403440e.(2) Liu, P.; Rodriguez, J. A. Catalysts for Hydrogen Evolution from the [NiFe] Hydrogenase to the Ni2P(001) Surface: The Importance of Ensemble Effect. J. Am. Chem. Soc. 2005, 127 (42), 14871–14878. https://doi.org/10.1021/ja0540019.(3) Bullock, M.; More, K. Basic Energy Sciences Roundtable: Foundational Science for Carbon-Neutral Hydrogen Technologies (Report); DOESC Office of Basic Energy Sciences, 2022. https://doi.org/10.2172/1834317.(4) Layan Savithra, G. H.; Muthuswamy, E.; Bowker, R. H.; Carrillo, B. A.; Bussell, M. E.; Brock, S. L. Rational Design of Nickel Phosphide Hydrodesulfurization Catalysts: Controlling Particle Size and Preventing Sintering. Chem. Mater. 2013, 25 (6), 825–833. https://doi.org/10.1021/cm302680j.(5) Rodriguez, J. A.; Kim, J.-Y.; Hanson, J. C.; Sawhill, S. J.; Bussell, M. E. Physical and Chemical Properties of MoP, Ni2P, and MoNiP Hydrodesulfurization Catalysts: Time-Resolved X-Ray Diffraction, Density Functional, and Hydrodesulfurization Activity Studies. J. Phys. Chem. B 2003, 107 (26), 6276–6285. https://doi.org/10.1021/jp022639q.(6) Menezes, P. W.; Indra, A.; Das, C.; Walter, C.; Göbel, C.; Gutkin, V.; Schmeiβer, D.; Driess, M. Uncovering the Nature of Active Species of Nickel Phosphide Catalysts in High-Performance Electrochemical Overall Water Splitting. ACS Catal. 2017, 7 (1), 103–109. https://doi.org/10.1021/acscatal.6b02666.(7) Ha, D.-H.; Han, B.; Risch, M.; Giordano, L.; Yao, K. P. C.; Karayaylali, P.; Shao-Horn, Y. Activity and Stability of Cobalt Phosphides for Hydrogen Evolution upon Water Splitting. Nano Energy 2016, 29, 37–45. https://doi.org/10.1016/j.nanoen.2016.04.034.(8) Parra-Puerto, A.; Ng, K. L.; Fahy, K.; Goode, A. E.; Ryan, M. P.; Kucernak, A. Supported Transition Metal Phosphides: Activity Survey for HER, ORR, OER, and Corrosion Resistance in Acid and Alkaline Electrolytes. ACS Catal. 2019, 11515–11529. https://doi.org/10.1021/acscatal.9b03359.

In situ synthesis of mesoporous NiS2-MoS2 sphere-flower hybrid for hydrodesulfurization of thiophene and 4,6-dimethyl-dibenzothiophene

A series of new NiS2-MoS2-x (x = 0–0.5) sphere-flower hybrids with different Ni/Mo molar ratios, synthesized via a one-pot hydrothermal method, were used as catalysts for hydrodesulfurization (HDS) of thiophene (TP) and 4,6-dimethyl-dibenzothiophene (4,6-DMDBT). The characterizations show that the microstructure of MoS2, including the size of MoS2 nano-flowers, the length of MoS2 slabs, and the number of defects, was regulated by changing Ni/Mo ratios. Increasing the Ni/Mo ratio in the NiS2-MoS2-x catalysts significantly boosts their HDS activity, with the optimum ratio being 0.2. In addition, the NiS2-MoS2-0.2 catalyst exhibits the best direct desulfurization performance, which is associated with the minimum ratio of average slab length (Lav) to average stacking number (Nav) as well as the highest concentration of Ni-promoted Mo sites and sulfur vacancies. Moreover, Ni-containing NiS2-MoS2-x catalysts, characterized by a highly stable sphere-flower configuration, exhibit superior structural stability and catalytic durability than the Ni-free NiS2-MoS2-0 catalyst.

Modifying the active phase structure of Ni2P/Al2O3 by Ga introduction for improved hydrodesulfurization of diesel

Modifying the structure of active phase is an effective protocol to improve the catalytic activity of hydrodesulfurization (HDS) catalyst. Here, a variety of mesoporous GaAlOx supports with various Ga doping amount were synthesized by a facile hydrothermal strategy. The corresponding Ni2P supported catalysts were fabricated via a conventional impregnation and temperature-programmed reduction method, and their catalytic performances for 4,6-DMDBT HDS were examined. The experimental analyses show that the introduction of Ga substantially influences the geometric and electrical structure of Ni2P active phase on Ni2P/GaAlOx catalysts. The metal-support interaction is effectively abated with the elevation of Ga doping amount, thereby increasing the d-electron density of Ni species and boosting the pre-hydrogenation (HYD) route, thereupon enhancing the HDS performances of corresponding Ni2P/GaAlOx catalysts. Therein, Ni2P/GaAlOx-0.50 exhibits the highest activity with 70.1% 4,6-DMDBT conversion because of the optimal morphology and percentage of active phase, as well as distinguished redox and acid property. Further increasing the Ga loading, however, inhibits the HDS activity of Ni2P/GaAlOx-1.0 catalyst due to the decrease in the fraction and dispersion of active phases. Therefore, this work may shine light on the understanding of structure–activity of HDS catalyst and thereafter the preparation of HDS catalysts with high efficiency in future.

3D Printing Technique Fortifies the Ultradeep Hydrodesulfurization Process of Diesel: A Journal of NiMo/Al2O3-MMT.

In this contribution, we rationally designed and controllably fabricated a NiMo/Al2O3-montmorillonite (3D-NiMo/Al2O3-MMT) monolithic catalyst via a 3D printing strategy with economical montmorillonite (MMT) as a binder. The catalytic performance of the resulting NiMo/Al2O3-MMT for 4,6-dimethyldibenzothiophene (4,6-DMDBT) hydrodesulfurization (HDS) was evaluated. The experimental results unveil that the 3D-NiMo/Al2O3-MMT monolithic catalyst exhibits robust stability and exceptional HDS activity with 99.2% 4,6-DMDBT conversion (residual 4 ppm of S), which is remarkably superior to that of conventional NiMo/Al2O3 (61.5%), NiMo/MMT (63.2%), and even NiMo/Al2O3-MMT (76.5%) prepared by the mechanical-mixing method. This should be ascribed to the synthetic effect between the MMT binder and the Al2O3 substrate, which effectively weakens the interaction between the Mo species and the Lewis acids on the original Al2O3 surface, thereby significantly increasing the content of reducible Mo species and considerably facilitating the formation of more highly active NiMoS phase (Type II) with optimal average stacking layers and thereafter remarkably enhancing the ultradeep HDS activity of the 3D-NiMo/Al2O3-MMT monolithic catalyst.

Design of active phase structure with high activity and stability in residue hydrotreating reactions

The catalyst with well-dispersed (Ni)MoS2 active phase characteristic of short slab length and low stacking numbers was designed by strengthening metal-support interaction (MSI) and metal dispersion, which displayed high activity and long-term stability in real-life residue hydrodesulfurization (HDS) reactions. Furthermore, the impacts of pseudo-boehmite and catalyst calcination temperature on surface properties were thoroughly investigated. Mo equilibrium adsorption method, Al27 NMR, XRD, Raman, UV–Vis DRS, and H2-TPR characterization showed that the hydroxyl groups concentration and tetrahedral cation vacancies increased upon reducing the pseudo-boehmite extrudates calcination temperature. Increasing calcination temperature of the catalysts further strengthened MSI, resulted in well-dispersed Mo species with enhanced MSI. Therefore, well-dispersed (Ni)MoS2 active phase was acquired on novel designed catalyst. XPS coupled with HRTEM indicated that the more potential active sites, less propensity for active phase evolution and gradual increase in sulfidation degree with processing time contributed to the high HDS performance of the designed active phase. This work can deepen our understanding toward evolution pattern of active phase during residue HDS catalysts, and give guidance for developing high performance catalyst by strengthening MSI and enhancing metal dispersion.

The Influence of Metal–Support Interactions on the Performance of Ni-MoS2/Al2O3 Catalysts for Dibenzothiophene Hydrodesulfurization

In this present work, a new kind of sulfurized hydrodesulfurization catalyst was synthesized via the hydrothermal treatment of MoS2, NiCO3·2Ni(OH)2·4H2O, and Al2O3 precursors, followed by annealing under a H2 atmosphere, which does not require a sulfurization process compared to traditional preparation methods. The influence of the annealing temperature and the type of Al2O3 precursor on the interactions between MoS2 and Al2O3 were studied using X-ray fluorescence spectroscopy, X-ray diffraction, N2 adsorption–desorption, Raman spectroscopy, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. The results indicated an increase in the number of stacked layers of the MoS2 catalyst, accompanied by a decrease in the degree of decoration of Ni atoms onto MoS2 nanoslabs, as a result of the strengthened MoS2–Al2O3 interaction. Subsequently, the efficiency of hydrodesulfurization (HDS) was evaluated using dibenzothiophene as a representative reactant, while establishing a correlation between the structure of the catalyst and its performance. The catalysts, using pseudo-boehmite as the precursor and calcined at 500 °C, synthesized by calcining pseudo-boehmite as the precursor for Al2O3 at a temperature of 500 °C and possessing suitable metal–support interactions, exhibited a reduced number of MoS2 stacking layers and lateral dimensions, along with an optimal decoration degree of Ni atoms, thereby resulting in the highest level of HDS activity.

Targeted fabrication of 1T-MoS2 enriched nanosheets vertically oriented on spiny-shaped nanospheres with sufficient sulfur vacancies and “rim” sites for co-enhancing the hydrodesulfurization activity and hydrogenation selectivity

The 1T-enriched spiny-shaped nanospheres with vertically oriented MoS2 nanosheets over the surface was successfully prepared with the novel solvent induced micelle-limited Mo-CTA+ composites self-assembly (SIMMS) strategy under the dual effects of mixed sulfur sources (thiourea and thioacetamide) and cetyltrimethylammonium bromide (CTAB). In the proposed strategy, the molybdenum source and CTAB are firstly assembled to Mo-CTA+ by strong electrostatic attraction to avoid the molybdenum source from polymerization and forming large polymolybdate anions. Meanwhile, the CTAB moleculars self-assemble to spherical micelles, which can adsorb Mo-CTA+ through van der Waals force and obtain spherical precursors with a controllable number of nucleation sites. Under the sulfurization from mixed sulfur source, appropriate reducibility can control the formation of crystal seeds and crystal growth during the crystallization process of MoS2, whereas CTAB can regulate and control the growth behavior and micro-morphology of MoS2, which is ultimately also retained between the MoS2 nanolayersto expand their interlayer spacing and stabilize the 1T phase. Therefore, the 1T-enriched spiny-shaped nanospheres with vertically oriented MoS2 nanosheets can be controllably prepared. In the hydrodesulfurization (HDS) reaction of dibenzothiophene (DBT) over these catalysts, the MoS2-75%/0.25 catalyst with the highest concentration of sulfur vacancies as well as “rim” and “rim-like” sites can reach the highest HDS activity (99.1%) and HYD/DDS ratio (4.76), which are much higher than those of the MoS2-H catalyst prepared by conventional hydrothermal method (HDSDBT%=46.0%, HYD/DDS ratio=0.90).

Al-modified yolk-shell silica particle-supported NiMo catalysts for ultradeep hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene: Efficient accessibility of active sites and suitable acidity

Yolk-shell SiO2 particles (YP) with center-radial meso-channels were fabricated through a simple and effective method. Al-containing YP-supported NiMo catalysts with different Al amounts (NiMo/AYP-x, x = Si/Al molar proportion) were prepared and dibenzothiophene (DBT) and 4,6-dimethyl-dibenzothiophene (4,6-DMDBT) were employed as the probes to evaluate the hydrodesulfurization (HDS) catalytic performance. The as-prepared AYP-x carriers and corresponding catalysts were characterized by some advanced characterizations to obtain deeper correlations between physicochemical properties and the HDS performance. The average pore sizes of series AYP-x supports are above 6.0 nm, which favors the mass transfer of organic sulfides. The cavity between the yolk and the shell is beneficial for the enrichment of S-containing compounds and the accessibility between reactants and active metals. Aluminum embedded into the silica framework could facilitate the formation of Lewis (L) and Brønsted (B) acid sites and adjust the metal-support interaction (MSI). Among all the as-synthesized catalysts, NiMo/AYP-20 catalyst shows the highest HDS activities. The improved HDS activity of NiMo/AYP-20 catalyst is attributed to the perfect combination of excellent structural properties of the yolk-shell mesoporous silica, enhanced acidity, moderate MSI, and good accessibility/dispersion of active components.

A novel ligand protection strategy based on lacunary polyoxometalate to precisely construct CoMoS active sites for hydrodesulfurization

Efficient CoMoS catalysts with intimate bimetallic synergy are derived from cobalt-substituted phosphomolybdate and exhibited excellent hydrodesulfurization (HDS) activity. Based on ligand protection strategy, the introduction of pyridine ligands onto the vacancies of the trivacant polyoxometalates (POMs) successfully overcame their low stability and isomerization behavior in solution. Subsequently, Co2+ was anchored in the molecular skeleton of [A-α-PMo9O31(py)3]3− (PMo9-py) to form CoxPMo9-py precursors with high Co/Mo ratios, which enhanced the reducibility of Mo species and transformed them to abundant CoMoS active phase during sulfidation process. The quenching effect of pyridine molecules on the acidic sites of support and carbon deposition generated in the high temperature sulfidation weakened the strong metal-support interactions (SMSI) while improving the dispersion and sulfidation of active metals. Due to the unique structure of CoxPMo9-py, the CoMoS phase with high dispersion, efficient synergy and high concentration was obtained. The combination of POMs precursors and pyridine ligands enabled the S-CoxPMo9-py/Al2O3 catalyst to achieve up to 99.5% conversion of dibenzothiophene (DBT).

Dendritic micro-mesoporous composites via nano-assembly strategy towards high-efficiency catalysts for hydrodesulfurization of dibenzothiophenes

Based on the three-dimensional center-radial framework structure of dendritic mesoporous silica nanospheres (DMSNs), a unique type of hierarchical micro-mesoporous composite material, namely, Beta-DMSNs (BD) was prepared through a nano-assembly method, which was utilized as superior supports for high-efficiency catalysts (NiMo/BD) for hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). The controllable introduction of Beta nanocrystals endows the NiMo/BD catalysts with more acidic and catalytic active sites, and shows no influence on the dendritic morphology of the mesoporous supports, resulting in the remarkable HDS performance of NiMo/BD catalysts. Owing to the dendritic open channels, high surface area, abundant acidic sites and highly dispersed MoS2 active phases, the optimized NiMo/BD exhibited superior HDS activities of 99.1% and 98.3% for DBT and 4,6-DMDBT, respectively, with the optimal reaction rate constant of 3.0 × 10−7 mol g−1 s−1 and 2.4 × 10−7 mol g−1 s−1, and with the turnover frequency of 5.9 × 10−4 s−1 and 4.8 × 10−4 s−1. Besides, the enhanced Brønsted acid and the synergistic effect of Brønsted & Lewis acid contributed to the superior isomerization selectivity for 4,6-DMDBT, which was conducive to its HDS.

One-Pot Three-Dimensional Printing of a Hierarchical NiMo/Al2O3 Monolithic Catalyst for 4,6-Dimethyldibenzothiophene Hydrodesulfurization.

The development of a competitive-cost and high-efficiency NiMo/Al2O3 hydrodesulfurization (HDS) catalyst remains challenging in the field of petrochemical industry. Herein, a highly efficient NiMo/Al2O3 monolithic HDS catalyst was elaborately designed and successfully fabricated via a one-pot three-dimensional (3D) printing strategy, and its HDS activity was examined for 4,6-dimethyldibenzothiophene conversion. The results unveil that the NiMo/Al2O3 monolithic catalyst prepared by the 3D printing strategy (3D-NiMo/Al2O3) exhibits hierarchical structure due to the combustion of hydroxymethyl cellulose serving as adhesive, which endows the weaker metal-support-interaction between Mo oxides and Al2O3, remarkably promoting sulfidation of both Mo and Ni species and the formation of "Type II" NiMoS active phase, thereby reducing the apparent activation energy (Ea = 109.2 kJ·mol-1) and increasing the catalytic activity (TOF = 4.0 h-1) and thereafter dramatically boosting the HDS performance of 3D-NiMo/Al2O3 compared with that of NiMo/Al2O3 (Ea = 150.6 kJ·mol-1 and TOF = 2.1 h-1) counterpart synthesized by conventional method with P123 serving as the mesoporous template. Therefore, this study offers a facile and straightforward strategy to fabricate an efficient HDS catalyst with hierarchical structures.