Hydrodesulfurization Performance Research Articles

Engineering the accessibility of active sites in mixed 1 T-2H MoS2 nanoflowers via NaClO etching for deep hydrodesulfurization of dibenzothiophene

A NaClO etching strategy was adopted to engineer the active structure of mixed 1T-2H MoS2 nanoflowers and prepare efficient hydrodesulfurization (HDS) catalysts. In the original MoS2-P catalyst, the 2H-MoS2 phase was exposed after MoS2 slabs were etched using NaClO. Sodium ion insertion with high concentrations increased the interlayer spacing of MoS2 slabs and increased the transformation of 2H-MoS2 to 1T-MoS2 phases. With increase in the concentration of NaClO solution, the proportions of 1T-MoS2 in the MoS2-N-x catalysts initially increased and then decreased. They then reached a maximum when the NaClO concentration was 1.0 mol/L. Owing to the thermodynamic instability of 1T-MoS2, the proportions of 1T-MoS2 in the sulfided MoS2-P and MoS2-N-x catalysts were less than those of the corresponding unsulfided catalysts. However, among sulfided MoS2-P and MoS2-N-x catalysts, the sulfided MoS2-N-1.0 catalyst demonstrated the highest proportion of the 1T-MoS2 phase, the best dispersion of the MoS2 slabs, and the most coordinatively unsaturated sites, thus providing itself with the optimal HDS performance for removing dibenzothiophene.

Regulating the microenvironments and the d-band center of hierarchical NiMoS/TS-1 catalyst by ZrO2 to enhance the hydrodesulfurization performance of dibenzothiophene

The microenvironments including the surface hydroxyls, the oxygen vacancies, and the d-band center of hierarchical TS-1 zeolite pickled by hydrochloric acid were regulated by ZrO2, the effect of ZrO2 on the physicochemical properties and the catalytic performances of the corresponding NiMoS supported catalysts were studied. The experimental and theoretical calculation results show that the d-band center, the surface hydroxyl groups, and the oxygen vacancies were regulated after incorporation of ZrO2. Resulting in the modulated acidity of the support and the metal support interaction of the catalysts, further promoting the formation of type-II NiMoS active phases. The catalytic performance evaluations show that catalyst NiMo/1-ZAT exhibits the superior HDS performance, kinetic study further demonstrated that the enhanced catalytic activity was mainly contributed by the improved direct desulfurization activity generated from the moderate support acidity, suitable MSI, highest sulfidation degrees, most type-II NiMoS active phase and highest activity of individual active sites.

Effects of lanthanum and ethylenediamine tetraacetic a cid

Using nickel-tungsten as active metals and TiO₂-Al₂O₃ as the support, Ni-W/TiO₂-Al₂O₃ catalysts for the hydrodesulfurization of heavy oil were prepared by wetness impregnation. The effects of the modification of lanthanum, ethylenediamine tetraacetic acid (EDTA)and La in cooperation with EDTA on the structure and hydrodesulfurization performance of the catalysts were investigated. The catalysts were characterized by XRD, BET, H₂-TPR and SEM. The results indicated that La and EDTA could weaken the interaction between support and active component, facilitate the reduction of active component, and benefit the formation of Ni-W-S phase. Addition of La or EDTA could increase the surface area and suppress the agglomeration of active metals on surface, forming smaller and highly dispersed active phase particles. The La, EDTA and combined La and EDTA modified catalysts possessed higher HDS activity than Ni-W sample, Ni-W-La-E catalyst had the highest HDS activity, and its thiophene conversion reached 99.7%.

Regulating the coordination environment of surface alumina on NiMo/Al2O3 to enhance ultra-deep hydrodesulfurization of diesel

Herein, a set of NiMo/Al2O3 catalysts with distinct coordination state of surface alumina were design and prepared by a facile calcination strategy. Various characterization methods were employed to analyze the structural properties of NiMo/Al2O3 catalysts, and the catalytic performances of corresponding catalysts were tested for hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT). The results indicate that the synthesized samples show uniform specific surface area (130 m2·g−1) and pore size (3.5 nm), but varying penta-coordinated aluminum content, which significantly influences the NiMo/Al2O3 catalysts’ surface acidity. Therein, NiMo/Al2O3-600 prepared by calcination at 600 °C exhibits the highest ratio of penta-coordinated aluminum species, which endows more abundant Brønsted acid than that of tetra- and hexa-coordinated aluminum counterparts, thereby substantially promoting the isomerization and direct desulfurization pathways of 4,6-DMDBT HDS, and thereafter considerably boosting the HDS performance of NiMo/Al2O3-600 with 94.5 % 4,6-DMDBT conversion, which is notably higher than that of NiMo/Al2O3-500 (74.4 %) and NiMo/Al2O3-700 (62.7 %).

Modulating hydrogen spillover effect to boost ultradeep hydrodesulfurization of 4,6-dimethyldibenzothiophene over Pt-Ni2P/Al2O3

The design and development of hydrodesulfurization (HDS) catalysts with superior catalytic activity has been highly desirable. Herein, a series of platinum (Pt)-triggered Ni2P/Al2O3 catalysts were fabricated and examined for 4,6-dimethyldibenzothiophene (4,6-DMDBT) HDS. The loading of Pt strengthened the interaction between the Pt and Ni2P and promoted the hydrogen atoms overflowing to the Ni2P surface, thereby enhancing the number of Lewis and Brønsted acid sites and facilitating the prehydrogenation and isomerization pathways, thereafter boosting the HDS performances of Pt-Ni2P/Al2O3 catalysts. Therein, 5%Pt-Ni2P/Al2O3 exhibited the optimal HDS performance with 97.1% 4,6-DMDBT conversion, remarkably higher than that of Ni2P/Al2O3 (25.6%) and the-state-of-the-art catalysts reported in literature due to its moderate acidity, temperate interaction between Pt and Ni2P, and excellent reducibility. Further increasing the Pt loading to 10% induced the serious aggregation of Pt particles, resulting in the sharp increase in particle size and subsequent reduction of Pt dispersion, thereby leading to the weakening of interaction between Pt and Ni2P and considerable decrease of the Brønsted acid number, which in turn inhibited the HDS performance of 10%Pt-Ni2P/Al2O3 catalyst. This work present a promising candidate for the ultradeep HDS of heavy oil and may contribute to the understanding of the hydrogen spillover effect in this reaction.

Tailoring the electronic structure of Ni2P/Al2O3 by Pt introduction to boost the ultradeep hydrodesulfurization performance

The catalytic performances of conventional Ni(Co)Mo(W)/Al2O3 catalysts for hydrodesulfurization (HDS) of fuel are far from meeting the near zero emission standards. Therefore, the development of more efficient ultradeep HDS catalyst is highly desirable. Herein, a novel Pt-Ni2P/Al2O3 catalyst with 0.5 wt% Pt loading was prepared, and its catalytic performance for HDS of 4,6-dimethyldibenzothiophene (4,6-DMDBT) was investigated. The introduction of Pt considerably promoted the reducibility and hydrogen atoms produced by the dissociated adsorbed hydrogen molecules on the Pt surface overflowing to the Ni2P because of the lower electronegativity of Pt than that of Ni, thereby increasing the number of stronger Lewis and Brønsted acid sites, and thereafter greatly boosting the direct desulfurization and isomerization pathways. As a result, Pt-Ni2P/Al2O3 catalyst achieved the ultradeep HDS of 4,6-DMDBT, with 100% conversion at 340 °C, remarkably higher than that of Ni2P/Al2O3 (49.8%) and NiMo/Al2O3 (62.0%) counterparts.

Optimizing the Incorporation Modes of TiO2 in TiO2-Al2O3 Composites for Enhancing Hydrodesulfurization Performance of Corresponding NiMoP-Supported Catalysts

TiO2-Al2O3 supports with different incorporation methods of titania were synthesized via three methods: impregnation (TA-I), co-precipitation (TA-CP), and co-precipitation–hydrothermal treatment (TA-HT). And the NiMoP catalysts prepared on the corresponding supports were evaluated for hydrodesulfurization (HDS) reactions. The results demonstrated that the Ti atoms in TA-I are attached to alumina through hydroxyl groups, while the Ti atoms in TA-CP and TA-HT can be dispersed in the alumina skeleton. Variations in the incorporation modes of TiO2 affect the support properties, consequently influencing the nature of the active metal on the supports. The Ti atoms dispersed in the Al2O3 skeleton allow an increase in the basic hydroxyl groups. Meanwhile, TiO2 in TA-CP and TA-HT can absorb hydrogen molecules and be partially reduced. Furthermore, metal species supported on the TA-CP and TA-HT are more easily reduced and better dispersed. For the NiMoP catalysts prepared with TA-CP and TA-HT, the Ti element promotes the sulfidation degree of Mo, besides shortening the average (Ni)MoS2 slab. The catalysts prepared with TA-CP exhibited superior activity for 4,6-DMDBT hydrodesulfurization. This can be ascribed not only to the relatively high sulfidation degree of Mo and proportion of the NiMoS active phase but also to the well-dispersed (Ni)MoS2 slabs. Moreover, the Ti4+ ions dispersed in the Al2O3 skeleton can be partially reduced to act as electron donors, enhancing the metallic character of the S layers in MoS2, which facilitates the improvement of the hydrogenation desulfurization activity.

Influence of the crystalline structure of Co-Mo precursors on the hydrodesulfurization performance of unsupported tube-like Co-Mo sulfide catalysts

Influence of the crystalline structure of Co-Mo precursors on the hydrodesulfurization performance of unsupported tube-like Co-Mo sulfide catalysts

Heavy oil atmospheric residue: HDS performance and life test using ARDS catalysts system

The objective of this study is to evaluate the catalyst by introducing atmospheric residue of heavy crude (H-AR) that secures full comprehensive characteristics and converts into a petroleum product, namely low sulfur fuel oil (LSFO). Furthermore, to estimate the catalyst’s lifespan under hydroprocessing conditions by monitoring its deactivation rate and maintaining consistent sulfur in LSFO products through gradual increases in reaction temperature. Prior to the hydrotreating test, the heavy crude oil underwent desalting, dewatering, and atmospheric distillation to obtained atmospheric residue (H-AR, i.e., 350°C+) for use as feedstock. The pilot plant employed a catalyst system comprising both hydrodemetallization (HDM) and hydrodesulfurization (HDS) catalysts, distributed across two fixed-bed reactors. The results showed the lifespan approximately 3.0 months as a function of time-on-stream (TOS). The H-AR feed, with its high sulfur, metals, asphaltenes, and micro carbon residue (MCR) content, poses several challenges including carbon deposition at start of run (SOR). The observed deactivation rate is attributing to the feedstock’s poor quality and its impact associated deposition of coke and metals (V and Ni) deposition with TOS.

N-octyltrimethylammonium bromide-assisted self-assembly of CoMo precursors to prepare CoMoS/Al2O3 catalysts for highly selective hydrodesulfurization of thiophene

A novel (C11H26N)2Co(MoS4)2 complex was prepared via the n-octyltrimethylammonium bromide-assisted self-assembly of CoMo precursors for the selective hydrodesulfurization (HDS) of thiophene. The complex was generated by the interaction between the negatively charged CoMo compound and the positively charged n-octyltrimethylammonium ions. Then positively charged bimolecular layers were formed owing to van der Waals forces between the C11H26N+ and the complex, and they were anchored on the negatively charged γ-Al2O3. Compared with CoMoS/γ-Al2O3 catalysts prepared by impregnation, the optimal CoMoN-0.3/γ-Al2O3 catalyst exhibited better performance for selective HDS due to the enhanced Mo dispersion, the close contact between Co and Mo, and the increased amount of CoMoS phases on γ-Al2O3. Among these catalysts, the optimal CoMoN-0.3/γ-Al2O3 catalyst with the highest concentration of CoMoS phases exhibited the highest HDS reaction rate constant of 6.95 × 10-6 mol·g−1·s−1 and the best selective factor of 26.1 for the selective HDS of thiophene with 1-hexene.

Boosting ultra-deep hydrodesulfurization of diesel by tuning sulfidation degree of metals on NiMo/AlOOH catalyst

By using a room-temperature discharge-based sulphurization (RT-DS) process, we efficiently tune sulfidation degree of metal on γ-AlOOH-supported NiMo catalyst via simply changing feedstock amount for preparing catalysts, thus preparing a NiMoS/AOH-4 catalyst for hydrodesulfurization (HDS) of diesel. NiMoS/AOH-4 shows an excellent HDS performance, with S content of diesel being reduced from 18000 μg g−1 to 3 μg g−1 and without catalytic efficiency decrease after 1000 h reaction. Moreover, NiMoS/AOH-4 shows higher rate constant, higher turnover frequency but lower activation energy in HDS reaction, as compared with those on widely reported catalysts. The excellent HDS performance of NiMoS/AOH-4 is resulted from the appropriate sulfidation degree of Mo, which creates more abundant catalytic active Ni-Mo-S phases. RT-DS process for preparing NiMoS/AOH-4 proceeds in Ar at room temperature and atmospheric pressure, without using H2S and heating. This makes RT-DS process suitable for large-scale industrial applications to fabricate more efficient HDS catalysts.

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.

The superior HDS catalyst derived from a new Waugh Co-Mo polyoxometalate via cationic substitution

In this paper, the Waugh Co-Mo polyoxometalate (POM) (NH4)6[CoMo9O32] was prepared and cationic substituted to increase the Co/Mo ratio to 0.44 with Mo and Co atoms in a new Waugh Co-Mo POM molecule. The method was verified by X-ray diffraction, X-ray fluorescence, and infrared spectroscopy. Then, two series of Co-Mo hydrodesulfurization (HDS) catalysts were prepared using the Waugh Co-Mo POMs and traditional precursors, respectively. The HDS evaluation results showed the activities of catalysts prepared from the new Waugh Co-Mo POM is higher than the reference catalysts. For the catalyst prepared from the new Waugh Co-Mo POM, the cationic substitution provides a higher Co/Mo ratio and atomic-level proximity between Mo and Co atoms, leading to shorter and less stacked MoS2 nano-particles and more exposure of unsaturated edges and corner sites. In addition, a weak interaction between the new Waugh Co-Mo POM and Al2O3 leads to more CoMoS active phases. Catalysts prepared from the new Waugh Co-Mo POM showed excellent HDS performance, demonstrating the new Waugh Co-Mo POM is a superior precursor to construct the efficient HDS 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.

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.

Designing flower-like La-Bi2WO6/Ni@N-rGO composite for the photocatalytic oxidation coupled in-suit hydrogenation desulfurization of diesel oil

The ultra-deep removal of 4,6-DMDB and decrease in loss of C/ H atoms is one of the bottlenecks in achieving ultra-low sulfur fuel oil, which is resolved with photocatalytic oxidation coupled with in-situ hydrodesulfurization. Herein, a flower cluster microsphere composite La-Bi2WO6/Ni@N-rGO as photocatalytic oxidation coupling with in-situ hydrodesulfurization catalysts was prepared by a one-step hydrothermal method. The characterization results of STEM, SEM, Raman, and XPS showed that La-Bi2WO6 combined with Ni@N-rGO formed flower-like microspheres with large specific surface areas. The experimental results showed that the catalysts had excellent photocatalytic oxidation coupling with in-situ hydrodesulfurization performance and good stability. A desulfurization ratio of 4,6-DMDBT reached 99.9% under mild conditions. A plausible mechanism for the photocatalytic desulfurization of 4,6-DMDBT was presumed by combining experiments with density functional theory. The designed La-Bi2WO6/Ni@N-rGO could be utilized for a large-scale process of diesel and other transpiration fuel oil.

Desulfurization of 2-phenylcyclohexanethiol over Pd and Pt catalysts on γ-Al2O3

The desulfurization of 2-phenylcyclohexanethiol (2-PCHT) was studied over Pd and Pt catalysts supported on γ-Al2O3 under 5.0 MPa H2 or Ar at 240 °C. The infrared spectra of the two catalysts during the reactions of 2-PCHT (PCHT-IR) were measured between 180 and 300 °C at 0.2 MPa H2 and Ar. The hydrodesulfurization (HDS) of 2-PCHT over Pd/Al2O3 and Pt/Al2O3 followed pseudo-first-order kinetics, and occurred mainly through β-elimination. Pd/Al2O3 was more active than Pt/Al2O3, mainly due to its higher β-elimination activity. Piperidine showed different inhibiting effects on their HDS performances. The species adsorbed on Pd/Al2O3 and Pt/Al2O3 were different under H2. Strong adsorption of 1-phenyl-1-cyclohexene on both catalysts was observed under Ar, which could be responsible for Langmuir-Hinshelwood kinetics and low activities. Pd/Al2O3 and Pt/Al2O3 were less active than transition-metal phosphides in the HDS of 2-PCHT, but were more active than the Mo-based sulfides.

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.

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.

Tuning active sites in MoS2-based catalysts via H2O2 etching to enhance hydrodesulfurization performance

A H2O2 etching strategy was adopted to introduce coordinatively unsaturated sites (CUS) on MoS2-based catalysts for dibenzothiophene (DBT) hydrodesulfurization (HDS). The CUS concentrations on MoS2 slabs were finely regulated by changing the concentrations of H2O2 solution. With the increasing H2O2 concentrations (0.1–0.3 mol/L), The CUS concentrations on MoS2 slabs increased gradually. However, the high-concentration H2O2 etching (0.5 mol/L) increased the MoOxSy and MoO3 contents on MoS2 slabs compared to etching with the H2O2 concentration of 0.3 mol/L, which led to the less CUS concentration in the sulfided Mo–H-0.5 catalyst than in the sulfided Mo–H-0.3 catalyst. A microstructure-activity correlation indicated that the CUS introduced by H2O2 etching on MoS2 slabs significantly enhanced DBT HDS. Different Co loadings were further introduced into Mo–H-0.3, which had the most CUS concentration, and the corresponding 0.2-CoMo catalyst with the highest CoMoS content (3.853 wt%) exhibited the highest reaction rate constant of 6.95 × 10−6 mol g−1 s−1 among these CoMo catalysts.