Hydrodesulfurization Of Dibenzothiophene Research Articles

On the role of niobium in nanostructured Mo/Nb-MCM-41 and NiMo/Nb-MCM-41 catalysts for hydrodesulfurization of dibenzothiophene

In the present work, Mo and NiMo catalysts were supported on the MCM-41 material modified with Nb2O5 and compared to similar catalysts supported on unmodified MCM-41 silica. Catalysts were characterized by different techniques and tested in the hydrodesulfurization of dibenzothiophene. Our interest was in clarifying the role of niobium in the above catalysts. It was observed that the Mo/Nb-MCM-41 and NiMo/Nb-MCM-41 catalysts were more active than their analogs supported on the MCM-41 material without niobia, and also they had higher hydrogenation ability. Based on the results of the characterization of calcined (oxide) and sulfided catalysts, it is proposed that niobium acts in the above catalysts as a support improving the dispersion of the MoS2 phase and increasing the amount of active sites and as a promoter, increasing the acidity of the Mo and NiMo catalysts. Although the promotion effect of niobium was not as strong as that of the nickel promoter. Also, the possibility of decoration of the edge surface of the Ni-Mo-S active sites with some Nb atoms cannot be excluded.

The Influence of Pore Structure and Acidity on the Hydrodesulfurization of Dibenzothiophene over NiMo-Supported Catalysts.

A series of mesoporous materials of SBA-16 were in situ incorporated into ZSM-5 crystallites via a two-step self-assemble method, and hydrodesulfurization (HDS) catalysts were prepared on the corresponding ZSM-5/SBA-16 (ZS) composites. The characterization results indicated that ZSM-5 nanoseeds were fabricated into the silica framework of the ZS composites, and the three-dimensional Im3m cubic structure of SBA-16 was retained simultaneously. In addition, the ZS series materials possessed open pores and large surfaces, which would facilitate the diffusion of reactants in the mesoporous channels. Moreover, the introduction of ZSM-5 seeds into composites could enhance the acidities of supports. As a result, the NiMo/ZS series catalysts exhibited high activities for DBT HDS processes. The NiMo/ZS-160 catalyst exhibited the highest catalytic efficiency (96.5%), which was apparently attributed to the synergistic contributions of the physicochemical properties of ZS supports and the dispersion states of active metals. Correspondingly, DBT HDS reactions over the NiMo/ZS series catalysts mainly proceeded via a hydrogenation desulfurization route that benefitted from the enhanced acidities especially the total Brønsted acid.

Synergistic effect of acidity and active phases for NiMo catalysts on dibenzothiophene hydrodesulfurization performance

Serial Al-Ti-SBA-16 materials with highly ordered degree were successfully synthesized by a simple two-step method. The characterization results showed that incorporation of Al and Ti atoms into SBA-16 silica could obtain the supports with different acidities and modulate the distribution and dispersion of active phases for NiMo catalysts. The dibenzothiophene (DBT) hydrodesulfurization (HDS) evaluation results disclosed that the synergistic effect of enhancing acidity and properties of active metals could significantly improve the HDS performance. Importantly, it was the first time that the ratios of S-edge and Mo-edge concentrations were found to be well linked with the hydrogenation pathway (HYD)/direct desulfurization pathway (DDS) ratios. The HDS result showed that the acidity of S-H groups in S-edge sites could be promoted by B acid and further facilitated the DDS selectivity. As the Al and Ti contents in the support were 7.5% and 2.5% respectively, the NiMo/AT-7.5 catalyst exhibited the highest HDS performance due to its appropriate acidity, highest proportion of MoS2 phase and concentration of S-edge sites with high efficiency. Finally, the kinetic and thermodynamic analyses were applied to investigate the intrinsic HDS reactivity for various catalysts. The results confirmed the existence of synergistic effect in the DBT HDS reaction. It was also discovered that the B acid sites could further increase the desulfurization route (DS) of THDBT to CHB. In addition, the S-edge/Mo-edge ratio and kDDS/kHYD could also be well linked.

Effect of the Co/Mo Ratio on the Morphology and Activity of the CoMo Catalyst Supported on MgO Nanosheets in Dibenzothiophene Hydrodesulfurization

MgO nanosheets were employed to prepare CoMo catalyst with different Co/Mo ratio (CoMo/NA-MgO) by aqueous co-impregnation method. The CoMo/NA-MgO showed an increased activity in the hydrodesulfuriza...

Synthesis of unsupported Co-Mo hydrodesulfurization catalysts with ethanol-water mixed solvent: Effects of the ethanol/water ratio on active phase composition, morphology and activity

Co-Mo sulfide catalysts with different particle size and structures were prepared in ethanol-water mixed solvent followed by a low-temperature sulfurization process, and were tested in dibenzothiophene hydrodesulfurization. The effects of the ethanol/water ratio on the particle size of precursors, active phase composition, active site number, morphology, and hydrodesulfurization activity of the final catalysts were investigated. The atomic ratio of Co/Mo and active phase morphology of catalysts closely relate to the dielectric constant of ethanol-water mixed solvent. Appropriate dielectric constant favors the formation of (Co)MoS2 slabs with shorter length (∼ 5.0 nm) and higher stacking number (∼ 4.3 layers), resulting in more coordinatively unsaturated sites, especially in the corner sites. The catalytic activity not only depends on the active sites of CoMoS phase, but also on that of Co9S8 and MoS2 phases because of synergistic effect. For MoS2 and CoMoS phases, the corner sites show higher direct desulfurization activity than the edge sites.

A novel catalyst of nickel-loaded graphene decorated on molybdenum-alumina for the HDS of liquid fuels

In the process of hydrodesulfurization (HDS) the activation of the dibenzothiophene (DBT) occurs on the catalysts’ active sites, in addition to the promoter. The distribution of both catalyst and promotor has a significant influence on the HDS activity and, along with improved nanoparticle distribution, more active sites will be available for the DBT molecules to be adsorbed and desulfurized. In this work the idea is to load the Ni promoter on graphene and the Mo catalyst on alumina separately, and then the obtained Ni/graphene will be loaded on Mo/alumina. The obtained alumina-molybdenum loaded with Ni nanoparticles on graphene (AlMoGNi) was assessed for the HDS of DBT. The characterization of the synthesized materials was conducted by using a surface area analyzer, temperature programmed analysis, an X-ray powder diffraction analyzer, scanning electron microscopy with an energy-dispersive X-ray spectroscopy, a transmission electron microscope, inductively coupled plasma and Fourier transform Infra-red spectroscopy. The catalytic efficiency of the catalysts was investigated in a reactor at a temperature of 573 K and under hydrogen pressure of 53 bar. The decalin was utilized as a fuel with 600 parts per million sulfurs (ppm-S). With the use of an AlMoGNi catalyst, the concentration of sulfur was reduced in the tested fuel to (9 ppm-S, 99% conversion) compared to about (95 ppm-S, 84% conversion) using the catalyst without graphene. The superior performance of the AlMoGNi catalyst can be explained by its textural properties, surface acidity, and nanoparticle dispersion. The hydrodesulfurization over the AlMoGNi catalyst occurred through both hydrogenolysis and hydrogenation desulfurization pathways.

Exotic Nanostructured Titania Supports for Deep Hydrodesulfurization Catalysts: Are They Better Than the Conventional Ones?

In the present work, we compared the hydrodesulfurization (HDS) behavior of NiMo catalysts supported on titania-based nanomaterials (hydrogen titanate nanotubes and nanotubes decorated with anatase nanocrystals), with that of the reference NiMo/γ-alumina and NiMo/TiO2 samples. Supports and calcined catalysts were characterized by nitrogen physisorption, powder XRD, UV–Vis diffuse reflectance spectroscopy, Raman spectroscopy, temperature-programmed reduction, scanning electron microscopy and high resolution transmission electron microscopy (HRTEM). The sulfided catalysts were characterized by HRTEM and evaluated in the HDS of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). In the hydrodesulfurization of DBT, all catalysts supported on nanostructured titania materials showed similar activity as the NiMo/Al2O3 reference. However, their selectivity towards the hydrogenation pathway of the reaction was significantly higher than that of the alumina-supported reference. In the hydrodesulfurization of 4,6-DMDBT, activities of the synthesized NiMo catalysts supported on titania-based nanomaterials were about 50% superior to that of the NiMo/Al2O3 reference. This is an interesting result, since the majority of the conventional NiMo or CoMo catalysts are significantly more active for the elimination of DBT than of the sterically-hindered 4,6-DMDBT. The presence of small titania anatase crystallites in the nanostructured supports had a slight positive effect on the catalytic activity of the NiMo catalysts in HDS of 4,6-DMDBT, and a more noticeable effect on an increase in their hydrogenation ability (production of larger amounts of methylcyclohexyltoluene in the products).

Influence of Conditions of Cryogenic Molybdenite Grinding on the Activity of Bulk Sulfide Hydrotreating Catalysts

The milling of molybdenite under cryogenic conditions in argon has been performed for the first time, and the physicochemical properties of its samples, their catalytic activity in model reactions of hydrodesulfurization of dibenzothiophene and diesel components, and the ability to initiate the isopropylbenzene oxidation reaction have been studied. The samples have been found to exhibit high catalytic activity.

Influence of Mechanical Activation on the Properties of Oil Refining Supports and Catalysts

Scientific publications and patents on mechanochemical synthesis of inorganic supports and catalysts of oil refining processes (cracking, reforming, hydrotreating, and hydrocracking) were analyzed. It was shown that the introduction of mechanical activation into the process of synthesis of inorganic supports and catalysts typically enhances their catalytic activity and selectivity. Features of the mechanochemical synthesis of complex nickel-molybdenum oxides, which are precursors of nickel-molybdenum sulfide hydrotreating catalysts, were considered. It was demonstrated that, under mechanical activation conditions, it is possible to prepare β-NiMoO4, a highly active and thermostable nickel-molybdenum oxide containing Mo in tetrahedral coordination. The technology of producing highly dispersed carbide-containing catalysts with the use of the mechanical activation method, developed at the Institute of Hydrocarbon Processing, Siberian Branch, Russian Academy of Sciences, was described. The texture and morphology of the resultant highly dispersed bulk carbide-containing catalysts were considered. The size of the active particles was estimated at 2–5 nm. Сatalytic tests revealed high catalytic activity of the highly dispersed carbide-containing catalysts in the model reaction of dibenzothiophene hydrodesulfurization.

Preparation of electron-rich Fe-based catalyst via electronic structure regulation and its promotion to hydrodesulfurization of dibenzothiophene

In this work, the sulfur removal rates of CeO2-x modified Fe/FeZn catalysts are increased by 5 %–20 %, attributed to the electron-rich Fe species but not the variation of acidity. The main active phases of pure Fe-based and FeZn bimetallic catalysts are pyrrhotite (Fe1-xS) and ferroan sphalerite (FeZnS), respectively. The results of characterizations and DFT calculations show that strong electron-donating effect of CeO2-x on Fe species can promote the dispersion of Fe species and weaken the Fe-O and Fe-S/FeZn-S bonds, resulting in higher sulfidation degrees and more active sites of Fe/FeZn catalysts. Besides, weak Al−OH peaks caused by CeO2-x could also increase the sulfidation degrees of Fe/FeZn catalysts. Furthermore, HYD/DDS ratios of Fe-based catalysts are reduced by CeO2-x because of the electron-rich Fe species and decrease of Lewis acid sites. This promising work has great potential for the industrial application of environmentally friendly and economical Fe-based catalysts in HDS field.

Kinetic Modelling of the Influence of H<sub>2</sub>S on Dibenzothiophene Hydrodesulfurization in a Batch System over Nano-MoS<sub>2</sub>

In this work, the possibility of enhanced activity during the hydrodesulfurization of dibenzothiophene over certain nano-MoS2 catalyst due to the presence of H2S was examined by focusing on the reaction kinetics. With H2S generated in situ, the overall reaction followed the autocatalytic rate law; while in the absence of H2S the kinetics indicated a pseudo-first-order reaction. H2S appears to modify the relative contributions of parallel hydrogenation and desulfurization reactions by drastically increasing the hydrogenation rate. Kinetic models were developed that describe the hydrodesulfurization reaction at various H2S concentrations, and the kinetic parameters and adsorption equilibrium constants associated with this process were estimated by fitting the experimental data. The results suggest that the promotion and/or inhibition of hydrodesulfurization by H2S likely result from the same overall reaction mechanism.

Nanoparticle catalyzed hydrodesulfurization of diesel fuel in a trickle bed reactor: experimental and optimization study.

This work focuses on the preparation, simulation, and optimization of the hydrodesulfurization (HDS) of dibenzothiophene (DBT) using a nanocatalyst. A homemade nanocatalyst (3 percent Co, 10 percent Mo/γ-Al2O3 nanoparticles) was used in a trickle bed reactor (TBR). The HDS kinetic model was estimated based on experimental observations over ranges of operating conditions to evaluate kinetic parameters of the HDS process and apply the key parameters. Based on these parameters, the performance of the TBR catalyzed by the nanocatalyst was evaluated and scaled up to a commercial scale. Also, the selectivity of HDS reactions was also modeled to achieve the highest yield of the desired hydrogenation product based on the desirable route of HDS. A comprehensive modeling and simulation of the HDS process in a TBR was developed and the output results were compared with experimental results. The comparison showed that the simulated and experimental data of the HDS process match well with a standard error of up to 5%. The best reaction kinetic variables obtained from the HDS pilot-plant (specific reaction rate expression, rate law, and selectivity) TBR have been utilized to develop an industrial scale HDS of DBT. The hydrodynamic key factors (effect of radial and axial dispersion) were employed to obtain the ratio of the optimal working reactor residence time to reactor diameter.

Carbon nanofiber-doped zeolite as support for molybdenum based catalysts for enhanced hydrodesulfurization of dibenzothiophene

Zeolite (Z) doped carbon nanofiber (CNF) was prepared as a support for a molybdenum (Mo) based catalyst and cobalt (Co) or nickel (Ni) were used as a promoter. The catalytic behavior of the synthesized catalyst zeolite-CNF/MoCo (ZFMoCo) or zeolite-CNF/MoNi (ZFMoNi) was evaluated for the hydrodesulfurization (HDS) reaction of dibenzo-thiophene (DBT) and compared with the catalyst without CNF (ZMoNi and ZMoCo). A set of characterizations were used to illustrate the physico-chemical properties of the catalyst. The catalytic activity of the catalyst was compared to the reference catalyst without CNF, and it was found that CNF has an effective role in improving the activity for sulfur removal from 90% (ZMoNi) to 95% (ZFMoNi) and from 92% (ZMoCo) to 98% (ZFMoCo). This could be due to the enhancement in the surface area after doping the CNF. Increasing the area for the dispersion of the active phase on the composite support surface (Z-CNF) showed higher catalytic performance.

NiMoW/P-Al2O3 four-component catalysts with different Mo:W molar ratios and P2O5 contents: the effect of the composition and active phase morphology on the catalytic activity

NiMoW/P-Al2O3 catalysts were synthesized with a different ratio of Mo:W (W-free sample, Mo:W = 2:1, Mo:W = 1:1, Mo:W = 1:2 and Mo-free sample) and various P2O5 contents in the carrier (up to 5 wt%). The surface of the sulfide phase of the samples was investigated by means of high-resolution transmission electron microscopy (HR TEM) and X-ray photoelectron spectroscopy (XPS). The catalytic activity of patterns was estimated in the reactions of hydrodesulfurization of dibenzothiophene (DBT) and hydrogenation of naphthalene. The results are presented in the form of three-dimensional diagrams “P2O5 content—ratio Mo/W—catalytic activity” or “P2O5 content—ratio Mo/W—property”. The influence of the phosphorus content on the maximum peak position of the binding energy S2p/1 of the S2− atomic group for the investigated systems is shown. Comparison of the shape of the curve of changes in the binding energy with the previously presented results on the catalytic activity of the samples in the HDS of a vacuum gas oil allows us to conclude that phosphorus is able to change the electronic state of the active phase of the catalysts, which leads to a change in their catalytic activity in the reactions of HDS.

Hierarchically Porous β/SBA-16 Composites: Tuning Pore Structure and Acidity for Enhanced Isomerization Performance in Hydrodesulfurization of Dibenzothiophene and 4,6-Dimethyldibenzothiophene

β/SBA-16 (BS) materials were fabricated using β-nanoclusters through self-assembly hydrothermal crystallization approach; subsequently, the corresponding NiMo/BS catalysts were synthesized. The inf...

Synthesis of highly ordered Al-Zr-SBA-16 composites and their application in dibenzothiophene hydrodesulfurization

Serial Al-Zr-SBA-16 composites are successfully prepared through a two-step synthetic method. The influences of Al and Zr species on the properties of Al-Zr-SBA-16 composites and NiMo corresponding catalysts are investigated by various measurements. The results showed that a series of Al-Zr-SBA-16 supports maintained the intact structure and highly ordered degree. Al and Zr modification could increase the proportion of inactive Mo (Td) and Mo(Oh) species, respectively. The DBT HDS evaluation results revealed that NiMo/AZ-2.5 presented the highest HDS efficiency of 96.2%. The reasons should be ascribed to the factors that the higher dispersion degree of active metals, the highest proportion of MoS2 and NiMoS active phases over NiMo/AZ-2.5 sulfide catalyst, and the highest selectivity of hydrogenation (HYD) route. In addition, principle of hierarchical reaction steps in HYD route was also proposed to explain the reason why the HYD/DDS (direct desulfurization) ratio and HDS efficiency were the highest for NiMo/AZ-2.5 catalyst.

Influence of Oxygen-Containing Compounds on Conversion and Selectivity of Dibenzotiophene and Naphthaline on Bulk and Supplied Co(Ni)MoS2 Catalysts

The supported CoMoS2/Al2O3 and NiMoS2/Al2O3 catalysts were prepared by impregnating of alumina to incipient wetness with aqueous solutions of 12-molybdophosphoric heteropoly acid and nickel or cobalt citrates. A bulk Ref-MoS2 catalyst was obtained by thermal decomposition of ammonium tetratiomolybdate. The synthesized catalysts were investigated by low temperature nitrogen adsorption and high resolution transmission electron microscopy. The catalytic properties were studied in the dibenzothiophene hydrodesulfurization and naphthalene hydrogenation in the presence of dodecanoic acid or guaiacol in a flow unit with a microreactor under hydrogen pressure. It was shown that the bulk catalyst Ref-MoS2 has minimal sensitivity to dodecanoic acid and guaiacol during the combined hydrotreatment of dibenzothiophene and naphthalene. The effective adsorption constants of dodecanoic acid and guaiacol were calculated using the Langmuir—Hinshelwood model.

Effect of naphthalene quinoline and H2S on DBT hydrodesulfurization over unsupported NiMoW catalyst

Unsupported catalysts have attracted much attention for high activity in comparison with the traditional supported catalyst. Meanwhile, the clear structure of unsupported catalysts is helpful for the recognition of active phase for conducting the industry production. The NiMoW unsupported catalyst was prepared by hydrothermal synthesis and characterized by BET, XRD and HRTEM. The effects of naphthalene, quinoline and H2S on the hydrodesulfurization reactivity of dibenzothiophene (DBT) were investigated in both a batch autoclave and a continuous 10 ml fixed bed micro-reactor over NiMoW and supported catalyst for comparison. The results showed that the hydrogenation reaction and the hydrogenolysis reaction occurred on different active sites. For supported catalyst, the inhibition was relatively weaker, and the inhibition of the hydrodesulfurization pathway was much higher than the direct desulfurization pathway. Although unsupported catalyst was very sensitive to quinoline and H2S in this experiment, the HDS ratio on the unsupported catalyst was maintained at a high level above 99.7%, which is attributed to the very high active site density of unsupported catalysts.

Hydrodesulfurization of coal tar pitch using Pt/Al2O3 and Pd/Al2O3 catalysts under mild conditions

Hydrodesulfurization (HDS) of coal tar pitch (CTP) using Pt/Al2O3 and Pd/Al2O3 catalysts in tetrahydrofuran at 333 K and atmospheric pressure was investigated. The HDS of dibenzothiophene (DBT) proceeded over both the Pt and Pd catalysts under the mild conditions. The effects of polycyclic aromatic hydrocarbons on the HDS of DBT were examined: a naphthalene ring suppressed the HDS, while a benzene ring did not. CTP underwent HDS as well as partial hydrogenation under the mild conditions. The Pt catalyst was more active than the Pd catalyst in the HDS of CTP. The sulfur content in CTP was reduced by over 50% through the HDS process.

Effect of pre-activation treatment temperature on hydrodesulfurization catalytic activity of CoMoS/KIT-6

Mesoporous silica-supported cobalt–molybdenum hydrodesulfurization catalysts have been prepared by wetness impregnation, drying and a thermal pre-treatment of impregnated support before activation. Characterization of materials was made by nitrogen adsorption, thermogravimetric analysis, Raman spectroscopy, TEM and XPS. Catalytic activity was determined by hydrodesulfurization of dibenzothiophene (DBT). The results indicate that the thermal pre-treatment carried out at the lower temperature allows the formation of smaller and less stacked active phase structures, with a higher amount of CoMoS phase.