HDS Of Dibenzothiophene Research Articles

Influence of precursor compounds on the structural and catalytic properties of CoNiMo/SBA-15 catalysts used in the hydrodesulfurization of dibenzothiophene

In the present research project, it was studied in detail how the incorporation of different precursor compounds and the supplementary addition of amounts of nickel in the MoS2 slabs can influence the structural and catalytic properties of trimetallic CoNiMo catalysts supported on SBA-15 mesoporous support with precise control of the amount and nature of the promoters. The catalysts were prepared by the incipient impregnation method using ammonium heptamolybdate and cobalt and nickel acetate, and nitrate as precursors adding nickel in molar amounts (5, 10, and 20%) of the cobalt atomic loading. Adding the Ni in small amounts allows us to keep the (Co + Ni)/(Co+Ni+Mo) molar ratio near 0.3. The catalysts formed were labeled according to the precursor compounds used (CoNixMo-Ac for acetates and CoNixMo-N for nitrates), where x is the percentage of nickel. Catalysts were then characterized by N2 adsorption-desorption isotherms, X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Catalysts were tested in the HDS of dibenzothiophene (DBT).Results show a significant impact of adding small amounts of nickel and the type of precursor compounds used for the CoNiMo trimetallic catalysts on the final HDS activity. In the case of the catalysts prepared with cobalt and nickel acetates, it was observed that the initial reaction rate values increased as the amount of Ni increased, being the CoNi5Mo-Ac, the catalyst with the lower catalytic activity. Increasing the amount of Ni causes an increase in the HDS of DBT. In the case of the catalysts prepared with nitrates, it could be observed a similar effect. The catalyst with the higher catalytic activity in both series was the CoNi20Mo-Ac. These results agree with the TEM analysis in which a decrease in the slab length of the MoS2 could be regarded as the de Ni amount increase. This means that the type of precursor used has an essential effect on the catalysts since modify their properties and catalytic activity and suggests that the materials synthesized with acetate precursors can help to improve the intrinsic activity of the HDS sites.

Engineering Transition Metals As Noble-Metal Free Bifunctional Electrode for Overall Water Splitting

The emerging need of clean and renewable energy drives the exploration of effective strategies to produce molecular hydrogen. With the assistance of highly active non-noble metal electrocatalysts, electrolysis of water is becoming a promising candidate to generate pure hydrogen with low cost and high efficiency.[1] This reaction takes place almost exclusively on Pt/C catalysts at the cathode which is expensive and need to be replaced by a metal-based catalyst which can show a comparable HER (Hydrogen evolution reaction) activity. Transition metal oxides, nitrides and sulfides have been widely explored as catalysts for HER and OER (Oxygen evolution reaction) due to their good electronic conductivity, stable and variable oxidation states, and superior corrosion resistance.[2] In this research, MoNi4 embedded MoO3 nanorods are synthesized using facile hydrothermal method. Further, Molybdenum Vanadium Nitride is coated on top the synthesized electrode using RF/DC magnetron co-sputtering.[3] This combination of hydrothermal and magnetron sputtering fabrication methods of the electrodes results in high surface area of the electrodes thereby improving the reaction kinetics of hydrogen production. The performance of the electrodes is tested in N2/O2 saturated 1M KOH solution using steady state technique called Staircase Voltammetry (SCV) instead of conventional dynamic LSV (Linear sweep voltammetry)/CV (Cyclic Voltammetry).[4] This alternative method for testing is performed due to the exaggeration of the catalytic performance through conventional LSV/CV arising from double layer charging for nanostructured electrode. The electrodes are characterized by X-ray diffraction and SEM for structural and morphological analysis. Hence, we report the synthesis of novel MoVN on MoNi4/MoO2 nanorods using DC/RF Magnetron co-sputtering as an efficient, bifunctional, binder free electrode for overall water splitting. The electrode is characterised for both full-cell and half-cell configurations proving its stability for 12 hours. This work provides a reliable approach to the production of low cost and high-effectiveness electrodes for the application in commercial electrolyzers.[1] J. Zhang et al., “Efficient hydrogen production on MoNi4 electrocatalysts with fast water dissociation kinetics,” Nat. Commun., vol. 8, no. May, pp. 1–8, 2017, doi: 10.1038/ncomms15437.[2] L. A. Santillán-Vallejo et al., “Supported (NiMo,CoMo)-carbide, -nitride phases: Effect of atomic ratios and phosphorus concentration on the HDS of thiophene and dibenzothiophene,” Catal. Today, vol. 109, no. 1–4, pp. 33–41, 2005, doi: 10.1016/j.cattod.2005.08.022.[3] B. Wei et al., “Bimetallic vanadium-molybdenum nitrides using magnetron co-sputtering as alkaline hydrogen evolution catalyst,” Electrochemistry Communications, vol. 93. pp. 166–170, 2018, doi: 10.1016/j.elecom.2018.07.012.[4] S. Anantharaj and S. Kundu, “Do the Evaluation Parameters Reflect Intrinsic Activity of Electrocatalysts in Electrochemical Water Splitting?,” ACS Energy Lett., vol. 4, no. 6, pp. 1260–1264, 2019, doi: 10.1021/acsenergylett.9b00686. Figure 1

Molybdenum boron based catalysts loaded on MnO alumina support for hydrodesulfurization of dibenzothiophene

The influence of boron on the activity of a hydrodesulfurization, HDS, catalyst was evaluated for the cleaner production of fuel. Thus, mixed oxides of γ-alumina and manganese oxide MnO were synthesized as a support and then loaded with molybdenum -copper, Mo-Cu, which work as an active phase and promoter. Different contents of boron were added to the synthesized catalysts to form AlMnO/MoCuB 0% (MAB 0), AlMnO/MoCuB 1% (MAB 1), AlMnO/MoCuB 2% (MAB 2) and AlMnO/MoCuB 5% (MAB 5). The textural properties of the materials were improved after the addition of boron from 164 m2/g of the control catalyst to 225, 258 and 265 m2/g for MAB (1), MAB (2) and MAB (5). X-ray diffraction (XRD) and Fourier transform infrared (FTIR) were utilized for structural characterization. X-ray photoelectron spectroscopy (XPS) was used to attain data on the chemical states and binding energies of the catalysts. A thermogravimetric analyzer (TGA) was utilized to assess the thermal stability of the catalysts. The catalytic activity was tested in a batch reactor system for the HDS of dibenzothiophene (DBT), under the following reaction parameters: T of 300 °C, hydrogen pressure of 55 bar and 6 h reaction time. After boron addition, it became 98% (MAB 5) compared to 87% of the MAB0 control catalyst and that clarified the role of boron in enhancing the catalyst performance.

Dispersed Ni-Mo sulfide catalysts from water-soluble precursors for HDS of BT and DBT via in situ produced H2 under Water gas shift conditions

The Ni-Mo catalysts formed in invert sulfur-containing emulsions through the high-temperature decomposition of water-soluble metal precursors were tested in HDS of benzo- and dibenzothiophenes via in situ hydrogen under WGSR conditions. The formation of highly dispersed sulfide species, fully covered by Ni atoms, as well as separate Ni and Mo sulfides was proved by FT-IR, XRD, TEM, EDX mapping, and XPS techniques. The catalytic evaluation revealed the high HDS activity at 380−420 °C, p(CO) = 5 MPa, the water content of 20 wt.%, and CO:H2O molar ratio of 1.8. The catalytic behavior was estimated depending on the reaction conditions, structural features, and active phase composition. As revealed from products distribution, the lower temperature and reaction time favor the HYD reaction pathway, while the surfactant leads to the dibenzothiophene transformation through the DDS reaction route at higher temperatures. The catalysts were found to be reused at least 6 cycles in the sulfur-assisted HDS of dibenzothiophene.

Preparation of the Ni2P/Al-MCM-41 catalyst and its dibenzothiophene HDS performance

Ni2P/Al-MCM-41 catalysts were prepared. The incorporation of Al could promote the formation of small sized crystalline Ni2P and modificate its surface, which will finally results in the increase in catalytic performance.

HDT of the model diesel feed over Ir-modified Zr-SBA-15 catalysts

Iridium catalyst using different zirconium modified-SBA-15 supports were tested in the HDT of tetralin and typical sulfur and nitrogen compounds present in diesel feed. The zirconium modified-SBA-15 supports were synthesized by sol-gel method using two sources of zirconium, zirconyl chloride and zirconium (IV) propoxide. Regarding XRD, N2 adsorption isotherms and TEM, we obtained better textural and structural properties using the alkoxide, especially when lactic acid was added in order to decrease the hydrolysis rate of zirconium propoxide. In addition, XPS and DRUV-Vis demonstrated that zirconium was incorporated mainly as tetrahedral Zr4+ species NH3-TPD showed that higher acidity is observed when tetrahedral Zr4+ species are present. Iridium dispersion was determined by TEM and H2-chemisorption and reducibility by XPS and TPR. Among the catalysts prepared, the catalyst synthesized using zirconium propoxide and lactic acid presented the highest dispersion, lowest cluster size and lowest reduction temperature. Consequently, this was the most active catalyst for the hydrogenation of tetralin, the HDN of indole and quinoline and the HDS of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). The presence of Zr+4 had a remarkable effect on the dispersion and reducibility capacity of the iridium actives species. In addition, the presence of moderate acidity in this material gives the best catalyst for HDN and HDS in the studied conditions. The inhibition effect of the sulfur and nitrogen compounds over tetralin hydrogenation was studied using individual feeds and a mixture feed. We observe that 4,6-DMDBT and quinoline were the most refractory compounds and they showed the highest inhibition effect. Tetralin hydrogenation was stronger inhibited when using the mixture feed compared with the individual feeds. This can be explained in terms of the competition between the different compounds that retard the rate of hydrogenation of tetralin. However, a high conversion of tetralin was achieved even when 300 ppm of S or N was added. The most active catalyst synthesized by direct synthesis using propoxide and lactic acid was stable after several catalytic cycles making this material as potential catalyst for HDT reaction at mild conditions.

Effect of citric acid and triethylene glycol addition on the reactivation of CoMo/γ-Al2O3 hydrotreating catalysts

Calcined CoMo/γ-Al2O3 hydrotreating catalysts were reactivated by a solution of citric acid and triethylene glycol. The reactivated catalysts were tested in HDS of dibenzothiophene and hydrotreating of SRGO. The reactivated catalysts were showed a significant increase in activity compared to calcined. The highest reactivation was observed for the sample reactivated using a solution of citric acid and triethylene glycol. All catalysts were characterized by means of UV-DRS, FTIR, Raman spectroscopy, XRD, XPS, and HTREM. It has been shown that the addition of triethylene glycol increases the proportion of CoMoS phase and the dispersion of sulfide particles.

Hydrotreating Performance of FCC Diesel and Dibenzothiophene over NiMo Supported Zirconium Modified Al-TUD-1 Catalysts

Zr modified mesoporous alumina Al-TUD-1 with different Zr content was successfully synthesized via sol–gel method and the optimal thermal treatment time was 4 h. The characterization results of HRTEM, XPS and pyridine FT-IR revealed that Zr atoms acted as electronic promoters not only enhanced the sulfidation degree and modulated the morphology of MoS2 active phases but also brought more acidities into the alumina framework. Additionally, the sulfided catalysts were evaluated using dibenzothiophene (DBT) and FCC diesel as feedstocks, respectively. NiMo/ZrAT-100 catalyst with the largest pore size, the highest active metal sulfidities, as well as the highest total acid and B/L value exhibited the highest HDS (99.1%) and HDN efficiencies (98.7%) in diesel hydrotreating reaction; moreover, it possessed the largest reaction rate constant in DBT HDS reaction. Furthermore, a possible reaction network was also proposed, in which DDS route was the predominant pathway for DBT HDS.

CoMo Hydrotreating Catalysts Supported on Al2O3, SiO2 and SBA-15 Prepared from Single Co2Mo10-Heteropolyacid: In Search of Self-Promotion Effect

CoMo hydrotreating catalysts with varied metal loading (1–4 Mo at nm− 2) based on Co2Mo10 heteropolyacid (HPA) and different supports (γ-Al2O3, SBA-15, SiO2) were prepared by incipient wetness impregnation. The catalysts were characterized by N2 physisorption, high resolution transmission electron microscopy (HRTEM), Raman and X-ray photoelectron spectroscopy (XPS). Catalytic activity was evaluated in co-hydrotreating (HDT) of the model feed containing dibenzothiophene (DBT) and naphthalene. The catalytic properties of CoMo catalysts were shown to depend on the morphological characteristics of CoMoS species, its promotion degree, and metal loading. The sulfidation degree of the initial precursor and effective cobalt amount in the CoMoS species increased with the Mo loading increase from 1 to 4 at nm− 2 in all studied catalysts. The DBT conversion maximum was achieved over CoMo/Al2O3 and CoMo/SBA-15 with 4 Mo at nm− 2. CoMo/SBA-15 catalysts had higher TOF numbers both in DBT HDS and in naphthalene hydrogenation (HYD) at the surface concentration of Mo same as in the other samples. These results can be attributed to optimal morphology of sulfide particles and the Co/Mo promotion degree due to a more suitable interaction between the active phase and support in mesoporous silica channels.

HDS of dibenzothiophene with CoMoS2 synthesized using elemental sulfur

An unsupported cobalt molybdenum sulfide catalyst was prepared using ammonium heptamolybdate, cobalt nitrate and elemental sulfur under reflux in ammonium hydroxide. The crystal structure of the precursor was identified using XRD and was determined to be a mix of CoMoO4 and elemental sulfur. The refluxed samples were decomposed in a tube furnace at 450°C under a constant flow of 10% H2:90% Ar gas mix. The freshly prepared catalyst was characterized using XRD and the LeBail fitting procedure, which confirmed the sample was a biphasic mixture of Co9S8MoS2. The synthesized sample was tested for the hydrodesulfurization of dibenzothiophene at 350°C. The removal of the dibenzothiophene was found to follow pseudo zeroth order reaction with two catalytic rates of 1.63×10−5molL−1·s−1 for the first 3.5h and 6.81×10−5molL−1·s−1 observed in the second 1.5h (or catalytic activities of 24.5 and 9.27molg−1s−1). After 5h of reaction, the catalyst showed approximately 93% conversion of the dibenzothiophene. The primary product of the hydrodesulfurization of the dibenzothiophene was biphenyl, which was approximately 80% of the products, and the minor product was cyclohexylbenzene at approximately 13%.

Preparation of Ni-Mo2C/carbon catalysts and their stability in the HDS of dibenzothiophene

The HDS activity and stability of Ni-Mo2C/AC catalysts, prepared by carbothermal hydrogen reduction (CHR) at different temperatures and with different Ni:Mo ratios, is reported. The highest HDS activity occurred for catalysts with Ni:Mo ratios of 0.38 and 0.19, when prepared at the relatively low CHR temperature of 550 and 600°C, respectively. Partial sulfidation of the Ni-Mo2C/AC catalysts occurred rapidly upon reaction in 2wt% dibenzothiophene (DBT) at 350°C and 2.1MPa H2. Uptake of S was enhanced with increased Ni content, resulting in the formation of Mo2C-MoS2 core-shell structures. The stack height of the MoS2 shell increased with increased Ni content and promoted the direct desulfurization of DBT.

Development of new hydrodesulfurization NiMo catalysts supported on Al2O3-TiSBA-15 hybrid materials

In the present work, a series of NiMo catalysts supported on hybrid materials consisting of mesoporous TiSBA-15 and conventional γ-alumina were prepared. Three hybrid supports were synthesized with 20, 40 and 60wt.% of TiSBA-15 and compared to pure γ-Al2O3 and TiSBA-15 counterparts. NiMo catalysts were prepared by incipient wetness co-impregnation of aqueous solutions of ammonium heptamolybdate and nickel nitrate precursors. Supports and catalysts were characterized by N2 physisorption, XRD, UV–vis DRS, temperature programmed reduction (TPR) and ammonia TPD. The sulfided NiMo catalysts were characterized by HRTEM and evaluated in the simultaneous hydrodesulfurization of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). All NiMo catalysts supported on hybrid materials showed better dispersion of the catalytically active MoS2 phase than the reference catalyst supported on the conventional γ-alumina material. Their activity was similar to that of the NiMo/γ-Al2O3 catalyst in HDS of DBT, but substantially higher in HDS of 4,6-DMDBT.

Hydrodeoxygenation of Phenol Over Hydrotreatment Catalysts in their Reduced and Sulfided States

The influence of the composition of reduced CoMo, NiMo and NiW catalysts on the catalytic performance in hydrodeoxygenation (HDO) of phenol has been investigated. γ-Al 2 O 3 and TiO 2 were used as supports. Different activity orders were obtained over γ-Al 2 O 3 and TiO 2 supported catalysts reflecting the critical role of the support. NiMo catalyst supported on γ-alumina proved to be the most active followed by the CoMo catalyst supported on titania. CoMo and NiMo lab made catalysts were proved to be more active compared to a reduced industrial CoMo catalyst supported on γ- alumina. An increase of phenol conversion in the range 52-230% was obtained at 350°C. A series of CoMo, NiMo and NiW catalysts supported on TiO 2 was also prepared using the Equilibrium - Deposition - Filtration (EDF) method. The application of this technique, instead of the classical impregnation, increased considerably the activity of the CoMo catalyst supported on titania (48% increase of phenol conversion at 350°C). The most active lab catalysts (wet impregnated NiMo catalyst supported on alumina, EDF CoMo catalyst supported on titania) and the industrial CoMo catalyst were evaluated after sulfidation for simultaneous HDO of phenol and HDS of dibenzothiophene. These catalysts exhibited comparable HDO activities while the first one proved to be superior in HDS. Overall, taking into account the significantly higher loading of the industrial catalyst in the supported elements compared to the lab made catalysts, the latter seems to be quite promising, even in the frame of a co-processing strategy.

Simultaneous tetralin HDA and dibenzothiophene HDS reactions on NiMo bulk sulphide catalysts obtained from mixed oxides

Large selectivity differences were found between supported and unsupported NiMoS catalysts in dibenzothiophene HDS and tetralin HDA.

One dimensional (1D) γ-alumina nanorod linked networks: Synthesis, characterization and application

A series of one dimensional (1D) alumina nanocomposites were prepared by a soft template sol–gel synthesis. The materials were calcined at 773K and an extensive characterization was carried out. Several arrays and individual 1D nanorods forming a linked network were observed by HRTEM. The presence of alumina nanorods induced novel electronic properties for alumina carrier. A decrease on the band gap energy detected by DRS UV–vis, and a shift on the binding energy of Al 2p core-level was observed by XPS revealing an increase on the conduction character. This unusual behavior for alumina materials is probably related with an oxygen deficiency over the nanorod surface confirmed by TEM–EDX analysis. Also, it was possible to correlate some surface morphological changes with the average molecular weight (AMW) of the “Pluronics”. The results show that a decrease for the nanorod average length is observed with an increase on the pluronic AMW. Besides, a proportional increase for the nanorods average diameter with the pluronic AMW is also observed. These results imply that it is possible to control de morphological characteristics of the nanostructures. The formation of the nanorods linked network give a rise to materials with high specific surface area and a very narrow pore size distribution in the mesoporous range. Some materials were used as a support to prepare NiWS catalysts and were tested in the HDS of dibenzothiophene with promising results. Finally a possible mechanism for the formation of the alumina nanorods is proposed in this work.

On the structure and hydrotreating performance of carbon-supported CoMo- and NiMo-sulfides

The sulfiding behaviour and hydrotreating performance of CoMo and NiMo on carbon catalysts were investigated, with a view to establishing the suitability of an active-carbon carrier for industrial hydrotreatment purposes. The sulfidation process (H2/H2S at 0.1 and 4MPa) was followed with 57Co Mössbauer emission spectroscopy, and X-ray absorption spectroscopy (Mo- and Co-edge). It turns out that the structural evolution of the CoMo/C catalyst is in broad terms very similar to that of a CoMo/Al2O3 one, including the type I→II phase transition at increased sulfiding pressure, albeit that some sintering takes place concomitantly. In the hydrotreating part a NiMo/C catalyst was employed, sulfided at 1 or 4MPa, in trickle-flow conditions at 3.5 (HDS) and 6 (HDN) MPa. It transpires that the adsorption properties of NiMo/C are quite different from those of a NiMo/alumina, in that dibenzthiophene, quinoline, and polyaromatics are much stronger adsorbed on the carbon-supported catalyst. This leads to very high dibenzothiophene HDS and quinoline HDN activities, but to a disappointing performance in the hydrotreatment of a heavy gasoil, where the polyaromatics can compete effectively for adsorption on the active HDS/N sites.

Unsupported NiMoAl hydrotreating catalysts prepared from NiAl-terephthalate hydrotalcites exchanged with heptamolybdate

Unsupported NiMoAl hydrotreating catalysts were prepared starting from NiAl-terephthalate layered double hydroxides (LDHs) with x values (Al/(Al+Ni) ratios) in the 0.3–0.8 range by ion exchange with ammonium heptamolybdate, followed by calcination at 723K. Mixed oxides containing ca. 33–43wt% molybdenum and Ni/Mo atomic ratios in the 0.5–1.4 range were obtained. There was loss in the long-range ordering of the LDHs in the c direction during the ion-exchange, but the local structure of the brucite layers was maintained. The calcined mixed-oxides had surface areas ranging from 26 to 122m2g−1. The catalysts were sulphided in situ and subsequently tested in the simultaneous dibenzothiophene (DBT) HDS and tetralin (THN) hydrogenation reactions in a high pressure batch reactor at 613K and 70bar. The catalysts had higher specific activity for both the HDS and the HDA reactions and much higher selectivity for the ring hydrogenation (HYD) route in the HDS of DBT than a conventional NiMo/Al2O3 catalyst. Their activities in both reactions were similar to those of an Al-free unsupported NiMo catalyst, but their preference for the HYD route was higher than that of the latter.

Synthesis, characterization and evaluation of unsupported porous NiS2 sub-micrometer spheres as a potential hydrodesulfurization catalyst

Nanostructured NiS2 has attracted interest due to its wide applications and special properties. Synthesis of a pure phase NiS2 in a single step has been a challenge. In this work, a new method for direct synthesis of uniform NiS2/SiO2 sub microspheres has been developed by ultrasonic spray pyrolysis. Colloidal silica was used as a sacrificial template to create the porous structure. After silica removal, hollow, porous NiS2 nano spheres were obtained. The product was characterized by using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction (XRD), transmission electron microscopy and N2 adsorption/desorption isotherm. XRD confirmed the formation of single phase pyrite NiS2. It was found that the porous spherical NiS2 has a surface area of ca. 300m2g−1. The HDS catalytic activity of NiS2 was evaluated using a model compound, dibenzothiophene (DBT). It showed a first order reaction rate constant of 1.51×10−4s−1gcata−1 at 320°C for HDS of DBT, which is significantly promising for further exploration.

Effect of titania grafting on behavior of NiMo hydrodesulfurization catalysts supported on different types of silica

In the present work, a comparison study of the NiMo hydrodesulfurization catalysts supported on different types of silica supports (nanostructured supports of MCM-41 and SBA-15-types and commercial amorphous silica) and the same ones modified by TiO2 grafting was undertaken. The aim of this study was to inquire on the effect of the characteristics of the primary silica supports on the activity and selectivity of the NiMo catalysts modified with titania in deep HDS. Supports and catalysts were characterized by nitrogen physisorption, small-angle and powder XRD, TPR, UV–vis DRS, and HRTEM, and tested in the simultaneous HDS of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). It was found that titania grafting on all silica supports resulted in a slight decrease of BET surface area and total pore volume. However, the characteristic p6mm hexagonal pore arrangement of the used nanostructured silica materials was not affected. Powder X-ray diffraction pointed out a good dispersion of Mo and Ni oxide species in all prepared catalysts. TPR characterization of the NiMo catalysts revealed some increase in the metal-support interaction after titania grafting on the silica surface. Further DRS characterization indicated that the best dispersion of Mo oxide species was obtained on the TiSBA-15 support. Titania addition to the silica supports also produced an increase in the dispersion of the sulfided NiMo phase, which was more marked for SBA-15 and commercial silica supports than for the MCM-41 (HRTEM). In line with the characterization results, titania addition to all silica supports resulted in an increase in the HDS activity of NiMo catalysts. However, this increase was smaller for the MCM-41 support than for the SBA-15 and amorphous silica supports used. The most active NiMo/Ti-SBA-15 catalyst resulted to be significantly more active (∼40%) than the reference NiMo/γ-Al2O3 catalyst in HDS of 4,6-DMDBT.

Effect of Potassium Content on the Performance of CoMo/Al2O3-MgO-K2O(x) Catalysts in Hydrodesulfurization of Dibenzothiophene

A series of CoMo catalysts supported on Al2O3-MgO modified with different amounts of potassium were prepared with the aim to study the influence of the content of that basic modifier on the physicochemical characteristics of the materials and its correlation with the observed catalytic performance. It was assumed that potassium addition would enhance the textural and structural stability to the magnesium formulations and also decrease the number of acidic sites and their strength. Materials were characterized by N2 physisorption, X-ray powder diffraction, thermodesorption of pyridine, and scanning electron microscopy. Catalytic performance was evaluated in the hydrodesulfurization reaction (HDS) using dibenzothiophene (DBT) as a model molecule. Results show that the addition of a small amount of potassium (below 5 wt % of the catalytic formulation of potassium oxide) decreases acidity of the catalytic formulation and enhances the direct desulfurization pathway of dibenzothiophene HDS.