Supported CoMo Catalysts Research Articles

Catalytic Deoxygenation of Oleic Acid Over CoMo/Zeolite Catalyst for Green Diesel Production

Due to the presence of certain oxygenated species, green diesel from deoxygenation (DO) technology was developed to replace traditional biodiesel. In this study CoMo-based catalyst was supported on zeolite for deoxygenation reactions. The catalyst was prepared by the wet impregnation method and then calcinated under a 20 mL min-1 N2 flow rate for 4 hours at a temperature of 550○C. The prepared catalysts were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), Thermo-Gravimetric Analysis (TGA), and Scanning Electron Microscopy (SEM) analysis. The effect of zeolite on the removal of the different oxygenated functional groups was investigated in the deoxygenation of oleic acid over supported CoMo catalysts at 350°C and atmospheric pressure. The deoxygenated liquid products were characterized by Fourier-transform infrared spectroscopy (FTIR), Gas Chromatography-Mass Spectrometry (GC-MS), and Higher heating value (HHV). Based on the study results, CoMo/Zeolite is give 90.86% hydrocarbon yield for 2 hrs. at 350°C and 300 rpm. Overall, The CoMo/Zeolite showed good catalytic performance due to its good physicochemical properties.

Synthesis of alumina-nitrogen-doped carbon support for CoMo catalysts in hydrodesulfurization process

More stringent environmental legislation imposes severe requirements to reduce the sulfur content in diesel to ultra-low levels with high efficient catalysts. In this paper, a series of CoMo/[email protected] catalysts were synthesized by combination of the chemical vapor deposition of nitrogen-doped carbon (NDC) using 1,10-phenanthroline and co-impregnation of Mo and Co active components. The optimal catalyst with additive of 25% 1,10-phenanthroline was screened by a series of property characterization and the hydrodesulfrization (HDS) active test. The amount of “CoMoS” active phase of the optimal CoMo/C3 catalyst increased 5.3% as compared with the CoMo/γ-Al2O3. The introduction of NDC improved the sulfidation degree of Mo by 21.8% as compared to the CoMo/γ-Al2O3 catalyst, which was beneficial to form more active sites. The HDS conversion of the NDC supported catalysts are higher than CoMo/γ-Al2O3 whether for the dibenzothiophene (DBT) or 4,6-dimethyl dibenzothiophene (4,6-DMDBT). Further hydroprocessing evaluation with Dagang diesel revealed that the CoMo/C3 catalyst possessed higher HDS property and the removal rate of DBTs in the diesel increased by 4%–11% as compared to the CoMo/γ-Al2O3 catalyst.

Hydrodeoxygenation of Anisole and Benzaldehyde Over Bifunctional CoMo/USY Catalyst

Hydrodeoxygenation (HDO) of anisole and Benzaldehyde over bifunctional zeolite USY (ultra-stable Y) supported CoMo catalysts has been studied. The catalyst consisted of metals that Co and Mo were loaded at three different sequences; Co loaded first (Co-Mo/USY), Mo loaded first (Mo-Co/USY), and simultaneously loaded (CoMo/USY). The experiments were conducted in a flow reactor within a temperature of 350 °C for an hour. The oxygen-free products from the HDO process were benzene and toluene compounds. CoMo/USY catalyst exhibited the best catalytic activity of anisole towards the total production of aromatic hydrocarbons yield by 9.17%. It was also found that Mo-Co/USY catalyst exhibited the best catalytic activity of Benzaldehyde with aromatic hydrocarbons yield by 10.46%.

Effective catalytic deoxygenation of palm fatty acid distillate for green diesel production under hydrogen-free atmosphere over bimetallic catalyst CoMo supported on activated carbon

Palm fatty acid distillate (PFAD) is considered as an inedible and renewable feedstock for the production of green diesel. In the current study, green diesel was successfully synthesised via catalytic deoxygenation of PFAD in an environment free of H2 using a mesoporous activated carbon (AC) supported CoMo catalyst with various molybdenum (Mo) concentrations (5–20 wt%). Based on the study results, bimetallic catalyst Co10Mo10/AC formulation exhibited excellent catalytic performance with 92% hydrocarbon components (C8-C20) yield and 89% selectivity for n-(C15 + C17) with a total acid number of 24 mg KOH mg−1. Based on a comparison study with various supports (AC, γ-Al2O3, TiO2), the AC-supported CoMo catalyst showed higher deoxygenation activity than both Co10Mo10/γ-Al2O3 and Co10Mo10/TiO2 owing to the super acid-base sites as a result of synergism between the CoMo and AC support. The Co10Mo10/AC catalyst demonstrated excellent stability during the study as it maintained the hydrocarbon components yield and selectivity of n-(C15 + C17) >80% until the sixth run.

Effect of Co-Mo catalyst preparation and CH4/H2 flow on carbon nanotube synthesis

Supported Co-Mo catalysts with a given ratio of metals were prepared from polyoxomolybdate Mo12O28(μ2-OH)12{Со(H2O)3}4 using impregnation and combustion methods. Effects of the type of catalyst and the ratio and flow of methane and hydrogen gases on the structure of carbon nanotubes (CNTs) synthesized by catalytic chemical vapor deposition (CCVD) method were studied using transmission electron microscopy and Raman spectroscopy. The catalyst prepared by combustion method yielded mainly individualized CNTs, while the CNTs were highly entangled or bundled when impregnation method was used. In both cases, addition of hydrogen to methane led to reduction of the CNT yield. The samples synthesized using two different catalysts and the same CH4/H2 ratio and flow of gases were tested in electrochemical capacitors. A higher specific surface area of the CNTs grown over impregnation-prepared catalyst caused a better performance at scan rates from 2 to 1000 mV/s.

Catalytic hydropyrolysis of biomass using supported CoMo catalysts – Effect of metal loading and support acidity

Catalytic hydropyrolysis of biomass to green fuels was performed using supported, sulfided CoMo catalysts. With MgAl2O4 as support material the CoMo loading was varied between 4.1 and 12.0 wt% at constant Co/Mo atomic ratio of 0.3. Increasing the metal loading decreased the amount of oxygen in the condensed organic phase from 9.0 to 4.7 wt% on dry basis (db) and the condensable organic yield decreased from 25.2 to 22.7 wt% on dry ash free (daf) basis, corresponding to a decrease in the carbon recovery from 39 to 37%. Using zeolite H-ZSM-5 mixed with alumina as support with a CoMo loading of 4.1 wt%, the condensed organics contained only 5.2 to 6.1 wt% db oxygen. The condensable organic yield was between 23.9 and 24.4 wt% db, and the carbon recovery was 39–40%. Thus using an acidic support can remove the oxygen without decreasing the carbon recovery. The latter was ascribed to alkylation of the aromatics when the zeolite support was used.Elemental maps of the spent catalysts were obtained using STEM-EDS, showing that the CoMo phase was mainly located as monolayer MoS2 slab structures (>93%) on the support and indicated a high dispersion of cobalt, consistent with incorporation of Co into the MoS2 structure in the CoMoS phase. Potassium was observed on all the spent catalysts, indicating transfer of alkali metal from the biomass to the catalyst. Potassium may decrease the acidity of the catalyst over time, thus reducing the positive effect of using a more acidic support.

Hydrogen production over Co-promoted Mo-S water gas shift catalysts supported on ZrO2

A series of CoMo-S/ZrO2 catalysts were prepared by modifying Co and Mo content using incipient wetness impregnation method, investigated in the water gas shift (WGS) reaction in the presence of H2S and characterized by TEM, XRD, Raman, TPR, and XPS. The supported CoMo-S catalyst corresponding to the CoMo-O monolayer coverage displayed the presence of highly dispersed CoMo-S species that were characterized by the highest extent of sulfidation. The presence of cobalt facilitated the formation of active CoMo-S species that were more H2S-dependent as compared to Mo-S entities. The Co/Mo = 0.3 catalyst at monolayer CoMo-O coverage was the most active and thermally stable, as well as the least H2S-dependent during 4 weeks of WGS reaction among all catalysts investigated.

Kinetic modeling of lignin catalytic hydroconversion in a semi-batch reactor

A kinetic modeling for lignin catalytic hydroconversion over a supported CoMoS catalyst in a semi-batch reactor has been constructed based on analysis results from Gel Permeation Chromatography (GPC) and two-dimensional Gas Chromatography (GC × GC). The model includes 15 pseudo-component lumped products classified by their states and functional groups. Hydrogen consumption, liquid-gas mass transfer resistance and vapor-liquid equilibrium are accounted for. Physical and chemical parameters were estimated from experiments carried out at 350 °C and 80 bar. The resulting model is able to fit the experimental data well. From estimated parameters, it is deduced that the bottlenecks of lignin catalytic hydroconversion are the deeper conversion of the soluble oligomeric fractions and the relatively slow hydrodeoxygenation rate.

CoMo/Al2O3 hydrotreating catalysts prepared from single Co2Mo10-heteropolyacid at extremely high metal loading

A series of alumina supported CoMo catalysts with different molybdenum surface density was prepared using incipient wet impregnation method and applying H6[Co2Mo10O38H4] (Co2Mo10HPA) as a single oxidic precursor. Dried and sulfided catalysts were characterized by a variety of techniques, such as N2 adsorption, micro-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM). Catalytic properties have been examined in co-hydrotreating of dibenzothiophene and naphthalene using a fixed bed high-pressure flow reactor. It was found that using Co2Mo10HPA as a single precursor enables more than the double increase of maximum metal loading compared to conventional compounds. This also contributed to a significant increase in catalytic activity in hydrotreating.

Comparison of γ and δ-Al2O3 supported CoMo catalysts in the hydrodesulfurization of straight-run gas oil

The effect of two different crystal species of alumina on hydrodesulfurization activity of the corresponding CoMo catalysts was studied. Cylindrical extruded alumina with two different crystal structures i.e. γ-Al2O3 and δ-Al2O3 was prepared using boehmite and nitric acid as a peptizing agent by calcination at 550 ˚C and 900 ˚C, respectively. The Al2O3 support were impregnated with 9 wt.% of Mo and 2 wt.% Co via incipient wetness impregnation method. The CoMo/Al2O3 catalysts were used for hydrodesulfurization (HDS) and hydrodenitrification (HDN) of Iranian straight-run gas oil (ISRGO). The supports and catalysts were characterized by nitrogen adsorption-desorption isotherm, XRD, UV-vis-DRS, TPD, TPR and ICP-OES. The HDS activity of CoMo/γ-Al2O3 catalyst was higher than that of CoMo/δ-Al2O3 and was found to be 95.74%. This result was due to the formation of larger CoMoO4 and MoO3 crystals in CoMo/δ-Al2O3 catalyst which reduces the active metal phase dispersion and the performance of the catalyst. The HDS activity of CoMo/γ-Al2O3 catalyst was remarkable as the metal content of the catalyst was low. The HDN activity of CoMo/γ-Al2O3 was also about 66%.

Hydrotreating of waste cooking oil over supported CoMoS catalyst – Catalyst deactivation mechanism study

The hydrotreating of waste cooking oil (WCO) to produce fuels not only solves waste problem but also recycles energy. CoMoS is regarded as an effective catalyst for the deoxygenation of triglyceride during the hydrotreating process; however, it is easy to deactivate. This article studied the deactivation mechanism of a supported CoMoS commercial catalyst during the hydrotreating of WCO. It was the first time to find triglyceride deoxygenation over different active sites during CoMoS catalyst deactivating process: saturated hydrocarbons were the primary products over MoS2 on the presulfided CoMoS catalyst, and unsaturated hydrocarbons were produced over MoO3 on the spent CoMoS catalyst as the transformation of the MoS2 into MoO3 occurred under high temperature operation. Three causes were observed for the deactivation of the studied catalyst: by-product water, loss of sulfur, and coke deposition. Low temperature operation at 275°C can control the deactivation of CoMoS catalyst due to coke deposition. In-situ drying and resulfiding the spent catalyst were proposed as methods to regenerate the spent catalyst.

Catalytic performance of CoMo catalysts supported on mesoporous ZSM-5 zeolite-alumina composites in the hydrodesulfurization of 4,6-dimethyldibenzothiophene

Composite materials (AZ-M-x) were prepared by mechanically mixing the mesoporous zeolite ZSM-5 (MZSM-5) and γ-Al2O3. This composite was employed as a support for CoMo catalysts (CoMoS/AZ-M-x). The CoMoS/AZ-M-x catalysts show high activity (TOF=2.1–3.0×10−3s−1) in the hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) as compared to the CoMo catalyst supported on γ-Al2O3 (CoMoS/γ-Al2O3, TOF=1.9×10−4s−1), and the HDS activity increased with the MZSM-5 content in the composites. In contrast, the HDS activity of a mixture of microporous ZSM-5 with γ-Al2O3 supported CoMo catalyst is similar to that of the CoMoS/γ-Al2O3 catalyst. Compared with microporous ZSM-5, introducing MZSM-5 into γ-Al2O3 improves the mesoporous structure of the composites, which benefits mass transfer of the reactant molecules. Furthermore, MZSM-5 in the composites modifies their surface properties with abundant acidic hydroxyl groups, which can weaken the Mo-support interaction, leading to modifications in the morphology of the MoS2 phases to form multi-stacked MoS2 active phases on the CoMoS/AZ-M-x catalysts.

Strategy to produce highly loaded alumina supported CoMo-S catalyst for straight run gas oil hydrodesulfurization

A simple postmodification synthesis is proposed to produce large pore volume alumina, with addition of a porogen during the peptization step, which is an industrial process preceding alumina shaping. By adjusting the synthesis parameters, obtained alumina present improved textural properties compared to conventional ones: specific surface areas between 380 à 430m2g−1, large pore diameters between 12 and 20nm and consequently large pore volumes. This allowed to prepare highly loaded catalysts, at a density of 4atMo.nm−2, without the formation of undesirable bulk molybdenum-cobalt oxide species despite the high molybdenum content. Catalysts performance were evaluated in thiophene HDS, where the activity varied by a factor 1.5. The most performant solid of the series was then tested in the HDS of a straight run gas oil under industrial conditions: it showed significantly improved activity compared to that of a catalyst prepared from a commercial alumina with the same molybdenum density, with a temperature gain of 17°C at 100ppm residual sulfur. Moreover, the catalyst activity remained stable after one week of testing. This work thus evidences that the development of alumina supports with enhanced textural properties is an efficient way to improve the performance of HDS CoMo catalysts.

Potential of templated mesoporous aluminas as supports for HDS CoMo catalysts

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

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

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

Effects of nano-structured CoMo catalysts on hydrodeoxygenation of fast pyrolysis oil in supercritical ethanol

Effects of in-house prepared CoMo catalysts supported on various nano-structured materials (activated carbon, γ-alumina, HZSM-5, MCM-41 and SBA-15) and a commercial catalyst of Ru/C were compared for hydrodeoxygenation (HDO) of fast pyrolysis oil (PO) in supercritical ethanol at 300 and 350°C. All catalysts proved to be effective for significantly reducing the molecular weight of the PO by HDO treatment at 350°C. Although Ru/C catalyst produced the highest oil yield at both temperatures (66.6wt% at 300°C and 61.0wt% at 350°C) with the lowest and negligible coke formation (<1wt%), the catalyst is very expensive and difficult for regeneration, so it is not a viable catalyst for bio-oil upgrading on a large scale. Among all the supported CoMo catalysts, CoMo/MCM-41 produced the highest yield of oil products (light oil (OL)+heavy oil (HO)) of the highest H/C molar ratio. With this catalyst, the oil yield attained 61.9wt% at 300°C and 57.8wt% at 350°C, and the spent catalyst after regeneration produced almost the same oil yields as the fresh one. In addition, CoMo catalysts supported on MCM-41 and SBA showed better resistance to coke/carbon deposition in the HDO process, compared with CoMo catalysts supported on HZSM-5 and Al2O3.

MgO Nanosheet Assemblies Supported CoMo Catalyst with High Activity in Hydrodesulfurization of Dibenzothiophene

A magnesium oxide nanosheet assembly (NS-MgO) with high surface area (255 m2/g) and nanopore volume (0.30 cm3/g) was prepared by a pressure-assisted carbonation method at large scale. After loading of cobalt and molybdenum (CoMo) species and followed by sulfidation, the NS-MgO supported CoMo catalyst (Co-MoS2/NS-MgO) exhibits high activity (94.2%) and good nitrogen tolerance in the hydrodesulfurization (HDS) of dibenzothiophene (DBT), compared with a conventional γ-alumina-supported CoMo catalyst (64.1%). These results are attributed to the difference in the basicity of the NS-MgO and γ-Al2O3 supports. The large amount of the middle strong basic sites on NS-MgO can avoid the polymerization of Mo species and form small Mo oxide clusters. After sulfidation, the small MoS2 clusters with shorter lengths and less stacking formed on the NS-MgO contribute to an increase in the sites available for Co promotion, resulting in the Co-MoS2/NS-MgO catalyst with high HDS activity.

Preparation of Alumina-supported Cobalt–molybdenum Catalysts by Sol-gel Method and Hydrodesulfurization Activities

Al2O3-supported Co and Mo catalysts were prepared by the sol-gel method, in which Co and/or Mo species were added at the hydrolysis of Al tri-s-butoxide. XRD patterns, N2 adsorption and desorption, amounts of NO adsorption and NO species by FT-IR were measured to characterize the catalysts. Catalysts with active components Co and Mo separately supported by the sol-gel method had higher activity for hydrodesulfurization of dibenzothiophene. Mo-Co/Al2O3, in which Mo species was supported on Co/Al2O3 by the sol-gel method, showed the highest activities at lower temperature, indicating that the Co species was effectively dispersed on Al2O3 during the preparation of Co/Al2O3. Catalysts in which Co and Mo species were simultaneously supported had lower activity, indicating that both Co and Mo species were dispersed and reduced interaction between Co and Mo. Co-Mo/sol-gelAl2O3, with the Co species supported on Mo/sol-gelAl2O3, showed the highest activity among sol-gelAl2O3 supported CoMo catalysts, indicating that the Mo species was effectively dispersed during the preparation of Mo/sol-gelAl2O3. Biphenyl was selectively obtained. NO adsorption measurement showed that the amount of NO adsorbed was almost same for Mo-Co/Al2O3 sulfided once or twice. In contrast, sol-gelCoMo/Al2O3, with the Co and Mo added simultaneously by the sol-gel method, showed significant decrease in NO adsorption after second sulfiding, which would be related to the lower stability of sol-gelCoMo/Al2O3 prepared by the sol-gel method. Al2O3-supported Co-Mo catalysts prepared using the sol-gel method had relatively high surface areas (282-544 m2/g) and relatively smaller pore sizes (3.7-6.3 nm).

Synthesis of CoMo catalysts supported on EMT/FAU intergrowth zeolites with different morphologies and their hydro-upgrading performances for FCC gasoline

The EMT, EMT/FAU intergrowths and FAU zeolites were synthesized and applied as the additives of the catalysts for FCC gasoline hydro-upgrading. The physico-chemical properties of the as-synthesized catalysts were characterized by various techniques including XRD, N2 adsorption–desorption, HRTEM, SEM, etc. The results revealed that the zeolite-incorporated catalysts exhibited high specific surface areas, pore volumes and suitable acidities. Among the supported CoMo catalysts containing pure EMT zeolite with different particle sizes, the micrometer-sized EMT-incorporated catalyst CoMo/AE-3 showed the highest HDS efficiency (96.1%), but with the greatest loss of octane number (2.3 unit) due to its excessive olefin saturation. Moreover, compared with the supported CoMo catalysts containing micrometer-sized EMT and EMT/FAU intergrowth zeolites, the EMT/FAU-incorporated catalyst CoMo/AE-5 (CoMo/EMT/FAU-2-γ-Al2O3) with excellent pore structure and suitable amounts of B and L acidity sites exhibited a good balance in HDS efficiency (94.6%) and RON preservation (0.5 unit). This could be ascribed to the synergy of zeolite EMT and zeolite FAU that balanced the functions among the HDS, aromatization and isomerization.

The suppression of a basic nitrogen compound influence on hydrodesulfurization activity of dibenzothiophene in treated diesel over Al2O3 supported CoMo catalysts by ZrO2 as a secondary support

In this study, the effect of ZrO2 as a secondary support on HDS activity of dibenzothiophene in treated diesel over CoMo/Al2O3 catalysts has been investigated. The HDS activity of all prepared catalysts was evaluated at 350°C and 8MPa. It was found that CoMo/Al2O3–ZrO2 catalyst with 10wt.% of ZrO2 exhibited the highest HDS activity. In the presence of pyridine, a basic nitrogen compound, the addition of ZrO2 obviously suppressed the influence of pyridine on the HDS activity of CoMo/Al2O3 based catalyst. These can be explained by the decrease of the total amount of acid sites on CoMo/Al2O3 catalyst when ZrO2 was added.