CoMo Catalysts Research Articles

Melamine foam-supported CoMo catalysts with three-dimensional porous structure for effective hydrodesulfurization of thiophene

The performance of the hydrodesulfurization (HDS) catalysts is generally subjected to the characteristics of supports. In this work, the melamine foam (MF) was employed as the support for fabricating a series of three-dimensional porous (3DP) CoxMo/MF supported HDS catalysts. The properties of the obtained HDS catalysts were characterized by XRD, TG, SEM, TEM, and low-temperature N2 adsorption–desorption techniques. The characterization results demonstrated that the CoxMo/MF supported catalysts possessed the 3DP structure, in which the metal oxides were attached to the prismatic pillars of the MF framework. The activity test results illustrated that the thiophene conversion over the Co2.0Mo/MF catalyst could reach 96.96% under 1 MPa and 360 °C. The unique 3DP structure with rich meso-/macropores, low average length and average stacking of crystalline MoS2 promoted the HDS activity of the Co2.0Mo/MF catalyst. This research shows the potential application of MF support in the field of catalysis and provides the possible direction for the further development of the supported HDS catalysts.

Extraction and Recovery of Metals from Spent HDS Catalysts: Lab- and Pilot-Scale Results of the Overall Process

The present study proposes an overall recycling process for spent hydrodesulfurization (HDS) catalysts. The process put together stages already known in the technical literature, tested again with samples coming from the roasting stage in a pilot kiln, which is the most limiting stage of metal recovery from spent catalysts. These catalysts contain valuable metals like cobalt (Co), molybdenum (Mo), nickel (Ni), and vanadium (V). In particular, one Co-Mo catalyst was treated in order to optimize the roasting step (time, soda ash, and temperature) at a pilot scale and thus maximize the extraction yield of molybdenum (Mo) and vanadium (V). In particular, a dry Co-Mo catalyst was used. After roasting at 700 °C for 2.5 h, the best conditions, the catalysts underwent water leaching, separating Mo and V from Co and the alumina carrier, which remained in the solid residue. The pregnant solution was treated to remove arsenic (As) and phosphorus (P), representing the main impurities for producing steel alloys. V was precipitated as NH4Cl, and further calcined to obtain commercial-grade V2O5, whereas Mo was recovered as molybdic acid by further precipitation at a pH of around one. Thus, molybdic acid was calcined and converted into commercial-grade MoO3 by calcination. The hydrometallurgical section was tested on a lab scale. The total recovery yield was nearly 61% for Mo and 68% for V, respectively, compared with their initial concentration in the spent Co-Mo catalysts.

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.

Ex Situ Upgrading of Extra Heavy Oil: The Effect of Pore Shape of Co-Mo/γ-Al2O3 Catalysts

Co-Mo/γ-Al2O3 catalysts with different pore shapes were synthesized for the ex situ upgrading of extra heavy oils by hydrodesulfurization (HDS), hydrodemetallization (HDM), and hydrodeasphaltization (HDA). The catalysts were synthesized using aluminum oxides that were prepared by various methods. It was found that using the product obtained by the thermochemical activation of gibbsite leads to the formation of slit-shaped pores in aluminum oxide, while the application of the hydroxide deposition method by the precipitation of sodium aluminate and nitric acid gives cylindrical pores in aluminum oxide. Co-Mo catalysts synthesized using these two types of pores exhibit different catalytic activities. The catalyst synthesized on a carrier with cylindrical pores exhibited a higher catalytic activity in sulfur, heavy metals, and asphaltenes removal reactions that are synthesized on a carrier with slit-like pores. This is because the presence of cylindrical pores leads to a decrease in diffusion restrictions when removing large molecules of asphaltenes and sulfur-containing and metal-containing compounds.

Hydrotreatment of Supercritical Carbon Dioxide Extracts of Hydrothermal Liquefaction Lignocellulosic Biocrude

Raw lignocellulosic biocrude produced by hydrothermal liquefaction and its supercritical carbon dioxide extract (SE) were hydrotreated at 350–405 °C and for 2–6 h utilizing commercial CoMo and NiMo catalysts. The hydrotreatment reduced the oxygen content of the SE down to 1.6 wt %, while the minimum oxygen content of the hydrotreated biocrude (HBC) was 3.1 wt %. No coke formation was observed in the hydrotreatment of the SE, while the yield of coke was 13 wt % when processing the raw biocrude. The hydrotreated SE (HSE) samples exhibited molecular weights 24–61% lower than that of the HBC samples, with larger low-boiling fractions (up to diesel). The better quality of the HSE and the absence of coke, together with the lower metal content of SE (0.2 g/kg) versus BC (8.5 g/kg), suggest that the implementation of hydrotreatment on SEs, instead of raw lignocellulosic biocrude, is a promising option.

Production of hydroprocessed renewable diesel from Jatropha oil and evaluation of its properties

Alternative fuel research is primarily motivated by the expeditious depletion in fossil fuel supplies and the need to fulfill rigorous emission regulations, particularly greenhouse gas (GHG) emission for modern diesel engines. Hydroprocessed (or Hydrogenated) renewable diesel (HRD) is seen takes the one’s place with possible option for replacement of fuels for Diesel engines in the hunt for a substitute to fossils based petroleum diesel from diverse sustainable feedstocks such as vegetable oils from non-edible seeds, animal fats or algae oil. Because when we compare cetane number for HRD and petro diesel, it is higher for HRD than the other, which is seen as a probable drop in alternate fuels for compression ignition engines. During production of renewable diesel Hydro-deoxygenation is done first with the help of a catalyst and hydrogen gas, which may be used to upgrade bio-oil instead of hydro-desulfurization (removing of sulphur derivatives from the crude vegetable oil). A sulfided Nickel Molybdenum (NiMo) or Cobalt Molybdenum (CoMo) catalyst based on gamma alumina is utilised as a reference catalyst for HDO in the generation of renewable diesel and is used as a standard catalyst for a hydro-desulfurization process in refineries. Jatropha oil may be thoroughly transformed into paraffins in the diesel range at a pressure of 40 to 90 bar. The obtained product includes gases and different products therefore, it is then transferred for fractional distillation which gets separated at different boiling temperatures. The Physicochemical properties of a hydroprocessed renewable paraffinic fuel were assessed and compared to Biodiesel and traditional petro diesel. The major properties of hydroprocessed renewable diesel like cetane number, flash point and pour point were higher compared that of petroleum diesel, whereas kinematic viscosity and thermal stability was almost similar for both HRD and diesel.

Monolayer CoMoS Catalysts on Hierarchically Porous Alumina Spheres as Bifunctional Nanomaterials for Hydrodesulfurization and Energy Storage Applications

In this work, CoMoS catalysts were synthesized onto porous alumina spheres obtained using Pluronic P-123 (PS) or urea (US) and used as bifunctional nanomaterials for two energy applications: hydrodesulfurization and energy storage. For the first application, the catalysts were assessed in a hydrodesulfurization reactor using two model sulfur molecules, dibenzothiophene and 4,6-dimethyl dibenzothiophene, as well as feeding a heavy oil fraction. The results indicated that the spheres obtained by Pluronic P-123 allowed a greater dispersion degree of MoS2 slabs than US, indicating that the size and hierarchically porous structure of alumina spheres played a principal role as a booster of the HDS catalytic efficiency of DBT, 4,6 DMDBT and diesel fuel. Then, these catalysts were used for the electrocatalysis of the oxygen reduction and oxygen evolution reactions (ORR/OER), which take place in rechargeable Zn-air batteries. For the ORR, the CoMoS catalyst on PS in the presence of a conductive support (N-doped carbon nanotubes + graphene) displayed an overpotential of only 90 mV in comparison with Pt/C. Importantly, the chalcogenide enabled an increase in the stability, maintaining almost two times higher current retention than Pt/C for the ORR and IrO2/C for the OER. These results suggest that expended chalcogenides from the hydrodesulfurization industry can have a second life as co-catalysts for renewable energy storage systems, enabling a circular economy.

Effect of CoMo metal loading on H2 and CNTs production from biogas by integrative process

Effect of CoMo metal loading to MgO (1, 5, 30 and 50 wt%) on conversion of biogas by an integrative process was investigated at 900 °C under atmospheric pressure. The integrative process combines the direct methanation of CO2 in biogas and the CH4 decomposition to upgrade biogas to CH4 and decompose to hydrogen and carbon nanotubes. Methane dissociative reaction is governed by the concentration of active metals on the catalyst surface, while DRM reaction is suppressed. The 30 wt%CoMo catalyst shows the optimal loading for production of high-purity H2 (>90v/v%) and high yield of MWCNTs (2.33 gCNT/gCat-h) with 100%CO2 conversion and 95%CH4 conversion. Meanwhile, 1 wt%CoMo catalyst provided the single-walled CNTs with diameter of 2.5 nm, high surface area of 165 m2/g and high graphitization of IG/ID = 6.14.

Synthesis and characterization of Mo-blue-based sulfided CoMo catalysts for guaiacol HDO

Saccharose (SA) and citric acid (CA) were used as additives in P-doped CoMo/Al2O3 catalysts (Mo, Co and P at 12, 3, and 1.6 wt%, respectively) intended to be applied in guaiacol hydrodeoxygenation (HDO). One-pot impregnating solutions were prepared by MoO3 digestion in aqueous H3PO4, followed by C4H6CoO4•4H2O addition. Organics were added (SA/Co=1, CA/Co=2) at two different preparation stages to assess the effect of that step on catalysts properties. Method I: SA or CA was added in as-prepared Co-Mo-P impregnating solution, followed by pore-filling impregnation of alumina support. Method II: SA or CA at aforementioned concentrations was impregnated on the pristine carrier, followed by drying (120 °C, 2 h). Co-Mo-P phases were further deposited on modified supports through corresponding one-pot solutions. All materials were dried (120 °C) but not calcined. Cobalt complexation by CA and Mo-blue LMCT complex formation (SA-modified solids) were identified (UV-vis, oxidic samples). Partially reduced molybdenum (Mo6+ => Mo5+, by XPS) was observed after either organics addition that effect being more evident in SA-modified solids. Materials were gas-phase sulphided (H2S/H2 10%, 400 °C, 2 h) then studied by HR-TEM. Co-Mo-P phases impregnation in one-pot solution simultaneously deposited with SA rendered the materials of the highest MoS2 dispersion.

Effects of temperature and time on the facile low-temperature pre-sulfurization of tube-like unsupported Co-Mo catalysts for hydrodesulfurization

A Co-Mo sulfide catalyst with tube-like structure was prepared through a low-temperature pre-sulfurization process using rod-like CoMoO4 as the precursor. The pre-sulfurization temperature greatly affected the total pore volume, the concentration of CoMoS species, the microstructure of (Co)MoS2 slabs and the catalytic desulfurization activity. The increased temperature can promote the formation of hollow structure and the sulfurization degree of the precursor. It was found that the excessive temperature induced the Co atoms to form more isolated Co9S8 species, hindering the formation of highly active CoMoS species. Therefore, appropriate temperature is more favorable to form the (Co)MoS2 slabs with shorter length and higher stacking number, leading to more coordinatively unsaturated sites, especially the corner sites. According to the results of hydrodesulfurization reaction, the reaction rate of dibenzothiophene and the yields of liquid products are highly depended on the number of surface-active sites, which are mainly originated from the Type II CoMoS species. Moreover, the extended pre-sulfurization time can further improve the catalytic desulfurization activity of the catalyst at an appropriate pre-sulfurization temperature.

Hydrodesulfurization on Supported CoMoS2 Catalysts Ex Ammonium Tetrathiomolybdate: Effects of Support Morphology and Al Modification Method

Hydrodesulfurization on Supported CoMoS2 Catalysts Ex Ammonium Tetrathiomolybdate: Effects of Support Morphology and Al Modification Method

A Facile Synthesis of Highly Efficient MXene Supported CoMoS Catalysts for Hydrodesulfurization

AbstractIn this study, ammonium tetrathiomolybdate (ATM) and 2D‐layer MXene support were used to prepare more efficient MoS2 catalysts with cobalt promoter for the elimination of sulfur atoms in thiophene. A series of well‐dispersed and highly active MoS2 and Co−Mo−S phase on MXene catalysts were derived by thermal activation of precursors varying promoter cobalt to molybdenum molar ratio up to 0.6. The physicochemical properties of synthesized catalysts were characterized by XRD, TPR, SEM/EDS, XPS, HRTEM, and Raman spectroscopy. The as‐prepared MoS2/MXene and Co−MoS2/MXene catalysts were examined for thiophene hydrodesulfurization (HDS) at 300–400 °C. The synergetic effect between Co and few‐layer MoS2 on MXene, enhanced their HDS activity to ∼ 20.6 mmol g−1 h−1 with an excellent turnover frequency of about 55 h−1 achieved on Co−MoS2/MXene catalysts, which were 8‐fold higher than the conventional CoMoS/alumina catalyst. Co−MoS2/MXene catalysts produce high butenes selectivity ∼73% at low temperature, whereas, at high‐temperature alkane levels were increased ∼42% in CoMoS phase through hydrogen activation. Hence, the few‐layer MoS2 obtained from ATM and promoter Co intercalated MXene catalysts enhances the rate of C−S bond cleavage in HDS, and the result is scrubbing a large volume of sulfur atoms in clean fuel processes.

Synthesis of Higher Alcohols from Syngas over a K-Modified CoMoS Catalyst Supported on Novel Powder and Fiber Commercial Activated Carbons.

In the present study, a series of K-modified CoMoS catalysts with compositions of 10% K, 3.6% Co, and 12 wt % Mo supported over novel commercial activated carbons such as powder materials (DAC and OBC-1) and fiber materials (fabric active sorption (TCA) and nonwoven activated material (AHM)) were prepared and characterized by Brunauer-Emmett-Teller (BET), X-ray fluorescence (XRF), scanning electron microscopy (SEM), SEM–energy dispersive X-ray (EDX), and transmission electron microscopy (TEM). The catalytic activities for higher alcohol synthesis from syngas, conducted at T = 300–360 °C, P = 5 MPa, GHSV = 760 L h–1 (kg cat)−1, and H2/CO = 1.0, were investigated. Cat-TCA and Cat-AHM have shown a filamentous morphology with a strip axial arrangement and that a few longitudinal grooves and many irregular particles are distributed on the fiber surfaces. The degree of entanglement of the strip axial arrangement in AHM was found to be more than that in TCA, thus leading to form tangled MoS2 slabs on AHM and long linear slabs on TCA with long rim sites. The obtained results revealed that the CO conversion increases in the order Cat-TCA < Cat-OBC-1 < Cat-DAC < Cat-AHM. Ethanol, propanol-1, and methanol are the most predominant alcohol products in the collected liquid products, with the byproducts containing mainly butanol-1, isobutanol, amyl alcohol, and isoamyl alcohol. Cat-DAC and Cat-OBC-1 show higher selectivity toward C3+, C4+, propanol-1, butanol-1, isobutanol, and amyl alcohol-1 than Cat-TCA and Cat-AHM. For powdered activated carbons, microporous catalysts inhibited isomerization because the catalyst that contains the highest micropores (Cat-DAC) produced a considerable amount of linear alcohols compared with Cat-OBC-1.

CoMoS/modified-kaolin bi-functional hydrodesulfurization-olefin skeletal isomerization catalyst for FCC naphtha hydro-upgrading

Aiming at developing a bifunctional selective hydrodesulfurization (HDS) - olefin skeletal isomerization catalyst for fluid catalytic cracking (FCC) naphtha hydro-upgrading, in this article we present an acid-assisted dealumination method, the acid-modified kaolin (AMK-850-27) with tailored porosity and acidity and CoMoS bi-functional catalysts CoMo/AMK-850-27 was obtained. The catalytic performance was assessed with model FCC naphtha that is composed of thiophene (300 mg/kg) and 1-hexene (20%) in heptane. Compared with two catalysts used γ-Al2O3 and HZSM-5 as supports, CoMoS catalyst prepared with AMK-850-27 displayed compromise catalytic performance: balanced HDS activity and selectivity, high skeletal isomerization activity and low cracking activity, and excellent octane number preservation performance. This can be attributed to the following reasons: (i) AMK-850-27 possesses micro-meso-macro porosities and appropriate Brönsted acidity that can benefit skeletal isomerization activity but depress cracking activity; and (ii) The olefin isomers are more difficult to be hydrogenated than the corresponding linear terminal ones due to the steric effect of the branched olefins. This investigation providesa novel route to achieving deep desulfurization, appropriate olefin reduction and octane number preservation for FCC naphtha upgrading, acidic support with meso-macro-porosity can benefit olefin skeletal isomerization and the HDS selectivity but lower hydrocarbon cracking activity.

Electronic structure regulation of CoMoS catalysts by N, P co-doped carbon modification for effective hydrodesulfurization

Extensive efforts have been devoting to remove sulfur from transportation fuels to protect the environment. Here we present the synthesis of highly efficient hydrodesulfurization (HDS) catalysts by loading Co/Mo sulfides on various carbon modified γ-Al2O3 substrates. The synthetic strategy features facile sequential impregnation and pyrolysis process. The morphology, surface property, and pore structure of the catalysts were characterized by various techniques, and the catalytic performance were evaluated by a fixed-bed hydrodesulfurization unit. The optimized CoMo/NPC@γ-Al2O3 showed superior dibenzothiophene (DBT) removal rates (99%) and kHDS value (5.12 × 10-7 mol g−1 s−1) than those of CoMo@γ-Al2O3 at a relatively low temperature of 280 °C, revealing the effective modulation of carbon backbone. This remarkable HDS activity originated from the high sulfidation degree as well as electron-rich Mo species, which was attributed to the electron donating effect by N, P co-doping in the carbon skeleton. In addition, after the carbon modification, the decreased acid sites in γ-Al2O3 support and the electron-rich Mo sulfide resulted in a high selectivity of direct desulphurization (DDS) pathway over hydrogenation (HYD), leading to significant hydrogen energy economy. The density functional theory (DFT) calculations confirmed that the electron-donating effect of NPC enhanced the dispersion of Mo species and weakened the Mo-O/Mo-S bonds, creating more active sites. This work provides an effective strategy for rational design and synthesis of highly-efficient HDS catalysts in practical industrial application.

Molybdenum co-catalytic promotion for Fe3+/peroxydisulfate process: performance, mechanism, and immobilization

In this work, we proposed that molybdenum (Mo) powder as the cocatalyst could promote the sulfamethoxazole (SMX) decomposition in the Fe3+/peroxydisulfate (PDS) Fenton-like process. Efficient SMX elimination (96.7%) was reached after 20 min under the circumstances of 0.20 g·L−1 Mo, 0.50 g·L−1 PDS, 0.07 g·L−1 Fe3+, and beginning pH 5.4. Sulfate radicals were verified as the main active species according to the quenching experiment and electron spin resonance spectroscopy analysis. The Mo cocatalyst improved the Fe3+ reduction and PDS activation. According to the investigation of X-ray photoelectron spectroscopy for the valence state change of Mo before and after the reaction, the mechanism of Fe3+/Fe2+ circulation being initiated through the Mo4+ and Mo0 was presented. There was no obvious change of surface structure between the original and used Mo, as certified through X-ray diffraction and scanning electron microscope analyses. The mass spectrometry was used to determine the SMX degradation byproducts, and their toxicities were evaluated by the computational toxicology. Importantly, even after five cycles, the Mo still displayed excellent recyclability, and above 93% SMX was degraded in the fifth recycle. In the end, the immobilization of Mo was attempted by fixing Mo on the cyanoacrylate and agar, which also both showed the good co-catalytic effect. This research affords a promising inorganic co-catalytic Fenton-like system for water treatment.

Co-processing of Atmospheric Gas Oil with Rapeseed Oil Over Sulfur-Free Supported and Phosphorus-Modified Co-Mo and Ni-Mo Carbide Catalysts

Co-processing of Atmospheric Gas Oil with Rapeseed Oil Over Sulfur-Free Supported and Phosphorus-Modified Co-Mo and Ni-Mo Carbide Catalysts

Enhanced product quality through hydrodesulfurization of pyrolysis gasoline over a mixed metal oxide catalyst: An experimental and DFT study

Manipulating electronic properties of the hydrodesulfurization (HDS) catalysts can greatly impact the resulting product distribution. To address such effect decently in theoretical and experimental approaches, high-performance cobalt-molybdenum-supported alumina-titania (CoMo/Al2O3-TiO2) with different TiO2 loadings of 10–28 wt% were synthesized. The characterization of the catalysts was implemented by FE-SEM, TEM, XRD, BET/BJH (based on N2 adsorption–desorption), Fourier transform infrared spectroscopy (FTIR), H2-Temperature programmed reduction (H2-TPR), NH3-Temperature programmed desorption (NH3-TPD), and Thermal gravimetric analysis (TGA). The synthesized catalysts were evaluated through HDS of an industrial feedstock– pyrolysis gasoline (Pygas) in a pilot plant tubular fixed bed reactor. It was found that the modification of the electronic properties by titania could also increase the surface acidity while improving the reductive behavior of the tetrahedral and octahedral molybdenum species. In addition, the CoMo/Al2O3-TiO2 with 10 wt% titania content could excellently remove over 96% of sulfur-containing molecules in Pygas. Besides, the developed CoMo catalyst showed an increase in the aromatic compounds, resulting in improved product quality and value through the HDS process. Furthermore, the contribution of TiO2 to the synthesized catalyst was theoretically interpreted through the density functional theory (DFT) method. It was found that lower adsorption energy levels were estimated for the adsorption of the sulfur-bearing molecules on the CoMo/Al2O3-TiO2 than the CoMo/Al2O3 catalyst.

Phonolite Material as Catalyst Support for the Hydrotreatment of Gas Oil and Vegetable Oil Type Feedstocks.

Phonolite material has shown to be promising catalyst support for the deoxygenation of triglycerides. In this work, we continue with our previous research by synthesising and testing three acid-treated phonolite-supported Co-Mo, Ni-Mo and Ni-W catalysts for the hydrotreating of atmospheric gas oil and co-processing with rapeseed oil at industrial operating conditions (350–370 °C, WHSV 1–2 h−1, 5.5 MPa) in the continuous regime for more than 270 h. The phonolite-supported catalysts showed hydrotreating activity comparable with commercial catalysts, together with a complete conversion of triglycerides into n-alkanes. During co-processing, the Ni-promoted catalyst showed strong stability, with similar activity previous to the rapeseed oil addition. Our results enable us to evaluate the suitability of phonolite as catalyst support for the development of plausible alternatives to conventional hydrotreating catalysts for the co-processing of middle distillates with vegetable oils.

Brønsted acid-enhanced CoMoS catalysts for hydrodeoxygenation reactions

Brønsted solid acids greatly promote the hydrodeoxygenation activity of CoMoS catalysts through weakening Car–O bonds by protonation of the OH group.