CoMo Catalysts Research Articles

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.

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.

Codeposition of Nanocrystalline Co-Mo Catalysts with a New Fluffy Microstructure for Hydrogen Evolution Reaction Based on N,N-Dimethylformamide and Ethylene Glycol System

Codeposition of Nanocrystalline Co-Mo Catalysts with a New Fluffy Microstructure for Hydrogen Evolution Reaction Based on N,N-Dimethylformamide and Ethylene Glycol System

Using Transient XAS to Detect Minute Levels of Reversible S-O Exchange at the Active Sites of MoS2-Based Hydrotreating Catalysts: Effect of Metal Loading, Promotion, Temperature, and Oxygenate Reactant

Modulation excitation spectroscopy (MES) coupled with time-resolved X-ray absorption spectroscopy (XAS) was applied to unpromoted and Co-promoted Mo-based hydrotreating catalysts (i.e., Mo and CoMo catalysts) for investigating the minute as well as instantaneous differences in active site composition under the influence of H2S and H2O. Transient experiments during alternating sulfur- and water-rich conditions were performed at temperatures between 400 and 500 °C using catalysts with varying Co/Mo metal loadings to study the correlative effect of these factors on the stability of the active sites. For both types of catalysts, the features of the demodulated Mo K-edge spectrum matching the difference spectra of the MoS2 and MoO3 references indicate a reversible oxidation–sulfidation process during H2O/H2S cycling. In the case of CoMo catalysts with increasing metal loadings, transient XAS at the Mo K- as well as Co K-edge revealed minute levels of S-O exchange at both sulfided Mo and Co sites, although 26 to 47% of the Co was bound as stable CoAl2O4, which does not form a bulk sulfide. Thus, even in the presence of multiple Co phases (oxide and sulfide) and a low number of active sites relative to the total number of Mo atoms, transient XAS can successfully detect the changes occurring over both the active Co and Mo sites. Furthermore, the comparison of the amplitude of the demodulated spectra showed that Mo atoms are more prone to S-O exchange with increasing temperature, while Co promotion stabilized the molybdenum sulfide. MES-coupled XAS experiments with 1-propanol performed to evaluate the degree of S-O exchange in the presence of another oxygenate reactant revealed the higher affinity of water toward these sulfided Mo sites as compared to 1-propanol.

Controllable Synthesis of Defect-Rich CoMoS Catalysts with Different Morphologies for the Ultradeep Hydrodesulfurization of 4,6-Dimethydibenzothiophene.

CoMoS catalysts with controllable morphology are prepared by a single-source precursor hydrothermal method using sodium diethyldithiocarbamate trihydrate (DDTC) as the ligand and the sulfur source. The effects of the single-source precursor, the pH of the hydrothermal solution, and the surfactant with respect to the morphology, nanostructure, and hydrodesulfurization (HDS) activity of the CoMoS catalyst are investigated. It is revealed that the coordination between the metal atom and DDTC can effectively control the in-plane and out-of-plane crystal growth of MoS2 and promote the formation of the CoMoS active phase. The lower pH value of the hydrothermal solution facilitates the synthesis of CoMoS catalysts with improved purity, lower crystallinity, and smaller nanocrystallites, and the different surfactants would significantly change the morphologies. For HDS activity, the conversion efficiency of 4,6-DMDBT is increased from 71 to 99% by the CoMoS catalysts that have fewer stacking layers of MoS2 slabs. While the high HDS activity is maintained, a notable improvement in selectivity for the direct desulfurization (DDS) pathway is observed for the CoMoS-CTAB catalyst, where the average slab length of MoS2 is the longest.

CoMo heterohierarchical foam-structured cathode for anion exchange membrane water electrolyzer

It is important to consider the synergy of heterostructures to improve the slow kinetics of water dissociation in the alkaline hydrogen evolution reaction (HER). Herein, we report a simple method to design a heterohierarchical CoMo catalyst. The CoMo catalyst was prepared by simple one-pot electrodeposition on carbon paper (CP). The CoMo/CP catalyst was optimized for the alkaline HER by controlling the electrodeposition bath conditions, potential, and time. The optimized catalyst shows the heterohierarchical structure containing the electrically conductive metallic Co in the bulk and Mo-incorporated Co containing Mo4+ at the surface. It exhibited a lower HER overpotential of 0.11 V at −20 mA/cm2 compared to those of the others owing to the synergetic effect of the between the Co and Mo incorporated Co. The results highlight the advantages of the simple method developed herein for the design of heterohierarchical catalysts.

Ultradispersed (Co)Mo catalysts with high hydrodesulfurization activity

In spite of the huge worldwide interest for single-atom and ultradispersed catalysts, metal atoms coordinated with sulfur are rarely addressed. In this work, ultradispersed molybdenum-based catalysts were obtained by adsorption of three thiomolybdates of different nuclearity (n = 1, 2, 3) on high-surface-area S-doped carbon, followed by sulfidation in H2S/H2 flow at 350 °C. Scanning transmission electron microscopy (STEM) and X-ray absorption spectroscopy (XAS) attest that single atoms and few-atom clusters are predominant on the surface of the materials after adsorption, as well as after sulfidation and thiophene HDS reaction. Independently on the nature of the thiomolybdate precursor, sulfidation leads to catalysts with specific thiophene HDS activity exceeding that of a conventional supported MoS2 reference. Ultradispersed clusters were further promoted with cobalt, yielding HDS turnover frequencies 2–3 times higher than those of reported benchmark CoMoS catalysts. These findings provide new insights into the previously debated issues of structure-activity relationships for HDS catalysts and expand the range of applications of atomically dispersed catalysts.

Oxygen functionality and chain length effects in HDO: Impact of competitive adsorption on reactivity

The unavoidable and significant impact of compounds with different oxygen functionalities and carbon number on each other in hydrodeoxygenation (HDO) has been experimentally assessed over NiMo and CoMo catalysts in a wide temperature range from 100 °C to 350 °C, at a total pressure of 6 MPa, a feed to catalyst ratio of 1.22 goxygenate gcat−1h−1 and a concentration of 1.5 wt% of each oxygenated compound in n-decane. Overall, the model component conversion over the NiMo catalyst was higher than that over the CoMo catalyst. Compounds with an aldehyde functionality exhibited higher reactivity compared to compounds of the same chain length with a carboxylic acid or an alcohol functionality. The presence of carboxylic acids in feed mixtures along with aldehydes and aromatic oxygenates, shifted the conversion of the latter two to higher temperatures. This behavior could be attributed to competitive adsorption effects between the components with different functionalities and chain lengths.

Mesityl Oxide Reduction by Using Acid-Modified Phonolite Supported NiW, NiMo, and CoMo Catalysts

Mesityl oxide is standardly used to produce methyl iso butyl ketone but it can be also used to produce other useful compounds. Three catalysts were used for the reaction of the mesityl oxide reduction. They were NiW, NiMo, and CoMo supported on phonolite modified by HCl (metals/Ph-HCl). The fresh catalysts were characterized by XRD, XRF, BET surface, Hg porosimetry, SEM, H2-TPR, NH3-TPD, CO2-TPD. The materials were directly used, previously reduced in H2 or sulfided for the mesityl oxide reduction under H2 atmosphere. The reaction was performed in an autoclave at T = 375 °C, p = 50 bar (H2), and TOS = 1.5 h. The products were analyzed by GC/MS, GC/FID-TCD, ATR. The main products were methyl isobutyl ketone, 2-methyl pentane, and 2-methyl-2-pentene. Sulfided metal catalysts were the most active in the methyl isobutyl ketone, where the NiWSx/Ph-HCl catalyst showed the highest activity. For the non-previously-activated and hydrogen activated catalysts the most active catalyst was the NiMo/Ph-HCl for the production of methyl isobutyl ketone. The catalyst CoMo/Ph-HCl activated in hydrogen was the most active for the production of 2-methyl pentane compared to the other two hydrogen-activated materials.

Extended Catalyst Lifetime Testing for HTL Biocrude Hydrotreating to Produce Fuel Blendstocks from Wet Wastes

This paper reports on the catalyst stability of the hydrotreatment of HTL (Hydrothermal Liquefaction) biocrudes to produce finished liquid transportation fuel blendstocks. We report the stable hydrotreating of HTL biocrude derived from sewage sludge and food waste over industrially relevant hydrotreating CoMo and NiMo catalysts at relevant catalyst activities. The use of wet-waste-derived HTL biocrudes derived from both food waste and sewage sludge in the hydrotreater campaign strengthens the case that HTL biocrudes derived from a variety of wet-waste feedstocks can be upgraded without significant catalyst instability over industrially relevant hydrotreater time-periods. Stable hydrotreating performance was obtained with each feedstock. The overall yield was approximately 85% with all HTL biocrudes. Over 1500 h of steady-state operation, minimal deactivation was observed. These results indicate that a hydrotreatment process to upgrade can be stable for industrially relevant times, a critical roadblock to derisking commercialization. The upgraded product produces a diesel-rich (∼70% in the 150–350 °C range) fuel blendstock, with high cetane due to the high fraction of alkanes. Further, we report the impact of process levers on hydrotreating performance on a fully broken-in catalyst (following 1500 h of steady-state operation). The long-term catalyst stability presented here is an important demonstration to derisk HTL commercialization.

Visible-Light-Active CuO x -Loaded Mo-BiVO4 Photocatalyst for Inactivation of Harmful Bacteria (Escherichia coli and Staphylococcus aureus) and Degradation of Orange II Dye.

In the present study, Mo-BiVO4-loaded and metal oxide (MO: Ag2Ox, CoOx, and CuOx)-loaded Mo-BiVO4 photocatalysts were synthesized using a wet impregnation method and applied for microbial inactivation (Escherichia coli and Staphylococcus aureus) and orange II dye degradation under visible-light (VL) conditions (λ ≥ 420 nm). The amount of MO cocatalysts loaded onto the surface of the Mo-BiVO4 photocatalysts was effectively controlled by varying their weight percentages (i.e., 1–3 wt %). Among the pure Mo-BiVO4, Ag2Ox-, CoOx-, and CuOx-loaded Mo-BiVO4 photocatalysts used in bacterial E. coli and S. aureus inactivation under VL irradiation, the 2 wt % CuOx-loaded Mo-BiVO4 photocatalyst showed the highest degradation efficiency of E. coli (97%) and S. aureus (99%). Additionally, the maximum orange II dye degradation efficiency (80.2%) was achieved over the CuOx (2 wt %)-loaded Mo-BiVO4 photocatalysts after 5 h of radiation. The bacterial inactivation results also suggested that the CuOx-loaded Mo-BiVO4 nanostructure has significantly improved antimicrobial ability as compared to CuOx/BiVO4. The enhancement of the inactivation performance of CuOx-loaded Mo-BiVO4 can be attributed to the synergistic effect of Mo doping and Cu2+ ions in CuOx, which further acted as an electron trap on the surface of Mo-BiVO4 and promoted fast transfer and separation of the photoelectron (e–)/hole (h+) pairs for growth of reactive oxygen species (ROS). Furthermore, during the bacterial inactivation process, the ROS can disrupt the plasma membrane and destroy metabolic pathways, leading to bacterial cell death. Therefore, we provide a novel idea for visible-light-activated photocatalytic antibacterial approach for future disinfection applications.

Non-oxidative conversion of real low density polyethylene waste into hydrogen and carbon nanomaterials over MgO supported bimetallic Co-Mo catalysts with different total Co-Mo contents

A series of bimetallic CoMo/MgO catalysts with different total metal contents from 10 up to 60 wt% and a fixed Co/Mo weight ratio of 4/1 were prepared and employed for the first time to transform real low-density polyethylene (LDPE) waste into hydrogen and carbon nanomaterials through a two-stage process. The waste was thermally cracked at 500 °C to non-condensable gases which then decomposed over CoMo/MgO catalysts at 700 °C to obtain the desired products. Both fresh and spent CoMo/MgO catalysts were characterized by XRD, H2-TPR, FTIR, Raman, BET, TEM, and TGA techniques. The results showed that the catalytic activity and stability were increased with the successive increase of CoMo content up to 40 wt%. Both 30CoMo/MgO and 40CoMo/MgO catalysts exhibited higher catalytic activity where more than 90% H2 yield was obtained. This behavior could be attributed to the excessive formation of different types of mixed oxide species such as MgCoOx, CoMoOx and MgMoOx as shown from XRD, TPR and Raman results. In fact, the presence of these species enhances the dispersion and stabilization of Co and Mo particles in the catalyst matrix, resulting in improved catalyst performance. TEM, Raman spectra, and TGA results showed that high-quality CNMs with various structures such as regular, bamboo, cup stacked carbon nanotubes were deposited over all CoMo/MgO catalysts depending on the CoMo content.

Hybrid CoMoS - polyaniline nanowires catalysts for hydrodesulfurisation applications

Catalytic performances of promoted CoMoS catalysts were greatly improved via a synthesis strategy based on the structuration of the active phase using self-assembled PANI (Polyaniline) nanowires followed by an addition step of cobalt acetylacetonate on oxidic or sulfided Mo-based hybrids. Taking into account the different promotion levels, slabs lengths determined by XPS and TEM, the highest rate constants normalized by mol of (MoS2)edges+corner in the hydrodesulfurization of 3-methylthiophene were obtained when Co(acac)2 is deposited on a MoS3/PANI hybrid precursor. The normalized HDS rate constants for the different samples followed the increase in Co/Moedges+corner atomic ratios whereas an optimum for HDS/HYD selectivity in the same ratio was observed.

Heteropolyacids supported on clay minerals as bifunctional catalysts for the hydroconversion of decane

The role of heteropolyacid (HPA) was studied as a precursor for the generation of NiMo and CoMo catalysts supported on a vermiculite and a bentonite previously delaminated and bolstered with the incorporation of AlZr and AlCe species. The solids were characterized using X-ray diffraction (XRD), N2 adsorption, Scanning Electron Microscopy (SEM) and High-Resolution Transmission (HR-TEM), Raman spectroscopy, Temperature-Programmed Reduction (H2-TPR), IR spectroscopy with probe molecule (NH3-DRIFTS) and acidity analysis “in-situ”, electronic X-ray spectroscopy (XPS,) and the catalytic performance was evaluated in the hydroconversion of decane. The controlled modulation of the properties of natural clay minerals combined with the anchoring of the active phase from the HPA type precursor, generates supported catalysts with different ranges of catalytic performance. The stability of the HPA type structure was evidenced even after the calcination and pre-reduction process. The catalysts in the present work register better physicochemical properties (textural, acidic, reducible species and metallic dispersion) and a superior catalytic performance in the hydroconversion of decane, compared with catalysts obtained from a conventional salt reported in the literature.

Photocatalytic Upgrading of Lignin Oil to Diesel Precursors and Hydrogen

AbstractProducing renewable biofuels from biomass is a promising way to meet future energy demand. Here, we demonstrated a lignin to diesel route via dimerization of the lignin oil followed by hydrodeoxygenation. The lignin oil undergoes C−C bond dehydrogenative coupling over Au/CdS photocatalyst under visible light irradiation, co‐generating diesel precursors and hydrogen. The Au nanoparticles loaded on CdS can effectively restrain the recombination of photogenerated electrons and holes, thus improving the efficiency of the dimerization reaction. About 2.4 mmol gcatal−1 h−1 dimers and 1.6 mmol gcatal−1 h−1 H2 were generated over Au/CdS, which is about 12 and 6.5 times over CdS, respectively. The diesel precursors are finally converted into C16–C18 cycloalkanes or aromatics via hydrodeoxygenation reaction using Pd/C or porous CoMoS catalyst, respectively. The conversion of pine sawdust to diesel was performed to demonstrate the feasibility of the lignin‐to‐diesel route.

Photocatalytic Upgrading of Lignin Oil to Diesel Precursors and Hydrogen

AbstractProducing renewable biofuels from biomass is a promising way to meet future energy demand. Here, we demonstrated a lignin to diesel route via dimerization of the lignin oil followed by hydrodeoxygenation. The lignin oil undergoes C−C bond dehydrogenative coupling over Au/CdS photocatalyst under visible light irradiation, co‐generating diesel precursors and hydrogen. The Au nanoparticles loaded on CdS can effectively restrain the recombination of photogenerated electrons and holes, thus improving the efficiency of the dimerization reaction. About 2.4 mmol gcatal−1 h−1 dimers and 1.6 mmol gcatal−1 h−1 H2 were generated over Au/CdS, which is about 12 and 6.5 times over CdS, respectively. The diesel precursors are finally converted into C16–C18 cycloalkanes or aromatics via hydrodeoxygenation reaction using Pd/C or porous CoMoS catalyst, respectively. The conversion of pine sawdust to diesel was performed to demonstrate the feasibility of the lignin‐to‐diesel route.

Tailoring of Surface Acidic Sites in Co-MoS2 Catalysts for Hydrodeoxygenation Reaction.

CoMo sulfides are typical catalysts for selective hydrodeoxygenation (HDO) of phenolics to aromatics which is important in bio-oil upgrading. However, it is still a challenge to promote the intrinsic activity of Co-MoS2 catalysts. Defect chemistry provides a good option to improve surface reactivity in catalysis. In this work, we report a facile H2O2 etching method to tailor the concentration of surface acidic sites. The molar ratio of H2O2/MoS2 can be altered to tune sulfur defects on the MoS2 surface for stabilizing Co species to form CoMoS active sites. The optimized Co-MoS2-2 catalyst, with the highest concentration of acidic sites, exhibits 3.4 times higher activity than the Co-MoS2-0 sample in the HDO of p-cresol to toluene. It is also found the HDO activity shows a linear relationship with the amount of surface acid (both Lewis and Brønsted acid) over the Co-MoS2-x catalysts. We believe that the understanding of the role of surface acidity would provide new opportunities for the rational design of efficient Co-MoS2 catalysts.

Insights into the HDS/HYDO selectivity with considering stacking effect of Co-MoS2 catalysts by combined DFT and microkinetic method

To investigate the desulfurization/olefin hydrogenation (HDS/HYDO) selectivity for thiophenic compounds, the adsorptions and reactions of thiophenic compounds including 2-methythiophene (2-MT), 3-methylthiophene (3-MT), 2,5-dimethylthiophene (2,5-DMT), 3,4-dimethylthiophene (3,4-DMT), and benzothiophene (BT) are calculated based on density functional theory (DFT). The ionization energy is found linearly related to the adsorption energy which could prove that the thiophenic compounds are NOT sterically hindered by stacking layers of Co-MoS2 catalysts, therefore the monolayer Co-MoS2 catalysts could be reasonably applied to study thiophenic compounds HDS process. Both the results of adsorption energies and Gibbs free energy variations suggest that there are stronger adsorptions for thiophenic compounds than 1-hexene. Microkinetic studies considering the whole HDS process declare: (1) the sulfur vacancy over S edge of Co-MoS2 catalysts also has high HDS/HYDO selectivity for thiophenic compounds and 1-hexene; (2) the DDS pathways are more feasible than HYD pathways for thiophenic compounds; (3) the reactivity is determined as T/2-MT/3-MT > 2,5-DMT/3,4-DMT/BT. Hence, the comprehensive investigation help to deeply understand the performance of the sulfur vacancy over the S edge of Co-MoS2 catalysts in the actual situation, which has significance to design the high HDS/HYDO selectivity catalysts.

Synthesis and Characterization of Co-Mo/γ-Alumina Catalyst from local Kaolin clay for Hydrodesulfurization of Iraqi Naphtha

This work deals with the hydrodesulfurization of three types of naphtha feedstocks; mixednaphtha (WN), heavy naphtha (HN) & light naphtha (LN) with a sulfur content of 1642.1,1334.9 & 709 ppm respectively, obtained from Missan refinery using prepared Co-Mo/γ-Al2O3catalyst. The Iraqi white kaolin was used as a starting material for the preparation of γ-Al2O3support, transferring kaolin to meta-kaolin was studied through calcination at differenttemperatures and durations, kaolin structure was investigated using X-Ray diffractiontechniques.High purity 94.83%. Crystalline γ-Al2O3 with a surface area of 129.91 m2/gm, pore volume0.9002 cm3/g was synthesized by extraction of Iraqi kaolin with H2SO4 at different acid to clayweight ratios, acid concentrations & leaching time. Ethanol was used as precipitating agent; theresultant gel was dried and calcined at 70OC, 10 hrs & 900 OC, 2 hrs respectively.The effects of different parameters on the average crystallinity and extraction % ofsynthesized γ-Al2O3 were studied like; acid: clay ratio, sulfuric acid concentration, leachingtime, leaching temperature & kaolin conversion to metakaolin. Characterization of prepared γ-Al2O3 & Co-Mo catalyst were achieved by X-ray diffraction, FTIR-spectra, texture properties& BET surface area, BJH N2 adsorption porosity, AFM, SEM, crush strength & XRF tests.
 Co-Mo/ γ-Al2O3 catalyst with final loading 5.702 wt% and 21.45 wt% of Co and Mo oxidesrespectively was prepared by impregnation methods.The activity of prepared Co-Mo/γ-Al2O3 catalyst after moulding to be tested forhydrodesulfurization (HDS) of naphtha feedstock W.N, H.N & L.N was performed using apilot hydrotreating unit at petroleum research & development centre, at different operatingconditions. Effects of temperature, LHSV, pressure, time & pore size distribution were studied,the best percentage of sulfur removal is increased with decreasing LHSV to 2 hr-1 as a generaltrend to be 89.71, 99.72, 99.20 % at 310oC for the whole naphtha, heavy naphtha and lightnaphtha feedstocks respectively, at 34 bar pressure and 200/200 cm3/cm3 H2/HC ratio.