Co-Mo Oxide Research Articles

Construction of mesoporous Ni-Co-Mo oxide/sulfide composite composite nanosheet arrays as bifunctional material for charge storage and oxygen evolution reaction applications

At present, energy conversion and energy storage devices are gradually integrated together, which puts forward higher requirements for the design and construction of electrode materials. Herein, bi-functional Co-Mo oxides and Ni/Co sulfides (NCMOS) composite nanosheet arrays on Ni foam are constructed for supercapacitors and oxygen evolution reaction (OER) of water splitting. The Ni-Co-Mo nanosheet precursor is firstly synthesized by stepwise hydrothermal processes and then converted into Ni-Co sulfide and Co-Mo oxide by in-situ sulfurization. The nanoarray and in-situ sulfurization of active materials bring more reactive active sites, optimize reaction kinetics, and shorten the transport path of electrons and charges, which enhance energy storage performance and OER catalytic activity of NCMOS material. In terms of supercapacitor applications, NCMOS exhibits high specific capacity (1332.1 C g–1) and good cycle stability. For OER application, NiCMOS shows lower OER overpotential (290 mV at 100 mA cm–2), smaller Tafel slope (87.2 mV dec–1) and excellent catalytic stability in oxygen evolution for 60 h. The excellent charge storage and OER properties suggest that bi-functional oxide/sulfide composites have great potential in energy conversion and storage-integrated devices.

Promoting electrocatalytic oxidation of methanol to formate through interfacial interaction in NiMo oxide-CoMo oxide mixture-derived catalysts

Designing efficient, stable, and easily scaled-up catalysts for nucleophile oxidation reactions (NOR) is a key step in promoting the industrial application of NOR. Here, a simple physical mixing strategy is adopted to prepare a mixture of NiMo oxide and CoMo oxide as catalyst for methanol electrocatalytic oxidation reaction (MOR). The mixture exhibits high catalytic activity for MOR and its performance far exceeds that of a single component. The interaction at the contact interface between nickel and cobalt components is clarified through operando electrochemical impedance spectroscopy, in-situ Raman spectroscopy, and a series of electrochemical tests. The interfacial interaction enhances the charge transport and promotes the formation of electrophilic OH* species, which significantly boosts the methanol oxidation reaction. This work provides a new idea for the design of efficient and easily scaled-up catalysts for nucleophile oxidation reactions.

Ultrafine Co-Mo oxide nanocrystals embedded in hierarchical N-doped carbon microflowers for high-performance lithium-ion batteries

Constructing hierarchical architecture consisting of low-dimensional building blocks is attracting attention as an efficient strategy for achieving high electrochemical performance for lithium-ion batteries (LIBs). Herein, convenient synthesis of Co-Mo oxide composites embedded in a hierarchical N-doped carbon microflower (Co-Mo oxide/NC) is demonstrated. The Co-Mo/polydopamine (PDA) precursor prepared by the spontaneous coordination between the metal ion and dopamine can be easily transformed into Co-Mo oxide/NC by a two-step thermal annealing process. The as-obtained hierarchical microflowers have the advantages of hierarchical structured electrode materials, such as increased contact area with the electrolyte, abundant ion storage sites, and high electrical conductivity. Concurrently, the synergistic effect between molybdenum and cobalt ions can improve the electrochemical performance. Consequently, the hierarchical microflowers as LIB anode materials exhibit a high reversible specific capacity of 1115 mA h g−1 at 1.0 A g−1 after 200 cycles and superior rate performance with a capacity of 577 mA h g−1 at 30.0 A g−1. Moreover, in the long-term cycling stability at a high current density (10.0 A g−1), the electrode shows excellent cycling stability with a capacity of 508 mA h g−1 for 500 cycles. The present study reveals the importance of designing hierarchical structured materials to enhance electrochemical energy storage applications.

Enhancing ammonia catalytic production over spatially confined cobalt molybdenum nitride nanoparticles in SBA-15

Ternary Co3Mo3N nitrides are reported to exhibit high catalytic activity in ammonia synthesis. However, synthesis of ternary nitrides requires thermal treatments at elevated temperatures and reactive atmospheres that lead to unavoidable surface reduction (∼ 10 m2 g-1). In this work, we have developed a novel approach to improve the catalytic activity of Co3Mo3N through its dispersion into a high surface area silica-based support (SBA-15). During ammonolysis and ammonia synthesis conditions reaction, SBA-15 demonstrated good thermal and chemical stability maintaining an ordered porous structure and high surface area (> 500 m2 g-1). For application in ammonia synthesis, SBA-15 supported cobalt molybdenum catalysts with different metal loading (10, 20 and 30 wt%) were prepared by a modified impregnation-infiltration protocol and their catalytic activity studied. The dispersion of CoMo nitride nanoparticles into SBA-15 structures resulted in the improvement of their structural and textural properties of nitrides as evidenced by XRD analysis, STEM-EDS, and N2- physisorption (e.g. 10-CoMo-N/SBA-15: 348 m2 g-1). Nevertheless, the surface composition of CoMo-N/SBA-15 catalysts was found to be similar to the non-supported Co3Mo3N. Furthermore, supported CoMo-N/SBA-15 displayed enhanced catalytic activity in ammonia synthesis (1714, 1429 and 810 µmol gactivephase-1 h-1 corresponding to the CoMo oxide loadings of 10, 20, 30 wt% respectively) that outperform the classical Co3Mo3N catalyst (259 µmol gcatalyst-1 h-1). The results reported in this work highlights a novel approach for the design of nitride-based catalysts with superior catalytic properties in ammonia synthesis.

Metallic Co and crystalline Co-Mo oxides supported on graphite felt for bifunctional electrocatalytic hydrogen evolution and urea oxidation

Oxygen evolution reaction (OER) and urea oxidation reaction (UOR) play important roles in the field of hydrogen energy preparation and pollution treatment. In this work, by merging bimetallic Co-Mo oxides with metallic Co on the graphite felt (GF), we effectively manufacture a 3D bifunctional and highly efficient electrocatalyst (CoMoO@Co/GF) with multi-site functionality for the simultaneous reduction of water and the oxidation of urea in an alkaline medium. The presence of metallic Co causes Co-Mo oxides to evolve from amorphous to crystalline structures. The coupling interface produced between metallic Co and Co-Mo oxides is proven to facilitate electron transport in addition to extensively accessible and highly electroactive Co-Mo oxide nanoflower architecture. The experimental results reveal that the overpotentials for OER and UOR in the CoMoO@Co/GF electrode require only 269 and 115 mV to obtain a current density of 10 mA cm−2, respectively. Furthermore, with the aid of urea, the overpotential for HER at the current density of 10 mA cm−2 is lowered to 155 mV. Most notably, the constructed CoMoO@Co/GF-based electrolytic cell only requires a 1.5 V dry battery to achieve effective H2 evolution and noteworthy stability, outperforming the commercial catalyst-based device and many previous results. The combination of experiments and theoretical calculations further clarifies the active sites in the catalyst. What’s more, the pathway of electron transfer in the catalytic process is defined.

Construction of vertically aligned Ni-Co-Mo hybrid oxides nanosheet array for high-performance hybrid supercapacitors

Multi-metal oxide materials have gained increasing attention due to their superior electrochemical performance for supercapacitors. In this work, Ni-Co-Mo oxides composite materials (NiCoMo/NF) are synthesized and anchored on Ni foam in the form of vertically aligned nanosheet arrays using a two-step hydrothermal method. It has confirmed that good electrochemical performance stems from a synergic interaction effect between the hybrid Ni-Co-Mo composite materials and the co-existence of Ni-Co and Co-Mo oxide, which can be attributed to a unique nanostructure in the hybrid Ni-Co-Mo composite materials and Ni-Co/Co-Mo oxide intersections with each other. The NiCoMo/NF binder-free electrode shows an enhanced specific capacitance of 1837.7 F g−1(3.31 F cm−2) at a current density of 1 A g−1 and maintains capacitance retention of 81.2% after 6000 cycles at 5 A g−1. Meanwhile, the fabricated hybrid capacitor achieves high specific energy of 41.1 W h kg−1. The results indicate that NiCoMo/NF has the potential for application in supercapacitors. Moreover, our work provides a practical approach for fabrication of multi-metal oxide materials and hold promise for high-power energy storage devices.

Significant impact of γ-Al2O3 facet structure on the character and performance of surface Co-Mo sulfides for CO removal in H2 fuel via water gas shift

Three morphologically uniform γ-Al2O3 crystallites [Al2O3 hexagonal plates (Al2O3-HP), stacked hexagonal plates (Al2O3-SHP) and rods (Al2O3-R)] were controllably synthesized. The Co-Mo oxide precursor was loaded on these γ-Al2O3 substrates via aqueous incipient wetness impregnation and transformed to the sulfides under 10% H2S/H2 (v/v) atmosphere. The mainly exposed facet of Al2O3-HP and Al2O3-SHP was identified to be the (110) and (100)/(111), respectively; whereas a polycrystalline structure was observed over Al2O3-R. The original structural feature of oxide precursors, i.e., 2D polymeric/monomeric as well as 3D polymeric/MoO3 species substantially varied over Al2O3-HP, Al2O3-SHP, and Al2O3-R, which in turn determines the effectiveness in sulfidation of surface oxide precursors. The richness of MoS2/Co9S8/Co-Mo-S species, and less fraction of partially sulphurated CoMoOxS2 as well as CoOx/SOx2− entities were recognized over Al2O3-HP. Based on the areal activity at 250 °C, the sulfides-Al2O3 (110) interface is approximately 6–13.8 times more active than the poly-crystalline or commercial γ-Al2O3 supported sulfides for water gas shift (WGS) in a hydrogen-rich stream. The sulfides-Al2O3 (110) interface also notably outperformed the sulfides-Al2O3 (100)/(111) interfaces for the reaction.

Single-step conversion of sugarcane bagasse to biofuel over Mo-supported graphene oxide nanocatalyst

Along with the great efforts in producing clean and low-cost fuel and chemicals, in this work, novel nanocatalysts are reported for the fast pyrolysis of the bagasse. To this end, different catalyst supports were employed to load Mo oxides or sulfides through incipient wetness impregnation. The prepared nanocatalysts were characterized by X-ray diffraction to determine the formed phases, N2 adsorption/desorption to clarify the surface properties, and SEM to observe the morphology and energy-dispersive X-ray to provide the atomic mapping. A series of nanocatalysts including the Mo sulfide loaded over graphene oxide (MoS2/GrO) or porous graphene (MoS2/graphene), Mo oxide loaded over charcoal, and Co-Mo oxide loaded over MgO were studied in the fast pyrolysis of the bagasse. The results revealed that the use of catalyst decreased the bio-oil yield of the process. Interestingly, it was found the fast pyrolysis of the bagasse is dependent on the used catalysts and the fractions of bio-oil can be determined according the catalysts types. It was found that with accordance to the demanded chemicals, the catalysts can be chosen which is highly valuable in producing chemicals and each catalysts support results in a specific set of products. In general, the acetic acid was the main product without using catalyst, and by using the MoS2/GrO nanocatalyst, the phenols were formed dominantly which are of great importance in different industries. This novel work successfully revealed that the metal-based catalysts can be employed instead of the zeolites which paves the way toward using low-cost metallic catalysts in producing bio-chemicals and bio-oils.

Size-dependent catalytic behavior of MoS2 nanoparticles in water-gas shift reaction

Well-dispersed and uniformly sized 5–84 nm Mo oxide and CoMo oxide nanoparticles were synthesized by varying the Mo and Co precursor concentrations. The water-gas shift (WGS) activity of sulfided Mo-based catalysts was found to increase with particle size and in the presence of Co. In particular, 84-nm CoMo-S nanoparticles exhibited 15 times higher effective CO consumption rate and 2.3 times higher turnover frequency (TOF) as compared to 5- nm Mo-S nanoparticles. The observed trends in size-dependent catalytic behavior correlated with the higher density of the proposed active sites present on larger (Co)Mo-S nanoparticles probed by CO chemisorption.

Leaching and Preparation of Co-Mo Sulfide/Oxide Nanoparticles from Spent Catalyst

Acid leaching of spent molybdenum (Mo) catalyst followed by a simple pH-selective precipitation route for recovery of Co-Mo sulfide/oxide complexes in high yield has been investigated. The effect of leaching parameters such as temperature, pulp density, particle size, time, and acid concentration on the dissolution efficiency of aforesaid metal ion was studied, revealing that the Mo and Co dissolution increased with increase in the acid concentration, temperature, and contact time but increase in the particle size led to the opposite effect on the metal ion dissolution. The optimized leaching parameters, which resulted in dissolution of 95% Mo along with 53% Co under the size fraction of 90 + 75 µm, were 20% pulp density, 3% H2SO4 concentration (V/V), 80°C, and contact time of 3 h. Precipitation experiments were carried out on mixed Co-Mo sulfide/oxide nanoparticles at different pH values, adjusted using Na2S or NaOH. The Co-Mo sulfide nanoflakes obtained at the optimum pH were annealed and their physicochemical properties characterized. The feasibility of precipitation of mixed Co-Mo oxide material by pH adjustment was also shown. At low pH, chemically bound Co-Mo oxide with crystalline nature was observed, whereas at high pH, physically entrapped Mo phase on Co(OH)2 was detected. Scanning electron microscopy (SEM) of the precipitate obtained at pH 5 revealed nanofiber crystalline grains, whereas the precipitate obtained at pH 7 showed gel-like nature with aggregate morphology, and at pH 12, the precipitate was formed of denser amorphous aggregates with larger particles. A flow sheet based on the optimal results for preparation of Co-Mo sulfides or oxides is presented and discussed.

Synergistic hollow CoMo oxide dual catalysis for tandem oxygen transfer: Preferred aerobic epoxidation of cyclohexene to 1,2-epoxycyclohexane

The CoMo hollow bimetallic oxide has been exploited in the aerobic epoxidation of cyclohexene containing labile allylic hydrogen atoms using ethylbenzene as a solvent. Cooperativity between Co(II) and Mo(VI) sites consisting of CoOMo or Mo−Oδ−⋯Coδ+ unit on hollow oxide surfaces is investigated for controlling preferred epoxidation catalysis via tandem oxygen transfer. Various characterization techniques like XRD diffraction, N2 physisorption, TEM, and Raman, XPS, Infrared, and UV–vis spectroscopies are employed to reveal the relationship between structure of active sites and catalytic performance. Together with these comprehensive experimental and computational studies, in this unique tandem catalytic process, Co(II) sites effectively mediate the first step of the overall oxidation cycle yielding a phenylethylperoxy radical by oxygen activation [Co(II) to Co(III) O2− to phenylethyl radical and finally to a phenylethylperoxy radical]. On the other hand, Mo(VI) sites are shown to be the excellent catalytic species for the subsequent epoxidation step by the transfer of oxygen atom of the phenylethylperoxy radical to cyclohexene. Hence, a 59% epoxidation selectivity with 33% cyclohexene conversion is accomplished through the required combination of Co(II) and Mo(VI) (2:1), allowing to tune epoxidation efficiency toward higher driving forces (relative to oxygenation of allylic hydrogen atom). This remarkably different catalytic performances between Co(II) and Mo(VI) can be attributed to the stronger overall polarization ability of Mo(VI) toward σ* OO orbital of the OO unit derived from its d-type orbitals, which helps the donor-acceptor interactions with the double bond.

(Invited) The Evolution of W-Co-C Catalyst during the CVD Growth of Chirality-Selective Growth of Single-Walled Carbon Nanotubes

Bimetallic catalysts such as Fe-Co and Co-Mo have been used for efficient growth of bulk single-walled carbon nanotube (SWNTs) and vertically aligned SWNTs [1]. Recently, bimetallic catalysts such as Co-W [2] or Co-Cu [3] are employed for structure controlled growth of SWNTs. Here, roles of bimetallic catalysts are explored by newly proposed SiO2 grid based in-plane TEM technique, which enables a direct TEM characterization of catalysts on SiO2, CVD growth of SWNTs in normal furnace, and TEM characterization of catalysts and grown nanotubes after CVD. The in-plane TEM results of the traditional Co-Mo bimetallic catalysts were consist with our previous report [1]; metallic Co nanoparticle embedded in Co-Mo oxide is responsible for the nucleation of SWNTs. By using Co-Cu catalysts, we can synthesize vertically aligned SWNTs with subnanometer diameters on quartz (and SiO2/Si) substrates [3]. EDS-STEM and HAADF-STEM imaging of the Co-Cu bimetallic catalyst system showed that small Co catalysts were captured and anchored by adjacent Cu nanoparticles, which grew small diameter of SWNTs. High-melting point W6Co7 alloy produced from metal cluster precursors is reported to grow a single chirality (12,6) with over 90 % abundance [2]. Here, we show that a sputtered Co-W catalyst can selectively grow (12,6) SWNTs by CVD at lower reduction and growth temperatures [4]. Statistical Raman mapping analysis and optical absorption spectrum of the as-grown SWNTs reveal that the abundance of (12,6) is over 60 %. The morphology and structure of catalyst is investigated by the in-plane TEM before and after CVD growth. The catalyst alloy we produced was W6Co6C and the only metallic Co was left after the CVD of 5 min. By comparing the catalyst TEM images with variable CVD period, we can discuss the evolution of the alloy catalysts. The W rich initial catalyst is composed of bcc W bound with W6Co6C. Once ethanol is introduced, additional W will be gradually removed to the gas phase product of WO3 and the ratio of W decreases. It is speculated that after the formation of pure W6Co6C, further loss of W will result the precipitation of Co; nucleation of Co cluster which is primary responsible for growth of an SWNT. This work was supported by JSPS KAKENHI Grant Numbers JP25107002, JP15H05760, and IRENA Project by JST-EC DG RTD, Strategic International Collaborative Research Program, SICORP. Part of this work is based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO). We also acknowledge supports from Advanced Characterization Nanotechnology Platform of the University of Tokyo, supported by "Nanotechnology Platform" of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

Synthesis and Study of Ni-Mo-Co Catalysts for Hydroprocessing of Oil Fractions

AbstractThe problems of synthesis of Ni-Mo, Ni-Mo Co and Co-Mo oxide catalysts for hydrodesulfurization and hydrogenation of aromatic hydrocarbons in the composition of kerosene, diesel and oil fractions are discussed. The influence of spent adsorbent and kaolin as the additives on the physical-chemical and catalytic properties of bimetallic and trimetallic catalysts is established.

Influence of Final Nitriding Temperature on the Preparation and the Catalytic Performance of CoMoN<sub>x</sub>/CNTs for Ammonia Decomposition

A series of cobalt-molybdenum nitride catalysts were prepared using Co-Mo oxide precursors via temperature-programmed reaction in N2-H2 mixed gases. The catalysts were characterized by N2 physical adsorption, X-ray diffraction, temperature-programmed desorption of H2. Their catalytic performance was evaluated in the model reaction of ammonia decomposition. The influence of the final nitriding temperatures on the surface properties and the catalytic perfomance of CoMoNx/CNTs were described. The catalyst nitrided at 650°C shows the best catalytic performance. The results indicated that a suitable final nitriding temperature contributes directly to the formation of nitrides and favor the catalyst activity.

Catalytic activity of CoMo catalysts supported on boron-modified alumina for the hydrodesulphurization of dibenzothiophene and 4,6-dimethyldibenzothiophene

Abstract Boria–alumina mixed oxides were prepared by impregnation and used as supports for CoMo catalysts (MoO 3 : 13 wt%; Co: 2.3 wt%) for the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). A detailed characterization of B 2 O 3 –Al 2 O 3 carriers showed that boric acid reacts with surface Al–OH groups to form a boria over-layer, stabilized via Al–O–B bridges. Using X-ray diffraction, we showed that the addition of B to the alumina carrier leads to a reduction in the formation rate of bulk α-CoMoO 4 , initially present on the surface of CoMo/Al 2 O 3 oxide precursors prepared by co-impregnation. This can be attributed to the strong interaction between Co and the B-modified carrier, as demonstrated using X-ray photoelectron spectroscopy (XPS). Further investigations using XPS showed that, because of this seemingly stronger interaction of Co-oxide species with the B 2 O 3 ( x )–Al 2 O 3 supports, the surface concentration of Mo was also affected for both oxide and sulfide CoMo catalysts. In the meantime, the degree of reducibility of Mo (XPS fraction of Mo 4+ /Mo total ) did not seem to be significantly affected for boria loadings below 5 wt%. However, for higher boria loadings (7 and 10 wt%), the Mo reducibility decreases with boron content due very probably to the presence of less reducible bulk MoO 3 in CoMo oxide precursors. The HDS activity of DBT and 4,6-DMDBT over CoMo/B 2 O 3 ( x )–Al 2 O 3 exhibit a maximum for B 2 O 3 loadings around 3–5 wt%. To a first approximation, this increase in the HDS activity can be attributed to the stronger interaction of Co-species with the B-modified carrier suppressing the formation of α-CoMoO 4 , which is known to yield the formation of less active Co 9 S 8 , after sulfurization, instead of generating the more active “CoMoS” phase. For boria loadings above 3–5 wt%, the DBT and 4,6-DMDBT HDS activity of CoMo/B 2 O 3 –Al 2 O 3 catalysts decreases due to a decrease in the dispersion and reducibility/sulfidability of Mo-supported species, as evidenced using XPS.

Cobalt molybdenum carbides as anode electrocatalyst for proton exchange membrane fuel cell

Cobalt molybdenum (Co-Mo) carbides were prepared by the carburization of Co-Mo oxides at temperatures of 723–973 K in a stream of CH 4/H 2 gas. The carburized catalysts were evaluated using a single-stack fuel cell and three-electrode cell. The results showed high activities for the anodic electrooxidation of hydrogen over the Co-Mo catalysts carburized at 873 and 923 K. The 873 K carburized Co-Mo catalyst had the highest activity and achieved 10.9% of the performance of a commercial Pt/C catalyst in a single-stack fuel cell. The XRD, TPC, TPR and XPS results showed that the Co-Mo oxycarbide in the bulk and on the surface are the active species for the hydrogen oxidation reaction.

Low-temperature water–gas shift reaction over cobalt–molybdenum carbide catalyst

The water–gas shift (WGS) reaction over a series of cobalt-molybdenum carbide catalysts was studied at 453 K. The cobalt-molybdenum (Co x Mo 1− x ) oxides were prepared using a mixture of aqueous solutions of cobalt nitrate and ammonium heptamolybdate and carburized by a temperature-programmed reaction with a 20% CH 4/H 2 mixture. The catalysts were characterized using X-ray diffraction, CO adsorption, temperature-programmed carburization (TPC) with a 20% CH 4/H 2 mixture, X-ray photoelectron spectroscopy, and transmission electronic microscopy. The 873 K-carburized Co 0.5Mo 0.5 was found to be the most active among the Co–Mo carbide catalysts; it was more active than a commercial CuZn at 5 min but less active than CuZn at 300 min. The TPC experiment determined the reduction and/or carburization of the Mo and CoMo oxides into the carbides through the oxycarbides. The TPC of the Co 0.5Mo 0.5 oxide showed that the first peak of H 2O at 747 K was due to the reduction and/or carburization of MoO 3 to MoO 2 and Mo oxycarbide and of CoMoO 4 to the Co–Mo oxycarbide, and the second peak at 893 K was due to the carburization of the Co–Mo oxycarbide to β-Mo 2C with Co metal and amorphous Co–Mo carbide. In addition, the Co 0.5Mo 0.5 carbide catalyst contained β-Mo 2C, Co metal, and the amorphous Co–Mo oxycarbide (the composition of CoMoC 6.2O 1.4), which grew into crystallites of Co 3Mo 3C after being heated in H 2. The amorphous Co–Mo oxycarbide is responsible for the WGS reaction.

Structural characterisation of silica supported CoMo catalysts by UV Raman spectroscopy, XPS and X-ray diffraction techniques

The structure of Co-Mo catalysts supported on commercial silica, doped with various amounts of sodium ions, was investigated by means of X-ray diffraction (XRD), UV-Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Two series of samples were considered. One series was prepared by classic incipient wet impregnation (WI) and the other series by co-impregnation in the presence of nitrilotriacetic acid (NTA). The effect of sodium on the catalyst structure depended on the preparation procedure: in the case of the WI catalysts, sodium promoted the transformation of the polymolybdate species into monomolybdate Na 2MoO 4; in the case of the NTA prepared samples, sodium induced transformation from heptamolybdates, Mo 2O 7 2− and mixed CoMo oxides into MoO 4 2− units with distorted tetrahedral symmetry without forming Na 2MoO 4 compound. In addition to purely structural modifications, sodium induced an electronic effect, evidenced by Mo 3d and Co 2p XPS binding energy shifts. The catalytic behaviour of the samples, previously tested in the HDS of thiophene, was explained in terms of structural and electronic changes.

Hydrodesulfurization of Dibenzothiophene over Cobalt−Molybdenum Nitride Catalysts

Molybdenum nitride (γ-Mo 2 N) and Co-promoted molybdenum nitrides (Co-Mo-N) catalysts with high surface area have been prepared from the reaction of MoO 3 and Co-Mo oxides with N 2 -H 2 and characterized by XRD and BET. The results of measurement of hydrodesulfurization-(HDS) of dibenzothiophene(DBT) supported the following conclusions: (1) γ-Mo 2 N and Co-Mo-N have higher HDS activity and selectivity for C-S bond breakage in dibenzothiophene; (2) different pretreatment conditions affect the HDS activity and selectivity; (3) the HDS activity of the γ-Mo 2 N is significantly improved with the addition of a Co promoter.

CoMo bimetallic nitride catalysts for thiophene HDS

CoMo bimetallic nitride catalysts were prepared by temperature-programmed reduction of CoMo oxides with flowing ammonia, and the effects of cobalt addition on the thiophene hydrodesulfurization (HDS) reaction were investigated. MoO3 transformed into Mo2N, while cobalt oxide was just reduced to Co metal rather than Co nitride. When Co was added to Mo, the surface area decreased significantly but the new bimetallic nitride phase of Co3Mo3N was produced. The addition of Co could improve the HDS conversion, and the high specific activity of the bimetallic nitride catalyst was believed to be related with the new Co3Mo3N phase.