Bimetallic NiMo Research Articles

Modified Nimo Nanoparticles for Efficient Catalytic Hydrogen Generation from Hydrous Hydrazine

Precious metal-free NiMoM (M = Pr2O3, Cu2O) catalysts have been synthesized through a simple coreduction method, without any surfactant or support material, and characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The resultant Pr2O3- or Cu2O-modified NiMo catalysts exhibit different structures, which is due to a difference in the synergistic effects of NiMo and the modifying elements. NiMoPr2O3 has an amorphous structure, with low crystallinity and uniform particle dispersion, while NiMo@Cu2O adopts the core–shell structure, where the core and shell are synergistic with each other to promote electron transfer efficiency. The support material-free nanocatalysts Ni9Mo1(Pr2O3)0.375 and Ni4Mo@Cu2O are both highly efficient compared with bimetallic NiMo catalysts, in terms of hydrogen generation from hydrous hydrazine (N2H4·H2O) at 343 K, with total turnover frequencies (TOFs) of 62 h−1 and 71.4 h−1, respectively. Their corresponding activation energies (Ea) were determined to be 43.24 kJ mol−1 and 46.47 kJ mol−1, respectively. This is the first report on the use of Pr-modified NiMo and core–shell NiMo@Cu2O catalysts, and these results may be used to promote the effective application of noble metal-free nanocatalysts for hydrogen production from hydrous hydrazine.

Hydrotreatment of the carbohydrate-rich fraction of pyrolysis liquids using bimetallic Ni based catalyst: Catalyst activity and product property relations

The use of novel nickel based catalysts for the catalytic hydrotreatment of pyrolytic sugars, the carbohydrate-rich fraction of pine derived pyrolysis liquids, is reported. The catalysts are characterized by a high nickel loading (38 to 57wt%), promoted by Cu, Pd, and/or Mo and a SiO2 based inorganic matrix. Experiments were carried out at 180°C and 120bar initial hydrogen pressure (room temperature) in a batch reactor set-up to gain insight in catalyst activity and product properties as a function of the catalyst composition. The most promising catalyst in terms of activity, as measured by the hydrogen uptake during reaction, was the Ni-Mo/SiO2-Al2O3 catalyst whereas the performance of the monometallic Ni/SiO2-Al2O3 catalyst was the lowest. As a result, the product oil obtained by the bimetallic Ni-Mo catalyst showed the highest H/C ratio and the lowest molecular weight of all catalysts tested. A detailed catalyst characterization study revealed that addition of Mo to the Ni catalyst suppresses the agglomeration of nickel nanoparticles during the catalytic hydrotreatment reaction.

Intermediate Species Revealed during Sulfidation of Bimetallic Hydrotreating Catalyst: A Multivariate Analysis of Combined Time-Resolved Spectroscopies

For the first time, the sulfidation process of a bimetallic NiMo catalyst supported on alumina has been followed by combining time-resolved laser Raman spectroscopy (LRS) and X-ray absorption spectroscopy (XAS) quasi simultaneously at both Ni and Mo K edges. Multivariate data analysis reveals that the thermal activation upon 15% H2S/H2 atmosphere of a dehydrated-calcined NiMo(VI) catalyst involves (i) a 5-stepped mechanism with oxysulfided or fully sulfided Mo intermediate species and (ii) a direct transformation of oxidic nickel species into NiSx and NiMoS ones. Complementary information extracted from LRS and Quick-XAS data permitted to identify at the early stage of the sulfidation the trimeric Mo(V/VI) oxysulfide species [Mo3(μ2O)4(μ2S)μ2{S2}(Ot)2(St)3] grafted to the support surface, which is quickly transformed into the Mo(IV) intermediate species [Mo3(μ3S)(μ2S)2μ2{S2}(Ot)2{S2}t]. Above 190 °C, the Mo(IV) second intermediate is transformed into Mo(IV)S3, itself transformed into the final Mo(IV)S2 at...

Hydrodeoxygenation of γ-valerolactone on bimetallic NiMo phosphide catalysts

A series of supported Ni-Mo-P alloy catalysts was studied for the catalytic hydrodeoxygenation (HDO) of the cyclic five-membered ester γ-valerolactone (GVL-C5H8O2) as a model compound for pyrolysis oil. Alloy formation in Ni-Mo-P was indicated by X-ray diffraction analysis and X-ray absorption near-edge spectroscopy, which showed systematic shifts with composition. The number of active sites of each metal species was estimated by factor analysis combining CO-uptake measurements and infrared (IR) spectra of adsorbed CO. It was found that the catalytic activity followed the order: Ni2P/MCM-41>NiMo(3:1)P/MCM-41>NiMo(1:1)P/MCM-41≅(Ni2P+MoP)/MCM-41>NiMo(1:3)P/MCM-41>MoP/MCM-41, whereas the normalized turnover frequency based on Ni sites were similar for all the catalysts, while retaining the same order. It is concluded that adjacent surface Ni atoms are the main active sites involved in the rate-determining step (rds). The Mo-containing catalysts produced more 1-pentanol and C5 hydrocarbons than Ni2P/MCM-41, indicating that while the exposed Ni sites governed catalytic activity, Mo sites controlled the selectivity to C5 hydrocarbons. Thus, steps following the rds were influenced by Mo sites, leading to preferences for different reaction pathway during the HDO of γ-valerolactone. The study reveals that the catalytic behavior of NiMoP catalysts can be tuned by the relative proportion of Ni and Mo sites.

Synthesis and catalytic performance of bimetallic NiMo- and NiW-ZSM-5/MCM-41 composites for production of liquid biofuels

This work presents a synthesis of bimetallic NiMo and NiW modified ZSM-5/MCM-41 composites and their heterogeneous catalytic conversion of crude palm oil (CPO) to biofuels. The ZSM-5/MCM-41 composites were synthesized through a self-assembly of cetyltrimethylammonium bromide (CTAB) surfactant with silica-alumina from ZSM-5 zeolite, prepared from natural kaolin by the hydrothermal technique. Subsequently, the synthesized composites were deposited with bimetallic NiMo and NiW by impregnation method. The obtained catalysts presented a micro-mesoporous structure, confirmed by XRD, SEM, TEM, EDX, NH3-TPD, XRF and N2 adsorption-desorption measurements. The results of CPO conversion demonstrate that the catalytic activity of the synthesized catalysts decreases in the series of NiMo-ZSM-5/MCM-41 > NiW-ZSM-5/MCM-41 > Ni-ZSM-5/MCM-41 > Mo-ZSM-5/MCM-41 > W-ZSM-5/MCM-41 > NiMo-ZSM-5 > NiW-ZSM-5 > ZSM-5/MCM-41 > ZSM-5 > MCM-41. It was found that the bimetallic NiMo- and NiW-ZSM-5/MCM-41 catalysts give higher yields of liquid hydrocarbons than other catalysts at a given conversion. Types of hydrocarbon in liquid products, identified by simulated distillation gas chromatography-flame ionization detector (SimDis GC-FID), are gasoline (150–200°C; C5–12), kerosene (250-300°C; C5–20) and diesel (350°C; C7–20). Moreover, the conversion of CPO to biofuel products using the NiMo- and NiW-ZSM-5/MCM-41 catalysts offers no statistically significant difference (P> 0.05) at 95% confidence level, evaluated by SPSS analysis.

Hydrocracking of Vacuum Gas Oil on Bimetallic Ni-Mo Sulfide Catalysts Based on Mesoporous Aluminosilicate Al-HMS

The activity and selectivity of a bimetallic Ni-Mo sulfide catalyst based on mesoporous aluminosilicate Al-HMS with Si/Al ratio of 10 in the vacuum gas oil hydrocracking process in a reactor with a fixed catalyst bed was studied. The dependence of the activity and selectivity of the NiS-MoS2/Al-HMS (Si/Al = 10) catalyst on the process parameters (temperature, hydrogen pressure, volume stock feed rate, etc.) was investigated. It was shown that in the 380-450°C range at 5 MPa hydrogen pressure the catalyst ensures conversion of the heavy part of the hydrocarbon stock into fuel fractions with high selectivity in the middle distillates and makes it possible to reduce the sulfur content of the liquid hydrocracking products.

K-promoted NiMo catalysts supported on activated carbon for the hydrogenation reaction of CO to higher alcohols: Effect of support and active metal

This study investigates the effect of active metal and the nature and pre-treatment of the support in a series of K-promoted NiMo catalysts supported on activated carbon (AC) for the hydrogenation reaction of CO. The NiMo synergistic effect was found to be essential for the activation of CO. The use of activated carbon as support led to a three-fold increase in the selectivity toward higher alcohols, compared to the unsupported material, probably due to a reduction in the crystallinity of the active NiMoO4 phase and its partial transformation from alpha to beta form. Pre-treatment of the activated carbon prior to its use as support with HNO3 aqueous solution led to significant increase in CO conversion, related to the lower amount of ash and the much higher acidity of the acid treated sample. The use of a higher surface area acid-treated support also increases activity, with the KNiMo/AC2a catalyst exhibiting a 45% higher conversion at 280°C compared to KNiMo/AC1a. The improvement in activity can be ascribed to better dispersion of the active phase on the higher surface area AC support and therefore higher exposure of active NiOMo sites. Overall, the KNiMo/AC2a catalyst exhibited the optimum performance, with high CO conversion (25% at 280°C) and high production of oxygenates, with a space time yield to oxygenates of 141.5mg/gcatalyst/h at 280°C. A clear tendency of increasing higher alcohol production with decreasing acidity was evidenced for all K-promoted bimetallic NiMo catalysts.

Bimetallic Ni-Mo Nitride as the Carbon Dioxide Hydrogenation Catalyst

The possibility of bimetallic Ni-Mo nitrides usage as the catalysts in carbon dioxide hydrogenation reaction was examined in this work. Powders were synthesized through thermo-programmed reduction of precursor, which was produced by evaporation of the metal-containing solution. Specimens were investigated by x-ray diffraction, thermogravimetry, low-temperature nitrogen adsorption and scanning electron microscopy. It is shown that final powders provide CO2 conversion of 29 % for contact time of 0.26 s.

Oil-soluble Ni-Mo sulfide nanoparticles and their hydrogenation catalytic properties

Oil-soluble bimetallic Ni-Mo sulfide nanoparticles (NiMoS) with narrow size distribution were successfully synthesized through a composite-surfactants-assisted-solvothermal process. The surface functionality and lipophilicity of the Ni-Mo sulfides were shown by transmission electronic microscopy, Fourier transform infrared and ultraviolet spectroscopy. The as-prepared Ni-Mo sulfides supported on activated carbon (NiMoS/AC) exhibited enhanced catalytic activity towards naphthalene hydrogenation instead of cracking. For comparison, CoMoS/AC and MoS2/AC catalysts were also prepared through similar procedures, and it was found that their catalytic performance decreased in the order of NiMoS/AC>CoMoS/AC>MoS2/AC. Furthermore, the activity of the bimetallic NiMoS nanocatalyst can be effectively tuned via variation of the atomic ratio of Ni/(Ni+Mo).

Unsupported sulfides obtained from high specific area mixed oxides as hydrotreating catalysts

Several bimetallic Ni-Mo, Co-Mo and Co-W materials were prepared by co-precipitation and a Ni-W material through hydrothermal synthesis. The characterization by X-ray diffraction (XRD) of molybdates confirmed the formation of layered fy phase, while the tungstates showed both fy semi-crystalline and wolframite. The thermal analyses (TGA and DTA) of these materials showed phase transition around 400°C, excepting by CoMofy to 350°C; these temperatures were selected to calcine the bimetallic precursors to obtain mixed oxides, which exhibited high specific surface areas as compared to analogous materials reported by different synthesis pathways. The Fourier transformed infrared spectroscopy (FTIR) confirmed the phase formation of the species in precursors and mixed oxides. The catalytic activity of the sulfurated mixed oxides was simultaneously evaluated in the hydrodesulphurization (HDS) of dibenzotiophene (DBT) and the hydrogenation (HYD) of tetraline. Results showed a similar behavior to commercial catalysts. The effect of promotors (Ni and Co) is discussed.

Development of new trimetallic NiMoW catalysts supported on SBA-15 for deep hydrodesulfurization

In the present work, we report results of a comparison study of bimetallic NiMo and NiW hydrodesulfurization (HDS) catalysts supported on SBA-15 silica and trimetallic ones, prepared by co-impregnation (NiMoW) and mechanical mixing (NiMoNiW). The aim of this study was to inquire on the possibility of preparation of highly active supported trimetallic catalysts for deep HDS and to evaluate their efficiency in hydrodesulfurization of refractory sulfur-containing compounds. SBA-15 support and prepared bi- and trimetallic catalysts were characterized by nitrogen physisorption, small-angle and powder XRD, temperature programmed reduction, UV–vis DRS, Raman and HRTEM, and tested in the simultaneous HDS of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). It was found that the trimetallic NiMoW/SBA-15 catalyst prepared by co-impregnation showed the highest catalytic activity in HDS of both model compounds tested. As it was shown by TPR, DRS, Raman and HRTEM, this behavior can be attributed to the difference in the characteristics of Mo and W species in this trimetallic catalyst and in the corresponding bimetallic NiMo/SBA-15 and NiW/SBA-15 counterparts.

Catalytic Activities of NiMo Carbide Supported on SiO2 for the Hydrodeoxygenation of Ethyl Benzoate, Acetone, and Acetaldehyde

Bimetallic NiMo carbide supported on SiO2 has been synthesized by means of a temperature-programmed reaction. Characterization was performed by elemental analysis, Brunauer−Emmett−Teller (BET) surface area analysis, temperature-programmed reduction (H2−TPR), temperature-programmed oxidation (TPO), temperature-programmed desorption of NH3 (NH3−TPD), and X-ray diffraction (XRD). Elemental analysis and TPO characterization indicated that carbon was successfully introduced into the lattice of NiMo carbide by a temperature-programmed reaction with a mixture of H2 and CH4. Ethyl benzoate was used as a model molecule to investigate the hydrodeoxygenation (HDO) activities of NiMo carbide. As a comparison, HDO reactions of ethyl benzoate were also investigated over Mo carbide as well as CoMo sulfide. The results indicated that NiMo carbide was the most stable catalyst for HDO among the samples. On the basis of the hydrodeoxygenation (HDO) evaluation of ethyl benzoate and characterization of passivated and used NiMo carbide, it can be deduced that the changes of catalytic activity of NiMo carbide, during HDO reactions, may be ascribed to oxygen accumulation as well as coke deposition on the surface of the catalyst. HDO reactions of acetone and acetaldehyde were also investigated over NiMo carbide. The results indicated that NiMo carbide was a highly active and stable catalyst for HDO of acetone and acetaldehyde.

Deoxygenation of vegetable oils over sulfided Ni, Mo and NiMo catalysts

Deoxygenation of vegetable oils has a potential to become an important process for production of biofuels. The present work focuses on investigation of Ni, Mo, and NiMo sulfided catalysts prepared by impregnation in deoxygenation of rapeseed oil at 260–280 °C, 3.5 MPa and 0.25–4 h −1 in a fixed-bed reactor. The activity of the catalysts decreased in the order NiMo/Al 2O 3 > Mo/Al 2O 3 > Ni/Al 2O 3. The catalysts exhibited significantly different product distributions. The bimetallic NiMo catalysts showed higher yields of hydrocarbons than the monometallic catalysts at a given conversion. Apart from the various oxygenated product intermediates, NiMo/Al 2O 3 yielded a mixture of decarboxylation and hydrodeoxygenation hydrocarbon products while Ni/Al 2O 3 yielded only decarboxylation hydrocarbon products and Mo/Al 2O 3 yielded almost exclusively hydrodeoxygenation hydrocarbon products. The effect of Ni/(Ni + Mo) atomic ratio in the range 0.2–0.4 on the activity and selectivity was not significant.

Comparison of P-containing γ-Al 2O 3 supported Ni-Mo bimetallic carbide, nitride and sulfide catalysts for HDN and HDS of gas oils derived from Athabasca bitumen

Phosphorus containing γ-Al 2O 3 supported bimetallic Ni-Mo carbide, nitride and sulfide catalysts have been synthesized from an oxide precursor containing 12.73 wt.% Mo, 2.54 wt.% Ni and 2.38 wt.% P and characterized by elemental analysis, pulsed CO chemisorption, surface area measurements, X-ray diffraction, temperature-programmed reduction and DRIFT spectroscopy of CO adsorption. DRIFT spectroscopy of adsorbed CO on activated catalysts showed that carbide and nitride catalysts have surface exposed sites of Mo ø+ (0 < ø < 3) and Mo δ+ (0 < δ < 2) sites respectively, and these sites are susceptible to sulfidation with H 2S/H 2 mixture at 370 °C. The hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) activities of the bimetallic Ni-Mo carbide, nitride and sulfide catalysts were compared against commercial Ni-Mo/Al 2O 3 catalyst in a trickle bed reactor using light gas oil and heavy gas oil derived from Athabasca bitumen in the temperature range 340–370 and 375–400 °C respectively at 8.8 MPa. The gradual transformation of Ni-Mo carbide and nitride phases into Ni-Mo sulfide phases was observed during precoking period, and the formed Ni-Mo sulfide phases enhanced the HDN and HDS activities of carbide and nitride catalysts. The γ-Al 2O 3 supported Ni-Mo bimetallic sulfide catalyst was found to be more active for HDN and HDS of light gas oil and heavy gas oil than the corresponding carbide and nitride catalysts on the basis of unit weight.

Supported (NiMo,CoMo)-carbide, -nitride phases: Effect of atomic ratios and phosphorus concentration on the HDS of thiophene and dibenzothiophene

A study on the catalytic properties of the transition metals (Ni,Co,Mo)-carbides, -nitrides for thiophene and dibenzothiophene hydrotreating was conducted. The (Ni,Co)-Mo carbides and the corresponding (Ni,Co)-Mo nitride phases showed a catalytic activity higher than conventional bimetallic (Ni,Co)-Mo sulfides. In addition, a study was done on the effect of the atomic ratios, i.e., 0.1 ≤ M +/(M + + Mo) ≤ 0.9 where M + stands for Ni or Co, and the concentration of promoters such as phosphorous, which was a structural stabilizing agent. The catalytic performance of the bimetallic NiMo and CoMo carbides and nitrides was studied using thiophene and dibenzothiophene hydrodesulfurization (HDS) as model reactions at 623 K and P = 1 atm. The catalytic activity of the dispersed carbide and nitride phases on the alumina carrier was more significant than that of the reference catalysts, alumina supported NiMo-S and CoMo-S. The metallic character of the NiMo and CoMo carbides was evidenced by their higher hydrogenation activity in thiophene HDS, while the nitrides favored both hydrogenation and hydrogenolysis type reactions.

Hydrodeoxygenation of Residual Fatty Acids Fraction over Ni-Mo / Al2O3 Catalyst

The hydrodeoxygenation of the residual fraction of fatty acids from sunflower oilwas performed on bimetallic Ni-Mo/-Al2O3. Experiments were carried out on a in a continuous system at temperatures below 340 �C and pressures less than 70 bar. The catalyst shows a total acidity of 1.192 meq / g, from which 0.714 meq / g represents the concentration of weak acid centers, 0.438 meq / g represents the concentration of medium strength acid centers, while the concentration of strong centers is very small, only 0.041 meq / g. The analysis of the reaction products mainly highlighted the presence of linear hydrocarbons.

99/00207 Catalytic hydrogenation of aromatic hydrocarbons in a trickle bed reactor

The work presented in this paper is a continuation of our earlier work aimed at acquiring a fundamental understanding of sulfided Ni-Mo/γ-Al2O3catalysts in HDN catalysis. A series of temperature-programmed desorption and reduction experiments were performed overin-situsulfided bare γ-alumina support, alumina-supported monometallic Ni, Mo, and bimetallic NiMo catalysts. The TPD and TPR results were linked to the active site assignment of Ni- and Mo-associated centers in HDN reactions. Postreaction XPS and SEM characterizations were performed for catalysts used in HDN for up to 1000 h. One of the major changes during the aging of the Ni-Mo/γ-Al2O3catalysts was the loss of some active sites associated with the Ni promoters. The decreased Ni content over the catalyst surface was consistent with the observed decrease in the hydrogenation function of the catalyst. Two possible mechanisms are suggested for the loss of Ni active sites. One is coking that spreads from the alumina support to the nickel sites. Another is segregation of some Ni atoms from the Ni-Mo-S structure due to loss of structural sulfur.

NiMoS/γ-Al2O3Catalysts: The Nature and the Aging Behavior of Active Sites in HDN Reactions

The work presented in this paper is a continuation of our earlier work aimed at acquiring a fundamental understanding of sulfided Ni-Mo/γ-Al2O3catalysts in HDN catalysis. A series of temperature-programmed desorption and reduction experiments were performed overin-situsulfided bare γ-alumina support, alumina-supported monometallic Ni, Mo, and bimetallic NiMo catalysts. The TPD and TPR results were linked to the active site assignment of Ni- and Mo-associated centers in HDN reactions. Postreaction XPS and SEM characterizations were performed for catalysts used in HDN for up to 1000 h. One of the major changes during the aging of the Ni-Mo/γ-Al2O3catalysts was the loss of some active sites associated with the Ni promoters. The decreased Ni content over the catalyst surface was consistent with the observed decrease in the hydrogenation function of the catalyst. Two possible mechanisms are suggested for the loss of Ni active sites. One is coking that spreads from the alumina support to the nickel sites. Another is segregation of some Ni atoms from the Ni-Mo-S structure due to loss of structural sulfur.

Kinetics of CO Hydrogenation over Ni−Mo/Al2O3 Catalysts with and without K Promotion

The effect of K promotion on the CO hydrogenation activity and C{sub 2}-C{sub 4} hydrocarbons selectivity of the 15 wt% Ni-10 wt% Mo/Al{sub 2}O{sub 3} catalyst was investigated in the 498--548 K range using unpromoted and 1--3 wt% K-promoted samples. CO{sub 2} methanation tests at 523 K were used as a probe to confirm activity trends. Intrinsic kinetic data were obtained in the initial rate region on both unpromoted and 1 wt% K-promoted Ni-Mo catalysts. K promotion of the bimetallic Ni-Mo catalyst decreases both the activity and the specific activity of the Ni sites while increasing the C{sub 2}-C{sub 3} olefin-to-paraffin ratio. The surface carbide mechanism with dissociative adsorption of hydrogen as the rate-limiting step gives the most plausible kinetic model among the models tested for both Ni-Mo and Ni-Mo-K catalysts.