NiMo Carbide Research Articles

Development of Ni–Mo carbide catalyst for production of syngas and CNTs by dry reforming of biogas

Biogas has been widely regarded as a promising source of renewable energy. Recently, the direct conversion of biogas over heterogeneous catalysts for the simultaneous production of syngas and carbon nanotubes exhibits a high potential for full utilization of biogas with great benefits. Involving the combined dry reforming of methane and catalytic decomposition of methane, the efficiency of process is strongly depended on the catalyst activity/stability, mainly caused by carbon deposition. In this study, Ni–Mo catalyst is engineered to provide a life-long performance and perform high activity in the combined process. The surface modification of catalysts by a controlled carburization pretreatment is proposed for the first time to produce a carbide catalyst along with improving the catalyst stability as well as the reactivity for direct conversion of biogas. The performance of as-prepared carbide catalysts is investigated with comparison to the oxide and metallic ones. As a result, the Ni–Mo2C catalyst exhibited superior activity and stability over its counterparts, even though the condensed nanocarbon was largely grown and covered on the surface. In addition, up to 82% of CH4 conversion and 93% of CO2 conversion could remain almost constant at 800 °C throughout the entire test period of 3 h under a high flowrate inlet stream of pure biogas at 48,000 cm3 g−1 h−1. The XPS spectra of catalysts confirmed that the presence of Mo2C species on the catalyst surface could promote the stability and reactivity of the catalyst, resulting in higher productivity of carbon nanotubes over a longer time.

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

NiMo carbide supported on algal derived activated carbon for hydrodeoxygenation of algal biocrude oil

The use of novel algae-derived activated carbon supported NiMo carbide catalysts for upgrading algal biocrude oil by hydrodeoxygenation was investigated. The carbide catalysts were prepared in a two-step process involving sequential impregnation or co-impregnation of NiMo on activated carbon and followed by carbonization through three different methods namely temperature-programmed reaction with 20%CH4-80%H2, carbothermal hydrogen reduction in H2, and carbothermal reduction in N2. The synthesized carbide catalysts were characterized using XRD, BET, TPD-NH3, TGA, and XPS techniques. The catalysts were screened for hydrodeoxygenation (HDO) of algal biocrude at various process conditions in a stirred tank reactor to produce liquid hydrocarbon fuels. The liquid hydrocarbon product was analyzed by 1HNMR, 13CNMR, Sim-dist, CHNS, and GC–MS to gain insight into algal biofuel properties. The NiMo carbide synthesized through co-impregnation and carbothermal reduction in N2 showed optimal activity for oxygen removal due to its high acidity and specific surface area and a greater amount of Mo2C as active phases on the surface. Response surface methodology was applied for NiMoC catalyst to optimize the effects of temperature (350–450 °C), catalyst loadings (5–15 wt%), and reaction time (1.5–4 h) at a constant pressure of 3 MPa. The upgraded biocrude oil revealed an oxygen reduction percentage of 94% with HHV of 43.9 MJ/kg.

Selective hydrogenation of aromatics in coal-derived liquids over novel NiW and NiMo carbide catalysts

Novel bimetallic NiW/Al2O3 and NiMo/Al2O3 carbide catalysts were prepared by temperature-programmed reaction with CH4-H2 mixture. The catalysts were characterized by N2 adsorption, XRD, TPR and their performance for selective hydrogenation of aromatics in coal derived liquids were compared with their sulfide counterparts. Direct coal liquefaction oil (DCLO) fraction in 180∼290 °C and aromatic component separated from low temperature coal tar (LTCT) fraction in 210∼290 °C were selected as feedstock and hydrogenated on a fixed bed micro-reactor. The results of elemental analysis, simulated distillation and GC-MS show that the hydrodearomatization (HDA) activity was: NiMo-C > NiW-C > NiW-S > NiMo-S. The HDA, Hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) for DCLO hydrogenation over NiMo-C is 91%, 29.54% and 75.23%, respectively. The hydroaromatics and cycloalkanes in hydrogenated LTCT and DCLO products were 67.1% and 74.8%, respectively. Thus, NiMo carbide is a promising catalyst for selective hydrogenation of CDLs to obtain high performance jet fuel blend which is rich in hydroaromatics and cycloalkanes.

Effect of initial Si/Al ratios on the performance of low crystallinity Hβ-x zeolite supported NiMo carbide catalysts for aromatics hydrogenation

The initial Si/Al ratio of supports influences the active metal composition and dispersion, acidity of NiMoC/Hβ-x catalysts, and performance of aromatic hydrogenation.

Effect of Ni–Mo Carbide Catalyst Formation on Furfural Hydrogenation

High-loading Ni–Mo carbide catalysts were prepared by the modified gel-combustion method under various thermal treatment conditions. All samples were studied by X-ray diffraction (XRD) analysis, which showed that the catalysts could contain cubic and hexagonal molybdenum carbides, nickel, nickel oxide and Ni–Mo solid solutions, depending on the thermal treatment conditions. Study of catalyst activity and selectivity in the hydrogenation of furfural was carried out in a batch reactor at 150 °C and hydrogen pressure 6.0 MPa. Analysis of the reaction products showed that the highest yields of 2-methylfuran (2-MF) and furfuryl alcohol (FA) were achieved using catalysts synthesized by calcination of the nickel-molybdenum-carbon precursor at 400 °С with the following reduction in a stream of hydrogen at 600 °C. The best results for production of FA with a yield of 80 mol % and 2-MF with a yield of 29 mol % were observed using Ni6MoC–SiO2 (400/600) and Ni1MoC–SiO2 (400/600) catalysts, respectively. It has been shown that the addition of nickel to the carbide molybdenum catalyst significantly increases the activity of the catalytic systems. In addition, nickel also contributes to the formation of products formed by hydrogenation of the aromatic ring tetrahydrofurfuryl alcohol (THFA) and 2-methyltetrahydrofuran (2-MTHF).

A Novel Bimetallic Nickel–Molybdenum Carbide Nanowire Array for Efficient Hydrogen Evolution

The design and fabrication of noble-metal-free hydrogenevolution electrocatalysts with high activity is significant to future renewable energy systems. In this work, self-supported NiMo carbide nanowires on carbon cloth (Ni3 Mo3 C@NPC NWs/CC; NPC=N,P-doped carbon) were developed through an electropolymerization-assisted procedure. During the synthesis process, NiMoO4 nanowires were first grown on CC through a hydrothermal reaction that was free of any polymer binder such as Nafion. By use of electropolymerization, the as-prepared NiMoO4 NWs/CC sample was then coated by a layer of polypyrole (PPy) that served as the carbon source for subsequent conversion into Ni3 Mo3 C@NPC NWs/CC by carbothermal reduction. The experimental results indicated that judicious choices of the amount of coated PPy and the pyrolysis temperature were essential for obtaining the pure-phase, nanowire array structure of Ni3 Mo3 C@NPC NWs/CC. Benefitting from the pure phase of the bimetallic carbide, the unique architecture of the nanowire array, and its self-supported nature, the optimized Ni3 Mo3 C@NPC NWs/CC electrode exhibited excellent performance in the hydrogen evolution reaction (HER) in both acidic and alkaline media. Low overpotentials of 161 and 215 mV were required to afford a high current density of 100 mA cm-2 toward the HER in acidic and alkaline media, respectively, and the catalytic activity was maintained for at least 48 h, which puts Ni3 Mo3 C@NPC NWs/CC among the best HER electrocatalysts based on metallic carbides yet reported.

Comparison of transesterification and thermal cracking methods on fuel specifications of castor oil biodiesel

A series of NiMo/γ-Al2O3 carbides were synthesized with the temperature programmed carburization method for the tri-reforming of methane. The relationship between the catalytic behavior and the impregnation sequence was investigated by XRD, TG-DSC, XPS, SEM, and so on. It was found that Mo2C species were the active species for the tri-reforming of methane. The amounts of Mo2C species on the fresh NiMo carbides decreased in the order of co-impregnated NiMo carbide > Ni-first NiMo carbide > Mo-first NiMo carbide. In contrast, Mo2C species on the latter two carbides would continue to be formed during the tri-reforming of methane. NiMoO4 species only existed on the co-impregnated NiMo oxidic precursor, exhibiting a strong synergistic effect between Ni and Mo species. NiMoO4 species were reduced more easily than MoO3 species on the step-impregnated NiMo oxides. Ni0 species promoted the dissociation of methane, induced the reduction of molybdenum oxide and supplied active hydrogen and carbon species for the carburization process. The co-impregnation method was conducive to refine the particles.

Effect of impregnation sequence on the catalytic performance of NiMo carbides for the tri-reforming of methane

A series of NiMo/γ-Al2O3 carbides were synthesized with the temperature programmed carburization method for the tri-reforming of methane. The relationship between the catalytic behavior and the impregnation sequence was investigated by XRD, TG-DSC, XPS, SEM, and so on. It was found that Mo2C species were the active species for the tri-reforming of methane. The amounts of Mo2C species on the fresh NiMo carbides decreased in the order of co-impregnated NiMo carbide > Ni-first NiMo carbide > Mo-first NiMo carbide. In contrast, Mo2C species on the latter two carbides would continue to be formed during the tri-reforming of methane. NiMoO4 species only existed on the co-impregnated NiMo oxidic precursor, exhibiting a strong synergistic effect between Ni and Mo species. NiMoO4 species were reduced more easily than MoO3 species on the step-impregnated NiMo oxides. Ni0 species promoted the dissociation of methane, induced the reduction of molybdenum oxide and supplied active hydrogen and carbon species for the carburization process. The co-impregnation method was conducive to refine the particles.

Effect of additives on the properties of nickel molybdenum carbides for the tri-reforming of methane

A series of NiMo carbides modified with different additives were prepared with the temperature programmed reduction method. Characterization and catalytic properties for the tri-reforming of methane were performed. It was found that the presence of nickel species in NiMo series carbides stimulated the dissociation of methane and supplied the active carbon for the carburization process. La-promoted NiMo carbide could prevent the aggregation of small particles, facilitate the topotactic transformation of Mo2C species and inhibit the carbon deposition, which were benefit for the excellent catalytic performance. Ce and Co additives deteriorated the activities of NiMo carbides to some extent due to the larger particle size. Mg favored the coke generation and decreased the surface area and pore volume of NiMoCMg carbide. The addition of K suppressed the carburization process of molybdemum oxide species and caused the phase transformation of active γ-Al2O3 to less active θ-Al2O3. Mg and K modified NiMo carbides, especially the latter, showed a dramatic decrease in the redox ability for the tri-reforming of methane. The oxidation of carbidic species, the agglomeration of small particles and the carbon deposition decreased the catalytic activities of NiMo series carbides for the tri-reforming of methane.

One-step synthesis of bulk Mo and Ni–Mo carbides for methanation

β-Mo2C and Ni/β-Mo2C catalysts were prepared by a single-step thermal decomposition method using hexamethylentetramine (HMT) as a reducing agent and carbon source.

Sulfidability and thiophene hydrodesulfurization activity of supported NiMo carbides

Ni–Mo carbides supported on activated carbon were synthesized by carbothermal hydrogen reduction and the effect of the sulfidability on the thiophene hydrodesulfurization catalytic activity was studied. The X-ray diffraction patterns of Ni–Mo carbides showed the presence of β-Mo2C and NiC when the atomic ratio AR=Ni/(Ni+Mo) was between 0.25 and 0.75, while for AR=1, it only was detected metallic Ni. The X-ray photoelectron spectroscopy results showed the distribution of different surface species in the passivated catalysts: Moδ+ (0≤δ≤2), Mo4+, Mo6+, Niδ+ and Ni2+. After sulfiding the carbides were modified in their surface and catalytic activity.

Maya crude oil hydrotreating reaction in a batch reactor using alumina-supported NiMo carbide and nitride as catalysts

The hydrotreating (HT) of Maya crude oil was carried out in a Parr batch reactor, using alumina-supported catalysts based on NiMo sulfides, carbides and nitrides, which were synthesized by temperature programmed reaction of the oxidic precursors. The catalysts were characterized by X-ray diffraction, N2 physisorption, scanning- and high resolution transmission-electron microscopy. Next, catalysts with the best performance in thiophene hydrodesulfurization (HDS) were selected to be used in the HT of Maya crude oil. HT reactions were carried out at 320°C and 70–80kg/cm2. All catalysts were sulfided ex situ with a mixture of CS2/H2, prior to reaction. Products of reaction were analyzed by simulated distillation, sulfur and metal contents. Specific weight was also obtained, which was further used to calculate specific gravity and API gravity. Here, it was shown a synergistic effect by using Ni as promoter to Mo carbides and nitrides which is in contrast to previous reports. Moreover, during Maya crude oil HT, it was accomplished the enhancement of API gravity by using NiMo sulfide. Sulfur and metal removal was also successful using these materials, confirming that active phases based on NiMo nitrides and/or carbides could be considered as new HT catalysts for real feedstocks processing.

Support effects on hydrotreating of soybean oil over NiMo carbide catalyst

As an alternative to conventional sulfide catalysts, NiMo carbide catalysts were prepared by impregnation method and studied for the hydrotreating of soybean oil to produce hydrocarbons in the gasoline to diesel range. The effect of the catalyst supports on activity and selectivity was investigated by using three different types of materials: mesoporous material (Al-SBA-15), alumina (γ-Al2O3) and zeolites (ZSM-5, Zeolite β and USY). The structural characterization of the catalysts was performed using XRD, BET and TEM. Catalytic tests were carried out in a bench scale flow reactor at 400°C and 650psi. The results showed that the Al-SBA-15 supported catalyst has the highest surface area of 711.5m2g−1 and largest pore volume of 0.71cm3g−1. Among the five catalysts, hydrotreating on NiMoC/Al-SBA-15 gave the highest yield of organic liquid product (96%) and highest selectivity (97%) to hydrocarbons in the boiling range of the diesel fraction. For the three zeolite-supported catalysts, hydrotreating of soybean oil produced more hydrocarbon products in the boiling range of green gasoline (about 15–40%).

Crystallographic Properties of the Unsupported Ni-Mo Carbides Phases

In the present work, the crystallographic properties of unsupported Ni-Mo catalyst serie were carried out. They were synthesized with a ratio of Mo from 10, 25, 50 to 75 wt%. The final catalysts were characterized by X-ray diffraction (XRD) in order to identify crystallographic phases present in the solids using DRXwinsoftware version 2.3. The crystal size was determinated by Bragg’s law. Ni-Mo catalyst model (MoC-75) structure was modeled by Carine Crystallography Software version 3.1 which was built based on its space group and atomic positions which were previous the results of XRD. Characteristical phases of Ni-Mo Carbides were identified for their typical planes (111), (200) and (311) for Ni-Mo series and the plane (101) for the a Mo-C series.

Catalytic Properties of Ni-Mo Carbide and Nitride Phases Supported on SBA-15 and -16 in the Hydrodesulfurization of DBT

In this paper, the incorporation of carbide and nitride phases supported on mesoporous materials like SBA type is described in order to obtain a better material than commercial catalysts (NiMoS/Al2O3, Sg=269 m2.gr-1) specifically in the HDS of dibenzothiophene. The XRD patterns exhibit the presence of carbide and nitride phases in each series, respectively. In the nitride materials, the presence of oxide phases was more evident than in the carbide catalysts. The principal product was biphenyl (BF) for all the analyzed series. This behavior suggests that the DBT desulphurization pathway for the carbide materials was similar to that of sulfide catalysts. Bicyclohexyl (BCH) was analyzed as a product, and cyclohexylbenzene traces (CHB) were determined in a single catalyst (NiMoC-2%P/SBA-16). This was attributed to the hydrogenation character of carbide catalyst reported previously.

Relationship Between Sulfidation and HDS Catalytic Activity of Activated Carbon Supported Mo, Fe–Mo, Co–Mo and Ni–Mo Carbides

Temperature-programmed sulfiding (TPS) and temperature-programmed reduction of the sulfided catalysts (TPR-S) have been employed to evaluate Mo, Fe–Mo, Co–Mo and Ni–Mo carbide catalysts supported on activated carbon (AC). The carbides were prepared by carbothermal hydrogen reduction from co-impregnated precursors, and submitted to presulfiding prior to HDS. Samples of passivated catalysts prepared from the sulfates of Fe and Co contained variable amounts of sulfur, as shown by XPS and elemental analysis, while all samples showed increased sulfur contents after HDS. The TPS traces (up to 400 °C) of the Mo and Co–Mo samples exhibited two H2S consumption peaks, the first one starting at 100 °C and the second within the 400 °C isothermal region, located immediately after a H2S production peak centered at 400 °C for Mo and at 340 °C for Co–Mo. The Fe–Mo and Ni–Mo carbides exhibited a broad H2S consumption signal between 100 and 400 °C. The low temperature signals can be attributed to reduction of Mo(VI) oxide into Mo(V) or Mo(IV) sulfides, while the broad, higher temperature band is assigned to further reduction to the fully sulfided surface species. The TPR-S spectra showed three H2S evolution peaks, where the area of the first peak (assigned to reduction of sulfur species adsorbed on coordinatively unsaturated edge/corner sites) follows the order Co–Mo ≫ Ni–Mo ≈ Mo > Fe–Mo, which fully agrees with the order of HDS activities at steady state. Elemental analysis of the pre-sulfided AC support suggest that a large part of the sulfur consumed in sulfiding the catalysts is retained as elemental sulfur within the microporous structure of the support, although HRTEM observations confirm that MoS2-like structures are present in these samples. These results reinforce the importance of sulfided surface phases in HDS on carbides of transition metal catalysts. Transmission electron microscopy shows that activated carbon supported (M-)Mo carbide catalysts (M = Fe, Co, Ni) present MoS2-like fringes on top of bimetallic carbide crystals. Temperature-programmed techniques and elemental analysis prove that a large amount of sulfur is retained in the catalyst, likely within the slit-shaped microporous structure of the support. A good correlation was established between thiophene HDS activity at steady state and the size of a TPR peak of sulfided catalyst samples.

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.

Effect of cobalt (nickel) content on the catalytic performance of molybdenum carbides in dry-methane reforming

The dry-methane reforming (DMR) behavior of Co–Mo and Ni–Mo carbide catalysts has been studied in order to establish the effect of the cobalt or nickel content of molybdenum carbide DMR catalysts. The results indicate that incorporating cobalt into the Mo 2C structure at a Co/Mo ratio of 0.4, i.e. a Co 0.4Mo 1C x catalyst, gives a DMR activity and stability that are markedly higher than those of Mo 2C catalysts. With respect to the Ni–Mo carbide catalysts, a Ni/Mo atom ratio of 0.2 (i.e. an Ni 0.2Mo 1C x catalyst), gives the maximum synergistic interaction between Ni and Mo. However, higher molar ratios decrease the promoting effect and facilitate the phase separation of the promoter. These results are proved by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy and N 2-adsorption studies, and are also reflected in the poor catalytic stability of both the Co–Mo and the Ni–Mo carbide catalysts.

Ring opening and kinetics study of hydrotreated LGO on Ni-Mo carbide supported on HY and H-Beta catalysts

Pt-Ir/HY, Ni-Mo carbide/HY and Ni-Mo carbide/H-Beta catalysts were used to improve the fuel quality of Hydrotreated Light Gas Oil (HLGO). All the catalysts are well characterized by using BET, Elemental, TPR, TPD and XRD analyzers. Screening of the catalysts were done and observed that Ni-Mo carbide/HY is an effective catalyst for improvement in cetane index of HLGO. A 12 unit increase in cetane index was observed on Ni-Mo carbide/HY at 325 °C, whereas Ni-Mo carbide/H-Beta could not improve the cetane index effectively. The Pt-Ir/HY deactivates in three days even though its activity is comparable with that of Ni-Mo carbide/H-Beta. NMR analysis showed that the Ni-Mo carbide/HY catalyst improves the cetane index of the fuel by selectively converting the naphthenes to paraffins in the temperature range of 300–325 °C. Low cetane index was observed above 325 °C due to the dominance of dehydrogenation and secondary cracking reactions. Simulated distillation results indicated the presence of high percentage of naphtha fraction above 325 °C, which decrease the fuel quality due to their low cetane values. A first order kinetic model was proposed and the model was well fit with the experimental values. Arrhenius activation energies of 111, 89 and 42 kJ/g mol were observed for dehydrogenation, aromatic saturation and cracking reactions, respectively.