Cobalt Bimetallic Catalysts Research Articles

Effect of Bimetallic Co-Cu/Dolomite Catalyst on Glycerol Conversion to 1,2-Propanediol

This present study examines the efficacy of using dolomite (Dol, CaMg(CO3)2)-supported copper (Cu) and cobalt (Co) bimetallic and monometallic catalysts for the hydrogenolysis of glycerol to propylene glycol (PG; 1,2-PDO). The proposed catalysts were generated using the impregnation process before they were calcined at 500°C and reduced at 600°C. Advanced analytical techniques namely Brunauer, Emmett, and Teller (BET) method; the Barrett, Joyner, and Halenda (BJH) method; temperature-programmed desorption of ammonia (NH3–TPD), hydrogen-temperature programmed reduction (H2-TPR), X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM) were then used to characterise the synthesised catalysts, whose performance was then tested in the hydrogenolysis of glycerol. Of all the synthesised catalysts tested in the hydrogenolysis process, the Co-Cu/Dol bimetallic catalyst performed best, with an 80.3% glycerol conversion and 85.9% PG selectivity at a pressure of 4 MPa, a temperature of 200°C, and a reaction time of 10 hours. Its high catalytic performance was attributed to effective interactions between its Co-Cu-Dol species, which resulted in acceptable acidity, good reducibility of metal oxide species at low temperatures, larger surface area (15.3 m2 g-1), large-sized particles, fewer pores (0.032 cm3 g-1), and smaller pore diameter (0.615 nm).

Nickel‒cobalt bimetallic catalysts prepared from hydrotalcite-like compounds for dry reforming of methane

Ni–Co/Mg(Al)O alloy catalysts with different Co/Ni molar ratios have been prepared from Ni- and Co-substituted Mg–Al hydrotalcite-like compounds (HTlcs) as precursors and tested for dry reforming of methane. The XRD characterization shows that Ni–Co–Mg–Al HTlcs are decomposed by calcination into Mg(Ni,Co,Al)O solid solution, and by reduction finely dispersed alloy particles are formed. H2-TPR indicates a strong interaction between nickel/cobalt oxides and magnesia, and the presence of cobalt in Mg(Ni,Co,Al)O enhances the metal-support interaction. STEM-EDX analysis reveals that nickel and cobalt cations are homogeneously distributed in the HTlcs precursor and in the derived solid solution, and by reduction the resulting Ni–Co alloy particles are composition-uniform. The Ni–Co/Mg(Al)O alloy catalysts exhibit relatively high activity and stability at severe conditions, i.e., a medium temperature of 600 °C and a high space velocity of 120000 mL g−1 h−1. In comparison to monometallic Ni catalyst, Ni–Co alloying effectively inhibits methane decomposition and coke deposition, leading to a marked enhancement of catalytic stability. From CO2-TPD and TPSR, it is suggested that alloying Ni with Co favors the CO2 adsorption/activation and promotes the elimination of carbon species, thus improving the coke resistance. Furthermore, a high and stable activity with low coking is demonstrated at 750 °C. The hydrotalcite-derived Ni–Co/Mg(Al)O catalysts show better catalytic performance than many of the reported Ni–Co catalysts, which can be attributed to the formation of Ni–Co alloy with uniform composition, proper size, and strong metal-support interaction as well as the presence of basic Mg(Al)O as support.

RETRACTED ARTICLE: Promoted Nickel–Cobalt Bimetallic Catalysts for Biogas Reforming

RETRACTED ARTICLE: Promoted Nickel–Cobalt Bimetallic Catalysts for Biogas Reforming

Dry methane reforming with nickel–cobalt bimetallic catalysts based on halloysite nanoclay modified by alkaline melting method

AbstractCatalysts, including (10% Ni)/AMHA, (10% Ni + 5% Co)/AMHA, (5% Ni + 5% Co)/AMHA, and (5% Ni + 10% Co)/AMHA, were prepared by simultaneous impregnation of Ni and Co on alkaline molten halloysite (AMHA) and characterized by X‐ray diffraction (XRD), field diffusion scanning electron microscopy (FESEM), temperature‐programmed reduction (TPR), temperature‐programmed oxidation (TPO), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), atomic force microscopy (AFM), and Brunauer–Emmett–Teller (BET). The catalysts were evaluated in dry reforming of methane (DRM) at temperatures of 700 to 850°C and with a volumetric composition of a feed gas of 40% CH4, 40% CO2, and 20% Ar in a fixed bed reactor. Catalyst performance tests showed that the nickel catalyst based on milled and alkaline molten nano‐halloysite had a relatively poor performance. After impregnation of cobalt metal with different concentrations in the presence of nickel, the functional properties increased. Characteristic observations and experiments showed a very positive effect of cobalt metal on the catalyst performance. The presence of cobalt reinforcing metal along with nickel improves the activity and stability and reduces catalyst coking. Moreover, increasing cobalt along with nickel leads to better dispersion of the active phase of nickel, improved catalyst regeneration, and stable production of synthetic gas from methane and carbon dioxide. The effect of cobalt and nickel ratio on the catalyst structure, conversion rate of methane and carbon dioxide, stability, and carbon deposition rate were investigated. The conversion rate increases at high temperatures. Also, the resulting gas composition is suitable for Fischer–Tropsch reactions.

Hydrogen augmentation of biogas through dry reforming over bimetallic nickel-cobalt catalysts supported on titania

The nickel and cobalt bimetallic catalysts (with 11 wt% metals content) supported on Titania were synthesized through wet-impregnation approach and investigated for biogas reforming. The catalysts were characterized using BET analysis, X-ray diffraction (XRD), Field-emission Scanning Electron Microscope (FESEM), and H2-temperature programmed reduction (H2-TPR) techniques. The H2-TPR analysis revealed that bimetallic catalysts have sturdy metal-support synergy which restrains the metallic sintering. The catalytic activity for biogas reforming was explored under ambient pressure condition with temperature varying from 650 to 900 ˚C and GHSV range of 24,000 to 72,000 ml/g/h with CH4/CO2 ratio of 1.5. The experimental results revealed that the catalytic performance is strongly dependent on the appropriate Ni/Co ratio for bimetallic catalysts. The bimetallic catalyst (7 wt.%) Ni-(4 wt.%) Co/TiO2 showed better catalytic activity and stability due to the synergistic effects of Ni and Co. The Ni/Co ratio could be fine-tuned to enhance pore textural properties, which assisted the metal particle distribution and led to reduction in metallic particle size, increment in activity, and retardation to coke deposition. At 900 °C, (7 wt.%) Ni-(4 wt.%) Co/TiO2 catalyst showed 87.13% CH4 and 92.6% CO2 conversion with 41.1% H2 production. The bimetallic catalysts also withstand the catalytic performance during 15 h of continuous reforming as an insignificant decrease was observed in the activity. XRD characterization of spent catalyst shows the re-oxidation of cobalt metal in single metal catalyst. Moreover, with addition of oxygen the increase in catalyst activity was obtained in terms of reactant conversion and hydrogen selectivity.

Removal of toluene from air streams by cobalt-copper bimetallic catalysts supported on sepiolite

Oxidative removal of toluene using copper and cobalt bimetallic catalysts with varying molar ratios supported on sepiolite was investigated. The catalysts prepared by a deposition precipitation method and were characterized using X-ray diffraction, nitrogen adsorption-desorption, field emission scanning electron microscopy, H2-temperature-programmed reduction, transmission electron microscope, and inductive coupled plasma atomic emission spectroscopy. The species supported on sepiolite are Co3O4, CuO, and CuCo2O4. The activities of the tested catalysts increased in the order 0Co-4Cu/Sep <1Co-3Cu/Sep <4Co-0Cu/Sep <1Co-1Cu/Sep <3Co-1Cu/Sep. The latter exhibiting 90% toluene oxidative degradation at 288 °C within 15 h, having high selectivity towards CO2, and being stable at 300 °C up to 15 h. In conclusion, this study showed that sepiolite has excellent properties as a support.

Au Based Ni and Co Bimetallic Core Shell Nanocatalysts for Room Temperature Selective Decomposition of Hydrous Hydrazine to Hydrogen

AbstractNickel and Cobalt bimetallic catalysts with Au as core metal has been synthesized and demonstrated for hydrazine decomposition reaction for producing hydrogen. Gold‐cobalt and gold nickel bimetallic system belonging to the class of strained structures with high lattice mismatch of approximately 14% are demonstrated for synergistic effects atypical of monometallic counterparts for the selective decomposition of hydrous hydrazine to H2 with N2 as the other product at room temperature.

Catalytic Decomposition of Nitrogen Oxides by Bimetallic Catalysts Synthesized by Dielectric Barrier Discharge Plasma Technology

Nitrous oxide (N2O) is a common greenhouse gas and urgent need to be contained. Direct catalytic decomposition of N2O by high activity catalyst into N2 and O2 is a low-cost and harmless method. Bimetallic catalysts show good catalytic activity in many classes of reactions, and plasma technologies, applied to prepare of catalyst, are considered to be a promising method. In our contribution, DBD cold plasma is applied to synthesize Rhodium and Cobalt bimetallic catalysts for catalytic N2O decomposition. The influence of cobalt and rhodium content on N2O decomposition activity shows that the optimal amount of metal is determined as 5wt. % cobalt and 0.5wt. % rhodium loaded on Al2O3. The best working voltage is determined as 18kV. The results indicated that the Rh/Al2O3 catalysts prepared by atmospheric-pressure DBD cold plasma showed smaller size and high dispersion of Rh particles, so that the metal-support interaction and the catalytic activity are enhanced. Atmospheric-pressure DBD cold plasma is proved to be an environmentally friendly and efficient method for preparing high performance Rhodium and Cobalt bimetallic catalysts for catalytic N2O decomposition.

Catalytic oxidation of benzene over ruthenium–cobalt bimetallic catalysts and study of its mechanism

A Ru–Co bimetallic catalyst was well demonstrated in benzene oxidation, and the reaction mechanism was studied.

Highly active and reusable silica-aerogel-supported platinum–cobalt bimetallic catalysts for the dehydrogenation of ammonia borane

In this study, platinum–cobalt bimetallic catalysts supported on mesoporous silica aerogel (SAG), abbreviated as PCx/SAG,x= 1–6, were prepared by facile chemical reduction and a simple, efficient microwave-assisted method using Co and Pt precursors.

Supported Nickel–Cobalt Bimetallic Catalysts Derived from Layered Double Hydroxide Precursors for Selective Hydrogenation of Pyrolysis Gasoline

Generation of bimetallic sites on supported catalysts has been proved to be capable of enhancing catalytic performance when compared to those of the corresponding monometallic ones. Herein we report the preparation of novel Al2O3-supported NiCo bimetallic catalysts (NiCo/Al2O3) derived from Ni2+Co2+Al3+-containing layered double hydroxides (NiCoAl-LDHs) precursors, which were in situ grown on the surface and in the pore canals of microspherical γ-Al2O3, and their catalytic performance for selective hydrogenation of pyrolysis gasoline. Bimetallic NiCo/Al2O3 derived from LDHs precursor exhibited the better catalytic performance than the sample prepared by impregnation. The appropriate amounts of substitution of nickel for cobalt improved the catalytic activity and stability dramatically, indicating the synergistic effects of nickel and cobalt in terms of the hydrogenation reactivity. The enhanced reducibility and smaller particles for NiCo/Al2O3 samples derived from LDHs precursor were proposed to suppress the coke formation during the hydrogenation reaction, leading to improve catalytic activity and stability.

Nickel and cobalt bimetallic hydroxide catalysts for urea electro-oxidation

Nickel–Cobalt bimetallic hydroxide electrocatalysts, synthesized through a one-step electrodeposition method, were evaluated for the oxidation of urea in alkaline conditions with the intention of reducing the oxidation overpotential for this reaction. The Nickel–Cobalt bimetallic hydroxide catalysts were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), Raman spectroscopy, cyclic voltammetry (CV), and polarization techniques. A significant reduction in the overpotential (150 mV) of the reaction was observed with the Nickel–Cobalt bimetallic hydroxide electrode (ca. 43% Co content) when compared to a nickel hydroxide electrode. The decrease of the urea oxidation potential on the Nickel–Cobalt bimetallic hydroxide electrodes reveals great potential for future applications of urea electro-oxidation, including wastewater remediation, hydrogen production, sensors, and fuel cells.

Biogas reforming for hydrogen production over nickel and cobalt bimetallic catalysts

Abstract Ni/Co bimetallic catalysts supported by commercial γ-Al2O3 modified with La2O3 for biogas reforming were prepared by conventional incipient wetness impregnation. The catalysts were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), BET surface area and porosity analysis (BET), H2 temperature-programmed reduction (H2-TPR), transmission electron microscopy (TEM) and thermogravimetry coupled to differential scanning calorimetry (TG–DSC). XRD and XPS analysis revealed that a Ni/Co alloy was formed in the bimetallic catalysts. The Ni/Co ratio could be adjusted to improve pore textural properties, which enhanced the metal particle dispersion and resulted in smaller metal particle size, and thus increased the catalytic activity and resistance to carbon deposition. The activity and stability of the catalysts for biogas reforming was tested at 800 °C, ambient pressure, GHSV of 6000 ml gcat−1 h−1 and a CH4/CO2 molar ratio of 1 without dilute gas. Experimental results showed that the catalytic activity could be closely related to the Ni/Co ratio. The bimetallic catalyst 7Ni3Co/LaAl exhibited better catalytic and anti-coking performance due to smaller metal particles, higher metal dispersion, uniform pore distribution, surface enrichment of Co, as well as the synergetic effect between Ni and Co. During a 290 h stability test over the catalyst 7Ni3Co/LaAl, the average conversion of CH4 and CO2, selectivity to H2 and CO, and ratio of H2/CO were 93.7%, 94.0%, 94.9%, 97.8%, and 0.97, respectively. The average coking rate was 0.0946 mg gcat−1 h−1.

Preparation and characterization of Pd–Co/sulfated zirconia catalysts for no selective reduction by methane

Abstract Palladium and cobalt bimetallic catalysts supported on sulfated zirconia (PdCo/SZ), obtained from different precursors of Pd (nitrate and acetylacetonate), were prepared to study their influence on the selective reduction of NO by CH4 (SCR–CH4). Catalysts with nominal Pd and Co concentrations of 0.2 and 2 wt%, respectively were characterized by XRD, DRS, XPS and Raman microprobe spectroscopy. The Raman signals denote a superficial increase of the zirconia monoclinic phase during the preparation stage in the catalysts obtained from Pd(NO3)2 but structural alterations in the surface were not observed when the organic palladium salt was used. Co2+ presence, very propitious for this reaction, was determined in fresh catalysts. Catalysts used in reaction exhibit the presence of Co3O4 and PdO agglomerates on the surface, loss of sulfates and a total transformation of the tetragonal to monoclinic phase on the support surface. Influence on SCR–CH4 of the Pd catalytic precursor was not detected. The catalyst from Pd(NO3)2 showed better stability than the catalyst from Pd(CH3COCH C(O )CH3)2 precursor.

Tailoring of activity and selectivity using bimetallic catalyst in hydrogenation of succinic acid

The liquid phase hydrogenation of succinic acid (SA) to γ-butyrolactone (GBL) and 1,4-butanediol (BDO) was investigated using ruthenium–cobalt bimetallic catalysts in a semi-batch slurry reactor. The doping of ruthenium (up to 1%) with cobalt resulted in increase (3–4 times) in the overall hydrogenation activity indicating a strong synergistic effect. Ru–Co bimetallic catalyst also influenced the product distribution by promoting specific hydrogenation steps in the overall reaction scheme. Based on the observed catalyst activity results, a speculative reaction pathway for cobalt as well as for ruthenium–cobalt catalyzed hydrogenation of succinic acid has been proposed.

Hydro-dehydrogenation of six-member hydrocarbon cycles on supported platinum–cobalt bimetallic catalysts

The dehydrogenation of cyclohexane and hydrogenation of benzene and toluene were studied on alumina- and NaY-supported Pt, Co and Pt–Co catalysts. The toluene/benzene adsorption equilibrium constant ratios were also determined. Hydro-dehydrogenation data were compared with the activities of these catalysts in CO conversion and methane 1 H– 2 H exchange data determined and published earlier for the same catalysts. Addition of Co to Pt reduced the hydro-dehydrogenation conversion rates. This effect was substantially stronger for benzene and toluene hydrogenation than that for dehydrogenation of cyclohexane. The turnover frequency (TOF) value for cyclohexane dehydrogenation indicated a synergy effect between Pt and Co in case of alumina supported Pt:Co sample of 50:50 at%. The TOF values indicated also the existence of significant “cooperation” between Pt and Co in PtCo/Al 2O 3 catalysts. Synergy, found for all samples in formation of oxygenates from CO is elucidated on the basis of Pt–Co interaction, indicated by the increased toluene/benzene adsorption equilibrium constant ratio on alumina supported PtCo catalysts. A positive correlation was observed between adsorption equilibrium constants and conversion rates of the different hydrocarbons.

Structure and Characterization of Supported Ruthenium--Cobalt Bimetallic Catalysts

Ruthenium, cobalt, and ruthenium–cobalt bimetallic samples, supported on SiO2, Al2O3, and NaY zeolite, were characterized by temperature-programmed reduction, CO chemisorption, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. Temperature-programmed reduction revealed that the reducibility for cobalt increases in the order NaY<SiO2<Al2O3, while for ruthenium the sequence was Al2O3<NaY<SiO2. If Ru/NaY samples are calcined in oxygen, then ruthenium migrates to the external surface of NaY and agglomerates, while in the case of He-treated zeolite samples the ruthenium metal particles are stabilized in the supercage in the range of 1 to 3 nm average diameter, as measured by X-ray diffraction, CO chemisorption, and transmission electron microscopy. Cobalt ions are irreducible when they are exchanged alone or first in the NaY zeolite for the bimetallic sample Ru–Co/NaY[I]. Here the reduction of Ru3+ions is not affected by the presence of cobalt, whereas when Ru3+ions exchanged first into NaY (Ru–Co/NaY[II]), the cobalt ions are easily reduced and bimetallic particles are formed but the migration of ruthenium particles to the outer surface of NaY zeolite is hampered.

Low-Temperature Methane Activation under Nonoxidative Conditions over Supported Ruthenium–Cobalt Bimetallic Catalysts

Dissociative chemisorption of methane over ruthenium, cobalt, and ruthenium–cobalt bimetallic catalysts supported by alumina, silica, and NaY was investigated under a wide range of temperatures. The extent of hydrogen loss from methane was monitored by deuterium uptake of the surface carbonaceous species (CHx) formed from methane and/or by the amount of hydrogen evolved during the course of methane chemisorption. The presence of a high average number of deuteriums in the desorbing methane suggested a wide spread dissociation of methane. The initial distribution of the deuterated products generally decreased in the sequence CD4>CHD3>CH2D2. The amount of chemisorbed methane and the evolution of hydrogen during methane chemisorption increase with temperature and follow the sequence of reducibility of the supported metals and the particle size which, in turn, depends on the support and the alloy formed. CH species prevailed on alumina- and silica-supported catalysts, while on NaY-supported metals, CH2species are dominant when small metal particles are stabilized inside the supercage.

Bimetallic catalysts: structure and reactivity

The effect of the support in constraining the formation and defining the structure of bimetallic particles has been considered. Alumina and NaY zeolite supported platinum and cobalt bimetallic catalysts are illustrated to rationalize this effect. The surface composition and dispersion of the bimetallic particles are further correlated with the catalytic activity of bimetallic catalysts in CO hydrogenation.