Cobalt Loading Research Articles

Mn doping of Co-Al spinel as Fischer-Tropsch catalyst support

Mn-doped spinel oxides CoAl2O4 marked as CMA-m (m = Co/Mn atom ratio) herein were synthesized and evaluated for the first time as supports of Co-based Fischer-Tropsch synthesis (FTS) catalysts. HAADF-STEM images showed that Mn doping caused more crystal defects on the surface of CMA-m grains, which may provide more attachment sites for cobalt loading, leading to much smaller Co0 particle size of 15Co/CMA-m than that of 15Co/CoAl2O4. Data of H2/CO chemisorption showed that the interaction of highly dispersed Co0 with lattice Mn-doped CMA-m grain has a promotive effect on CO adsorption capability. FTS evaluation results demonstrate that 15Co/CMA-20 showed the highest CO conversion, C5+ selectivity and C5+ STY, benefiting from its high Co0 dispersion and CO chemisorption capability as a result of suitable Mn doping into the lattice of CoAl2O4, which was confirmed very different from the influence of impregnated Mn oxide over CoAl2O4.

Ultralow Co Loading Phenanthroline‐based Porous Organic Polymer as a High‐efficient Heterogeneous Catalyst for the Fixation of CO2 to Cyclic Carbonates at Ambient Conditions

AbstractThe exploration of cost‐effective and efficient catalysts for the transformation of CO2 into chemicals at room temperature and low CO2 pressure is a key challenge. Here, a green synthesis method of porous organic polymer was developed, which was obtained by the Scholl coupling reaction via polycondensation of 1,3,5‐triphenylbenzene and 1,10‐phenanthroline at room temperature. The polymer has a large surface area (1074 m2 g−1) and exhibited excellent CO2 capture of 77.26 cm3 g−1 at 273.15 K and 1.00 bar. After loading cobalt acetate, an ultralow Co loading phenanthroline‐based porous organic polymer was obtained with very high catalytic efficiency in TOF of 263 h−1 for the fixation of CO2 to cyclic carbonates at room temperature and atmospheric with free‐solvent, which is over six‐fold than that of a molecular analogue, 1,10‐phenanthroline‐Co(OAc)2. This work provided a facile, powerful, green, and efficient strategy for designing porous organic polymers as high‐efficient heterogeneous catalysts in the fixation of carbon dioxide.

Controlled Thermal Conversion Strategy to Provide Metal-Organic Framework-Supported Composite Catalysts.

Metal-organic framework (MOF)-supported metal/metal compound nanoparticles (NPs) have emerged as a new class of composite catalysts. However, huge challenges prevail in placing such NPs in the MOF pores because of the poor solubility of metal/metal oxides, limited availability of suitable precursors, metastable attribute of given metal ions, and lower thermal stability of MOFs compared to conventional porous materials. Based on the difference between the thermal stability of the precursor and MOFs, we successfully developed a controlled thermal conversion (CTC) method to load cobalt(II) oxide (CoO) NPs into the framework of MOF (MIL-101) to conveniently obtain a composite catalyst, CoO@MIL-101, which is a very rare example of pure CoO NP-loaded composite catalyst that shows excellent catalytic activity in the selective oxidation of benzyl alcohol. This CTC strategy opens up a pathway for impregnating MOF supports with specific NPs, which is further confirmed by preparing the first CuBr@MOF-type composite catalyst.

Non Noble-Metal Copper-Cobalt Bimetallic Catalyst for Efficient Catalysis of the Hydrogenolysis of 5-Hydroxymethylfurfural to 2,5-Dimethylfuran under Mild Conditions.

The efficient catalysis of the hydrogenation of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF) over non noble-metal catalysts has received great attention in recent years. However, the reaction usually requires harsh conditions, such as high reaction temperature and excessively long reaction time, which limits the application of the non noble-metal catalysts. In this work, a bimetallic Cox-Cu@C catalyst was prepared via the pyrolysis of MOFs, and an 85% DMF yield was achieved under a reaction temperature and time of 160 °C and 3 h, respectively. The results of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX) mapping, and other characterization techniques showed that the synthesis method in this paper realized the in situ loading of cobalt into the copper catalyst. The reaction mechanism studies revealed that the cobalt doping effectively enhanced the hydrogenation activity of the copper-based catalyst on the C–O bond at a low temperature. Moreover, the bimetallic Cox-Cu@C catalyst exhibited superior reusability without any loss in the activity when subjected to five testing rounds.

Hierarchical ZSM-5 Supported CoMn Catalyst for the Production of Middle Distillate from Syngas

Bifunctional catalysts using hierarchical ZSM-5 zeolite as a support have received more attention for their specific characteristic, which is in favor of producing middle distillate hydrocarbons in Fischer–Tropsch synthesis. The hierarchical structure together with the Bronsted acidity of ZSM-5 zeolites result in the secondary reaction for hydrocracking or isomerization of heavy hydrocarbons. Herein, hierarchical ZSM-5 zeolites with different acidities and mesopore volumes are synthesized by treating zeolites with TPAOH solution. The hierarchical zeolite supported CoMn catalysts are prepared by impregnation method, and all the catalysts are characterized by XRD, BET, XPS, CO/NH₃-TPD, and Py-IR. The results show that the 0.5 M TPAOH solution treated ZSM-5 (Z5-0.5M) possesses the largest mesopore volume and a proper Bronsted acidity. In addition, the Z5-0.5M supported CoMn catalyst exhibits a selectivity of jet fuel range (C₈–C₁₆) as high as 50%, which is much higher than the maximum of 41% predicted by the Anderson–Schulz–Flory model. Moreover, the effect of cobalt loading indicates that the increased cobalt loading leads to the enhancement of CO conversion and the upshift to heavier hydrocarbons.

Total Oxidation of Toluene and Propane over Supported Co3O4 Catalysts: Effect of Structure/Acidity of MWW Zeolite and Cobalt Loading

A set of supported Co3O4 catalysts have been designed and prepared to study the effect of textural characteristics and Brønsted acid sites concentration of MWW zeolite support, as well as cobalt loading on catalyst activity. Detailed characterization of the catalysts with a thorough study on their performance in the total oxidation of toluene and propane revealed that MCM-22 is the optimal support and that increasing Si/Al and decreasing external surface of MCM-22 positively affect the activity of supported Co3O4 catalysts, which is determined by their low-temperature reducibility. The activity of the Co/MCM-22 catalysts increased with cobalt content (5-20 wt %), consistent with enhancing the amount of low-temperature reducible Co3O4. The optimized catalyst containing 20% Co supported on dealuminated MCM-22 presented high turnover frequency (TOF) values in both toluene (2.6 × 10-5 s-1 at 270 °C) and propane (3.9 × 10-5 s-1 at 215 °C) oxidation and was characterized by outstanding cycling stability, long-term durability, water tolerance, and sintering resistance.

Nano CoO-Cu-MgO catalyst for vapor phase simultaneous synthesis of ortho-chloroaniline and γ-butyrolactone from ortho-cholonitrobenzne and 1,4-butanediol

The article aims at developing an efficient and stable catalysts for simultaneous hydrogenation of o-chloronitrobenzene to o-chloroaniline and 1,4-butanediol dehydrogenation to γ-butyrolactone. A series of CoO-Cu-MgO catalysts, composed of 10 wt% of copper, various amount of cobalt loadings (1, 5 and 10 wt%) and remaining of MgO were developed by co-precipitation followed by thermal treatment. o-Chloroaniline and γ-butyrolactone were the main products with high yield of 85% and 90%, respectively. The advantage of the coupling process is that the hydrogenation reaction was conducted without external hydrogen, demonstrating minimize the hydrogen consumption known as hydrogen economy route. From N2O characterization results, the high activity of 5CoO-10Cu-MgO was found that it has high amount of Cu species (Cu0/Cu+1) which govern the stable activity and selectivity on time on stream study in presence of cobalt in Cu-MgO.

Study on the Extraction and Separation of Zinc, Cobalt, and Nickel Using Ionquest 801, Cyanex 272, and Their Mixtures

Both Cyanex 272 (bis (2,4,4-trimethylpentyl) phosphinic acid) and Ionquest 801 (2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester) are commonly used for metal extraction and separation, particularly for zinc, cobalt, and nickel, which are often found together in processing solutions. Detailed metal extractions of zinc, cobalt, and nickel were studied in this paper using Cya-nex 272, Ionquest 801, and their mixtures. It was found that they performed very similarly in zinc selectivity over cobalt. Cyanex 272 performed much better than Ionquest 801 in cobalt separation from nickel. However, very good separation of them was also obtained with Ionquest 801 at its low concentration with separation factors over 4000, indicating high metal loading of cobalt can significantly suppress nickel extraction. Slop analysis proved that two moles of dimeric extractants were needed for one mole extraction of zinc and cobalt, but three moles were needed for the extraction of one mole nickel. A synergistic effect was found between Cyanex 272 and Ionquest 801 for three metal extractions with the synergistic species of M(AB) determined by the Job’s method.

Preparation of SiO2 immobilized Co-based catalysts from ZIF-67 and the enhancement effect for Fischer-Tropsch synthesis

ZIF-67-derived Co@C catalysts show great potential for Fischer-Tropsch synthesis (FTS) due to high cobalt (Co) loading and proper cobalt crystalline size, while improving the FTS activity and stability is still a major challenge. In this work, SiO2 was embedded to immobilize Co particles by introducing a silicon source into ZIF-67 using ex-situ or in-situ methods to prevent cobalt particles from aggregating. Due to exposure of more active cobalt sites and elimination of microcrystalline Co on the ex-situ soaking catalysts, increased FTS activity and decreased CH4 selectivity were achieved, but undesirable stability was observed due to the weak immobilization ability of SiO2. To enhance the immobilization effect of SiO2, E-ZIF-67@nSiO2 precursors were prepared by an in-situ soaking method in which the formation of ZIF-67 and introduction of SiO2 occurred simultaneously. The obtained E-Co3O4@4SiO2 catalyst exhibits not only much high FTS activity but also good stability.

Hydrogen rich syngas from CO2 reforming of methane with steam catalysed by facile fusion-impregnation of iron and cobalt loaded MgAl2O4 catalyst with minimal carbon deposits

The newly synthesised catalysts via facile fusion-impregnation of iron and cobalt onto MgAl2O4 were successfully accomplished with relatively high surface area and pore volume which exhibited mesoporous structure with narrow pore distribution. These catalysts were employed for CO2 reforming of CH4 with steam which was carried out at different reaction temperatures of 700, 750, 800, 850 and 900 °C. Different metal loadings of cobalt at 5, 15, 25, 40 and 50 wt% were also synthesised to study the effect of catalytic activity on CH4 and CO2 conversion as well as H2 yield. It was observed that CH4 and CO2 conversion achieved its highest value at Co loading of 25 wt%. Addition of steam, basic properties, lattice-textural of MgAl2O4 and magnesium metal oxides were suggested to be factors that keep out the coke formation on catalyst surface. However, the metal loading of more than 40 wt% Co started to show declination of catalyst activity and formation carbon deposits on catalyst surface. This circumstance suggests an agglomerated particle condition that decreases the active sites and hampers the gasification of carbon on catalyst surface. Possible reaction pathways are proposed in this study to elucidate the engagement of Fe and Co in CH4 and CO2 activation as well as their combination with surface carbon which further eliminates the coke deposition. The removal of carbon by oxidation was examined by XRD, TEM, TPO, Raman spectroscopy and TGA, which concludes its mechanism through oxidation of metal particles and surface carbon gasification from lattice oxygen.

Insight into the Influence of the Graphite Layer and Cobalt Crystalline on a ZIF-67-Derived Catalyst for Fischer-Tropsch Synthesis.

Due to the special framework structure, ZIF-67 is a promising material as the precursor to prepare the Co@C catalysts with high cobalt loading and superior cobalt dispersion. Unfortunately, these Co@C-X catalysts exhibit not only unsatisfied activity but also high CH4 selectivity. This limited its further application due to the lack of in-depth analysis of the reasons behind it. In this work, the Co@C-X catalysts were prepared by pyrolyzing the ZIF-67 precursor at different temperatures. A series of characterizations were conducted to explore the behavior of the graphite carbon coated on cobalt species, realizing that the role of active Co sites on these Co@C catalysts was restricted by the graphite carbon layer since it suppressed the adsorption and activation of syngas on Co sites. TEOS was introduced to suppress the aggregation of cobalt species and more active sites were exposed after the graphite carbon layer was eliminated. As a result, the FTS performance was greatly improved by a factor of 5. The effect of O2 concentration on the microcrystalline size of Co and the reconfinement effect of SiO2 were investigated. The model catalyst was prepared and the key factors determining CH4 selectivity of the ZIF-67-derived Co@C catalyst were revealed. This provides a good basis for rational designing ZIF-67-derived Co-based FTS catalysts.

Preparation, Performances and Mechanisms of Co@AC Composite for Herbicide Atrazine Removal in Water

In this study, a high-performance adsorbent Co@AC was prepared by loading cobalt ions (Co2+) on activated carbon (AC) via solution impregnation and high-temperature calcination technology, and was used to remove atrazine in water. The preparation factors on the adsorbent properties were studied, and the characteristics were analyzed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectrometer (FTIR). The results showed that Co@AC possessed the best performance when the factors were 7.0% of Co2+ (w/v), 7.0 h of immersing time, 500 °C of calcination temperature and 4.0 h of calcination time. The adsorption conditions and mechanisms for atrazine removal by Co@AC were also studied scientifically. As the conditions were pH 4.0, reaction time 90 min and temperature 25 °C, Co@AC had the largest adsorption capacity, which was 92.95 mg/g, and the maximum removal rate reached 94.79%. The correlation coefficient of the Freundlich isotherm was better than that of the Langmuir isotherm, and the adsorption process followed the pseudo-second-order kinetic model. Cycle experiments showed that the removal efficiency of atrazine by Co@AC remained above 85% after five repeated experiments, indicating that Co@AC showed a strong stable performance and is a promising material for pesticides removal.

XPS characterization of cobalt impregnated SiO2 and γ‐Al2O3

SiO2 and γ‐Al2O3 impregnation with nominal 10 and 20% of cobalt was examined using wet impregnation method starting with Co(NO3)2·6H2O. The samples were dried and analyzed by XPS prior to calcination to study the surface species in the solids and the role of the support in the processing of supported cobalt catalysts. The results showed that cobalt introduction alters the few top nanometers of the support materials as there are significant changes recorded in the XPS spectra. Most importantly, there is a remarkable similarity between the O 1s XPS signal of SiO2 and γ‐Al2O3 following Co 20% impregnation, which suggests that these materials could have similar properties in terms of the oxidation ability and the general redox behavior. The shift of Al 2p peaks to higher binding energy (BE) in the XPS investigations and the shift of Si 2p peaks to lower BE were observed for high nominal cobalt loading. These results suggest that the choice of the support in cobalt‐based catalysts would tune the chemical characteristics of cobalt in the final materials.

Improvement of photoelectrochemical HClO production under visible light irradiation by loading cobalt oxide onto a BiVO4 photoanode

Loading CoOx species onto BiVO4/WO3 photoanodes was effective to improve the oxidative HClO production from aqueous NaCl solution under simulated solar-light irradiation.

Surface Tuning to Promote the Electrocatalysis for Oxygen Evolution Reaction: From Metal-Free to Cobalt-Based Carbon Electrocatalysts.

Heterogeneous electrocatalytic reactions only occur at the interface between the electrocatalyst and reactant. Therefore, the active sites are only necessary to be distributed on the surface of the electrocatalyst. Based on this motivation, here, we demonstrate a systematic study on surface tuning for a carbon-based electrocatalyst from metal-free (with the heteroatoms N and S, NS/C) to metal-containing surfaces (with Co, N, and S, CoNS/C). The CoNS/C electrocatalyst was obtained by pyrolyzing the Co precoordinated and p-toluenesulfonate-doped polypyrrole (PPy). It was found that the coordination of Co on the PPy ring tuned the final carbon electrocatalyst into a catalyst with a CoNx moiety-rich surface. In addition, the as-synthesized CoNS/C was determined to have a very high loading of cobalt up to 2.02 wt %. The pyrolysis of the cobalt-containing precursor tends to proceed toward a characteristic of a higher sp2 carbon content, a higher surface area, and more nitrogen as well as active nitrogen sites than its metal-free counterpart. The most distinguished feature for such a catalyst is that the truly most active component is only distributed on the surface, in contrast with that of the conventional metal-N-based catalyst present throughout the bulky structure. Especially, the electrocatalytic activity toward oxygen evolution reaction (OER) has been investigated experimentally and theoretically. The results showed that the OER performance of the carbon-based electrocatalyst was remarkably boosted after the introduction of Co with an overpotential decrease from 678 to 345 mV at 10 mA cm-2. Furthermore, CoNS/C displayed an excellent durability upon a long-term measurement. The apparent activation energy measurements revealed that the metal-rich surface contributed to overcome the energy barrier for OER. In addition, density functional theory calculations have been conducted to explain the correlated OER mechanism. This study is expected to provide an effective strategy for the design and the synthesis of highly active metal-nitrogen-type electrocatalysts with a high metal loading for various electrocatalytic reactions.

Green synthesized cobalt-bipyridine constructed conjugated microporous polymer: An efficient heterogeneous catalyst for cycloaddition of epoxides via CO2 fixation under ambient conditions

Abstract The conversion of carbon dioxide into valuable cyclic carbonates has been of intensive interest owing to the 100% atomic economy. Conjugated microporous polymers (CMPs) are attractive porous materials contain organic functionalities for applications in gas capture, energy storage, and catalysis. Herein, we developed a new synthesis method of CMP, obtained at room temperature which is one of the “dream reaction”, possessing large surface areas (1356 m2/g) and exhibiting excellent CO2 capture (77.26 cm3/g at 273.15 K/1.00 bar). After loading cobalt acetate, we obtained Co-coordinated CMP (named as TBB-BPY-Co), exhibiting extraordinary activities (turnover frequencies of up to 250 h-1) for the coupling epoxides with CO2 forming cyclic carbonates at room temperature and atmospheric with free-solvent. Moreover, the heterogeneous catalyst showed even better catalytic efficiency than relevant homogeneous catalyst and a higher recyclability (up to 10 times). This study provided an effective and efficient strategy for the carbon dioxide conversion of industrial and economic value.

Electrosynthesis of H2O2 over Cobalt-N-Doped Ordered Mesoporous Carbon Materials (Co-N-OMC)

Electrochemical generation of hydrogen peroxide (H2O2) via two-electron oxygen reduction is a promising alternative to the conventional industrial anthraquinone process. The current challenges include discovering a sample and cost-effective electrocatalysts with high activity, selectivity, and stability. Herein, we reported a straightforward preparation of cobalt-N-doped ordered mesoporous carbon (Co-N-OMC) using dry-state low energy ball milling, followed by controlled pyrolysis. This fast, solvent-free, and scalable method used inexpensive materials containing cobalt acetate as the metal precursor, mesoporous SiO2 (KIT6) with a high surface area as the template for controlling the mesoporous structure; and imidazole as carbon and nitrogen sources, allowing simultaneous carbon matrix formation and nitrogen incorporation. Moreover, the Co-N-OMC electrocatalytic performance was compared with various materials, including N-OMC, Co-OMC, OMC, and non-mesoporous carbon, to separately examine each component's role, embedded Co, N dopant, and mesoporous morphology on the catalyst behavior. The optimal Co-N-OMC catalyst displayed an excellent electrocatalytic activity with H2O2 selectivity above 95% in an acid medium at very positive potentials. Furthermore, batch H2O2 electrolysis measurements confirmed the high H2O2 faradaic selectivity over 90% and H2O2 production of 555 mmol g-1 for a 60 min test. Finally, laboratory-scale H2O2 production was demonstrated in a flow electrolytic reactor with a Co−N−OMC cathode layer. The H2O2 electrolysis in flow cell configuration exhibitedabout a five-time-increase in H2O2 production ~ 2900 mmol g-1 for 60 min test with H2O2 faradaic selectivity above 90%. Such a considerable improvement in H2O2 production and selectivity is probably due to cobalt particles' coexistence with nitrogen dopants supported on a mesoporous structure. The optimal loading of cobalt might facilitate the two-electron pathway towards H2O2 generation.In addition, nitrogen dopants and the mesoporous structure may have lowered the ORR overpotential and improved mass transport in the catalyst layer, respectively.

The application of high fidelity reactor simulation on Cobalt-59 activation calculation

The direct whole core calculation is applied on Cobalt-59 activation calculation. The coupled neutronics, thermal hydraulics and depletion calculation is conducted, where the neutronics is solved by the Monte Carlo code JMCT and the thermal hydraulics is treated with sub-channel method. In the neutronics calculation, the reactor core is pin-by-pin modeled and the cobalt rods are modeled without approximation in geometry. The first reactor cycle is calculated with and without cobalt rods. The power distribution, coolant temperature and boron concentration curve are shown. And the boron concentration curve is compared with the reference value provided by the power plant. The effect of loading cobalt rod on power distributions and critical boron concentration is investigated. With the direct whole core solution, the average specific activity of cobalt rods and their distribution are obtained. In the end, the sensitivity study on number of tracking particles, the coupling strategy and the position of cobalt rods are conducted respectively. And the optimization to enhance the specific activity of cobalt rods is discussed as well.

Light intensity-dependence studies on the role of surface deposits for titania-photocatalyzed oxygen evolution: Are they really cocatalysts?

The effects of surface loading of iridium(II) oxide (IrO2), manganese(IV) oxide (MnO2), and cobalt(II) phosphate (CoPi) on the rate of photocatalytic oxygen evolution by anatase or rutile titania particles suspended in aqueous solutions of an electron acceptor, iodate ions, were studied by light intensity-dependence (LID) kinetic analyses. Although the role of these deposits has been reported to be a cocatalyst without showing results of any kinetic analysis, the present LID kinetic study suggested that the deposits may act as a "positive-hole capturer" for oxygen evolution, not as a cocatalyst for both metal oxides and CoPi. Further studies on the effects of loading amount, deposit types, titania crystalline type, and titania-particle size on the reaction order were also performed by LID analysis based on the proposed kinetic model. The observed LID behaviors could be interpreted consistently using a virtual parameter of "effective volume" as the target volume of photoabsorption by one positive-hole-bearing titania particle to govern the probability of two positive-hole accumulations in a titania particle.

Abatement of n-Butane by Catalytic Combustion over Co-ZSM-5 Catalysts

Catalytic combustion has become a promising technology to address the accelerating volatile organic compounds (VOCs) emissions. In this work, cobalt modified ZSM-5 zeolite catalysts (3–18 wt % Co) were prepared to investigate the combustion of n-butane (one typical model component of VOCs). The performances of catalysts were evaluated by conducting experiments in a flow tube reactor. XRD, BET, FT-IR, and XPS were also utilized to characterize their physicochemical properties. A significant enhancement of the catalytic activity was demonstrated in terms of the cobalt supported over ZSM-5, with an optimal cobalt loading of 7 wt %. The excellent catalytic activity of 7 wt % Co-ZSM-5 is mainly attributed to a higher concentration of active surface Co3+ species. Furthermore, DFT calculations indicated that the role of Co can enhance the activity by decreasing the activation barriers for C–H bond cleavage. In addition, the primary reaction mechanism of n-butane combustion on Co-ZSM-5 was also revealed.