Carbon Supported Cobalt Catalysts Research Articles

Porous Carbon-Supported Cobalt Catalyst for CO Hydrogenation to Gasoline Range Hydrocarbons

Porous Carbon-Supported Cobalt Catalyst for CO Hydrogenation to Gasoline Range Hydrocarbons

Solar-Driven CO2 Conversion via Optimized Photothermal Catalysis in a Lotus Pod Structure.

Photothermal CO2 reduction is one of the most promising routes to efficiently utilize solar energy for fuel production at high rates. However, this reaction is currently limited by underdeveloped catalysts with low photothermal conversion efficiency, insufficient exposure of active sites, low active material loading, and high material cost. Herein, we report a potassium-modified carbon-supported cobalt (K+ -Co-C) catalyst mimicking the structure of a lotus pod that addresses these challenges. As a result of the designed lotus-pod structure which features an efficient photothermal C substrate with hierarchical pores, an intimate Co/C interface with covalent bonding, and exposed Co catalytic sites with optimized CO binding strength, the K+ -Co-C catalyst shows a record-high photothermal CO2 hydrogenation rate of 758 mmol gcat -1 h-1 (2871 mmol gCo -1 h-1 ) with a 99.8 % selectivity for CO, three orders of magnitude higher than typical photochemical CO2 reduction reactions. We further demonstrate with this catalyst effective CO2 conversion under natural sunlight one hour before sunset during the winter season, putting forward an important step towards practical solar fuel production.

Understanding the role of surface oxygen-containing functional groups on carbon-supported cobalt catalysts for the oxygen evolution reaction

A high content of acidic surface OFGs on a carbon support enables the fine dispersion of Co-based nanocatalysts, enhancing its OER mass activity, while also inducing additional COOH surface groups that act as O2 spillover sites.

Single atom cobalt catalyst derived from co-pyrolysis of vitamin B12 and graphitic carbon nitride for PMS activation to degrade emerging pollutants

This study prepared the carbon-supported cobalt catalyst (Co-C-X) for activating peroxymonosulfate (PMS), and investigated the effect of co-pyrolysis temperature of graphitic carbon nitride (g-C3N4) and vitamin B12 on the catalytic activity. It was found that with the increase of co-pyrolysis temperature, the catalytic activity of Co-C-X increased, due to the different coordination structures of cobalt. At 500 °C (Co-C-500), cobalt existed as CoO; while it was single atom Co at 600 °C (Co-C-600); and small size CoO at 700 °C (Co-C-700). Co-C-X could activate PMS to produce hydroxyl radicals, sulfate radicals, high-valent cobalt-oxo and singlet oxygen, which depended on the pyrolysis temperature. Although Co-C-700 had the highest catalytic activity, the leaching cobalt was also highest (3.23 mg/L), compared with that of Co-C-500 (0.27 mg/L) and Co-C-600 (0.14 mg/L). Co-C-600 had fast degradation for atrazine, nitrobenzene, bisphenol A, phenol and 4-chlorophenol, which also had wide pH range and high tolerance to inorganic ions.

Effective oxidative esterification of 5–hydroxymethylfurfural over a N-doped biomass-based carbon supported cobalt catalyst

The metallic cobalt supported on nitrogen dopped carbon material was employed as an efficient catalyst in the oxidative esterification of 5-hydroxymethylfurfural (HMF) to furan-2,5-dimethylcarboxylate (FDMC). The carbonization temperature has a significant effect on the morphology and structure of Co/N-C samples. The Co/N-C calcined at 900 °C exhibits the best catalytic performance and a 73.8% FDMC yield at 91.7% HMF conversion is measured at 130 °C for 20 h with K2CO3 under 1 MPa O2. The catalytic activity of Co/N-C was benefited by the synergistic effect between the metallic cobalt and nitrogen-doped carbon material. The reaction mechanism of FDMC formation was proposed.

N-doped carbon supported cobalt electrospun nanofibers activated peroxymonosulfate system for benzothiazole degradation: Multifunctional role of nitrogen species

Nitrogen doping is an effective way to enhance the activation performance in peroxymonosulfate (PMS) heterogeneous catalysis. However, the unique role of different nitrogen species was still controversial. Herein, N-doped carbon supported cobalt catalyst was synthesized by electrostatic spinning method and employed to activated PMS. Firstly, various nitrogen species in catalyst including graphitic N, pyridinic N, pyrrolic N and Co-Nx was identified. Subsequently, the specific role of various nitrogen species was revealed by a series of experiments (adsorption experiments, degradation experiments, quenching tests, characterization analysis.), that is: (1) graphitic N changes the electrical of surrounding C atoms for PMS adsorption; (2) pyrrolic N with special pentacyclic structure leaded to obvious defects in carbon structure, thus enhancing the PMS activation ability of carbon materials; (3) pyridinic N bind with metal Co to form Co-Nx, which acted as an efficient active site for PMS activation. In addition, the effects of pH, temperature, and coexisting ions were also studied. This study revealed the activation behavior of different N species on N-doped carbon supported transition metal base catalysts, which provides theoretical basis for further synthesis of N-containing catalysts with high activation efficiency and release the activation potential of N species.

A Novel Tannic Acid-Based Carbon-Supported Cobalt Catalyst for Transfer Hydrogenation of Biomass Derived Ethyl Levulinate.

The catalytic conversion of ethyl levulinate (EL) to γ-valerolactone (GVL) is an important intermediate reaction in the conversion and utilization of biomass resources. The development of novel and efficient catalysts is significantly important for this reaction. In this work, using the biomass-derived tannic acid as carbon precursor and the transition metal cobalt as active component, a novel tannic acid carbon supported cobalt catalyst (Co/TAC) was prepared by pyrolysis and subsequent hydrazine hydrate reduction method. The hydrogenation of EL and other carbonyl compounds by hydrogen transfer reaction was used to evaluate the performance of the catalysts. The effects of different preparation and reaction conditions on the performance of the catalysts were investigated, and the structures of the prepared catalysts were characterized in detail. The results showed that the carbonization temperature of the support had a significant effect on the activity of the catalyst for the reaction. Under the optimized conditions, the Co/TAC-900 catalyst obtained the highest GVL yield of 91.3% under relatively mild reaction conditions. Furthermore, the prepared catalyst also showed high efficiency for the hydrogenation of various ketone compounds with different structures. This work provides a new reference for the construction of the catalysts during the conversion of biomass and a potential pathway for the high-value utilization of tannin resource.

Mechanochemical-Assisted Synthesis of Nitrogen-Doped Carbon Supported Cobalt Catalysts for Efficient and Selective Hydrogenation of Furfural

Mechanochemical-Assisted Synthesis of Nitrogen-Doped Carbon Supported Cobalt Catalysts for Efficient and Selective Hydrogenation of Furfural

Nitrogen-doped carbon supported nanocobalt for the synthesis of functionalized triazines via oxidative cleavage of biomass derived vicinal diols as carbon synthons

The efficient conversion of renewable biomass resources into value-added nitrogen-containing chemicals has become the focus of recent research. Herein, we report the preparation of nitrogen-doped carbon supported cobalt catalysts comprising a unique core−shell structure, and the regulation of their catalytic behavior in the dehydrocyclization reaction. Abundant biomass-derived diols were employed as carbon synthons to react with amidines, and they furnished structurally diverse 1,3,5-triazines, a class of compounds found in numerous natural and biomedical products. The synthetic protocol has the advantages of a broad substrate scope, good functional group tolerance, a reusable metal catalyst, and easily available reactants. The method is convenient and practical for the synthesis of versatile triazines with advantageous biological and physical properties.

A novel and efficient N-doping carbon supported cobalt catalyst derived from the fermentation broth solid waste for the hydrogenation of ketones via Meerwein–Ponndorf–Verley reaction

Most of the non-noble metal catalysts used for the Meerwein–Ponndorf–Verley (MPV) reaction of carbonyl compounds rely on the additional alkaline additives during preparation to achieve high efficiency. To solve this problem, in this work, we prepared a novel N-doped carbon supported cobalt catalyst (Co@CN), in which the carriers were derived from the nitrogen-rich organic waste, i.e., oxytetracycline fermentation residue (OFR, obtained from oxytetracycline refining workshop). No additional nitrogen sources were used during preparation. The results showed that inherent nitrogen in OFR could provide N-containing basic sites, and formed Co-N structures via coordinating with cobalt. The Co-N sites together with the coexisting Co(0) cooperated to catalyze the conversion of ethyl levulinate (EL) to γ-valerolactone (GVL) by MPV reaction. Co(0) dominated the activation of H in isopropanol, while Co-N dominated the formation of the six-membered ring transition state.

Bubble-templated synthesis of nanocatalyst Co/C as NADH oxidase mimic.

Designing highly active nanozymes for various enzymatic reactions remains a challenge in practical applications and fundamental research. In this work, by studying the catalytic functions of natural NADH oxidase (NOX), we devised and synthesized a porous carbon-supported cobalt catalyst (Co/C) to mimic NOX. The Co/C can catalyze dehydrogenation of NADH and transfers electrons to O2 to produce H2O2. Density functional theory calculations reveal that the Co/C can catalyze O2 reduction to H2O2 or H2O considerably. The Co/C can also mediate electron transfer from NADH to heme protein cytochrome c, thereby exhibiting cytochrome c reductase-like activity. The Co/C nanoparticles can deplete NADH in cancer cells, induce increase of the reactive oxygen species, lead to impairment of oxidative phosphorylation and decrease in mitochondrial membrane potential, and cause ATP production to be damaged. This ‘domino effect’ facilitates the cell to approach apoptosis.

Hydrogen generation from sodium borohydride hydrolysis promoted by MOF-derived carbon supported cobalt catalysts

Co-based catalysts represent a kind of low-cost non-noble metal catalysts with attractive performance for catalyzing NaBH4 hydrolysis to produce hydrogen. In the present work, a series of carbon-supported Co catalysts are fabricated through pyrolysis with activated carbon as substrate and metal organic frameworks as Co precursor. Due to the features of metal organic frameworks including well-defined and stable structure and high surface area, Co species is well dispersed in the catalysts with narrow size distribution. The results of NaBH4 hydrolysis experiments indicate that the fabricated catalysts have excellent catalytic activity, especially under alkaline conditions. The catalyzed NaBH4 hydrolysis provides a hydrogen generation rate of 4.9 LH2/(min gCo) at 30 °C, and the activation energy of the reaction is calculated to be 35.09 kJ/mol. Moreover, the good distribution of Co species in the catalysts makes the Co efficiency not decrease significantly even when the Co content in the catalyst increases up to 20.1 wt%, providing possibility to fabricate catalysts with both high metal loading and high metal efficiency. This kind of Co catalyst could provide a very promising choice for controllable hydrogen generation from NaBH4 hydrolysis.

Utilization of caffeine carbon supported cobalt catalyst in the tandem synthesis of pyrroles from nitroarenes and alkenyl diols

Employing bio-waste caffeine carbon-supported heterogeneous cobalt catalyst, synthesis of various substituted pyrrole derivatives is reported. In this methodology, pyrroles were synthesized through coupling between nitroarenes and alkenyl diols in a tandem manner. Among all the heterogeneous catalysts Co(OAc)2-CC-800 displayed the highest catalytic activity. Preparative scale synthesis of pyrroles and synthesis of anti-tubercular agent 5-(4-(1H-pyrrol-1-yl)phenyl)-1,3,4-oxadiazole-2-thiol revealed the practical applicability of this protocol. Several kinetic experiments and Hammett studies were conducted to understand the probable mechanism and electronic effects on this transformation.

Reaction kinetics study of ethylene oligomerization into linear olefins over carbon-supported cobalt catalysts

Ethylene oligomerization over carbon-supported cobalt catalysts at 200 °C selectively produces linear olefins (>80% linearity up to C12 olefins at < 48% conversion) and linear alpha olefins (LAOs) (>30% LAO isomer distribution up to C8 olefins at < 10% conversion). Increasing the catalyst pretreatment temperature from 230 to 560 °C in argon prior to a reaction reduces cobalt oxide to cobalt metal and increases the catalytic activity. Cobalt metal supported on carbon deactivates during the reaction, likely due to higher rate of polyethylene formation which decreases the catalytic activity. The product distribution follows a Schulz-Flory distribution. The reaction is first order with respect to ethylene partial pressure, suggesting a mechanism where ethylene reacts with adsorbed olefins on a surface that is highly covered with olefins.

Alcohol Synthesis via Fischer–Tropsch Synthesis over Activated Carbon Supported Alkaline Earth Modified Cobalt Catalyst

Although numerous efforts have been made in direct syngas conversion to higher alcohols via Fischer–Tropsch synthesis, the higher alcohols distribution remains a challenge. Here, we introduce alkaline earth metal oxide as promoter into activated carbon supported cobalt catalyst to tune distribution of higher alcohols. With the addition of Mg, the distribution of C2-5 alcohols increase from 41.2 to 75.8% accompanying with distribution of C6-18 alcohols decrease from 52.8 to 14.0%. Ba-promoted Co based catalyst (CoBa/AC) presents similar alcohols distribution to un-promoted catalyst, while the alcohol selectivity over CoBa/AC is higher than Co/AC. For promoted catalysts, the distribution of C6-18 alcohols increased in the order of Mg < Ca < Sr < Ba. The characterization results exhibit that the promoter addition facilitates the cobalt carbide formation, which leads to enhancement of selectivity to higher alcohols. The available active cobalt sites of promoted Co based catalysts increase in the same above order of Mg < Ca < Sr < Ba.

Constructing efficient hcp-Co active sites for Fischer-Tropsch reaction on an activated carbon supported cobalt catalyst via multistep activation processes

A highly efficient activated carbon supported cobalt based catalyst for Fischer-Tropsch synthesis was constructed. The catalyst was prepared by incipient wetness co-impregnation. The obtained catalyst was activated by multistep activation processes, which was composed of reduction of calcined sample in H2, syngas treatment, carburization in CO, and re-reduction in H2 successively. The multistep activation processes derived catalyst (CoZr/AC-RSCR) demonstrated far higher CO conversion and lower CH4 selectivity than those of conventional H2 reduction derived catalyst (CoZr/AC-R). The excellent performance of CoZr/AC-RSCR catalyst resulted from its higher amount of exposed active sites and the dominant hexagonal closed-packed (hcp) metallic cobalt phases. Furthermore, the catalytic performance could be further improved by tuning the content of hcp metallic cobalt phase stacking using the proper and effective treatment conditions of the multistep activation method. Finally, extremely high productivity of the mixture of alcohols and hydrocarbons with carbon number larger than 5 (194.6 g/h·kg-cat.) was acquired over CoZr/AC catalyst.

Synthesis and characterization of a novel activated carbon–supported cobalt catalyst from biomass mixture for tetracycline degradation via persulfate activation

In this study, a new activated carbon (AC)-supported Co-based catalyst was synthesized from a biomass mixture by single-step pyrolysis for tetracycline (TC) degradation with persulfate (PS). The catalyst was characterized by BET-surface area, total pore volume, pore size, SEM, EDS, XRD, and VSM analysis. Its catalytic performance in the oxidative TC degradation was investigated depending on catalyst dosage, PS concentration, contact time, pH, and co-existing anion. The results show that the catalyst has 515.46 m2/g surface area, 0.2661 cm3/g pore volume, 79.14% C, and 14.63% Co. The catalyst exhibited high catalytic activity in oxidative degradation of TC with PS. One hundred percent mineralization could be achieved at the conditions of 0.5 g/L of catalyst dosage, 1 mM PS, pH 5.88, and 45 min. Quenching tests showed that the catalyst successively activated PS to generate SO4·− and OH·. However, SO4·− was identified as the main oxidizing radical in TC degradation. TC degradation was found to fit to first-order kinetics. The activation energy of the reaction was calculated to be 7.095 kJ/mol. Unlike conventional impregnation and precipitation methods applied for AC-supported catalyst synthesis, a superior catalyst can be obtained from cheap and abundant biomasses and Co-salt by a single-step pyrolysis. The high catalytic performance of the catalyst and short degradation period show that it can be a promising catalyst for degradation organic pollutants with PS.

Methane dry reforming using oil palm shell activated carbon supported cobalt catalyst: Multi-response optimization

Dry reforming of methane with carbon dioxide was investigated using oil palm shell activated carbon (OPS-AC) supported cobalt catalyst. The cobalt loaded OPS-AC catalysts were prepared by wet-impregnation method and characterized using SEM, FESEM, BET, TPR and TPD. Surface morphology of OPS-AC supported cobalt catalysts exhibited higher porosity, surface area and micropore volume with different densities of cobalt particles and support. Furthermore, greater amount of H2 chemisorbed and acidity were observed with increasing cobalt contents. Response surface methodology (RSM) was employed to design the experiments based on factorial central composite design. Catalytic testing was performed using a micro reactor system by varying four variables: temperature, gauge pressure, CH4/ CO2 ratio and gas hourly specific velocity (GHSV). H2 and CO yields were analyzed and quantified by gas chromatography with thermal conductivity detector (TCD). Both responses (H2 and CO) yields were optimized simultaneously using desirability function analysis. Reaction temperature was the most influential variable with high desirability prevalent for both responses. The optimum response values of H2 and CO yields corresponded to 903 °C, 0.88 bar(g), CH4/ CO2 = 1.31 and GHSV = 4,488 mL/h.g-catalyst.

Deoxygenation of Macauba acid oil over Co-based catalyst supported on activated biochar from Macauba endocarp: A potential and sustainable route for green diesel and biokerosene production

Conventional biofuels, as biodiesel and bioethanol, are oxygenated compounds that have different physical-chemical properties when compared to fossil fuels. Otherwise, drop-in biofuels are bio-hydrocarbons that have the same chemical composition of fossil fuels. These oxygen-free fuels can be used without changes in structure that already exists to fossils fuels, as engines, turbines and tanks. This work presents the synthesis of bio-hydrocarbons via deoxygenation over Co/C catalyst using Macauba acid oil as feedstock. It is an inedible oil, with high acidity (about 38%) from a perennial palm tree with high oil productivity. Macauba endocarp activated carbon supported cobalt catalyst was synthesized and tested in order to develop a low cost and sustainable conversion route. Degree of deoxygenation of 98.4 %wt was achieved using Macauba pulp oil as feedstock, 10 wt% of catalyst, at temperature of 350 °C, pressure of 30 bar H2 for 4 h. The synthesized bio-hydrocarbons presented carbon chains equivalent to the fractions of gasoline, aviation kerosene and, mostly, diesel. These drop-in biofuels and the innovative catalyst appear as an important alternative for transport sector and for improving the sustainability of Macauba biorefinery.

Ammonia decomposition reaction to produce COx-free hydrogen using carbon supported cobalt catalysts in microwave heated reactor system

In this study, COx-free hydrogen production via decomposition of ammonia was investigated in the microwave reactor using carbon supported cobalt-containing catalysts. Two different carbon sources, namely mesoporous carbon and activated carbon, were utilized and catalysts were successfully synthesized following an impregnation procedure. Different characterization techniques, such as ICP-OES, X-Ray Diffraction (XRD), Nitrogen Physisorption, Transmission Electron Microscopy (TEM), Raman Spectroscopy were applied to determine the structural properties of the catalysts. Total conversion of ammonia was achieved over carbon supported cobalt catalysts at about 350–400 °C under pure ammonia flow (GHSVNH3 of 36,000 ml/gcat.h). Significantly higher conversion values could be achieved in microwave reactor due to the its superior properties, such as selective heating, compared to conventional reactor. Microwave energy would probably facilitate the recombinative desorption of bonded N atoms from cobalt active species during ammonia decomposition reaction resulted in higher conversion values comparatively lower reaction temperature.