Effect Of Cobalt Loading Research Articles

Hydrodeoxygenation of lignin-derived compounds for alkane fuels using bifunctional Co/HZ-HT

The selective hydrodeoxygenation of lignin-derived compounds is an effective pathway for producing liquid fuels. Here, a series of Co-based catalysts were prepared for converting lignin-derived phenols into alkane fuels. The effects of cobalt loading, Si/Al ratio, reaction temperature, time, and pressure on the distributions of alkane fuels were systematically investigated. The experimental results demonstrated that the in-situ grown LDH structure in Co/HZ-HT significantly improved the pore structure of the catalyst, not only enhancing the dispersion of the metallic particles and overall stability but also strengthening the interaction between the metal and the support. The complete conversion of guaiacol was achieved, and the selectivity of cyclohexane reached 97.5% under the conditions of 200 °C, 2 h, 3 MPa H2, and Si/Al ratio of 25. Co/HZ-HT exhibits excellent hydrogenolysis performance and wide applicability, outperforming Co/HZ catalysts prepared using conventional impregnation methods. By extending the feedstock to lignin-derived compounds, the complete deoxygenation of the components and hydrogenation of the aromatic rings were both realized with minimal side reactions.

CO2 methanation vs reverse WGS activity on Co/γ-Al2O3 catalysts at atmospheric pressure: effect of cobalt loading and silica addition on selectivity and stability

Catalysts containing 5 wt% and 13.6 wt% cobalt on pure alumina and 5 wt% silica-containing alumina were prepared by conventional impregnation procedure and calcined at 1023 K for 5 h. The samples were characterized both as prepared, pre-reduced and after reaction by means of X-ray Diffraction, FTIR and DR-UV-Vis-NIR spectroscopies and by X-ray Pholotoelectron Spectroscopy. After pre-treatment in H2/N2 atmosphere, they were tested in CO2 hydrogenation at atmospheric pressure in the temperature range 523–773 K. The material with 5 wt% Co on pure γ-Al2O3 was found predominantly active as a reverse Water Gas Shift (rWGS) catalyst producing mainly CO and approaching rWGS forecasted thermodynamic equilibrium at the highest temperatures. The addition of silica decreases selectivity to CO, with an enhanced methanation activity. Instead, the materials with 13.6 wt% Co on pure γ-Al2O3 was found to act mainly as a methanation catalyst, although with the coproduction of limited amounts of CO. The rWGS catalytic activity is apparently stable while slight deactivation for methanation was found, attributed to deposits of stick-like carbon residues. Investigated 13.6 wt% Co/γ-Al2O3 is less selective for methanation than comparable Ni/γ-Al2O3 catalysts while but more stable than unsupported cobalt and Co/SiO2 catalysts. Silica addition to 13.6 wt% Co does not modify significantly the catalytic activity while it slightly decreases stability. The effect of silica is a combination of two partially contrasting phenomena, i.e. the increase of the total surface area of the support and the decrease of the available surface area fraction for cobalt dispersion.

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.

Studies of CO2 hydrogenation over cobalt/ceria catalysts with in situ characterization: the effect of cobalt loading and metal–support interactions on the catalytic activity

Metal–oxide interactions affect the catalytic properties of Co/CeO2 and can be used to control activity and selectivity.

Loading and promoter effects on the performance of nitrogen functionalized graphene nanosheets supported cobalt Fischer-Tropsch synthesis catalysts

The effects of nitrogen functional groups on graphene surface and also the effects of cobalt loading and ruthenium promoter on the performance of nitrogen functionalized graphene nanosheets (N-GNS) supported cobalt catalysts in Fischer–Tropsch synthesis (FTS) are investigated. A 15 wt% Co/PGNS catalyst, a series of Co/N-GNS (15–30 wt% loading) and ruthenium promoted catalysts (25 wt% Co,0.5 wt% Ru/N-GNS and 25 wt% Co,0.5 wt% Ru/PGNS) were prepared by impregnation method. The purified GNS and functionalized GNS and all catalysts were characterized by Raman spectroscopy, FTIR, SEM, EDS, ICP, BET, TEM, XRD and TPR. The catalysts assessed in FTS in a fixed bed micro-reactor at 220 °C, 1.8 Mpa and H2/CO ratio of 2. Functionalization of GNS shifted the TPR reduction peaks to lower temperature, increased the dispersion of cobalt particles and increased the percentage CO conversion from 70.6% to 74.5%. Increasing the cobalt loading resulted in increasing the average cobalt cluster size, improvements in the reducibility of Co3O4. The maximum FTS activity for N-GNS supported catalyst is achieved at 30 wt % cobalt loading. The C5+ selectivity for the 30 wt % cobalt catalyst was higher than that of the 15 wt % Cobalt catalyst. Addition of 0.5 wt%Ru increased the FTS rate (gCH/(gcat·h)) from 0.377 to 0.412 and the liquid products selectivity from 86.5% to 91.2%.

Effects of Cobalt Loading, Particle Size, and Calcination Condition on Co/CNT Catalyst Performance in Fischer–Tropsch Reactions

The strong electrostatic adsorption (SEA) method was applied to the synthesis of a cobalt (Co) catalyst on a multi-walled carbon nanotube (CNT) support. In order to uptake more of the cobalt cluster with higher dispersion, the CNT was functionalized via acid and thermal treatment. The Co/CNT catalyst samples were characterized by a range of methods including the Brunauer–Emmet–Teller (BET) surface area analyzer, transmission electron microscopy (TEM), X-ray powder diffraction (XRD) analysis, atomic absorption spectroscopy (AAS), and H2-temperature programmed reduction (H2-TPR) analysis. The data from the TEM images revealed that the catalyst was highly dispersed over the external and internal walls of the CNT and that it demonstrated a narrow particle size of 6–8 nm. In addition, the data from the H2-TPR studies showed a lower reduction temperature (420 °C) for the pre-treated catalyst samples. Furthermore, a Fischer–Tropsch synthesis (FTS) reaction was chosen to evaluate the Co/CNT catalyst performance by using a fixed-bed microreactor at different parameters. Finally finding the optimum value of the cobalt loading percentage, particle size, and calcination conditions of Co/CNT catalyst resulted in a CO conversion and C5+ selectivity of 58.7% and 83.2%, respectively.

Effect of cobalt loading on suppression of carbon formation in carbon dioxide reforming of methane over Co/MgO catalyst

Carbon dioxide reforming of methane was studied over Co/MgO catalyst which was prepared by using the direct sol–gel method with different Co loadings. The performance of Co/MgO catalyst was thoroughly investigated over methane (CH4) and carbon dioxide (CO2) conversions, CO and H2 selectivity, syngas ratio (H2:CO) and the rate of carbon deposition. The rate of carbon deposition of Co/MgO catalyst decreased with the lower Co content, which resulted in the formation of small metal crystal size and well distribution. The rate of carbon deposition increased from 0.0016 to 0.2227 gc/gcat h as the Co loadings of Co/MgO catalyst also increased from 10 to 25 mol%. High Co loading formed a weak interaction and larger particles size that promoted the carbon deposition on Co/MgO catalyst during the reaction. The Co/MgO catalyst with 10 mol% of Co loading posed the small particle sizes, which resulted in high CH4 and CO2 conversions of 80 and 86%, respectively, along with the lowest rate of carbon deposition after a 50 h reaction time stream, which was enhanced via strong metal support interaction.

Effect of cobalt loading on structure and catalytic behavior of CoOx/SiO2 in CO2-assisted dehydrogenation of ethane

Structural and catalytic properties of flame-made CoOx/silica catalysts for the CO2-assisted dehydrogenation of ethane were observed to vary strongly depending on the Co-loading (0.1–4.5 wt%). X-ray diffraction showed that both fresh and spent catalysts were amorphous. UV–vis, XPS and XAS indicated that at Co-loadings lower than about 1 wt% highly dispersed tetrahedral Co2+ strongly bound to the silica matrix in a cobalt silicate like mixed oxide phase, was the prevalent cobalt species. At higher Co-loadings the presence of CoOx clusters became significant. All cobalt species showed strong resistance towards reduction, as shown by TPR. Comparative XAS analyses of catalysts exposed to ambient atmosphere and thermally pretreated catalysts (400 °C, vacuum for 2 h) showed that the presence of water facilitates the transformation of tetrahedrally to octahedrally coordinated Co2+. Best catalytic performance was achieved with a catalyst containing 0.75 wt% Co, affording 46% ethane conversion at 85% selectivity to ethene under the standard reaction conditions applied (700 °C, CO2/C2H6 ratio of 2.5 and gas hourly space velocity of 6000 L kg−1 h−1). Some coke deposition in the form of disordered and graphitic carbon was observed with all Co-loaded catalysts. The catalyst with optimal Co-loading (0.75 wt%) showed nearly stable performance during 10 h time-on-stream.

Influence of Co loading on structural and morphological properties of Co-doped ZnO thin films grown by pulsed electron beam ablation

We report on the effect of cobalt loading in the target material on the properties of thin film nanocomposites of Co-doped zinc oxide (CZO) Zn1-xCoxO. The films have been deposited by pulsed electron beam ablation (PEBA) at 450°C on pre-annealed (1100°C) c-sapphire and Si (100) substrates. The experimental results, based on scanning electron and atomic force microscopies (SEM, AFM), indicate that Co doping significantly affects the morphology of the films. X-ray diffraction (XRD) measurements reveal that the films on both substrates exhibit a prominent ZnO hexagonal wurtzite structure for x = 0.05, whereas higher Co loading (x = 0.1, 0.2) results in a strong deformation of ZnO wurtzite lattice and in a higher content of hexagonal close-packed (hcp) metallic Co in CZO films. X-ray photoelectron spectroscopy (XPS) data confirm the presence of non-oxidized metallic Co (Co°) in the deposited films. Both XRD and XPS results indicate an increase in Co° content in the films as Co loading in the target is increased.

Removal of toluene from industrial gas over 13X zeolite supported catalysts by adsorption‐plasma catalytic process

AbstractBACKGROUNDTo find an appropriate catalyst in the adsorption plasma catalytic process, degradation of toluene over 13X zeolite supported catalysts were studied.RESULTS13X zeolite exhibited excellent toluene adsorption capacity but weak catalytic ability. After loading Cu, Co, Ce and Mg active compounds by the impregnation method, adsorption capacity was reduced and catalytic performance was significantly improved. Co/13X exhibited good adsorption capacity and excellent catalytic performance, which carbon balance was 81.6% with 74.4% of COx for toluene adsorption capacity of 0.51 mmol. The effect of cobalt loading and calcination temperature on Co/13X for toluene degradation were studied, and it was found that 5% and 500°C were the optimum loading value and calcination temperature. The characterization results of BET, FTIR, XRD, XPS and SEM were correlated with catalyst performance.CONCLUSIONSThe active compounds block the pores and reduce the specific surface area of 13X zeolite, but active sites of catalysts can decompose ozone to produce more atomic oxygen species. Co3+ could form π‐complexation bonding with toluene and Co3O4 is a P‐type semiconductor, which has large oxygen adsorption capacity and converts oxygen into O− and O2− easily. Co3O4 present in Co/13X is the active point for toluene degradation by adsorption and plasma catalytic activity. © 2017 Society of Chemical Industry

Dicyclopentadiene Hydroformylation to Value-Added Fine Chemicals over Magnetically Separable Fe3O4-Supported Co-Rh Bimetallic Catalysts: Effects of Cobalt Loading

Six Co-Rh/Fe3O4 catalysts with different cobalt loadings were prepared by the co-precipitation of RhCl3, Co(NO3)2, and Fe(NO3)3 using Na2CO3 as the precipitant. These catalysts were tested for dicyclopentadiene (DCPD) hydroformylation to monoformyltricyclodecenes (MFTD) and diformyltricyclodecanes (DFTD). The results showed that the MFTD formation rate increased with increasing cobalt loading, whereas the DFTD formation rate initially increased and then decreased when the cobalt loading was greater than twice that of Rh. The DFTD selectivity was only 21.3% when monometallic Rh/Fe3O4 was used as the catalyst. In contrast, the selectivity was 90.6% at a similar DCPD conversion when the bimetallic 4Co-2Rh/Fe3O4 catalyst was employed. These catalysts were characterized by temperature-programmed reduction (TPR), temperature-programmed desorption (TPD), and thermogravimetric and differential thermal analyses (TG-DTA). The results obtained by these complimentary characterization techniques indicated that adding cobalt to the Rh/Fe3O4 catalyst enhanced the Rh reducibility and dispersion; the Rh reducibility was easily altered, and increasing the cobalt loading improved the Rh dispersion. It was concluded that the enhanced catalytic performance with increasing cobalt loading might be due to the formation of a more reactive Rh species with a different Rh–phosphine interaction strength on the catalyst surface.

Effect of cobalt loading on the solid state properties and ethyl acetate oxidation performance of cobalt-cerium mixed oxides

Cobalt-cerium mixed oxides were prepared by the wet impregnation method and evaluated for volatile organic compounds (VOCs) abatement, using ethyl acetate (EtAc) as model molecule. The impact of Co content on the physicochemical characteristics of catalysts and EtAc conversion was investigated. The materials were characterized by various techniques, including N2 adsorption at −196°C, scanning electron microscopy (SEM), X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) to reveal the structure–activity relationship. The obtained results showed the superiority of mixed oxides compared to bare CeO2 and Co3O4, demonstrating a synergistic effect. The optimum oxidation performance was achieved with the sample containing 20wt.% Co (Co/Ce atomic ratio of ca. 0.75), in which complete conversion of EtAc was attained at 260°C. In contrast, temperatures above 300°C were required to achieve 100% conversion over the single oxides. Notably, a strong relationship between both the: (i) relative population, and (ii) facile reduction of lattice oxygen with the ethyl acetate oxidation activity was found, highlighting the key role of loosely bound oxygen species on VOCs oxidation. A synergistic Co-Ce interaction can be accounted for the enhanced reducibility of mixed oxides, linked with the increased mobility of lattice oxygen.

A green and robust solid catalyst facilitating the magnesium sulfite oxidation in the magnesia desulfurization process

Effect of cobalt loading on the dispersity and catalysis performance.

The Effect of Cobalt Loading on Fischer Tropsch Synthesis Over Silicon Carbide Supported Catalyst

A series of Co (5-30 wt%) based SiC supported catalysts were prepared by impregnation method and investigated for FTS reaction. The FTS reaction was carried out in a fixed bed reactor system with the H2/CO molar ratio of 2, reaction temperature of 230 degrees C and reaction pressure of 20 bar for 120 h. All catalysts were characterized by N2 physisorption, XRD, TPR, SEM and TEM techniques. It was found that 15 wt% Co/SiC catalyst showed better catalytic performance with high selectivity of C(5+) hydrocarbons than the other catalysts. The results, suggest that the catalytic performance of the catalysts depends on average pore size of support and surface density of cobalt, metal and support interactions.

Preferential oxidation of CO (PROX) over CoOx/CeO2 in hydrogen-rich streams: Effect of cobalt loading

PROX reaction over Co catalysts supported on ceria nano-particles was investigated with a special focus on the effect of Co loading. High surface area ceria nano-particles were prepared through a precipitation technique using cerium (III) nitrate hexahydrate and sodium hydroxide. Co incorporation was achieved using a wet impregnation method in aqueous media. Catalysts were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, temperature-programmed reduction, dispersion measurements, and in situ diffuse reflectance Fourier transform infrared spectroscopy and X-ray absorption spectroscopy. Activity and selectivity of CoOx/CeO2 catalysts with different Co loadings showed higher Co loadings to favor higher CO oxidation at the expense of oxygen selectivity. Higher activation energies for H2 oxidation compared to CO oxidation were observed, regardless of the Co loading, implying a higher temperature sensitivity for the H2 oxidation reaction. The Co phase was identified as Co3O4 and was stable in the reducing environments present in PROX reactions.

Effect of Cobalt Loading in Nitrogen-Doped Carbon on Oxygen Reduction Reaction for PEM Fuel Cells

Nitrogen-doped carbon supported Co catalysts (CoNC) were synthesized via condensation reaction of pre-polymer of melamine formaldehyde resin with addition of cobalt nitrate salt, followed by carbonization in nitrogen. Rotating disk electrode technique (RDE) and scanning electron microscopy (SEM) with energy dispersive X-ray spectrometry (EDS) were used to identify the structure and oxygen reduction reaction (ORR) kinetics of the catalysts. The results show that the catalysts with 3.77 wt% Co loading yield the best ORR catalytic activity. Koutecky-Levich plots indicate ORR mechanism is governed by mixed mechanisms and the measured electron number varies between 2 and 4. SEM image shows an irregular lamellar structure of CoNC catalyst formed at high temperature, and different Co loadings in CoNC catalyst do not change its surface morphology.

Synthesis, characterization and magnetic performance of Co-incorporated ordered mesoporous carbons

Co-incorporated ordered mesoporous carbon (Co-OMC) with magnetic frameworks has been synthesized via a one-pot self-assembly strategy. The effects of cobalt loading on carbon matrix, adsorption properties and magnetic properties of the resultant mesostructured cobalt/carbon composites were investigated by nitrogen sorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TG) and magnetometer measurements. The results show that the mesoporous composites with a high cobalt content (such as 18.0 wt%) possess an ordered and uniform mesoporous structure (5.3 nm), high surface areas (up to 687 m 2/g) and high pore volumes (up to 0.54 cm 3/g). Cobalt nanoparticles of size 4–9 nm are confined inside the mesopores or walls of the mesoporous carbon. These materials exhibit typical ferromagnetic characteristics. The saturation magnetization strength can be easily adjusted by changing the content of cobalt. The carbonization temperatures have significant effects on the structure and magnetic properties of Co-OMC also.

Effects of Cobalt Loading on Properties of Co-PPy-TsOH/C as Catalyst for Oxygen Reduction

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Liquid phase oxidation of p-vanillyl alcohol over synthetic Co-saponite catalyst

Effect of cobalt loading on porosity of synthetic Co-saponite catalysts and on the air oxidation of p-vanillyl alcohol was studied by varying Co content in the range of 5% to 30% using in situ precipitation method. The pore size increased from 1.29 to 3.69 nm indicating a transition from micro to meso porosity, with increase in Co loading from 5% to 30%. The distribution ratio of Co 3O 4/CoO phases as estimated from TPR studies, also increased from 0.84 to 1.67 with increase in Co loading from 5% to 13% and remained almost constant (1.7) with further increase in Co loading up to 30%. The highest activity (conversion 55%) and selectivity of 99% to p-vanillin obtained for 13% Co-saponite in p-vanillyl alcohol oxidation was due to the highest distribution ratios of Co 3O 4/CoO phases.

NO x storage and reduction performance of Pt–CoO x–BaO/Al 2O 3 catalysts: Effects of cobalt loading and calcination temperature

The NO x storage and reduction (NSR) performance of low platinum (0.5 wt%) 0.5Pt–CoO x –15BaO/Al 2O 3 catalysts with varied Co loadings and calcination temperatures was studied to investigate the promotional effect of CoO x on the NSR catalysis. The NSR performance was tested under cyclic lean–rich conditions, and was evaluated in terms of NO x storage capacity (NSC) under the lean condition, the N 2 selectivity and the amount of nitrogen-containing products (namely, the NO x reduction capacity (NRC)) under the rich condition. For the catalysts calcined at 800 °C, addition of CoO x to the 0.5Pt–15BaO/Al 2O 3 catalyst enhanced the NSC but lowered significantly the NRC, which made the NRC/NSC ratios dropped significantly from 0.82 for the reference 0.5Pt–15BaO/Al 2O 3 catalyst to around 0.50 for the catalysts containing 1 and 5 wt% Co, and to 0.37 for the catalyst containing 10 wt% Co. Moreover, the N 2 selectivity remained at around 50% for the 0.5Pt–CoO x –15BaO/Al 2O 3 catalysts when the Co loading was kept low (0–5 wt%), and decreased significantly to 30% when the Co loading was 10 wt%. The calcination temperature of the 0.5Pt–CoO x –15BaO/Al 2O 3 sample containing 5 wt% Co was varied in the range of 350–800 °C to improve the NSR performance. The catalyst calcined at 550 °C was found to produce the highest NRC/NSC ratio (0.80) and N 2 selectivity (76.1%) under the rich condition. The maximum efficiency for NSR catalysis of this catalyst seemed to be associated with the amount of binary Pt–Co oxides.