Carbon Monoxide Chemisorption Research Articles

Enhanced CO oxidation performance over hierarchical flower-like Co3O4 based nanosheets via optimizing oxygen activation and CO chemisorption

Enhancing low-temperature activity is a focus for carbon monoxide (CO) elimination by catalytic oxidation. In this work, the hierarchical flower-like silver (Ag) modified cobalt oxides (Co3O4) nanosheets were prepared by solvothermal method and applied into catalytic CO oxidation. The doped Ag species in the form of AgCoO2 induced the prolongated surface Co–O bond and weaker bond intensity. Consequently, the oxygen activation/migration ability and redox capacity of Ag0.02Co were enhanced with more oxygen vacancies. The chemisorbed CO was preferentially converted to CO2 but not carbonates. The inhibited carbonates accumulation could avoid the coverage of active sites. According to Density functional theory (DFT) calculations, the electron transfer from AgCoO2 to Co3O4 promote electron donation ability of Co3O4 layer, benefiting for oxygen activation. Moreover, the longer Co–C and C–O bond length suggest the weakened chemisorption strength and higher active of CO molecule. The Ag modified Co3O4 exhibited more satisfactory activity at lower temperature. Typically, it realized 100% CO conversion at 90 °C, and displayed 6.3-fold higher reaction rate than pristine Co3O4 at 40 °C. Moreover, the Ag0.02Co exhibited outstanding long-term stability and water resistance. In summary, the optimized oxygen activation, CO chemisorption and interfacial electron transfer synergistically boosted the CO oxidation activity on Ag modified Co3O4.

Performance studies of Pt, Pd and PtPd supported on SBA-15 for wet CO and hydrocarbon oxidation

Climate change is one of the most pressing issues confronting modern society due to the greenhouse gas emissions. Reducing anthropogenic greenhouse gas emissions is critical to preventing further global warming. This work explores the oxidation of methane, propane and ethylene in the presence of carbon monoxide (CO) and water vapors over Pt and Pd mono and bimetallic catalysts supported on SBA-15. Pt and Pd catalysts with uniform distribution are prepared on high surface area SBA-15 support using different precursors and solvents. The performance of catalysts is evaluated as a function of temperature and time. The inhibitory effect of water vapors and co-feeding of carbon monoxide is studied on the light-off temperature and stability of Pt, Pd and bimetallic catalysts. We performed in-depth characterization using XRD, BET, XPS, TEM, CO chemisorption and ICP-OES techniques to correlate the properties of catalysts with oxidation results. In terms of their oxidation activity, Pd exhibited higher activity towards alkanes (methane and propane) at low temperatures, while Pt is more active for ethylene. Carbon monoxide undergoes oxidation at the lowest temperature over both Pt and Pd, followed by the oxidation of all other components in the feed. It is confirmed that PdO remains highly active when reductants are only alkanes. However, the coexistence of M/MOx ionic species (Pt0, Pt2+, Pd0, Pd2+) appears be to more active when mixed feed is used. Optimal alloying compositions have the potential to minimize the decrease in conversion activity in the presence of CO and water vapors. This work is expected to advance the rational synthesis and application of multicomponent and multifunctional catalytic materials.

Partially Reduced MIL-100(Fe) as a CO Carrier for Sustained CO Release and Regulation of Macrophage Phenotypic Polarization.

Carbon monoxide (CO) is a bioactive molecule with high potential as it shows promising efficacy for regulating inflammation. Materials capable of storing and delivering CO are of great potential therapeutic value. Although CO-releasing molecules (CORMs) have been developed to deliver CO, the short CO duration of minutes to 2 h confines their practical use. In this study, partially reduced MIL-100(Fe) as a new CO-releasing nanoMOF was developed and used for sustained CO release and macrophage (MA) phenotypic polarization regulation. MIL-100(Fe) was synthesized and mildly annealed in vacuum for partial reduction. When the annealing temperature was lower than 250 °C, less Fe(II) present in MIL-100(Fe) and the subsequent CO adsorption and desorption profiles displayed typical features of physisorption. While it was annealed at 250 °C, it showed about 20% of Fe(III) was reduced, which resulted in chemisorption of CO due to the high coordination affinity of Fe(II) to CO. The loading amount of CO was increased, and the CO release was prolonged for about 24 h. Furthermore, the CO release from this nanoMOF could alter the lipopolysaccharide (LPS)-induced macrophage from M1 to the alternative M2 phenotype and promoted the growth of endothelial cells (ECs) by paracrine regulation of MA. It can be envisioned as a promising CO-releasing solid for biomedical application.

Activating Molybdenum Carbide Nanoparticle Catalysts under Mild Conditions Using Thermally Labile Ligands.

Transition-metal carbides are promising low-cost materials for various catalytic transformations due to their multifunctionality and noble-metal-like behavior. Nanostructuring transition-metal carbides offers advantages resulting from the large surface-area-to-volume ratios inherent in colloidal nanoparticle catalysts; however, a barrier for their utilization is removal of the long-chain aliphatic ligands on their surface to access active sites. Annealing procedures to remove these ligands require temperatures greater than the catalyst synthesis and catalytic reaction temperatures and may further result in coking or particle sintering that can reduce catalytic performance. One way to circumvent this problem is by replacing the long-chain aliphatic ligands with smaller ligands that can be easily removed through low-temperature thermolytic decomposition. Here, we present the exchange of native oleylamine ligands on colloidal α-MoC1–x nanoparticles for thermally labile tert-butylamine ligands. Analyses of the ligand exchange reaction by solution 1H NMR spectroscopy, FT-IR spectroscopy, and thermogravimetric analysis–mass spectrometry (TGA-MS) confirm the displacement of 60% of the native oleylamine ligands for the thermally labile tert-butylamine, which can be removed with a mild activation step at 250 °C. Catalytic site densities were determined by carbon monoxide (CO) chemisorption, demonstrating that the mild thermal treatment at 250 °C activates ca. 25% of the total binding sites, while the native oleylamine-terminated MoC1–x nanoparticles showed no available surface binding sites after this low-temperature treatment. The mild pretreatment at 250 °C also shows distinctly different initial activities and postinduction period selectivities in the CO2 hydrogenation reaction for the ligand exchanged MoC1–x nanoparticle catalysts and the as-prepared material.

Suppressing Electron Back‐Donation for a Highly CO‐tolerant Fuel Cell Anode Catalyst via Cobalt Modulation

AbstractPlatinum on carbon (Pt/C) catalyst is commercially adopted in fuel cells but it undergoes formidable active‐site poisoning by carbon monoxide (CO). In particular, given the sluggish kinetics of hydrogen oxidation reaction (HOR) in anion‐exchange membrane fuel cell (AEMFC), the issues of Pt poisoning and slow rate would combine mutually, notably worsening the device performances. Here we overcome these challenges through incorporating cobalt (Co) into molybdenum‐nickel alloy (MoNi4), termed Co‐MoNi4, which not only shows superior HOR activity over the Pt/C catalyst in alkali, but more intriguingly exhibits excellent CO tolerance with only small activity decay after 10 000 cycles in the presence of 500 parts per million (ppm) CO. When feeding with CO (250 ppm)/H2, the AEMFC assembled by this catalyst yields a peak power density of 394 mW cm−2, far exceeding the Pt/C catalyst. Experimental and computational studies reveal that weakened CO chemisorption originates from the electron‐deficient Ni sites after Co incorporation that suppresses d→CO 2π* back‐donation.

Dynamics at Polarized Carbon Dioxide–Iron Oxyhydroxide Interfaces Unveil the Origin of Multicarbon Product Formation

Surface-sensitive ambient pressure X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy combined with an electrocatalytic reactivity study, multilength-scale electron microscopy, and theoretical modeling provide insights into the gas-phase selective reduction of carbon dioxide to isopropanol on a nitrogen-doped carbon-supported iron oxyhydroxide electrocatalyst. Dissolved atomic carbon forms at relevant potentials for carbon dioxide reduction from the reduction of carbon monoxide chemisorbed on the surface of the ferrihydrite-like phase. Theoretical modeling reveals that the ferrihydrite structure allows vicinal chemisorbed carbon monoxide in the appropriate geometrical arrangement for coupling. Based on our observations, we suggest a mechanism of three-carbon-atom product formation, which involves the intermediate formation of atomic carbon that undergoes hydrogenation in the presence of hydrogen cations upon cathodic polarization. This mechanism is effective only in the case of thin ferrihydrite-like nanostructures coordinated at the edge planes of the graphitic support, where nitrogen edge sites stabilize these species and lower the overpotential for the reaction. Larger ferrihydrite-like nanoparticles are ineffective for electron transport.

Continuous Hydrogenation of Monomeric Sugars and Binary Sugar Mixtures on a Ruthenium Catalyst Supported by Carbon-Coated Open-Cell Aluminum Foam

Developing a structured catalyst was performed successfully, and carbon-coated aluminum foam-supported ruthenium catalysts were prepared. Seven different characterization techniques such as scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction, inductively coupled plasma-mass spectrometry, carbon monoxide chemisorption, and nitrogen physisorption were applied on the solid catalysts. The carbon-coated foams were checked for their mechanical stability, and the results indicated that the foam catalysts were mechanically stable. The Ru/C foam catalysts were used in a multiphase reactor setup, which had six tubular reactors working in parallel. Continuous hydrogenation of d-glucose, l-arabinose, and a mixture of l-arabinose and d-galactose was studied in the experimental setup. Through investigating different reaction parameters, the temperatures 100–110 °C and the liquid flow rates 0.5–1 mL/min were found to be suitable for catalyst screening and activity testing. The experiments were carried out at 20 bar hydrogen pressure. The continuous hydrogenation experiments were successful, the reproducibility was good, and the foam catalysts were stable. High selectivities of the desired products, sugar alcohols and sugar alcohol mixtures, were obtained.

The Application of Attenuated Total Reflection Infrared Spectroscopy to Investigate the Liquid Phase Hydrogenation of Benzaldehyde Over an Alumina-Supported Palladium Catalyst

The hydrogenation of benzaldehyde in cyclohexane over a 5 wt% Pd/Al2O3 catalyst at 313 K is firstly investigated at ambient pressure in a stirred batch reactor. The formation of benzyl alcohol is a facile process and a small mass imbalance is indirectly attributed to the formation of benzene as a by-product. No hydrogenolysis reaction to form toluene is observed. Secondly, examination of this reaction system by attenuated total reflection infrared (ATR-IR) spectroscopy enables the chemistry at the liquid/solid interface to be probed. Specifically, the ν(C=O) modes of solvated and adsorbed benzaldehyde are evident at 1712 and 1691 cm−1 respectively, providing information on how the reagent is partitioning within the reaction medium. Spectral acquisition on initiation of hydrogenation then enables the benzaldehyde → benzyl alcohol transition to be tracked. The additional presence of a broad CO stretching band of chemisorbed carbon monoxide (1852–1929 cm−1) is attributed to the hydrogen-assisted decarbonylation pathway that forms the benzene by-product.

Selective Hydrogenation of Cinnamaldehyde over the Stepped and Plane Surface of Pd Nanoparticles with Controlled Morphologies by CO Chemisorption.

Carbon monoxide (CO) molecules are attracting attention as capping agents that control the structure of metal nanoparticles. In this study, we aimed to control the shape and surface structure of Pd particles by reducing the supported Pd precursor with CO. The reduction of Pd nanoparticles with CO promoted the exposure of step sites and generated spherical and concave-tetrahedral Pd particles on carbon and SiO2 supports. On the other hand, conventional H2-reduced Pd particles show a flattened shape. The preferential exposure of the step sites by the adsorbed CO molecules was supported by the density functional theory-calculated surface energy and the Wulff construction. Morphology- and surface-controlled Pd nanoparticles were used to study the surface structure and morphology effects of Pd nanoparticles on cinnamaldehyde (CAL) hydrogenation. With an increase in the fraction of step sites on Pd nanoparticles, the hydrogenation activity and selectivity of hydrocinnamaldehyde (HCAL) increased. On step sites, the adsorption of the C═C bond of CAL proceeded preferentially, and HCAL was efficiently and selectively generated.

EFFECT OF DURATION OF OXYCHLORINATION ON DEGREE OF ACCESSIBILITY FOR CATALYSIS OF PLATINUM CENTERS OF PLATINUM-RHENIUM REFORMING CATALYST

The work presents the results of a chemisorption analysis of a platinum-rhenium catalyst on an alumina support after regeneration and reduction with hydrogen. Adsorption-desorption diagrams were obtained by stepwise-pulsed chemisorption of carbon monoxide on reforming catalyst samples. With an increase in the number of carbon monoxide injections from 1 to 4, the catalyst sample is poisoned, and subsequent desorption peaks indicate the termination of the interaction. With an increase in the time of oxychlorination, the CO/Pt ratio in the carrier volume increases linearly. The effect of the oxychlorination process on the chemisorption of CO and the subsequent availability of platinum nanoparticles for catalysis has been shown. The absorption on freshly prepared platinum-rhenium catalyst samples reaches a CO/Pt molar ratio of about 0.4. The results show that the duration of oxychlorination for 16–20 h allows us to achieve the value of the ratio CO/Pt, which is in the range of 0.4-0.5. This indicates that the availability of platinum centers in its composition reaches the level of a fresh catalyst, and, on the other hand, taking into account a slight excess of this ratio, we can assume that some of the Re atoms participate in the absorption of CO molecules. The presence of finely dispersed platinum particles in the composition of the regenerated catalyst was confirmed by IR spectroscopy. The analysis of catalyst samples on an IR spectrometer in the frequency range of 1900-2200 cm-1 revealed a rather wide absorption band with a pronounced extremum at 2060 cm-1. In this frequency range, there is another, slightly pronounced extremum at 2149 cm-1. However, for samples with a short duration of oxychlorination, it did not appear. An absorption band with an extremum of 2060 cm-1 can be attributed to linear vibrations of adsorbed CO molecules on the surface of particles of metallic platinum.

Effects of Cobalt and Chromium Loadings to The Catalytic Activities of Supported Metal Catalysts in Methane Oxidation

A series of alumina supported cobalt and chromium catalysts with different metal loadings were prepared by impregnation method. Six types of alumina supported cobalt and chromium catalysts contained 5 wt%, 10 wt%, and 15 wt% loadings were produced and tested in methane oxidation. The catalysts were characterized by using x-ray diffraction (XRD) and carbon monoxide chemisorption (CO chemisorption). The XRD results do not confirmed any features of cobalt and chromium metal. The metal sizes for both catalysts were larger in high loading as shown by CO chemisorption results. Methane conversion results showed that the conversion increases with increasing the metal loading, however supported chromium catalysts were higher in activities compared to supported cobalt catalysts. Thermal stability tests on 15 wt% Co/Al and 15 wt% Cr/Al catalyst showed that supported chromium catalyst is more stable and maintain the particle size due to its strong interaction with support, while supported cobalt catalyst decrease in methane conversion due to deactivation of the catalyst. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Highly stable fullerene-based porous molecular crystals with open metal sites.

The synthesis of conventional porous crystals involves building a framework using reversible chemical bond formation, which can result in hydrolytic instability. In contrast, porous molecular crystals assemble using only weak intermolecular interactions, which generally do not provide the same environmental stability. Here, we report that the simple co-crystallization of a phthalocyanine derivative and a fullerene (C60 or C70) forms porous molecular crystals with environmental stability towards high temperature and hot aqueous base or acid. Moreover, by using diamond anvil cells and synchrotron single-crystal measurements, stability towards extreme pressure (>4 GPa) is demonstrated, with the stabilizing fullerene held between two phthalocyanines and the hold tightening at high pressure. Access to open metal centres within the porous molecular co-crystal is demonstrated by in situ crystallographic analysis of the chemisorption of pyridine, oxygen and carbon monoxide. This suggests strategies for the formation of highly stable and potentially functional porous materials using only weak van der Waals intermolecular interactions.

Chemisorption of carbon monoxide, carbon dioxide and “methanephobia” on the [0001] titanium surface

We performed simulations with density functional theory and molecular dynamics to investigate the interaction of CO, CO2, and CH4 with the surface of a [0001] titanium slab made of four titanium layers. Our simulations were performed at atmospheric pressure and 300 K. We found that the CO molecule is chemisorbed, with dissociation at the surface with an adsorption energy of −3.11 eV. The CO2 molecule can be physisorbed or chemisorbed. In physisorption, the molecule ends up at a distance from the surface of around 3.8 Å. The adsorption energy is −0.3157 eV. The chemisorption occurs in three possible ways. In the first, the molecule is adsorbed with no dissociation in the process, with an adsorption energy of −3.157 eV. In the second, the molecule is dissociated to CO and O, with an adsorption energy of ‐5.2028 eV. In the third case, the dissociation is complete, and the adsorption energy is −8.595 eV. We also used the nudged-elastic-band (NEB) method to calculate the chemisorption energies for this molecule, and we found very similar results. Finally, it is found that the CH4 molecule is repelled from the surface. These calculations were performed these calculations using standard GGA, and afterwards we utilized Vdw-DF2, which includes long-range correlation effects as Van der Waals interactions. The same results are obtained. It can be said that the [0001] titanium surface presents “methane phobia.”

Facile synthesis and enhanced catalytic activity of electrochemically dealloyed platinum–nickel nanoparticles towards formic acid electro-oxidation

Abstract To obtain the electrocatalyst with an improved electrocatalytic performance towards formic acid electro-oxidation (FAEO), a simple impregnation method is used to prepare Pt3Ni nanoparticles loaded on carbon black, assisted with electrochemically dealloying process. The X-ray powder diffraction (XRD) results as well as transmission electron microscopy (TEM) analysis of as-synthesized electrocatalyst demonstrates that the reduction temperature has a great influence on the FAEO activity of the dealloyed Pt3Ni nanoparticles. X-ray photoelectron spectroscopy (XPS) analyses confirm the variation in the electronic structure of platinum by incorporation of nickel atoms which reduces chemisorption of toxic carbon monoxide and promotes the dehydrogenation pathway of FAEO. The size of the dealloyed Pt3Ni nanoparticles remains within the range of about 2.7 nm. All electrochemical results illustrate that the performance of the as-obtained electrocatalyst towards the FAEO is significantly enhanced. Moreover, the carbon black content, incorporation of Ni atoms, and reduction temperature conditions have been proven to be the key factors for modification of the crystal structure and morphology which leads to enhanced catalytic performance.

Chemical vapor deposition of magnetic iron-cobalt alloy thin films: Use of ammonia to stabilize growth from carbonyl precursors

In previous work, it was demonstrated that FexCo(1−x) alloy thin films with near ideal magnetic properties can be grown by chemical vapor deposition (CVD) from the precursors Fe(CO)5 and Co2(CO)8; previous attempts to grow such films by CVD, using these or other precursors, had not been able to afford high saturation magnetization. However, it was found that the morphology and composition were extremely sensitive to small variations in the deposition temperature and the precursor partial pressures. In a second work, it was showed that the CVD of pure iron films from Fe(CO)5 is subject to a self-poisoning effect in which the growth surface accumulates carbon, which causes the growth rate to decline progressively to zero. Then it was shown that the poisoning effect can be eliminated by adding a coflow of NH3 during CVD, which does not introduce measurable quantities of nitrogen into the film. In the current work, the authors return to the compositional instabilities in FexCo(1−x) alloy growth and show that, as seen for pure Fe growth, these instabilities can be as attributed to a surface poisoning effect involving dissociative chemisorption of carbon monoxide. It was found that a coflow of ammonia, which inhibits CO adsorption, enables the growth of FexCo(1−x) films over a wide temperature window with highly reproducible morphology and stoichiometry. Alloys that were grown under the NH3 coflow with suitable compositions (x ∼ 0.6) achieve near ideal values of the saturation magnetization.

Detoxification of NO and CO gases over effectively substituted Pd and Rh in cupric oxide catalysts

Precious metals like Pd and Rh mixed with metal oxides exhibit a superior CO adsorption capacity, and thus their substitution has considerable effect on surface property of cupric oxide. This communication focuses on Pd and Rh substitution in cupric oxide and their catalytic application in detoxification of both nitric oxide (NO) and carbon monoxide (CO) gases by redox reaction. The synthesised catalysts were characterised by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and Brunauer–Emmett–Teller. In our study, we discovered that when doped with not more than 5% concentration of Pd and Rh the catalytic activity of cupric oxide was found to be increased. These electron-rich metals have a promotional effect on the catalytic activity for detoxification reactions. Effect of partial pressures of O2 and CO on the CO–O2 and NO–CO redox reactions was studied. Chemisorption of CO and NO was investigated using pulse titrations. Pd-doped CuO gave good catalytic reaction and showed better reaction stability in the presence and absence of the moisture.

Cobalt Catalysts Preparation and Characterization over Alumina Support for Fischer Tropsch Synthesis

Abstract An investigation was done to develop and characterize the alumina supported cobalt catalyst for Fischer-Tropsch Synthesis to produce biodiesel from biomass with the aim to produce alumina-supported cobalt catalysts containing 7 to 19 wt.% cobalt content. By using incipient wetness impregnation of γ-Al2O3 supports with cobalt nitrate hexahydrate with ethanol and distilled water solutions; the 14 wt.% cobalt content in catalyst was achieved. Nitrogen adsorption-desorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray fluorescence (XRF), H2temperature programmed reduction (H2-TPR), temperature programmed desorption (TPD), temperature programmed oxidation (TPO) and carbon monoxide chemisorption were used for the characterization of the catalysts to attain an appropriate cobalt catalyst. In order to investigate the effect of the impregnation on the crystalline size, surface area and cobalt content, three different impregnation methods with various durations were investigated. In addition, increasing the impregnation duration increased the cobalt content and its dispersion. Based on results, positive effect of the alumina support and impregnation duration on the crystallite size, surface area, and pore diameter, reducibility of the catalyst and cobalt dispersion were investigated. Thus, cobalt catalyst for using in fixed bed reactor to produce biodiesel from biomass through Fischer-Tropsch Synthesis was prepared and characterized.

Hydrogenation of sodium hydrogen carbonate in aqueous phase using metal/activated carbon catalysts

The catalytic hydrogenation of sodium hydrogen carbonate in aqueous phase (NaHCO3) to produce sodium formate (or formic acid) on activated carbon-supported metal (Pd, Ru, Ni, Co and Re) species at 25°C and 1bar of hydrogen was studied. The reaction was performed in a semi-continuous flow reactor, and the formate (or formic acid) production was quantified by HPLC, while the gas feed and possible products were quantified by gas chromatography. The catalysts were characterized by N2 adsorption, Temperature-Programmed Reduction (TPR), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and carbon monoxide chemisorption. All the catalysts displayed activity in the hydrogenation of sodium hydrogen carbonate and the selectivity to sodium formate was 100%. The Pd/C catalyst presented the highest activity, attributed to stabilized adsorption of reactant which favors the hydrogenation process. The highest intrinsic hydrogenation performance of this metal is related to stability of reduced phases of Pd species observed by XPS and TPR results, favoring the formation of formic acid.

Promoting Effects of Lanthan on Ru/AC for Ammonia Synthesis: Tuning Catalytic Efficiency and Stability Simultaneously

AbstractLa−Ba‐K−Ru/AC catalysts for ammonia synthesis were prepared by co‐impregnation method using graphited active‐carbon as the support and water‐soluble chloride‐free Ru complex as the precursor. The results demonstrate that the La promoted Ba‐K−Ru/AC catalysts exhibit good catalytic activity, high thermal stability and strong resistance against methanation. TEM (Transmission Electron Microscope) and CO (carbon monoxide) chemisorption analysis indicate that the Ru particles had a relatively uniform size of 3∼5 nm and the particle surface might be partially covered by LaOx and BaOx. H2‐TPR (Temperature Programmed Reduction) results suggest that strong interactions might exist between the Ru particles and the promoters (La and Ba). The N2‐TPD (Temperature Programmed Desorption) and H2‐TPD measurements show that the presence of small amount of La enhances the adsorption of N2 and inhibits the adsorption of H2, resulting in higher TOF values and better catalytic performances. Moreover, no obvious agglomeration of Ru particles was observed on the catalysts after heat resistance. The superior catalytic stability of La−Ba‐K−Ru/AC is associated with its strong resistance against methanation of active‐carbon due to highly coverage of ruthenium surface and strong inhibition of hydrogen by promoters.

Effect of Calcination Conditions on the Dispersion of Cobalt Over Re, Ru and Rh Promoted Co/γ-Al2O3 Catalysts

The effects of catalyst calcination conditions, such as calcination temperature and calcination atmosphere composition on the dispersion of cobalt particles over Co/γ-Al2O3 catalysts for Fischer–Tropsch conversion of synthesis gas are studied. A number of catalysts were prepared by incipient wetness impregnation of 20-wt% of cobalt onto γ-Al2O3 and promoted with 0.5 wt% ruthenium, rhenium, and rhodium. Metal dispersions of active metals were studied by chemisorption of carbon monoxide. The highest dispersion for Co/γ-Al2O3 catalyst was achieved by calcination at 400 °C in a flow of N2. Co metal dispersion seem to be increased in the calcination steps if a flowing gas was used instead of static calcination conditions. The addition of promoter metals like Ru, Re or Rh enhances the dispersion of the active metal.