Magneto-chemical characteristics of copper-cobalt catalysts

Murty, A. N.; Donatto, U.A.; Washington, John W.; Hoard, T.L.; Akundi, Murty A.; Harris, C.M.

doi:10.1109/20.334201

Cited by 3 publications

(3 citation statements)

References 11 publications

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“…These features are responsible for their specific magnetic as well as their valuable catalytic properties. 18,19 Significant changes in the saturation magnetization M s have been reported for a number of ferromagnetic catalysts due to chemisorptions of H 2 and CO. Here we studied the magnetic character of Co and Fe deposited micro-reactors after they were exposed to the syngas (CO+H 2 ).…”

Section: Magnetization Studies Of Co and Fe Deposited Micro-reactorsmentioning

confidence: 99%

Novel Preparation and Magneto Chemical Characterization of Nano-Particle Mixed Alcohol Catalysts

Naidu¹

2003

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We have produced Co, Cu, and Fe nano-particles by Laser-induced solution deposition (LISD) as evidenced by TEM investigations. Sizes of the nano-particles created are in the order of 5 nm. The LISD system could generate nano-particles in quantities only in the order of a milligram. This may be mainly due to the limited photo induced reactions taking place on the surface of the solutions. We have designed experiments to use drop flow technique with LISD for nano-particle deposition on microreactors. Preliminary work has been done on Co and Fe thin film deposited microreactors. We are also investigating the catalytic properties of nano-particles of FeO and CoO prepared by ball milling and dispersed into sol-gel prepared alumina granules.We have continued our investigation of catalytic reactions of Cu, Co, Fe, Cu/Co, Cu/Fe and Co/Fe on alumina support. The metal oxides were first reduced with hydrogen and used for the conversion of CO/H 2 . The surface area of the catalysts has been determined by nitrogen disorption. They are in the range of 200-300 m 2 /g. Cu, Co, Fe, Co/Fe , Cu/Co and Cu/Fe showed increasing order of catalytic activity for CO/H 2 conversion. We are also studying catalytic conversion rates for CO 2 /H 2 and CO/CO 2 /H 2 mixtures using these catalysts. Our investigations of Co and Fe thin film deposited microreactors showed higher CO/H 2 conversion for Fe compared to Co.We have used vibrating sample magnetometer (VSM) to study the magnetic characteristics of as prepared, reduced, post-reaction catalysts. Comparative study of the ferromagnetic component of these samples gives the reduction efficiency and the changes in metal centers during catalytic reactions. Magnetic studies of post-reaction Co and Fe micro-reactors show that more carbide formation occurs for iron compared to cobalt.4

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Section: Magnetization Studies Of Co and Fe Deposited Micro-reactorsmentioning

confidence: 99%

Novel Preparation and Magneto Chemical Characterization of Nano-Particle Mixed Alcohol Catalysts

Naidu¹

2003

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“…These features are responsible for their specific magnetic as well as their valuable catalytic properties [8,21]. We studied [22][23][24] the magnetic characters of Co/Fe encapsulated Al 2 O 3 sol-gel deposited 25 µm wide and 100 µm deep micro-reactors as deposited, reduced and exposed to the syngas (CO+H 2 ) using Vibrating Sample Magnetometer (VSM) in collaboration with Institute for Micromanufacturing (IfM), LaTech.…”

Section: Magnetization Studies Of Co/fe Encapsulated Al 2 O 3 Sol-gelmentioning

confidence: 99%

Novel Preparation and Magneto Chemical Characterization of Nanoparticle Mixed Alcohol Catalysts

Seetala¹,

Siriwardane²

2005

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We have developed and streamlined the experimental systems: a) Laser-induced solution deposition (LISD) photosynthesis, ball-milling, and chemical synthesis of Fe, Co, and Cu nanoparticle catalysts; b) Sol-gel method for mesoporous γ-Al 2 O 3 , SiO 2 , hybrid alumina/silica granular supports; c) Three sol-gel/oil-drop catalyst preparation methods to incorporate metal nanoparticles into mesoporous 1 mm granular supports; d) Low-cost GC-TCD system with hydrogen as carrier gas for the determination of wide spectrum of alkanes produced during the F-T reactions; and e) Gas-flow reactor and microchannel reactor for fast screening of catalysts.The LISD method could produce Co, Cu, and Fe (5 nm) nanoparticles, but in milligram quantities. We could produce nanoparticles in gram quantities using high-energy ball milling and chemical synthesis methods. Ball milling gave wide particle size distribution compared to the chemical synthesis method that gave almost uniform size (~5 nm) particles.Metal nanoparticles Cu, Co, Fe, Cu/Co, Cu/Fe and Co/Fe were loaded (2-12 wt%) uniformly into γ-Al 2 O 3 , SiO 2 , or alumina/silica hybrid supports by combined sol-gel/oil-drop methods followed by calcination and hydrogenation steps, prior to syngas FT reaction studies. The properties of metal loaded γ-Al 2 O 3 granules were compared for the two precursors: aluminum tri-sec-butoxide (ALTSB) and aluminum tri-iso-propoxide (ALTIP). The effect of solgel supports alumina, silica, and alumina/silica hybrid were examined on catalytic properties.Metal loading efficiencies for pure metal catalysts increased in the order Co, Cu and Fe in agreement with solubility of metal hydroxides. In case of mixed metals, Co and Cu seams to interfere and reduce Fe metal loading when metal nitrate solutions are used. The solubility differences of metal hydroxides would not allow precise control of metal loading. We have overcome this problem by introducing a novel method of nanoparticle metal oxide co-entrappedsol-gel that gave the highest metal loading with precise control and reproducibility, and greater mechanical strength of granules than the metal nitrate solution co-entrapping and wet impregnation methods.Both, slurry-phase-batch and gas-phase-continuous-flow, reactors were used for syngas conversion reactions. Our investigations of Co and Fe thin film deposited micro-reactors showed higher CO/H 2 conversion for Fe compared to Co. The catalytic activity for CO/H 2 conversion was observed in the increasing order for the nanocatalysts Cu, Co, Fe, Co/Fe , Cu/Co and Cu/Fe in alumina sol-gel support, and Co/Fe showed the highest yield for methane. The optimization of CO/H 2 ratio indicated that 1:1 ratio gave more alkanes distribution in F-T process with Co/Fe (6% each) impregnated on alumina. We could estimate the activity of catalysts (involving Co, Fe) during hydrogenation and after catalytic reaction using magnetization studies.In summary our accomplishments are: 1) Novel chemical methods for the synthesis of (5 nm) Fe, Co, Cu nanoparticles with na...

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“…The state of the unfilled d-shells and unpaired electrons, morphology and metallic charge distribution of these catalysts are known to govern both their catalytic and magnetic behavior 18 . The addition of small amounts of other metals such as Al, Cu, Ti have shown to enhance the dispersion of Fe/Co catalytic centers in the support and also influence the selectivity [19][20][21][22] . In the present work, we examine the inter-relations between catalytic and magnetic properties of sol-gel prepared iron/copper and cobalt nano-catalysts for CO hydrogenation to mixed alcohols.…”

Section: Introductionmentioning

confidence: 99%

Novel Preparation and Magneto Chemical Characterization of Nano-Particle Mixed Alcohol Catalysts

Seetala

Siriwardane²,

Murty³

2004

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The preparation of Cu, Co, Fe, Cu/Co, Cu/Fe and Co/Fe nano-particle metal loaded mesoporous 1 mm spherical granular γ-Al 2 0 3 catalysts, by combined sol-gel/oil-drop methods followed by calcination and hydrogenation steps, is accomplished. Parameters for calcination process were optimized using DTA. The properties of metal loaded γ-Al 2 O 3 granules were compared for the preparations starting with two precursors: aluminum tri-sec-butoxide (ALTSB) and aluminum tri-iso-propoxide (ALTIP). Three sol-gel/oil-drop catalyst preparation methods; 1) Metal nitrate solutions co-entrapped-sol-gel 2) nano-particle metal oxide co-entrapped-sol-gel, and 3) Metal impregnation on preformed alumina granules, were used.Structure and composition of metal-loaded-granules were investigated using XRD, SEM, EDX, and surface area measurements (BET method). The nano-particle nature of catalysts was confirmed using SEM and X-ray diffraction. The reduction efficiency of hydrogenation of catalysts was examined by magnetic studies using a vibrating sample magnetometer (VSM). Catalysts could be effectively calcined at 450°C and the surface area values obtained were between 200-350 m 2 /g, indicating the mesoporous nature of catalyst support. Parameters affecting the metal loading process were also studied, and the optimum conditions were identified and reported for reproducible synthesis of the metal loaded γ-alumina granular particles.The catalyst activities of Fe, Co, and Co/Fe on alumina for the conversion of CO/H 2 and CO 2 /H 2 mixtures were investigated using Gas chromatography (GC) with N 2 as a standard carrier gas. Both, slurry-phase-batch and gas-phase-continuous-flow, reactors were used. Magnetization studies on reduced, CO/H 2 post-reaction catalyst in both gas and slurry phase were performed using vibrating sample magnetometer (VSM). Magnetic studies of post-reaction Co and Fe nano-catalysts showed that the formation of carbides is higher for iron compared to cobalt. In the Fe/Co mixed catalyst, it is observed that the presence of iron enhances the cobalt oxide reduction. Catalyst with mixed metal Fe/Co compositions at 12% nitrate solutions (prepared by sol-gel/oildrop) showed the best conversion rates for the syngas (CO+H 2 ). Nano-particle catalysts on solgel prepared mesoporous γ-alumina (particularly the nano-particle metal oxide co-entrapped-solgel) showed higher conversion rates compared to conventional catalysts prepared by coprecipitation methods.

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Magneto-chemical characteristics of copper-cobalt catalysts

Cited by 3 publications

References 11 publications

Novel Preparation and Magneto Chemical Characterization of Nano-Particle Mixed Alcohol Catalysts

Novel Preparation and Magneto Chemical Characterization of Nano-Particle Mixed Alcohol Catalysts

Novel Preparation and Magneto Chemical Characterization of Nanoparticle Mixed Alcohol Catalysts

Novel Preparation and Magneto Chemical Characterization of Nano-Particle Mixed Alcohol Catalysts

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