On the mechanism of the Fischer-Tropsch synthesis involving unreduced iron catalyst

Blanchard, Florent; Reymond, J.P.; Pommier, B.; Teichner, S. J.

doi:10.1016/0304-5102(82)85028-1

“…It is believed that spinel compound of Fe 3 O 4 is good for the catalytic reaction as it able to provide more active sites. Based on the mechanism of the Fischer-Tropsch synthesis involving unreduced iron catalyst [Blanchard., 1982], it is attractive to consider the oxidized state of iron as the active phase in Fischer-Tropsch synthesis. It is of interest to note that the partially pre-reduced catalyst containing Fe 3 O 4 as a major phase was more active than the catalyst pre-reduced to -Fe 2+ .…”

Section: X-ray Photoelectron Spectroscopy (Xps)mentioning

confidence: 99%

Modern Applied Science, Vol. 3, No. 2, February 2009, all in one file

MAS¹

2009

MAS

0

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Experiment was carried out in two parts to investigate the degradation profile of trimethoprim and sulphamethoxazole, antibacterial compounds in aqueous phase. In the first part of study, the effects of UV and TiO 2 on two antibiotics using the UV-water flow system (UVWFS) were examined. Obtained results revealed that trimethoprim and sulphamethoxazole pronounced 44 to 45% and 6 to 314% elevated rate of degradation in two TiO 2 doses, 0.05 and 0.1 g/l treatments with UV than only UV treatments which affords to draw a substantial conclusion that though both UV and TiO 2 have a crucial impact but the synergistic photocatalytic effects of the TiO 2 with UV attributes a rapid and higher degree of degradation of antibiotics compared to that of only UV at the same water flow rate. In this context, it may also be observed that effect of the dose of TiO 2 was very little in trimethoprim degradation but a significantly greater effects was revealed in sulphamethoxazole that indicating same number of TiO 2 molecules acted more favourably on higher number of sulphamethoxazole molecules than trimethoprim by photocatalytic activity which enhancing the rate of degradation reaction resulting in the rapid decrease of sulphamethoxazole concentration level in water. In second part of the study, three (15, 42 and 80 cc/min) water flow rates were employed using UVWFS maintaining same UV and TiO 2 dose 0.1 g/l to ascertain the effect of water flow rate in the antibiotic transformation process. The degradation efficiency in 80 cc/min water flow treatment was 113 and 61% higher in trimethoprim and 103 and 51% higher in sulphamethoxazole compared to that of 15 and 42 cc/min water flow treatments, respectively which clearly indicated that the rate of water flow is a paramount important, largely influencing the photocatalysis reaction process of TiO 2 and UV with antibiotics in water medium possibly enhancing movement velocity of their molecules. Besides it, trimethoprim degraded rapidly over sulphamethoxazole which might be inferred that higher water flow substantially increases the rate of oxidation and photocatalytic transformation of trimethoprim over sulphamethoxazole in the presence of TiO 2 and UV.

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“…Table 6 gives some examples of metal-doped aerogels and their application in catalytic reactions. [94], [95] epoxidation of olefins Al 2 O 3 -SiO 2 [96] [AlCl 3 þ ethylene oxide] þ Si(OEt) 4 [73] catalyst support Al(OAc) 3 , Al(acac) 3 3 4 [97] preparation of high-purity ceramics Fe 2 O 3 -SiO 2 [98] Fe(acac) 3 þ Si(OMe) 4 Fischer -Tropsch syntheses…”

Section: Metal Oxide Aerogelsmentioning

confidence: 99%

Aerogels

Hüsing

¹

,

Schubert

²

2006

Ullmann's Encyclopedia of Industrial Chemistry

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The article contains sections titled: 1. Introduction 2. Synthesis 2.1. Network Formation and Structure 2.1.1. Inorganic Aerogels 2.1.1.1. SiO 2 Aerogels 2.1.1.2. Metal Oxide Aerogels 2.1.2. Inorganic/Organic Hybrid Aerogels 2.1.3. Organic Aerogels 2.2. Drying Methods 2.2.1. Supercritical Drying 2.2.1.1. Drying in Organic Solvents 2.2.1.2. Supercritical Drying with CO 2 2.2.2. Freeze Drying 2.2.3. Ambient Pressure Drying 2.3. Modification of Aerogels after Drying 3. Properties 3.1. Structural Properties 3.2. Physical and Chemical Properties 3.2.1. Optical Properties 3.2.2. Mechanical and Acoustic Properties 3.2.3. Thermal Conductivity 3.2.4. Hydrophobicity 4. Applications 4.1. Çerenkov Detectors 4.2. Thermal Insulation 4.3. Catalysis 4.4. Application as Storage Media 4.5. Electrical and Electronic Applications 4.6. Acoustic and Mechanical Applications 4.7. Optical Applications 4.8. Other Applications 5. Future Perspectives Aerogels are unique among solid materials. They have extremely low densities (up to 95 % of their volume is air), large open pores, and a high inner surface area. This combination of properties results in interesting physical properties, e.g., for silica aerogels extremely low thermal conductivities and low sound velocities are combined with optical transparency. Aerogels are typically prepared via wet chemical processes, such as sol – gel processing, and thus their pore system is initially filled with liquid. Only special drying techniques allow for exchange of the pore liquid against air while maintaining the filigrane solid framework. The most common drying technique is supercritical extraction, and sometimes chemical modification of the inner surface can be used to facilitate drying. The structure of the gel network, and thus the physical properties of aerogels, decisively depends on the choice of the precursors and the chemical reaction parameters for preparing the gels. Therefore, the later materials properties can be deliberately designed in the starting reaction solution.

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“…We used solgel/oil-drop methods 14,15 to prepare nano-particle syngas conversion catalysts containing ferromagnetic metals (Fe, Co). The nanometer scale metal clusters are known to exhibit size dependent physical properties 16,17 . 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 .…”

Section: Introductionmentioning

confidence: 99%

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

Seetala

¹

,

Siriwardane²,

Murty³

2004

0

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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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On the mechanism of the Fischer-Tropsch synthesis involving unreduced iron catalyst

Cited by 94 publications

References 20 publications

Modern Applied Science, Vol. 3, No. 2, February 2009, all in one file

Modern Applied Science, Vol. 3, No. 2, February 2009, all in one file

Aerogels

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

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