Supported Iron Oxide Catalysts Research Articles

Comparative study on the removal of methyl orange using zeolite/biochar- supported iron oxide catalyst from industrial by-products

Comparative study on the removal of methyl orange using zeolite/biochar- supported iron oxide catalyst from industrial by-products

Insights into enhanced stability and activity of silica modified SiC supported iron oxide catalyst in sulfuric acid decomposition

The agglomeration and sintering of metal nanoparticles due to poor thermal stability are major causes of catalyst deactivation in many metal loaded catalysts used in industrially important high temperature reactions. This work is taken up choosing an iron oxide nano-catalyst dispersed on a silica surface grown on a SiC support material for an endothermic high temperature and highly corrosive reaction condition such as sulfuric acid decomposition. These combined theoretical and experimental findings not only allow us to design cheaper and stable catalysts but also provide an atomistic insight into the mechanism of the metal-support interaction. Consequently, the successful tuning of the latter helps in enhancement of overall activity and stability. The high activity and stability are attributed to the presence of oxygen deficit sites in the catalyst developed for the model reaction under consideration.

Preparation of Nanostructured Pd‐Fe2O3 Catalyst for C–C Coupling Reaction

AbstractWe have synthesized palladium nanoparticles supported iron oxide catalyst by controlled deposition of palladium in presence of triethanolamine and polyvinylpyrrolidone (PVP), where triethanolamine act as mild reducing agent and PVP act as capping agent. Prepared (0.9% Pd‐Fe2O3CD) catalyst showed high activity towards Heck coupling reaction, under mild reaction conditions. Different analytical techniques were systematically employed to characterize the prepared material in order to find the specific surface area, Pd loading, crystal structure, surface morphology, particle size, reducibility behavior, surface chemical state, phase purity and crystallinity, optical property and local environment of active species etc. 0.9% Pd‐Fe2O3CD catalyst showed high activity toward Heck coupling with iodo‐derivatives at room temperature in solvent‐free reaction conditions and prevented the leaching of active species, during catalysis. The catalyst possessed strong metal‐support interaction due to smaller Pd nanoparticles (2‐12 nm) and maintained its heterogeneous nature during recycling experiments.

Catalytic Dehydrogenation of para-Diethyl Benzene to para-Divinyl Benzene over Iron Oxide Supported Catalyst

The vapor-phase catalytic dehydrogenation of para-diethyl benzene (PDEB) to para-divinyl benzene (PDVB) with super-heated steam as a diluent was investigated using alumina supported iron oxide catalyst system. During the catalytic dehydrogenation reaction, ethyl styrene (EST) and thermal cracking products were observed as side products. It was found that various reaction parameters influence the rate of dehydrogenation reaction. However, the reaction is favored by high temperature and low reaction pressure. Moreover, addition of potassium into iron-oxide catalyst acts as a promoter and thereby increases the efficiency of the catalyst. The conversion of PDEB and yield of PDVB also increases as the Water/PDEB flow ratio increases.

Synthesis of Highly Active Pd Nanoparticles Supported Iron Oxide Catalyst for Selective Hydrogenation and Cross‐Coupling Reactions in Aqueous Medium

AbstractPost synthetic approach was successfully employed for the synthesis of Pd supported iron oxide (Pd‐Fe2O3TA) catalyst using polyvinylpyrrolidone as capping agent and triethanolamine as reducing agent. Performance of Pd‐Fe2O3TA catalyst was investigated for selective hydrogenation of nitro compounds and Suzuki coupling reactions. Prepared catalyst exhibited excellent yield of corresponding substituted amines and biphenyls, under optimized reaction conditions. Different analytical techniques such as BET‐surface area measurements, XRD, ICP‐AES, SEM, TEM, XPS, TPR, FT‐IR, RAMAN, UV‐Vis and EXAFS analysis were employed to characterize the catalyst. Average particle size of palladium nanoparticles (NPs) was found to be ∼5.2 nm supported on 60–120 nm size of iron oxide nanocrystals. Various reaction parameters such as time, temperature, solvents, active metal loading, base and different substituent were investigated in detail. Different catalysts were also prepared and compared their activity with that of Pd‐Fe2O3TA catalyst. Experimental observations revealed that size of palladium NPs and metal‐support interaction favoured the superior activity of Pd‐Fe2O3TA catalyst compared to other catalysts. Stability of Pd‐Fe2O3TA catalyst was confirmed by its recyclability tests indicated true heterogeneous nature of catalyst.

Synthesis of light olefins and alkanes on supported iron oxide catalysts

Catalytic synthesis of C1–C4 hydrocarbons from clean synthesis gas, representative of natural gas, biomass or coal, was investigated over conventional supported catalyst (FeOx/Al2O3 and FeOx/ZrO2) and compared with catalytic cartridges made from anodized Al plates (FeOx/AAO-Al). Porous aluminum oxide layers (ca. 50 and 100μm thick) and uniform meso/macro pores (ca. 25–50nm, 50–75nm diam.) were established on Al plates by anodization treatment. Iron was supplied by incipient wetness impregnation (particles), wet impregnation and ultrasonic spray deposition (plates). Catalysts were characterized by SEM, XPS, H2-TPR N2-BET and Hg porosimetry. Synthesis performance was studied at 350–500°C, H2/CO ratios 1–3 and atmospheric pressure. Loading of FeOx and its reducibility was favoring gaseous products and determining reaction mode. Conditions were strongly favoring accumulation of carbonaceous material, being governing for performance and limiting lifetime. Low olefins selectivity (< 5%) and yields (< 1%) were obtained. Addition of 1wt.%K favored syngas conversion and deactivation, 1.2wt.% Cu caused no effect. Results indicate that large pores favor olefin selectivity and lifetime. The catalyst working state, as evolving during reaction was independent on initial state (calcined oxide, reduced, precursor nitrate salts), indicating that thermodynamics was structure controlling.

Fatty acid decarboxylation reaction kinetics and pathway of co-conversion with amino acid on supported iron oxide catalysts

Reaction kinetics and pathways of palmitic acid decarboxylation on Fe2O3/Al-MCCM-41 catalyst.

Hydrogen Production from the Water-Gas Shift Reaction on Iron Oxide Catalysts

Unsupported and supported iron oxide catalysts were prepared by incipient wetness impregnation method and studied in the water-gas shift reaction (WGSR) in the temperature range 350–450°C. The techniques of characterization employed were BET, X-ray diffraction, acid-base measurements by microcalorimetry and in situ diffuse reflectance infrared Fourier transform spectroscopy. MgO, TiO2, or SiO2 was added in order to (i) obtain a catalyst exempt of chromium oxide and (ii) study the effect of their acid-base properties on catalytic activity of Fe2O3. X-ray diffraction studies, and calorimetric and diffuse reflectance infrared Fourier transform measurements reveal a complete change in the physicochemical properties of the iron oxide catalyst after MgO addition due to the formation of the spinel oxide phase. These results could indicate that the MgFe2O4 phase stabilizes the reduced iron phase, preventing its sintering under realistic WGSR conditions (high H2O partial pressures).

Montmorillonite–carbon nanotube nanofillers by acetylene decomposition using catalytic CVD

Montmorillonite–carbon nanotube nanofillers (a binary hybrid material) were successfully synthesised for polymer reinforcing applications. Montmorillonite (Mt) supported iron oxide (20 and 25wt.%) catalysts were prepared using the conventional wet impregnation method and calcined at 450°C. In situ reduction of the catalysts and synthesis of CNT was carried out in a horizontal furnace at 750°C using acetylene along with nitrogen and hydrogen. The influence of gas composition on the carbon nanotube growth characteristics of montmorillonite supported iron oxide catalysts was studied. Growth experiments with two different gas compositions containing 5 and 8vol.% of acetylene were used to evaluate the effect of the concentration of acetylene gas on the yield, morphology and purity of the carbon nanotubes over each catalyst. Highly selective, crystalline and defect free carbon nanotubes were obtained at low acetylene concentration in the total gas flow.

Co-catalytic effect of sewage sludge-derived char as the support of Fenton-like catalyst

Sewage sludge-derived char was successfully employed as the support of heterogeneous Fenton-like catalyst for the first time. Physicochemical properties of the prepared sewage sludge-derived char supported iron oxide catalyst (FeSC) have been evaluated by XRD, SEM, EDS and N2-adsorption/desorption analysis. FeSC exhibited better performance in discoloration of AOII than wood sawdust-based carbon supported iron oxide catalyst (FeWC) both in batch experiment and continuous tests. The high inorganic components content of sewage sludge was concluded to have strong correlations with the high catalytic activity of FeSC. To further interpret the co-catalytic effect of inorganic components in sewage sludge, the inorganic components were removed from the sewage sludge and then a series of catalysts were prepared by the addition of iron, as well as silica and/or alumina to the sewage sludge free of the inorganic components. It was found that the removal of inorganic fraction remarkably decreased the catalytic activity of iron-containing catalyst. The insertion of SiO2 favors the increase in catalytic activity due to the formation of both hydrogen bonds between H2O2 and siloxane bridges and the acidic microenvironment near the surface of silica phase. While the addition of Al2O3 in sewage sludge as basic sites can facilitate the degradation of H2O2, and the characteristic of Lewis acidity of alumina can accelerate the reduction of Fe3+ to Fe2+ by H2O2.

Spatially and Size Selective Synthesis of Fe-Based Nanoparticles on Ordered Mesoporous Supports as Highly Active and Stable Catalysts for Ammonia Decomposition

Uniform and highly dispersed γ-Fe(2)O(3) nanoparticles with a diameter of ∼6 nm supported on CMK-5 carbons and C/SBA-15 composites were prepared via simple impregnation and thermal treatment. The nanostructures of these materials were characterized by XRD, Mössbauer spectroscopy, XPS, SEM, TEM, and nitrogen sorption. Due to the confinement effect of the mesoporous ordered matrices, γ-Fe(2)O(3) nanoparticles were fully immobilized within the channels of the supports. Even at high Fe-loadings (up to about 12 wt %) on CMK-5 carbon no iron species were detected on the external surface of the carbon support by XPS analysis and electron microscopy. Fe(2)O(3)/CMK-5 showed the highest ammonia decomposition activity of all previously described Fe-based catalysts in this reaction. Complete ammonia decomposition was achieved at 700 °C and space velocities as high as 60,000 cm(3) g(cat)(-1) h(-1). At a space velocity of 7500 cm(3) g(cat)(-1) h(-1), complete ammonia conversion was maintained at 600 °C for 20 h. After the reaction, the immobilized γ-Fe(2)O(3) nanoparticles were found to be converted to much smaller nanoparticles (γ-Fe(2)O(3) and a small fraction of nitride), which were still embedded within the carbon matrix. The Fe(2)O(3)/CMK-5 catalyst is much more active than the benchmark NiO/Al(2)O(3) catalyst at high space velocity, due to its highly developed mesoporosity. γ-Fe(2)O(3) nanoparticles supported on carbon-silica composites are structurally much more stable over extended periods of time but less active than those supported on carbon. TEM observation reveals that iron-based nanoparticles penetrate through the carbon layer and then are anchored on the silica walls, thus preventing them from moving and sintering. In this way, the stability of the carbon-silica catalyst is improved. Comparison with the silica supported iron oxide catalyst reveals that the presence of a thin layer of carbon is essential for increased catalytic activity.

The effect of thermodynamic properties of zirconia-supported Fe3O4 on water-gas shift activity

The thermodynamics of the oxidation and reduction of a series of zirconia- and alumina-supported iron-oxide catalysts were measured using coulometric titration and then compared to their activity for the water-gas shift (WGS) reaction. For the supported iron oxide catalysts with weight loadings of 5–30 wt%, the Gibbs free energy for the phase transition between Fe2O3 and Fe3O4 decreased by factor of two compared to that for bulk, unsupported iron oxide. This difference in thermodynamic properties was also found to affect the WGS reaction rates, with the rates on the supported catalysts being an order of magnitude lower than that for bulk iron oxide. We propose that the differences in the thermodynamic properties of the supported and unsupported catalysts are due to lattice strain in the supported iron oxide resulting from interactions at the FeOx-support interface.

Effect of the calcination temperature on the properties of Fe2O3/SiO2 catalysts for oxidation of hydrogen sulfide

The effect of the calcination temperature on the properties of supported iron oxide catalysts for hydrogen sulfide oxidation prepared by impregnation of silica with iron(III) nitrate has been studied. An increase in the calcination temperature was found to diminish the catalytic activity of the Fe2O3/SiO2 catalysts in hydrogen sulfide oxidation. This behavior can be explained by the agglomeration of iron oxide particles and by a decrease in the surface concentration of active sites. It has been shown that an increase in the calcination temperature makes the catalyst more stable towards the sulfidation of the active component (Fe2O3) to the iron disulfide phase.

Epoxidation of propylene in the gas phase

The gas-phase epoxidation of propylene using N2O, air and air-ammonia mixture as an oxidants was studied. Propylene can be epoxidized by nitrous oxide with a yield as high as 13.3% over silica supported iron oxide catalysts modified by amines. The iron oxide dispersion, the acidity of the support and the nitrogen-containing modifiers are the key factors determining the catalytic performance. We suggest a reaction pathway involving two concurrent mechanisms: the radical oxidation of propylene to acroleine, hexanediene, etc., and a non-radical oxidation leading to epoxide. Propylene is epoxidized with air over silica-supported iron oxide catalysts at a conversion of about 0.2%. Using air as an oxidizing agent, the presence of gaseous ammonia improves the propylene conversion by 10-fold preserving the considerable selectivity (up to 60%). This observation suggests a reaction mechanism involving the oxidation of ammonia to nitrous oxide in the first step, which subsequently produces active oxygen species, which selectively oxidize propylene to propylene oxide (PO).

Photoassisted fenton degradation of nonbiodegradable azo-dye (Reactive Black 5) over a novel supported iron oxide catalyst at neutral pH

A novel supported iron oxide, prepared using a fluidized-bed reactor (FBR), was utilized as a catalyst of the heterogeneous photoassisted Fenton degradation of azo-dye Reactive Black 5 (RB5). This catalyst is much cheaper than Nafion-based catalysts, and can markedly accelerate the degradation of RB5 under irradiation by UVA ( λ = 365 nm). The effects of the molar concentration of H 2O 2, the pH of the solution and the catalyst loading on the degradation of RB5 are elucidated. A simplified mechanism of RB5 decomposition that is consistent with the experimental findings for a solution with a pH of up to 7.0 is proposed. About 70% decolorization was measured and 45% of the total organic carbon was eliminated on the surface of the iron oxide at pH 7.0 after 480 min in the presence of 0.055 mM RB5, 5.0 g iron oxide/L, 29.4 mM H 2O 2, under 15 W UVA.

Support effects in catalytic wet oxidation of H 2S to sulfur on supported iron oxide catalysts

Iron oxide catalysts supported on MgO, Al 2O 3, SiO 2 and ZrO 2 were prepared by an impregnation method. They were characterized by BET surface analysis, X-ray diffraction (XRD), temperature-programmed reduction (TPR) and Mössbauer spectroscopy. Fe/MgO catalyst shows the highest H 2S removal capacity in wet oxidation at room temperature. Both the XRD and the TPR analyses of the catalysts indicate that H 2S removal capacity correlates with the dispersion of iron oxide on supports. Mössbauer spectroscopy shows that four kinds of Fe 3+ species are present in the supported iron oxide catalysts: two highly dispersed species, Fe 3+ oxide clusters, and α-Fe 2O 3 particles. Two highly dispersed species, Fe 3+ cation and MgFe 2O 4, are present in Fe/MgO. Fe 3+ oxide clusters and α-Fe 2O 3 crystals are evident in both Fe/SiO 2 and Fe/ZrO 2. α-Fe 2O 3 crystals are only observed in Fe/Al 2O 3.

Direct gas-phase epoxidation of propene with nitrous oxide over modified silica supported [formula omitted] catalysts

Vapour phase epoxidation of propene with nitrous oxide over alkaline containing silica supported iron oxide catalysts was experimentally investigated. A reaction network is deduced from the trends of product selectivities as function of propene conversion using different catalysts. Important side reactions are parallel propanal formation and consecutive isomerisations of propylene oxide (PO) to propanal, acetone and allyl alcohol. Rates of these reactions were affected by catalyst composition, which influenced acid-base properties, number of silanol groups and surface area. A PO selectivity of ∼ 75 % and PO space–time yields of 0.02– 0.03 g PO g cat - 1 h - 1 were obtained with a catalyst containing ironoxo-species and caesium ions/-oxides. These results can only be obtained at a high surplus of N 2 O versus propene concentration in the reactor feed. Likely reasons for that is an inhibition of propylene oxide's formation rate by propene and propylene oxide itself.

04/02193 Recycling of waste lubricant oil into chemical feedstock or fuel oil over supported iron oxide catalysts: Bhaskar, T. et al. Fuel, 2004, 83, (1), 9–15

04/02193 Recycling of waste lubricant oil into chemical feedstock or fuel oil over supported iron oxide catalysts: Bhaskar, T. et al. Fuel, 2004, 83, (1), 9–15

Recycling of waste lubricant oil into chemical feedstock or fuel oil over supported iron oxide catalysts

The recycling of waste lubricant oil from automobile industry was found to be best alternative to incineration. Silica (SiO2), alumina (Al2O3), silica–alumina (SiO2–Al2O3) supported iron oxide (10 wt% Fe) catalysts were prepared by wet impregnation method and used for the desulphurisation of waste lubricant oil into fuel oil. The extent of sulphur removal increases in the sequence of Fe/SiO2–Al2O3<Fe/Al2O3<Fe/SiO2 and this might be due to the presence of smaller crystalline size (7.4 nm) of Fe2O3 in Fe/SiO2 catalyst. X-ray diffraction results suggest the presence of iron sulphide in the used catalyst. Gas chromatography with thermal conductivity detector analysis confirms the presence of H2S in gaseous products. In addition, Fe/SiO2 catalyst facilitated the formation of lower hydrocarbons by cracking higher hydrocarbons (≈C40) present in waste lubricant oil.

Study on the Reduction Behavior of Zirconia Supported Iron Oxide Catalysts by Temperature-Programmed Reduction Combined within SituMössbauer Spectroscopy

The reduction properties of Fe2O3/ZrO2catalysts with various Fe2O3loading and the interactions between iron oxide and zirconia have been studied by using temperature-programmed reduction combined within situMössbauer spectroscopy. This is shown that the intermediates formed during reduction depend strongly not only on the reduction temperature but also on the iron loading. Several iron species such as bulk phase α-Fe2O3, small α-Fe2O3particles, and surface iron oxide species are found in the zirconia supported iron oxide catalysts. Reduction of the small α-Fe2O3particles is easier than that of the bulk phase α-Fe2O3. In contrast, the surface iron oxide species are much more difficult to reduce because of their strong interactions with the support. The phenomena of partial oxidation of Fe2+cations and Fe3O4to Fe3+cations in the reduction processes are observed.