Nano-structured Iron Catalyst Research Articles

Deuterium Labelling of (Hetero)Arenes Enabled by a Nanostructured Iron Catalyst

Key words Deuteration - H/D exchange - heterocycles - iron catalysis - isotope labelling

Scalable and selective deuteration of (hetero)arenes

Isotope labelling, particularly deuteration, is an important tool for the development of new drugs, specifically for identification and quantification of metabolites. For this purpose, many efficient methodologies have been developed that allow for the small-scale synthesis of selectively deuterated compounds. Due to the development of deuterated compounds as active drug ingredients, there is a growing interest in scalable methods for deuteration. The development of methodologies for large-scale deuterium labelling in industrial settings requires technologies that are reliable, robust and scalable. Here we show that a nanostructured iron catalyst, prepared by combining cellulose with abundant iron salts, permits the selective deuteration of (hetero)arenes including anilines, phenols, indoles and other heterocycles, using inexpensive D2O under hydrogen pressure. This methodology represents an easily scalable deuteration (demonstrated by the synthesis of deuterium-containing products on the kilogram scale) and the air- and water-stable catalyst enables efficient labelling in a straightforward manner with high quality control.

Nanoscale confinement in carbon nanotubes encapsulated zero-valent iron for phenolics degradation by heterogeneous Fenton: Spatial effect and structure–activity relationship

• Confinement effect was significant for 3–7 nm carbon nanotubes (CNTs) cavity encapsulated Fe. • The better reusability of Fe 0 @CNTs (3)-(7) was exhibited for five runs compared with other CNTs. • The active enhancement attributed to electron transfer and interaction between Fe and CNTs. • The confinement role reached 2.13-folds of homogeneous role for phenol removal by Fe 0 @CNTs (5). • Fe 0 @CNTs ( x ) with positive charges was conductive to adsorb the negatively charged phenols. In heterogeneous Fenton, nanostructured iron catalysts with confinement effect greatly improve the effectiveness for organic pollutants removal, however, this effect dependence on the space of substrate remains unclear and thereby limit the application of confined catalysis. Herein, Fe particles encapsulated in carbon nanotubes with inner diameter of 3–30 nm (Fe 0 @CNTs ( x )) were prepared and tested as catalysts to degrade model pollutant of phenol and four phenolic compounds ( p -diphenol ( p -DP), p -aminophenol ( p -AP), p -nitrophenol ( p -NP) and p -chlorophenol ( p -CP)). With the increasing of CNTs inner diameter from 3 to 30 nm, the encapsulated Fe particles linearly increased from 2.68 to 14.75 nm. The confinement effect was significant in the range of 3–7 nm of CNTs cavity, especially at 5 nm, which was critical to decrease iron leaching and enrich hydroxyl radical generation for efficient pollutants removal by surface heterogeneous reaction (2.13-folds compared with the homogeneous Fenton). In addition, the Fe 0 @CNTs (3) - (7) with positive charges was conductive to adsorb the negatively charged phenols ( p -DP and p -AP) compared with non-spatial confinement of Fe-CNTs with negative charge. According to the experiment and DFT calculations, the quantitative structure–activity relationship about electron transfer was established, indicating that the electron from highest occupied molecular orbital (HOMO) of p -AP could migrate to lowest unoccupied molecular orbital (LUMO) of Fe 0 @CNTs and further to HOMO of Fe 0 @CNTs. The electron in HOMO of Fe 0 @CNTs could migrate into H 2 O 2 to generate · OH. This finding suggested a new paradigm to fulfill selective oxidation of the pollutants with electron-withdrawing group by suitable heterogeneous catalysts having significant confinement effect with more effective utilization of · OH in Fenton reaction.

MOF derived novel zero-valent iron @ graphitic carbon-based nanoreactors for selective reduction of hazardous 4-nitrophenol

Fabrication of stable and efficient zerovalent non-noble metal-based nanostructured catalyst has emerged as the hot area of research for wastewater treatment due to their low cost and facile natural source availability. In this work, the rationally controlled calcination of iron-terephthalate MOF has produced the magnetically active zero-valent iron-based nanostructured catalyst. Unlike other synthesis approaches, MOF’s temperature-controlled calcination has offered highly effective and stable metallic iron nanoparticles encapsulated in few-layered porous graphitic carbons. The developed nanostructured catalyst was applied for room temperature conversion of hazardous 4-Nitrophenol (4-NiP) to a value-added industrial intermediate 4-Aminophenol (4-AP) by exploiting sodium borohydride as a hydrogen donor agent. The synthesized zerovalent iron-based nanostructured catalysts were thoroughly investigated and characterized by powder X-ray diffraction (pXRD), infrared and Raman spectroscopy, thermogravimetric analysis (TGA), energy dispersive X-Rays (EDS), X-ray photoelectron (XPS) spectroscopy, and transmission electron microscopy (TEM). The UV–Vis spectroscopy was used for the monitoring of the conversion of the 4-NiP into 4-AP. The conversion analysis result has shown that the MOF-based precursors’ calcination temperature has played a critical role in the potency of the catalyst for converting the 4-NiP into 4-AP. The outer porous architecture provided the facile adsorption and desorption of the 4-NiP on the active nanostructured metallic iron catalyst. The maximum degradation of 4-NiP into 4-AP has taken place in a short time of 3 ​min at a rate constant of 0.0149 s −1 . In terms of economic perspective and high catalytic efficiency, the developed low coast nanostructured catalyst is the right choice over the reported noble metal-based catalyst for the room temperature conversion of 4NiP to a value-added product. • Synthesis of MOF derived stable Zero-valent Iron @ Graphitic Carbon-based Nanoreactors. • Room temperature reduction of hazardous water pollutant 4-Nitrophenol. • Conversion of 4-Nitrophenol pollutant to a value-added 4-Aminophenol. • Magnetic iron nanoparticles for selective hydrogenation.

Fe(III)-Exchanged Zeolite As Efficient Electrocatalysts for Electrodegradation of Congo Red Dye

The role of the nanostructured iron catalysts hosted by different type of zeolite structures (NaY and ZSM5) on the electrochemical degradation of Congo Red dye (C32H22N6Na2O6S2) was investigated. Here, the nano-iron zeolite catalysts with high surface areas (up to 853 m2 g-1) were prepared by ion-exchange method1 serving tunable particle size and acidity that is highly sensitive to the local reaction environment at the electrode surface. The structural and morphological analysis was carried out using scanning electron microscopy (SEM), X-ray diffraction and N2-sorption techniques. In order to clarify the electrocatalytic trend observed by constant potential electrolysis, we further considered the acidity properties of the zeolites determined by microcalorimetric measurements. Moreover, it was noted that the presence of NH4 +, H+ and Na+ ions in the case of ZSM5 zeolite allows the rearrangement of the iron-zeolite architecture, resulting in a more favorable stabilization of the degradation process as a function of the production rate. Compared with the FeNaY catalysts, the FeZSM5 catalysts (Fe(Na)ZSM5, Fe(H)ZSM5 and Fe(NH4)ZSM5) exhibited excellent activity and stability, with a maximum dye degradation around 64% on the Fe(H)ZSM5 catalyst. This work, revealing the synergetic interactions between the acid sites of the zeolite and the catalytic active sites, provides a new route for the development of electrochemical sensing low-metal content zeolite structures.Acknowledgements:This work was conducted in the framework of the BioTecNorte projects: NORTE-01-0145-FEDER-000004, PTDC/AAGTEC/5269/2014, UID/QUI/00686/2013, and UID/QUI/0686/2016. Z. B. is grateful for ERASMUS research grant.Reference:1. M. Ferreira, F. Pinto, O. S. G. P. Soares, M. F. R. Pereira, J. J. M. Órfão, J. L. Figueiredo, I. C. Neves, A. M. Fonseca, P. Parpot, Chemical Engineering Journal, 228 (2013) 374.

Colloid and Nanosized Catalysts in Organic Synthesis: XXII. Hydrogenation of Cycloolefins Catalyzed by Immobilized Transition Metals Nanoparticles in a Three-Phase System

The processes of unsaturated cyclic hydrocarbons hydrogenation in a three-phase gas-liquid-solid catalyst system in the presence of nanostructured nickel, cobalt, or iron catalysts in a flow reactor at 130°C and atmospheric pressure have studied. RX3Extra activated carbon, γ-Al2O3, NaX zeolite, and Purolite CT-175 cation-exchange resin have been used as supports; NaBH4 and NH2NH2·H2O were used as reducing agents. The catalytic activity of supported nanoparticles and their selectivity with respect to the product of exhaustive hydrogenation have been investigated.

Ultra-Fast Degradation of p-Aminophenol by a Nanostructured Iron Catalyst.

Full degradation of p-aminophenol in aqueous solution at room temperature by using a heterogeneous nanostructured iron hybrid catalyst in the presence of hydrogen peroxide is described. A nanostructured iron catalyst was prepared by in situ formation of iron carbonate nanorods on the protein network using an aqueous solution of an enzyme, lipase B from Candida antarctica (CAL-B). A second kind of iron nanostructured catalyst was obtained by the sunsequent treatment of the hybrid with an aqueous liquid extract of Mentha x piperita. Remarkable differences were observed using TEM imaging. When M. piperita extract was used, nanoparticles appeared instead of nanorods. Catalytic activity of these iron nanocatalysts was studied in the degradation of the environmental pollutant p-aminophenol (pAP) under different operating parameters, such as pH, presence of buffer or hydrogen peroxide concentration. Optimal conditions were pH 4 in acetate buffer 10 mM containing 1% (v/v) H2O2 for FeCO3NRs@CALB, while for FeCO3NRs@CALB-Mentha, water containing 1% (v/v) H2O2, resulted the best. A complete degradation of 100 ppm of pAP was achieved in 2 and 3 min respectively using 1 g Fe/L. This novel nanocatalyst was recycled five times maintaining full catalytic performance.

KINETIC MODEL FOR FISCHER-TROPSCH SYNTHESIS OVER NANOPARTICLES IRON CATALYSTS WITH POLYMER MATRIX IN A SLURRY REACTOR

Influence of additives of synthetic polymers of various natures on reactionary ability of the nanostructured iron catalysts in the three-component Fe-paraffin-polymer system in Fischer-Tropsch (FTS) in the slurry reactor was studied. The polymers used: polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polystyrene, cross-linked with divinylbenzene (PS-DVB), polyamide-6 (PA). The catalysts obtained by droplet thermolysis is influenced by, the nature of the stabilizing polymer. Besides the conversion of the synthesis gas depends on the contact time and is between 10 to 80%. The highest rate of FTS is observed in the Fe-paraffin-PAN. The conditions of synthesis in Fe-paraffin-polymer systems produced a wide range of saturated and unsaturated compounds. It is found that the nature of the stabilizing polymer also affects the olefin /paraffin ratio. Based on experimental data the analysis of kinetic models for the flow of CO is carried out, a kinetic and thermodynamic characteristics of the process was obtained. The relationship between the values of the activation energies and the nature of the stabilizer was established.

Activation Energies for Chain Growth Propagation and Termination in Fischer–Tropsch Synthesis on Iron Catalyst as a Function of Catalyst Particle Size

The influence of the catalyst particle size in determining Fischer–Tropsch synthesis (FTS) performance for nano-structured iron catalysts was investigated. The catalysts were prepared by a microemulsion method and to achieve a series of catalysts with different iron particle size, the water-to-surfactant molar ratio (W/S) in the microemulsion system varied from 4 to 12. The results demonstrate that by decreasing the levels of active phase of the iron catalyst, the termination rates for chain growth are increased compared to the propagation rates. In addition, the activation energy for chain propagation is lower than for chain termination, and this difference (Et – Ep) for the hydrocarbon product distributions which is characterised by α1, is lower than the hydrocarbon product distribution which is characterised by α2 The results indicate the H2 concentration on the catalyst surface is decreased by increasing the catalyst particle size. Thus, the dependence of α (α1, and/or α2) on H2 partial pressures is increased by decreasing of catalyst particle size and the dependence of α2 on H2 partial pressures is weaker than for α1.

Structural Sensitivity of Carbon Monoxide Hydrogenation by Nano-Structured Iron Catalyst.

A new size dependence kinetic equation for chain growth factor in Fischer-Tropsch synthesis (FTS) was developed using a thermodynamic analysis method. For evaluation of structural sensitivity of FTS reaction, a series of iron oxide nanoparticles were prepared as a catalyst via precipitation by microemulsion method. The experimental results indicated that the difference between activation energies for propagation and termination reactions (Et-Ep) decreased with decreasing the catalyst particle size. Calculated size dependent model parameters were employed for evaluation of surface tension energy (σ) and size-independent activation energy for chain growth probabilities.

Iron-catalyzed synthesis of secondary amines: on the way to green reductive aminations.

Amines represent important intermediates in chemical and biological processes. Herein, we describe the use of a nanostructured iron-based catalyst for the tandem reductive amination between nitroarenes and aldehydes using hydrogen as reductant. The nanostructured iron-catalyst is prepared by immobilization of an iron-phenanthroline complex onto a commercially available carbon support. In the reaction sequence a primary amine is formed in situ from the corresponding nitro compound. Reversible condensation with aldehydes forms the respective imines, which are finally reduced to the desired secondary amine. This synthesis of secondary amines is atom-economical and environmentally attractive using cheap and readily available organic compounds as starting materials.

Studies on product distribution of nanostructured iron catalyst in Fischer–Tropsch synthesis: Effect of catalyst particle size

The dependencies of hydrocarbon product distributions of Fischer–Tropsch synthesis by iron catalysts on catalysts particle size are studied. The concept of two superimposed Anderson–Schulz–Flory distributions applied for represent size dependency of product distributions. A series of catalysts with different particle size are prepared by microemulsion method. It is found that the carbon number of produced hydrocarbon decreased with decreasing the catalyst particle size. These results indicate the H2 concentration on catalyst surface decreased by increasing the catalyst particle size. Thus the concentration of monomers that exhibited higher degree of hydrogenation (like CH2 species) on the surface of catalyst increased with decreasing the catalyst particle size.

Synergetic Effect of La and Ba Promoters on Nanostructured Iron Catalyst in Fischer-Tropsch Synthesis

Effect of promoters such as Barium and Lanthanum has been investigated on the conventional nanostructured iron catalyst in Fischer-Tropsch synthesis (FTS). The nanosized iron-based catalysts were prepared by a microemulsion method with the general formulation of 100Fe/4Cu, 100Fe/4Cu/2La, 100Fe/4Cu/1La/1Ba, and 100Fe/4Cu/2Ba. The phase, structure, and morphology of the catalysts were characterized by X-ray diffraction, N 2 adsorption, transmission electron microscopy, temperature-programmed desorption of CO 2 , and temperature-programmed reduction. The results indicated that the addition of promoters could improve the activity of Fe catalysts for FTS and WGS (water-gas shift reaction) and lower the gas fraction at the outlet. In addition, both Ba- and La-promoted Fe catalysts exhibit the highest activity due to the synergetic effect. The effect of promoters such as Ba and La has been investigated on the conventional nanostructured iron catalyst in Fischer-Tropsch synthesis (FTS). The results indicate that adding promoters could improve activity of Fe catalysts for FTS and water-gas shift reaction and lower the gas fraction at the outlet. In addition, both Ba- and La-promoted Fe catalysts exhibit the highest activity due to the synergetic effect.

Deactivation studies of Fischer–Tropsch synthesis on nano-structured iron catalyst

Deactivation kinetics of bulk and nano-structured microemulsion prepared iron catalysts were studied in Fischer–Tropsch synthesis (FTS), from fitting of data to a generalized power-law expression (GPLE), r d = k d ( a − a ∞) m . Conventional bulk iron catalyst was prepared by general bulk co-precipitation method and nano-structured iron catalyst was prepared by microemulsion method. A deactivation model involving parallel paths is proposed, i.e. simultaneous conversion of (a) atomic to polymeric to graphitic carbon and (b) active carbon-rich carbides to inactive carbon-poor carbides. Compositions of bulk iron phase and phase transformations of carbonaceous species during catalyst deactivation in FTS reaction were characterized by temperature-programmed surface reaction with hydrogen (TPSR-H 2), XRD and TEM techniques.

Kinetics of the water-gas shift reaction in Fischer-Tropsch synthesis over a nano-structured iron catalyst

Based on formate and direct oxidation mechanisms, three Langmuir-Hinshelwood-Hougen-Watson (LHHW) kinetic models of the water-gas-shift (WGS) reaction over a nano-structured iron catalyst under Fischer-Tropsch synthesis (FTS) reaction conditions were derived and compared with those over the conventional catalyst. The conventional and nanostructured Fe/Cu/La/Si catalysts were prepared by co-precipitation of Fe and Cu nitrates in aqueous media and water-oil micro-emulsion, respectively. The WGS kinetic data were measured by experiments over a wide range of reaction conditions and comparisons were also made for various rate equations. WGS rate expressions based on the formate mechanism with the assumption that the formation of formate is rate determining step were found to be the best.

Kinetics studies of nano-structured iron catalyst in Fischer-Tropsch synthesis

Kinetic parameters of nano-structured iron catalyst in Fischer-Tropsch synthesis (FTS) were studied in a wide range of synthesis gas conversions and compared with conventional catalyst. The conventional Fe/Cu/La catalyst was prepared by co-precipitation of Fe and Cu nitrates in aqueous media and Fe/Cu/La nanostructure catalyst was prepared by co-precipitation in a water-in-oil micro-emulsion. Nano-structured iron catalyst shows higher FTS activity. Kinetic results indicated that in FTS rate expression, the rate constant ( k) increased and adsorption parameter ( b) decreased by decreasing the catalyst particle size from conventional to nano-structured. Since increasing in the rate constant and decreasing in the adsorption parameter affected the FTS rate in parallel direction, the particle size of catalyst showed complicated effects on kinetic parameters of FTS reaction.

Water-gas-shift kinetic over nano-structured iron catalyst in Fischer–Tropsch synthesis

Kinetic modeling of the water-gas-shift (WGS) reaction over a nano-structured iron catalyst under Fischer–Tropsch synthesis (FTS) reaction conditions is investigated. The Fe/Cu/La/Si nano-structured catalyst was prepared by co-precipitation in a water-in-oil microemulsion. A number of Langmuir–Hinshelwood–Hougen–Watson type rate equations based on possible reactions sets originated from the formate and direct oxidation mechanisms, are derived. By considering experimental data measured over a wide range of reaction conditions, discrimination between the various rate equations is investigated during this study. WGS rate expressions based on the formate mechanism were found to provide an improved description of the WGS kinetic data.

Fischer-Tropsch synthesis by nano-structured iron catalyst

Effects of nanoscale iron oxide particles on textural structure, reduction, carburization and catalytic behavior of precipitated iron catalyst in Fischer-Tropsch synthesis (FTS) are investigated. Nanostructured iron catalysts were prepared by microemulsion method in two series. Firstly, Fe 2O 3, CuO and La 2O 3 nanoparticles were prepared separately and were mixed to attain Fe/Cu/La nanostructured catalyst (sep-nano catalyst); Secondly nanostructured catalyst was prepared by co-precipitation in a water-in-oil microemulsion method (mix-nano catalyst). Also, conventional iron catalyst was prepared with common co-precipitation method. Structural characterizations of the catalysts were performed by TEM, XRD, H 2 and CO-TPR tests. Particle size of iron oxides for sep-nano and mix-nano catalysts, which were determined by XRD pattern (Scherrer equation) and TEM images was about 20 and 21.6 nm, respectively. Catalyst evaluation was conducted in a fixed-bed stainless steel reactor and compared with conventional iron catalyst. The results revealed that FTS reaction increased while WGS reaction and olefin/paraffin ratio decreased in nanostructured iron catalysts.

Deactivation studies of nano-structured iron catalyst in Fischer-Tropsch synthesis

A nano-structured iron catalyst for syngas conversion to hydrocarbons in Fischer-Tropsch synthesis (FTS) was prepared by micro-emulsion method. Compositions of bulk iron phase and phase transformations of carbonaceous species during catalyst deactivation in FTS reaction were characterized by temperature-programmed surface reaction with hydrogen (TPSR-H 2), and XRD techniques. Many carbonaceous species on surface and bulk of the nano-structured iron catalysts were completely identified by combined TPSR-H 2 and XRD spectra and which were compared with those recorded on conventional co-precipitated iron catalyst. The results reveal that the catalyst deactivation results from the formation of inactive carbide phases and surface carbonaceous species like graphite, and it will be increased when the particle size of iron oxides was reduced in FTS iron catalyst.

Kinetic studies of the Fischer–Tropsch synthesis over La, Mg and Ca promoted nano-structured iron catalyst

The kinetic of the Fischer–Tropsch synthesis (FTS) over nano-structured iron catalyst promoted with Mg, La and Ca, was studied in a continuous spinning basket reactor. Fe/Cu/Si nano-structured catalyst was prepared by co-precipitation in a water-in-oil microemulsion. The results indicated that both the rate constant ( k) and the adsorption parameter ( b) in a common two-parameter Fischer–Tropsch rate expression decreased with increasing the catalyst surface basicity. Since decreases in rate constant ( k) and the adsorption parameter ( b) affected the FTS rate in reverse direction, the basicity of catalyst surface showed complicated effects on kinetic parameters of FTS reaction. The optimum promoter would be one that its rate constant ( k) should not be too low and its adsorption parameter ( b) should not be too high.