Statistical Optimization of the Biodiesel Production Process Using a Magnetic Core‐Mesoporous Shell KOH/Fe3O4@γ‐Al2O3 Nanocatalyst

A magnetic core‐mesoporous shell KOH/Fe₃O₄@γ‐Al₂O₃ nanocatalyst was synthesized using the Fe₃O₄@γ‐Al₂O₃ core‐shell structure as support and KOH as active component. The prepared samples were characterized by X‐ray diffraction (XRD), field‐emission scanning electron microscopy (FE‐SEM), energy‐dispersive X‐ray spectroscopy (EDS), Fourier transform infrared (FTIR), Brunauer‐Emmett‐Teller (BET), and vibrating sample magnetometry (VSM) techniques. Transesterification of canola oil to methyl esters (biodiesel) in the presence of the magnetic core‐mesoporous shell KOH/Fe₃O₄@γ‐Al₂O₃ nanocatalyst was investigated. Response surface methodology (RSM) based on the Box‐Behnken design (BBD) was employed to optimize the influence of important operating variables on the yield of biodiesel. A biodiesel yield of 97.4 % was achieved under optimum reaction conditions. There was an excellent agreement between experimental and predicted results.     

A comparative study on the selective hydrogenation of α,β unsaturated aldehyde and ketone to unsaturated alcohols on Au supported catalysts

The hydrogenation of trans,4-phenyl,3-buten,2-one (benzalacetone) and trans,3-phenyl, propenal (cinnamaldehyde) was carried out on Au supported on iron oxides catalysts. Commercial goethite (FeOOH), maghemite (γFe₂O₃) and hematite (αFe₂O₃) were used as supports. The catalytic activity of Au/Fe₂O₃ reference catalyst, supplied by the World Gold Council, was also investigated. Gold catalysts and the parent supports were characterized by BET, X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption of ammonia (NH₃-TPD) and high resolution transmission electron microscopy (HRTEM).Among the catalysts investigated Au supported on FeOOH shows the highest activity and selectivity to UA in the hydrogenation of unsaturated carbonyl compounds whereas Au supported on αFe₂O₃ are the less active and selective catalysts.The catalytic activity and selectivity to unsaturated alcohols (UA) in the hydrogenation of benzalacetone and cinnamaldehyde are less influenced by the morphology of gold particles and are mainly influenced by the nature of the support.A correlation between the reducibility of the catalysts and the activity and selectivity to UA has been found. Increasing the reducibility of the catalysts both the activity and selectivity to UA increase. These results let us to argue that active and selective sites are formed by negative gold particles formed through the electron transfer from the reduced support to the metal.     

Global kinetic modelling of the reaction of soot with O2 and NOx on Fe2O3 catalyst

This study deals with the catalytic reaction of NO_x and soot on Fe₂O₃ to yield N₂ and CO₂ in excess of oxygen. Based on the three types of kinetic experiments, i.e. temperature programmed oxidation (TPO), transient examinations and gradient-free loop reactor experiments, as well as mechanistic studies presented recently a global kinetic model is established. The model includes catalytic effect of the iron oxide on soot/O₂ reaction, whereas it is assumed that NO_x reduction occurs on the soot without direct participation of Fe₂O₃. Furthermore, the model implies global kinetic expressions for the CO_x formation and NO_x reduction. These equations include the evolution of the surface area of soot and the correlation of reactive carbon sites (C_f) with those specifically involved in NO_x reduction (C*). The kinetic model is sequentially developed by accounting for the catalytic and non-catalytic soot/O₂ as well as soot/NO_x/O₂ conversion. Kinetic parameters are taken from the literature and are also determined from a fit to experimental data. Comparison of measured and calculated data shows accurate reproduction of the experiments and the model. Finally, the kinetic model is validated by some simulations.     

Preparation of Highly Active Nickel Catalysts Supported on Mesoporous Nanocrystalline γ‐Al2O3 for Methane Autothermal Reforming

Autothermal reforming (ATR) of methane was carried out over nanocrystalline Al₂O₃‐supported Ni catalysts with various Ni loadings. Mesoporous nanocrystalline γ‐Al₂O₃ powder with high specific surface area was prepared by the sol‐gel method and employed as support for the nickel catalysts. The prepared samples were characterized by X‐ray diffraction, Brunauer‐Emmett‐Teller, temperature‐programmed reduction, temperature‐programmed hydrogenation, and scanning electron microscopy techniques. It is demonstrated that the methane conversion increased with increasing in Ni content and that the catalyst with 25 wt % Ni exhibited the highest activity and a stable catalytic performance in the ATR process, with a low degree of carbon formation. Furthermore, the effects of the reaction temperature, the calcination temperature, the steam/CH₄ and O₂/CH₄ ratios, and the gas hourly space velocity on the catalytic performance of the 25 % Ni/Al₂O₃ catalyst were investigated.     

High‐Performance Small‐Amount Fe2O3‐Doped (K,Na)NbO3‐Based Lead‐Free Piezoceramics with Irregular Phase Evolution

[(K_0.43Na_0.57)_0.94Li_0.06][(Nb_0.94Sb_0.06)_0.95Ta_0.05]O₃ + x mol% Fe₂O₃ (KNLNST + x Fe, x = 0~0.60) lead‐free piezoelectric ceramics were prepared by conventional solid‐state reaction processing. The effects of small‐amount Fe₂O₃ doping on the microstructure and electrical properties of the KNLNST ceramics were systematically investigated. With increasing Fe³⁺ content, the orthorhombic‐tetragonal polymorphic phase transition temperature (T_O‐T) of KNLNST + x Fe ceramics presented an obvious “V” type variation trend, and T_O‐T was successfully shifted to near room temperature without changing T_C (T_C = 315°C) via doping Fe₂O₃ around 0.25 mol%. Electrical properties were significantly enhanced due to the coexistence of both orthorhombic and tetragonal ferroelectric phases at room temperature. The ceramics doped with 0.20 mol% Fe₂O₃ possessed optimal piezoelectric and dielectric properties of d₃₃ = 306 pC/N, k_p = 47.0%, = 1483 and tan δ = 0.023. It was revealed that the strong internal stress in the KNLNST + x Fe ceramics with higher Fe³⁺ contents (x = 0.40, 0.60) stabilized the orthorhombic phase, leading to the irregular “V” type rather than the usually observed monotonic phase transition with composition change in the ceramics.     

Low-temperature CO oxidation of Pt/Al<Subscript>0.1</Subscript>Ce<Subscript>0.9</Subscript>O<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> catalysts: Effects of supports prepared with different precipitants

We prepared 0.1Al-0.9Ce supports using various precipitants such as NH₄OH, KOH, NaOH, K₂CO₃, and Na₂CO₃ to prepare Pt-based CO oxidation catalysts. Of the studied catalysts, the Pt/0.1Al-0.9Ce_NH₄OH catalyst showed the optimum activity for CO oxidation. Catalysts prepared with carbonate-form precipitants revealed relatively lower activity than carbonate-free precipitants. A temperature at 50% CO conversion of all samples was observed in the low-temperature region in the presence of water vapor because of the promotional effect of the water-gas shift reaction. Several characterization results revealed that catalytic activity was related to oxygen capacity and Pt dispersion was attributable to precipitant nature.     

Bio‐Based Hybrid Magnetic Latex Particles Containing Encapsulated γ ‐Fe2O3 by Miniemulsion Copolymerization of Soybean Oil‐Acrylated Methyl Ester and Styrene

This work reports the use of acrylated fatty acid methyl ester (AFAME) as a biomonomer for the synthesis of bio‐based hybrid magnetic particles poly(styrene‐co‐AFAME)/γ‐Fe₂O₃ produced by miniemulsion polymerization. Poly(styrene‐co‐AFAME)/γ‐Fe₂O₃ can be tailored for use in various fields by varying the content of AFAME. The strategy employed is to encapsulate superparamagnetic iron oxide nanoparticles (SPIONs) as γ‐Fe₂O₃ into a styrene/AFAME‐based copolymer matrix. Raman spectroscopy is employed to ensure the formation of the SPIONs (γ‐Fe₂O₃) obtained by a co‐precipitation technique followed by oxidation of Fe₃O₄. The functionalization of SPIONs with oleic acid (OA) is carried out to increase the SPIONs–monomer affinity. The presence of OA on the surface of γ‐Fe₂O₃ is certified by identification of main absorption bands by fourier‐transform infrared spectroscopy (FTIR). Thermal analysis (differential thermogravimetry/differential thermo analysis and differential scanning calorimetry) results of poly(styrene‐co‐AFAME)/γ‐Fe₂O₃ show an increase in AFAME content leading to a lower copolymer glass transition temperature (T _g). Dynamic light scattering (DLS) measurements result in poly(styrene‐co‐AFAME)/γ‐Fe₂O₃ particles with diameter in the range of 100–150 nm. It is also observed by transmission electron microscopy (TEM) and cryo‐TEM techniques that γ‐Fe₂O₃ particles are successfully encapsulated into the poly(styrene‐co‐AFAME) matrix.     

Partial oxidation of methane over VOx/α-Al2O3 catalysts

The catalytic behavior of a series of VO_x/α-Al₂O₃ catalysts for the partial oxidation of methane has been evaluated. Samples with different vanadia loading were prepared from NH₄VO₃ and V(AcAc)₃. Characterization performed by TPR and oxygen uptake measurements indicates that different VO_x species are present on the samples. The catalytic patterns indicate that each V-surface species possesses different activity and selectivity. Isolated vanadates are the most active and selective towards HCHO, while V₂O₅ crystallites are detrimental to the catalytic performance.     

Effect of precipitants during the preparation of Cu-ZnO-Al2O3/Zr-ferrierite catalyst on the DME synthesis from syngas

The synthesis of dimethyl ether (DME) from biomass-derived model synthesis gas has been investigated on Cu-ZnO-Al₂O₃/Zr-ferrierite bifunctional catalysts. The catalysts are prepared by co-precipitation–impregnation method using Na₂CO₃, K₂CO₃ and (NH₄)₂CO₃ as the precipitants. The catalytic activity tests reveal that the best yield of DME can be obtained on the catalyst precipitated by using (NH₄)₂CO₃. Detailed characterization studies conducted on the catalysts to measure their properties such as surface area, acidity by temperature-programmed desorption of ammonia (NH₃-TPD), reducibility of Cu oxide by temperature-programmed reduction (TPR), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and copper surface area and particle size measurements by N₂O titration method. Increasing the number of moderate acidic sites and facilitation of easily reducible copper species with small particle size are found to be the prime reasons for the superior functionality of the (NH₄)₂CO₃ precipitated catalyst. The usage of (NH₄)₂CO₃ also leaves no residual ions, whereas the presence of residual K⁺ and Na⁺ ions in the case of K₂CO₃ and Na₂CO₃ precipitated catalysts leads to lower activity and selectivity.     

Synthesis and characterization of polyimide‐γ‐Fe2O3 nanocomposites

Novel polyimide‐γ‐Fe₂O₃ hybrid nanocomposite films (PI/γ‐Fe₂O₃) has been developed from the poly(amic acid) salt of oxydianiline with different weight percentages (5, 10, 15 wt %) of γ‐Fe₂O₃ using tetrahydrofuran (THF) and N,N‐dimethylacetamide (DMAc) as aprotic solvents. The prepared polyimide‐γ‐Fe₂O₃ nanocomposite films were characterized for their structure, morphology, and thermal behavior employing Fourier transform infrared spectroscopy (FTIR), scanning electron micrograph (SEM), transmission electron micrograph (TEM), X‐ray diffraction (XRD), ¹³C‐NMR, and thermal analysis (TGA/DSC) techniques. These studies showed the homogenous dispersion of γ‐Fe₂O₃ in the polyimide matrix with an increase in the thermal stability of the composite films on γ‐Fe₂O₃ loadings. Magnetization measurements (magnetic hysteresis traces) have shown very high values of coercive force indicating their possible use in memory devices and in other related applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 834–840, 2007     

Selective catalytic reduction by urea in a fluidized‐bed reactor

The selective catalytic reduction (SCR) of NO_x by urea as a reducing agent was carried out over fresh and sulfated CuO/γ‐Al₂O₃ catalysts in a fluidized‐bed reactor. The optimum temperature ranges for NO reduction on the fresh and sulfated CuO/γ‐Al₂O₃ catalysts were 300–350 °C and 400–450 °C, respectively. NO reduction with the sulfated CuO/γ‐Al₂O₃ catalyst was somewhat higher than that with the fresh CuO/γ‐Al₂O₃ catalyst. N₂O formation increased with increasing reaction temperature. Ammonia (NH₃) slip increased with increasing gas velocity and decreased with increasing reaction temperature. Copyright © 2003 Society of Chemical Industry     

Oxygen Nonstoichiometry and Thermodynamic Explanation of Large Oxygen‐Deficient Ruddlesden–Popper Oxides LaxSr3−xFe2O7−δ

The oxygen nonstoichiometry of large oxygen‐deficient Ruddlesden–Popper oxides La_xSr_3?xFe₂O_7?δ (LSFO7‐x) (x = 0, 0.25, 0.5) was measured by the high‐temperature gravimetry and the coulometric titration. In the composition series, the P(O₂) dependencies exhibited typical plateaus at δ = (2?[])/2. Meanwhile, La_0.5Sr_2.5Fe₂O_7?δ showed the smallest oxygen nonstoichiometry and was the most thermochemically stable compound against P(O₂), temperature, and the La content. Based on the defect equilibrium model and the statistical thermodynamic calculation derived oxygen nonstoichiometric data, the substitution of La for Sr‐site can promote the forward reaction of oxygen incorporation, the backward reaction of the disproportionation of the charge carriers, and oxygen redistribution between the O1 and O3 sites, resulting in the reduction of oxygen‐deficient and the lower decomposition P(O₂). The obtained thermodynamic quantities of the partial molar enthalpy of oxygen, , and the partial molar entropy of oxygen, , calculated from the statistical thermodynamic calculation are in good agreement with those using the Gibbs–Helmholtz equation.     

Reduction of Nitrogen Oxides by Ammonia Over Iron‐Containing Catalysts

Selective catalytic reduction (SCR) of NO_x by NH₃ is an efficient technology for the removal of nitrogen oxides from diesel exhaust. It is a disadvantage that the active component in commercial catalysts, V₂O₅, is toxic and melts at ～650 °C. An alternative catalyst system, based on iron as the active component, was developed in this work. For this purpose, a number of supports were taken and impregnated with Fe₂O₃ and Fe₂O₃/WO₃ by an incipient wetness technique. The synthesized catalysts were tested in a diesel model exhaust using temperature programmed reaction. The screening accomplished to date, resulted in a 5.8 mol.‐% Fe₂O₃/Al₂O₃ catalyst that exhibited outstanding activity in the temperature range between 150–375 °C with selective formation of N₂. However, this catalyst was significantly deactivated by thermal aging at 600 °C. In contrast, the activity of the sample with 1.4 mol.‐% Fe₂O₃ and 0.8 mol.‐% WO_x showed very high thermal stability as well as selective N₂ production over the whole temperature regime, but it had lower SCR activity.     

Synthesis of high‐molecular weight poly(trimethylene terephthalate) catalyzed by MoO3 supported Al2O3‐TiO2 catalysts

Poly(trimethylene terephthalate) (PTT) is an excellent fiber materials. Although it was synthesized as early as 1940s, obtaining high‐molecular weight PTT suitable for spinning is not easy due to no evident breakthrough in the catalysts for PTT synthesis. Patents and literatures disclosed a lot of the catalysts of preparing PTT, but which are more or less disadvantageous. Based on acid catalytic mechanism of PTT preparation, a series of solid acid as x% MoO₃/(50% Al₂O₃ ? 50% TiO₂) (briefly written as xM/(A ? T), x = 0, 10, 15, 20 by weight) were prepared by sol–gel coprecipitation and wetting impregnation methods, and first used for PTT synthesis in this work. When 50% Al₂O₃ ? 50% TiO₂ (briefly written as A ? T) was supported by MoO₃ using wetting impregnation technique of (NH₄)₆Mo₇O₂₄.4H₂O aqueous solution, a lot of Brφnsted acid and Lewis acid sites were formed on xM/(A ? T) catalyst surfaces, which was confirmed by the characteristics of their NH₃‐TPD (temperature programmed desorption). All the prepared catalysts were highly active ones toward synthesis of PTT. PTT with high‐intrinsic viscosity (IV) was obtained in the presence of trace amount of the catalysts. IV ranging of the PTT synthesized from 0.66 to 0.95 dL g^?1 corresponds to weight average molecular weight from 49,197 to 73,004. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Post‐Plasma Catalysis for Methane Partial Oxidation to Methanol: Role of the Copper‐Promoted Iron Oxide Catalyst

Methane‐air partial oxidation to methanol over a ceramic‐supported Fe₂O₃‐CuO catalyst was investigated in a post‐plasma catalytic reactor at ambient conditions. The multicomponent catalyst exerted a better catalytic performance than the monocomponent Fe₂O₃ catalyst. Characterization of the catalysts by XPS showed that incorporation of the CuO additive to a Fe₂O₃‐based catalyst resulted in an increase of lattice oxygen in the surface of the catalyst which facilitated selective methane oxidation. Hydrogen temperature‐programmed reduction revealed that addition of the CuO promoter could improve the reduction performance of the catalyst. Moreover, this catalyst showed excellent stability and resistance against carbon deposition in the extended reactions while maintaining catalytic activity. A post‐plasma catalytic mechanism is proposed with three main pathways to methanol synthesis.     

Decolorization of methylene blue by heterogeneous Fenton reaction using Fe3−xTixO4 (0 ≤ x ≤ 0.78) at neutral pH values

In this work, a series of Fe_3−xTi_xO₄ (0 ≤ x ≤ 0.78) was synthesized using a new soft chemical method. The synthetic Fe_3−xTi_xO₄ were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Mössbauer spectroscopy, thermogravimetric and differential scanning calorimetry (TG–DSC) analyses. The results showed that they were spinel structures and Ti was introduced into their structures.Then, decolorization of methylene blue (MB) by Fe_3−xTi_xO₄ in the presence of H₂O₂ at neutral pH values was studied using UV–vis spectra, dissolved organic carbon (DOC) and element C analyses. Furthermore, the degradation products remained in reaction solution after the decolorization were identified using ionic chromatography (IC), ¹³C nuclear magnetic resonance spectra (NMR), liquid chromatography and mass spectrometry (LC–MS). Although small amounts of MB were mineralized, the aromatic rings in MB were destroyed completely after the decolorization. Decolorization of MB by Fe_3−xTi_xO₄ in the presence of H₂O₂ was promoted remarkably with the increase of Ti content in Fe_3−xTi_xO₄ due to the enhancement of both adsorption and degradation of MB on Fe_3−xTi_xO₄.     

Improvement of the Electrochemical Performance of Ln0.58Sr0.4Fe0.8Co0.2O3 – δ IT‐SOFC Cathodes by Ternary Lanthanide Combinations (La‐Pr‐Sm)

Active perovskite‐based SOFC cathodes have been developed through lanthanide combination in the (La_{1 – x – y}Pr_xSm_y)_0.58Sr_0.4Fe_0.8Co_0.2O_{3 – δ} system following a ternary mixture experimental design. These compositions were prepared through a sol–gel method and characterised by electrochemical impedance spectroscopy (EIS) as symmetrical cells on GDC‐electrolyte samples in the 450–650 °C temperature range. The electrochemical properties of the single lanthanide‐based Ln_0.58Sr_0.4Fe_0.8Co_0.2O_{3 – δ} compounds were enhanced when different lanthanides were combined together in the same crystalline structure. The observed improvement does not follow a mere additional effect of the performance from the parent Ln_0.58Sr_0.4Fe_0.8Co_0.2O_{3 – δ} compounds, i.e. it does not follow a linear behaviour, and the better performance is ascribed to synergetic catalytic effects among lanthanide cations. A reduction in electrode polarisation resistance with respect to non‐substituted compositions is stated for most Ln_0.58Sr_0.4Fe_0.8Co_0.2O_{3 – δ} electrode compositions combining two or three lanthanides. Samarium addition to the electrode material involves a substantial reduction in the activation energy and the reduction degree is directly dependant on the samarium amount incorporated in the lattice. The best performing composition comprises a praseodymium‐rich lanthanum‐based electrode material. The experimental data derived from the ternary mixture design were modelled using nonlinear functions and this modelling allowed finding an electrode composition minimising the polarisation resistance while maintaining the activation energy at reduced values. Selected cathode compositions were tested in fully assembled anode‐supported cells and electrochemical characterisation supports the cooperative effect of lanthanide combination.     

SO42−/ZrO2 supported on γ‐Al2O3 as a catalyst for CO2 desorption from CO2‐loaded monoethanolamine solutions

In this work, the composite catalysts, SO₄²/ZrO₂/γ‐Al₂O₃ (SZA), with different ZrO₂ and γ‐Al₂O₃ mass ratios were prepared and used for the first time for the carbon dioxide (CO₂)‐loaded monoethanolamine (MEA) solvent regeneration process to reduce the heat duty. The regeneration characteristics with five catalysts (three SZA catalysts and two parent catalysts) of a 5 M MEA solution with an initial CO₂ loading of 0.5 mol CO₂/mol amine at 98°C were investigated in terms of CO₂ desorption performance and compared with those of a blank test. All the catalysts were characterized using X‐ray diffraction, Fourier transform infrared spectroscopy, N₂ adsorption–desorption experiment, ammonia temperature programmed desorption, and pyridine‐adsorption infrared spectroscopy. The results indicate that the SZA catalysts exhibited superior catalytic activity to the parent catalysts. A possible catalytic mechanism for the CO₂ desorption process over SZA catalyst was proposed. The results reveal that SZA1/1, which possesses the highest joint value of Brφnsted acid sites (BASs) and mesopore surface area (MSA), presented the highest catalytic performance, decreasing the heat duty by 36.9% as compared to the catalyst‐free run. The SZA1/1 catalyst shows the best catalytic performance as compared with the reported catalyst for this purpose. Moreover, the SZA catalyst has advantages of low cost, good cyclic stability, easy regeneration and has no effect on the CO₂ absorption performance of MEA. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3988–4001, 2018     

Synthesis of Nano‐γ‐Ferric Oxide by Thermolysis of the 2‐Mercapto‐5‐Methylpyridine‐N‐Oxide‐Iron(III) Complex via Factorial Design

2‐Mercapto‐5‐methylpyridine‐N‐oxide (MMPNO) and its sodium salt (NaMMPNO) were synthesized. The reaction of the latter with Fe³⁺ generates Fe(MMPNO)₃ chelate. The thermolysis of this chelate at 350 °C yielded highly pure reddish‐brown γ‐Fe₂O₃ nanocrystallites with an average particle size of 6.2 nm, a particle size range of 4.2 to 14.8 nm, and a specific surface area of 51.5 m²g^–1. The thermolysis process was optimized using the 2² fractional design. Quantitative tests and characterization of products were carried out by UV‐vis spectroscopy, XRD, LLS, SEM, TGA, BET, TEM, FT‐IR, elemental microanalysis, and classical analytical measurements.     

Low-temperature synthesis of La0.6Sr0.4Co0.2Fe0.8O3−δ perovskite powder via asymmetric sol–gel process and catalytic auto-combustion

La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ powder was synthesized by a combined EDTA-citrate complexing process via low-temperature auto-combustion synthesis with NH₄NO₃ as an oxidizer and a combustion trigger. Two novel methods were explored to improve this auto-combustion technology with reduced NH₄NO₃ addition: the use of La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ as the combustion catalyst and the application of asymmetric sol–gel process to provide the precursor with different NH₄NO₃ concentrations. The prepared perovskite powder was characterized by BET, SEM, XRD and iodometric titration techniques. The catalytic performance of the powder was also examined in the decomposition of peroxide hydrogen. Experimental results indicate that powders from catalytic combustion and asymmetric precursor routes have more advantages in terms of better crystallites, higher specific surface area, higher B-site valence state, improved sintering capability and better catalytic performance in peroxide hydrogen decomposition than that from the synthesis with uniform NH₄NO₃ distribution.