Grafted NiO on natural olivine for dry reforming of methane

Natural olivine is used for gasification of biomass in a fluidised bed. Characterisations by X-raydiffraction and electron microscopies (SEM and TEM) have proved the presence of a (Mg,Fe)₂SiO₄ structure (Mg/Fe ratio: 9/1) with a rather broad distribution in elemental composition. Temperature programmed reduction has revealed equally the presence of iron oxides outside of this structure. The nature of free iron oxides can be both modified by increasing the temperature of calcination and confirmed by measurements of magnetism.

The introduction of nickel oxide upon natural olivine is obtained by impregnation with a nitrate salt. The type of interaction of nickel oxide with olivine is different depending upon the preparationmethod and the calcination temperature. For calcination at 1100 ºC, the effects of the amount ofNiO and the number of impregnation have been studied. At a high temperature of calcination (1400 ºC), NiO is integrated into the olivine structure and the amount of free iron increases. Integrated NiO on olivine is non-reducible, resulting in an inactive catalyst. At lower calcination temperatures grafted NiO is formed, a species which is reduced under catalytic test conditions without aggregation of particles. A single impregnation of nickel (5.5 wt% of NiO) gives a stable catalyst activated directly under reaction conditions (CH₄ + CO₂) yielding 96% CO and 76% H₂. Catalysts with lower amounts of NiO or a double impregnation of nickel salt lead to a less stable system.

Analysis reveals that no change in olivine structure nor size of nickel deposit occurs under test conditions. Equally there are no carbon deposits formed on these catalysts. A model of the evolution of each catalytic system arising from the different preparation methods is proposed. The observed deactivation of such catalysts is attributed to the increase in the amount of free iron, which favours the oxidative properties of the catalytic system.     

Grafted NiO on natural olivine for dry reforming of methane

Natural olivine is used for gasification of biomass in a fluidised bed. Characterisations by X-ray diffraction and electron microscopies (SEM and TEM) have proved the presence of a (Mg,Fe)₂SiO₄ structure (Mg/Fe ratio: 9/1) with a rather broad distribution in elemental composition. Temperature programmed reduction has revealed equally the presence of iron oxides outside of this structure. The nature of free iron oxides can be both modified by increasing the temperature of calcination and confirmed by measurements of magnetism.The introduction of nickel oxide upon natural olivine is obtained by impregnation with a nitrate salt. The type of interaction of nickel oxide with olivine is different depending upon the preparation method and the calcination temperature. For calcination at 1100 °C, the effects of the amount of NiO and the number of impregnation have been studied. At a high temperature of calcination (1400 °C), NiO is integrated into the olivine structure and the amount of free iron increases. Integrated NiO on olivine is non-reducible, resulting in an inactive catalyst. At lower calcination temperatures grafted NiO is formed, a species which is reduced under catalytic test conditions without aggregation of particles. A single impregnation of nickel (5.5 wt% of NiO) gives a stable catalyst activated directly under reaction conditions (CH₄+CO₂) yielding 96% CO and 76% H₂. Catalysts with lower amounts of NiO or a double impregnation of nickel salt lead to a less stable system.Analysis reveals that no change in olivine structure nor size of nickel deposit occurs under test conditions. Equally there are no carbon deposits formed on these catalysts. A model of the evolution of each catalytic system arising from the different preparation methods is proposed. The observed deactivation of such catalysts is attributed to the increase in the amount of free iron, which favours the oxidative properties of the catalytic system.     

Structural and optical properties of nitrogen‐iron co‐doped titanium dioxide films prepared via sol‐gel dip‐coating: Effect of urea and iron nitrate concentration in the sol

In this study, nitrogen‐iron co‐doped titanium dioxide films were prepared via sol‐gel dip‐coating method using urea and iron nitrate as nitrogen and iron source, respectively. Nonmetal doping of TiO₂ have some disadvantages such as massive charge carrier recombination and losing the photo‐catalytic capability. Three different nitrogen‐iron co‐doped titanium dioxide sols with different urea and iron nitrate concentration were prepared. The resulting sols were homogeneous and transparent, and no precipitation was observed in any of them. It was observed that the film prepared with middle urea‐iron nitrate concentration sol got opaque in a short time after the dip‐coating process. All prepared films were characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy, scanning electron microscopy, confocal microscopy and ultraviolet–visible (UV‐Vis) spectroscopy. It was found that the concentration of the urea and iron nitrate in the sol had an effect on the crystal structure, microstructure, surface morphology and optical properties of the resulting films. Samples with middle concentrations had amorphous structure and bigger particle size. It was seen that sample with higher iron amount has lower band‐gap. It is concluded that we can prepare transparent anatase, transparent amorphous and opaque amorphous titanium dioxide films by changing the urea and iron nitrate concentration in the sol.     

Hydrophobic fluorinated TiO2–ZrO2 as catalyst in epoxidation of 1-octene with aqueous hydrogen peroxide

A new heterogeneous oxidation catalyst was prepared by impregnation of TiO₂ from titanium(IV)tetra-2-propoxide on the surface of ZrO₂. The surfaces of TiO₂–ZrO₂ particles were then modified by the fluorination of ammonium hexafluorosilicate and followed by alkylsilylation of n-octadecyltrichlorosilane (OTS). The resulting catalysts were characterized by X-ray diffraction (XRD), nitrogen adsorption isotherm, UV–Vis Diffuse Reflectance (UV–Vis DR), and Energy Dispersive X-Ray Analysis (EDAX) techniques. The catalytic potential of catalysts for oxidation reactions has been verified in the liquid phase epoxidation of 1-octene to 1,2-epoxyoctane with aqueous hydrogen peroxide. It is demonstrated that the fluorination and alkylsilylation enhance the catalytic activity of TiO₂–ZrO₂. A high catalytic activity of the modified TiO₂–ZrO₂ was related to the modification of the local environment of titanium active site and increasing the hydrophobicity of catalyst particles by fluorination and alkylsilylation.     

Ultrasonic-assisted synthesis and magnetic studies of iron oxide/MCM-41 nanocomposite

Iron oxide nanoparticles were stabilized within the pores of mesoporous silica MCM-41 amino-functionalized by a sonochemical method. Formation of iron oxide nanoparticles inside the mesoporous channels of amino-functionalized MCM-41 was realized by wet impregnation using iron nitrate, followed by calcinations at 550 °C in air. The effect of functionalization level on structural and magnetic properties of obtained nanocomposites was studied. The resulting materials were characterized by powder X-ray diffraction (XRD), high-resolution transmission electron microscopy and selected area electron diffraction (HRTEM and SAED), vibrating sample and superconducting quantum interface magnetometers (VSM and SQUID) and nitrogen adsorption–desorption isotherms measurements. The HRTEM images reveal that the most of the iron oxide nanoparticles were dispersed inside the mesopores of silica matrix and the pore diameter of the amino-functionalized MCM-41 matrix dictates the particle size of iron oxide nanoparticles. The obtained material possesses mesoporous structure and interesting magnetic properties. Saturation magnetization value of magnetic iron oxide nanopatricles stabilized in MCM-41 amino-functionalized by in situ sonochemical synthesis was 1.84 emu g⁻¹. An important finding is that obtained magnetic nanocomposite materials exhibit enhanced magnetic properties than those of iron oxide/MCM-41 nanocomposite obtained by conventional method. The described method is providing a rather short preparation time and a narrow size distribution of iron oxide nanoparticles.     

Cerium incorporating into MCM-41 mesoporous materials for CO oxidation

Ceria doped MCM-41 materials were synthesized by surfactant-assisted hydrothermal and wet impregnation methods. All the obtained Ce-MCM-41 materials were characterized by N₂ physical adsorption, X-ray diffraction (XRD), diffuse reflectance UV–visible spectroscopy (DRUV–vis), infrared spectroscopy (IR), solid-state cross-polarization magic angle spinning nuclear magnetic resonance spectroscopy (CP/MAS-NMR), and transmission electron microscopy (TEM). The catalytic properties were evaluated in CO oxidation under atmospheric pressure and various temperatures. The results showed that in the materials synthesized by hydrothermal method, most of Ce ions were well incorporated in the tetrahedral coordinated sites into the framework of the MCM-41 as Si/Ce molar ratio is 30 and 50. High cerium content may lead to mesostructure partial collapsing and ceria particles segregation. For CO oxidation, the catalytic activity of Ce-MCM-41 synthesized by hydrothermal method was significantly greater than that of the materials prepared by impregnation route. Over the Ce-MCM-41 materials prepared via hydrothermal technique, 100% CO conversion was achieved at 504, 514 and 528 K, respectively, as the Si/Ce molar ratio decreased from 50 to 30 and 10. For the first time, we found an interesting correlation of Q₃ species relative area in the ²⁹Si CP/MAS-NMR spectra of the Ce-MCM-41materials with the reaction rates of CO oxidation, which indicates that both surface hydroxyls and tetrahedral-coordinated Ce⁴⁺ ions in the MCM-41 take important roles in the CO oxidation.     

Ni and Cu incorporated mesoporous nanocomposite catalytic materials

Nickel and copper incorporated MCM-41-like mesoporous nanocomposite materials prepared by the direct hydrothermal synthesis and the impregnation procedures showed highly attractive pore structure and surface area results for catalytic applications. The XRD patterns showed that characteristic MCM-41 structure was preserved for the materials synthesized following an impregnation procedure before the calcination step. The surface area of the Cu impregnated material with a quite high Cu/Si atomic ratio (0.19) was 631 m2/g. Very narrow pore size distributions with an average pore diameter of about 2.7 nm were obtained as a result of plugging of some of the smaller pores by Cu nanoballs. For lower metal to Si ratios (for instance for Ni/Si = 0.06) much higher surface area values (1130 m2/g) were obtained. In the case of nanocomposite materials synthesized by the direct hydrothermal route, MCM-41 structure was not destroyed for samples containing metal to Si atomic ratios as high as 0.12. In the case of materials containing Cu/Si and Ni/Si ratios over 0.2 wider pore size distributions and some decrease of surface area were observed.     

Catalytic activity of Co/MCM-41 and Co/SBA-15 materials in toluene oxidation

Cobalt-containing MCM-41 and SBA-15 mesoporous materials were prepared by the pH-adjusting of the impregnation solution. The modified materials were investigated by X-ray diffraction, N₂ physisorption, temperature-programmed reduction, DR UV–Vis diffuse reflectance, and FT-IR spectroscopy of adsorbed pyridine. The pH of the impregnation solution influences the surface charge of the mesoporous support and therefore determines the strength of interaction between the cobalt precursor and the mesoporous support. The formation of different cobalt oxide species in different ratios, depending on the pH of the impregnation solution, was established for both materials. The modified Co/MCM-41 and Co/SBA-15 materials were active in toluene oxidation. Their catalytic activity is predetermined by the nature, the reducibility, and the dispersion of the obtained cobalt oxide species.     

Rapid synthesis of low-fractal dimension titanium oxide polymers by a sol-gel technique using hydrazine monohydrochloride

Titanium oxide polymers having a low-fractal dimension (d(f) < 2) were rapidly synthesized from titanium tetra-n-butoxide via a catalytic sol-gel process with a hydrazine monohydrochloride catalyst. Different from conventional sol-gel processes aimed at producing low-fractal dimension titanium oxide polymers, the present synthetic strategy needed neither organic ligand to enhance the stability of titanium alkoxides nor an extremely long reaction time in a strongly acidic solution condition, thanks to a drastically accelerated polycondensation reaction. We pursued the structure evolution of the titanium oxide polymers by means of time-resolved small-angle X-ray scattering (Tr-SAXS). The SAXS data unambiguously demonstrate the generation of the expanded polymer-like structure characterized by the fractal dimension of d(f) approximately equal 5/3. The results offer an efficient route to the synthesis of the weakly-branched titanium oxide polymers, which are expected to be used to create a wide range of optical materials having a high refractive index, such as anti-glare coating.     

Efficient photocatalysis and sustainable degradation of methylene blue by titanium dioxide and zinc oxide supported on spent FCC catalyst

Journal of Materials Science: Materials in Electronics - Zinc oxide (ZnO) and titanium dioxide (TiO2) are loaded on the spent fluid catalytic cracking catalyst (FCC) via an impregnation method to...     

Preparation of mesoporous titania solid superacid and its catalytic property

Mesoporous titania (TiO(2)) was synthesized by hydrothermal method using cetyltrimethyl ammonium bromide (CTAB) as a template and using anhydrous ethanol and tetra-n-butyl titanate (TBOT) as raw materials. Mesoporous titania solid superacid and nanosized titania solid superacid catalysts were prepared by wet impregnation method. The structure and property of as-prepared samples were characterized by means of XRD, FT-IR and N(2) physical adsorption. The esterification of salicylic acid with isoamyl alcohol and the condensation of cyclohexanone with ethylene were used as model reactions to test the catalytic activities of the catalysts. On the other hand, the comparison of catalytic activities of the prepared solid superacid catalysts and the conventional liquid acid H(2)SO(4) was also carried out under the same experimental conditions. The results show that the catalytic activities of the prepared solid superacid catalysts were higher than that of the conventional liquid acid H(2)SO(4), and that the catalytic activity of mesoporous TiO(2) solid superacid is the highest among the three catalysts. Mesoporous TiO(2) solid superacid is a good catalyst for the synthesis of isoamyl salicylate or cyclohexanone ethylene ketal.     

Improvement of thermal conductivity in 2D carbon–carbon composites by doping with TiC nanoparticles

Titanium-doped CC composites were prepared by liquid impregnation of a 2D carbon fibre preform using a mesophase pitch doped with TiC nanoparticles as matrix precursor. The effect of the addition of titanium carbide on the microstructure and thermal properties of CC composites is investigated. A higher degree of order was developed in the matrix of the Ti-doped composite which is the result of the catalytic graphitisation of carbon promoted by titanium. As a consequence, the thermal conductivity is higher in this doped material, despite the low dopant content introduced in the matrix, which points out the relevant contribution of the matrix to the thermal properties of the whole composite.     

Iron Carbides: Control Synthesis and Catalytic Applications in COx Hydrogenation and Electrochemical HER

Catalytic transformation of CO_x (x = 1, 2) with renewable H₂ into valuable fuels and chemicals provides practical processes to mitigate the worldwide energy crisis. Fe‐based catalytic materials are widely used for those reactions due to their abundance and low cost. Novel iron carbides are particularly promising catalytic materials among the reported ferrous catalysts. Recently, a series of strategies has been developed for the preparation of iron carbide nanoparticles and their nanocomposites. Control synthesis of FeC_x‐based nanomaterials and their catalytic applications in CO_x hydrogenation and electrochemical hydrogen evolution reaction (HER) are reviewed. The discussion is focused on the unique catalytic activities of iron carbides in CO_x hydrogenation and HER and the correlation between structure and catalytic performance. Future synthesis and potential catalytic applications of iron carbides are also summarized.     

Industrially-styled room-temperature pulsed laser deposition of titanium-based coatings

Titanium-based compounds are widely used as coating materials for mechanical, tribological, electrical, optical, catalytic, sensoric, micro-electronical applications due to their exceptionally physical and chemical properties. Recently, the trend of using temperature-sensitive materials like polymers and tool steels with the highest hardness demands new low-temperature coating techniques for protective surface finishing as well as for surface functionalization, but up to now there is lack of industrially scaled vacuum coating techniques at temperatures below 50 °C. An alternative for overcoming this problem is the pulsed laser deposition (PLD) technique, which was up-scaled for industrial demands at Laser Center Leoben of JOANNEUM RESEARCH Forschungsgesellschaft mbH.The current paper summarizes the application of the industrially-scaled PLD technique on the deposition of the presently most important Ti-based coatings: metallic titanium, titanium nitride (TiN), titanium oxide (TiO₂) and titanium carbonitride (TiCN). PLD coating allows, even at room temperature, the formation of film structures of Zone-T type of Thornton's structure zone model, both on substrates aligned normal and parallel to the incident vapor flux. The high-energetic deposition conditions are revealed by the occurrence of (2 2 0) textures for the fcc TiN-based films. The dense grown structure affects advantageously the tribological behavior—generally, low wear rates and (for TiCN) very low friction coefficients were found. For TiO₂ coatings, growing as a mixture of β-TiO₂ and amorphous phases, the easily reproducible change of deposition parameters in the room-temperature PLD allows large differences in the optical transmission and electrical resistance.     

Preparation of highly ordered Fe-SBA-1 and Ti-SBA-1 cubic mesoporous silica via sol-gel processing of silatrane

Silatrane prepared from fumed silica and triethanolamine (TEA) was used as a precursor for the sol-gel synthesis of M-SBA-1 (M = Fe and Ti) at room temperature using cetyltrimethylammonium bromide as a template, and dilute solutions of ferric chloride and titanium glycolate as metal sources. Powder X-ray diffraction (XRD) showed the mesoporous materials to be well-ordered cubic structures, while N₂ adsorption/desorption measurements yielded high surface areas. Diffuse reflectance UV-visible spectroscopy demonstrated that iron (Fe³⁺) and titanium (Ti⁴⁺) were incorporated in the framework of the calcined materials to loadings of 6 wt.% Fe and 10 wt.% Ti without perturbing the ordered mesoporous structure.     

Studies on nanosized iron based modified catalyst for Fischer-Tropsch synthesis application

To improve catalytic performance iron based catalyst, the effects of some metal promoters, especially potassium, copper and other transition metal oxides as well as different supports have been reported. A series of Fe/K/Cu catalysts promoted with magnesium and ceria by precipitation method, followed by impregnation method; keeping Cu and K content same. The catalysts were characterized by XRD, N2 physisorption, TPR and TEM techniques. From XRD, the presence of hematite (Fe2O3) phase was detected in all precipitated iron catalysts and CFe2.5 phase in all used catalysts. TPR results showed that addition of Mg facilitated the reduction of Fe2O3 and decrease in reduction temperature. The catalytic performance was investigated in a fixed-bed reactor at 250 degrees C, 2 MPa pressure and H2/CO molar ratio of 2. Concentration of Mg was found to affect the CO conversion and product distribution. It was found that precipitated iron catalyst Fe/Mg/Cu/K with Mg/Fe ratio of 0.1 showed highest conversion (60.6%) and C5(+) selectivity (92.4%) among all catalysts tested.     

Spin conversion of hydrogen using supported iron catalysts at cryogenic temperature

Alumina-supported iron oxides have been prepared by incipient wetness impregnation method and employed for orthohydrogen to parahydrogen spin conversion at cryogenic temperature. These materials were characterized using a series of characterization techniques such as SEM, XRD, Raman and in situ FTIR spectroscopy. The spin conversion was investigated at low temperature by a batch mode of operation. The in situ FTIR spectra were collected in a transmission mode to obtain the spin conversion. While the iron oxide was highly dispersed over alumina support at low loading percent, a rodlike crystallite of iron oxide was formed at high loading percent. The 10 and 20 wt% iron oxides on alumina were proved to be the most active catalysts. The spin conversion process was very slow and time-dependent. It was concluded that the spin conversion was a function of various factors including the iron oxide loading percent, calcination temperature, and different supports.     

Producing High‐Strength Metals by I‐ECAP

Incremental equal channel angular pressing (I‐ECAP) is used in this work to produce ultrafine‐grained (UFG) pure iron, aluminum alloy 5083, commercial purity titanium (grade 4), and magnesium alloy AZ31B. Pure iron is processed at room temperature, aluminum alloy at 200 °C, titanium at 320 °C, and magnesium alloy at 150 °C. Strength improvement, attributed to the grain refinement below 1 μm, is reported for all processed materials. The yield strength increase is the most apparent in pure iron, reaching almost 500 MPa after one pass of I‐ECAP, comparing to 180 MPa in the as‐forged conditions. UFG titanium, aluminum, and magnesium alloys obtained in this study reached yield stress of 800, 350, and 300 MPa, respectively, in each case exhibiting the yield strength increase by at least 30%, comparing to the alloys processed by conventional metal forming operations such as forging and rolling.     

Direct synthesis of highly ordered Ti-containing Al-SBA-15 mesostructured catalysts from natural halloysite and its photocatalytic activity for oxidative desulfurization of dibenzothiophene

Here we show that bimetallic Ti-Al-SBA-15 materials were synthesized successfully from titanium tetraisopropoxide (TTIP) and natural halloysite clay via the direct hydrothermal method. The results revealed that the incorporation of titanium species in the Al-SBA-15 framework retained the characteristic peaks and possessed an increased Brunauer-Emmett-Teller (BET) surface area in comparison to the conventional Al-SBA-15 material. The successful isomorphous substitution of titanium in the Al-SBA-15 framework was confirmed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopies. The transmission electron microscopy (TEM) images showed that the composite material exhibited a highly ordered 2-D hexagonal mesostructure. The photocatalytic activity of these Ti-Al-SBA-15 mesoporous materials were assessed by dibenzothiophene (DBT) conversion under UV light irradiation, showing that the Al-SBA-15 sample containing 7.5 wt% of titanium possessed the highest photocatalytic activity with a conversion of 92.68% at 70 °C and maintained the catalytic performance after four cycles. These results suggest a promising technique to produce the Ti-Al-SBA-15 photocatalyst from an abundant and low-cost clay material.     

Facile synthesis of ordered mesoporous silica with high γ-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> loading via sol-gel process

A series of ordered mesoporous silica loaded with iron oxide was synthesized by facile one-step sol-gel route using Pluronic P123 as the template, tetraethylorthosilicate as the silica source, and hydrated iron nitrite as the precursor under acid conditions. The as-synthesized materials with Fe/Si molar ratio ranging from 0.1 to 0.8 were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), and N₂ adsorption porosimetry. All samples possess ordered hexagonal mesoporous structure similar to SBA-15, with a high surface area, large pore volume, and uniform pore size. Although higher iron content causes a distortion of hexagonal ordering structure to some extent, the materials still maintain the ordered mesopore structure even with Fe/Si molar ratio as high as 0.8. Pore structure and TEM data suggest that iron oxide nanoparticles are buried within the silica wall, and increasing the iron oxide loading has little effects on the pore structure of the mesoporous silica. VSM results show as-synthesized samples exhibit superparamagnetic behavior.