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Ethanol has been used as a renewable hydrogen‐donor in the conversion of a lignin model molecule in subcritical conditions. Noble metal‐free porous mixed oxides, obtained by activation of Cu−Ni−Al and Cu−Ni−Fe layered double hydroxide (LDH) precursors, have been used as heterogeneous catalysts for Meerwein‐Ponndorf‐Verley (MPV) hydrogen transfer and further hydrogenation by ethanol dehydrogenation products. Both the Cu/(Cu+Ni) ratio and the nature of the trivalent cation (Al or Fe) affect the activity of the catalysts, as well as the selectivity towards the different steps of the hydrogenation reactions and the cleavage of lignin‐like phenylether bonds. Accounting for the peculiar behaviour of Cu2+ and M(III) cations in the synthesis of LDHs, the coprecipitation of the precursors has been monitored by titration experiments. Structural and textural properties of the catalysts are closely related to the composition of the LDH precursors. [ABSTRACT FROM AUTHOR]

Mesostructured mixed metal oxides are one of the best candidates for various oxidations. Here, mesostructured Cux/Cey mixed oxides with various Cu/Ce ratios were prepared using mesoporous silica as a hard template to improve their selectivity and efficiency as the oxidative catalysts. Investigation of the different ratios of Cu/Ce showed that all catalysts are significantly more active than their salts in the oxidation of alcohols and sulfides with some green oxidants. The results demonstrated that the balance of the number of active catalytic centers (concentration of Cu) and the structural characteristics (surface area and oxygen vacancy) determine the activity of the catalysts. It also seems to be a powerful interplay among copper and cerium ions that helps the reduction of both Cu (II) and Ce (IV). [ABSTRACT FROM AUTHOR]

Mixed Ni-Al oxide catalytic precursors with different elemental ratios (20, 50, and 80 wt.% Ni0) were synthesized using green supercritical antisolvent co-precipitation (SAS). The obtained oxide precursors and metal catalysts were characterized in detail by X-ray diffraction (XRD) analysis, atomic pair distribution function (PDF) analysis, CO adsorption, and high-resolution transmission electron microscopy (HRTEM). It was found that the composition and structure of the Ni-Al precursors are related to the Ni content. The mixed Ni1−xAlxO oxide with NiO-based crystal structure was formed in the Ni-enriched sample, whereas the highly dispersed NiAl2O4 spinel was observed in the Al-enriched sample. The obtained metal catalysts were tested in the process of anisole H2-free hydrogenation. 2-PrOH was used as a hydrogen donor. The catalyst with 50 wt.% Ni0 demonstrated the highest activity in the hydrogenation process. [ABSTRACT FROM AUTHOR]

• Sr 0.5 Ca 2.5 Al and Ca 3 Al calcined HT-like catalysts synthesized by co-precipitation method. • Sr 0.5 Ca 2.5 Al is strong solid base, environmentally friendly, and reusable catalyst. • Sr 0.5 Ca 2.5 Al is a highly active catalyst for Knoevenagel condensation reaction. • Catalytic activity is strongly dependent on the number of stronger basic sites. • Conversion (%) of benzaldehyde reaches 97% (selectivity 84%) on 0.04% of Sr 0.5 Ca 2.5 Al. The Knoevenagel condensation reaction is one of the most important reactions in the industry for the synthesis of organic materials, medicinal, and biological compounds. In this work, we have proposed an original and efficient solid-base catalytic system for the Knoevenagel condensation reaction. For the first time, a mixed oxide catalyst derived from hydrotalcite-like Sr 0.5 Ca 2.5 Al precursor was synthesized by co-precipitation method and subsequently calcined for 5 h at 850 °C. The catalysts were characterized by various techniques. The Sr 0.5 Ca 2.5 Al mixed oxide was also compared with the usual Ca 3 Al sample in terms of structural characteristics and catalytic activity in the Knoevenagel reaction between active methylene compounds and benzaldehyde. The findings revealed that the Sr 0.5 Ca 2.5 Al mixed oxide sample is considerably active in this reaction compared to the Ca 3 Al sample due to its stronger basicity. The kinetics of the Knoevenagel condensation reaction over the Sr 0.5 Ca 2.5 Al catalyst was investigated and indicated that it follows from the second-order model. The stability and reusability of the catalyst sample were studied and it was found that the Sr 0.5 Ca 2.5 Al catalyst has high stability and a good lifetime. The effects of reaction time, amount of catalyst, and reaction temperature on benzaldehyde conversion (%) and product selectivity (%) were assessed in this study using the Box-Behnken design. The appropriateness of the quadratic regression model was evaluated through the ANOVA method. Under optimal conditions, the conversion percentage of benzaldehyde and product selectivity reached 97% and 84%, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

Chitosan with mixed oxides as [NCS/NiO:CuO], [NCS/NiO:CO3O4] and [NCS/NiO:ZnO] nanocomposites were synthesized via hydrothermal method and studied by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray fluorescence spectrometry (EDX) and atomic force microscope (AFM). The anticancer activity was screened against human cancer cell such a human liver [HEP G2] cancer cells and the antibacterial activity also was screened compared to chitosan, against [Escherichia coli, Pseudomonas aeruginosa] as gram negative and [Staphylococcus aurous, Bacillus ceruse] as gram positive for the synthesized nanocomposites. The results of these assay indicated that the compounds that were exposed to this study showed an increase in cellular toxicity at certain concentrations and also concluded that the nanocomposites are more effective as anti-bacterial agents compared to the nano chitosan. As a result, these nanocomposites can be used as an effective agent against bacterial and carcinogenic risk factors. [ABSTRACT FROM AUTHOR]

A number of cracking catalyst samples containing Me–Mg–Al mixed oxides have been prepared. Cobalt, zinc, copper, and cerium were used as additional metals in the mixed oxide composition. When studying the cracking of a vacuum gas oil–sunflower oil mixture, catalysts containing Co–Mg–Al or Zn–Mg–Al mixed oxides were found to increase both the conversion rate of the mixed feedstock by 5.0 wt % compared to a sample containing the mixed oxide free of additional metal, and the gasoline yield by 1.6–3.0 wt %. It was discovered that the modification of mixed oxides with cobalt or zinc cations has no significant effect on the distribution of inorganic products, thereby indicating sustained catalytic activity during the decarboxylation reaction. The catalytic tests also demonstrated that catalyst samples containing mixed Mg–Al oxides with copper cations exhibited enhanced decarbonylation effect, as well as low conversion rates of the mixed feedstock and low gasoline yield, which is probably associated with the poisoning impact of copper oxide on Y zeolite. [ABSTRACT FROM AUTHOR]

We propose efficient regimes of the formation of mixed-oxide conversion coatings by plasma-electrolytic oxidation (PEO) of aluminum alloys in pyrophosphate and alkaline electrolytes. It is shown that the variations of the concentrations of electrolyte components and the parameters of PEO (current density and the duration of treatment) lead to the appearance of oxide coatings formed by the material of the metal matrix and oxides of transition metals of various compositions and morphologies, which definitely affect their functional properties. Mixed oxide coatings formed as a result of PEO are characterized by microglobular structures, small sizes of conglomerates, and elevated microhardness. Moreover, they are corrosion and wear resistant. In view of the microglobular structure of the surface and the composition of Al Al2O3·MnOx and Al Al2O3·CoOx oxide coatings, we can expect that the obtained materials may exhibit catalytic activity in the redox reactions with participation of oxygen and, in particular, in the working processes running in internal-combustion engines. [ABSTRACT FROM AUTHOR]

A large number of heterogeneous catalysts were tested in the aldol condensation of heptanal with cyclopentanone. There are many possible products from this aldol condensation, among which the most desired is 2-heptylidenecyclopentanone. As heterogeneous catalysts, the following were tested: caesium modified zeolites, functionalized MCM-41, and single (MgO, CaO, ZnO) and double (Mo–Si, Mg–Al, Zn–Al) metal oxides. The activity of modified zeolites and functionalized zeolites in this aldol condensation was low, whereas single and double metal oxides possessed high activity. The highest selectivity to the desired 2-heptylidenecyclopentanone (52%) was obtained using magnesium oxide as catalyst. [ABSTRACT FROM AUTHOR]

Oxygen evolution reaction (OER) electrocatalysts play the critical role in efficiency and durability for different hydrogen production systems. We have successfully synthesized the earth abundant WO 3 coupled with IrO 2 as mixed oxide composite by a facile two-step chemical method. 50% reduction in noble metal contents (IW-50) followed by two times enhancement in activity, four-folds increase in bulk mass specific activity along with the stability of mixed oxide composite as compared to state –of –the art IrO 2 catalyst are affirmed. Superior performance of mixed oxide composites are perceived due to four times increase in electrochemical surface area, reduction of Tafel slope, four-fold increase of turn over frequency, electronic distortion in Ir-4f spectrum of IW-50 along with the bridging of lattice oxygen atoms between iridium and tungsten metals. We believe that it would open up the new avenues for effective utilization of noble metal with high valence tungsten metal in corrosive environment. Image 1 • Effective support of WO 3 with IrO 2 particles for efficient oxygen evolution reaction. • Mixed oxide composite with 50% noble metal contents robustly performs in acid media. • Electronic distortion in Ir-4f spectra along with bridging of lattice oxygen atoms. • Improvement of numerous electrochemical properties as compared to homemade IrO 2. [ABSTRACT FROM AUTHOR]

The oil classified as heavy is the one with the largest number of deposits at present. However, these deposits are usually difficult to exploit since they contain a high concentration of asphaltenes which cause problems in the refineries at the time of extraction. Different strategies were used to decrease the effects of asphaltenes, being the most effective the use of adsorbents based on metal oxides. This is because metal oxides prevent the re-precipitation of asphaltenes under oil extraction; these methods can be easy implemented in modern refineries. In this work, we propose the synthesis of mixed oxide (Ni(3/2)xFe2-xO4) by self-combustion technique, being then used as an effective asphaltene adsorbent. Its asphaltene adsorption capacity was compared with nickel oxide and hematite, which were synthesized by controlled precipitation. The oxides were characterized by the techniques of X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR); their morphological characterization was carried out by scanning electron microscopy (SEM). The capacity of adsorption of asphaltenes was determined with the technique of UV-Vis spectroscopy. The results show that the Ni(3/2)xFe2-xO4 is a good adsorbent being compared with hematite and nickel oxide, both for asphaltenes with ether and amino groups. The mixed oxide shows a mayor affinity to asphaltenes containing amino groups, being compared with the hematite and nickel oxide; in addition, the mixed oxide has a low affinity to petroleum, which makes it selective to asphaltenes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Acidobasic Sr-Ti mixed oxides were prepared for producing bio-jet fuel precursors. • The mixed oxides were highly dispersed in the siliceous framework of SBA15. • The acid-base properties dominated aldol condensation of furfural with 2-butanone. • The desired branched C9 yield of 78.3% was obtained at 99% conversion. Herein, furfural, which is a lignocellulose-derived platform chemical, was converted into a bio-jet fuel precursor via aldol condensation with 2-butanone using strontium (Sr) and titanium (Ti) mixed oxides (STO) loaded onto mesoporous silica SBA-15 (SBA15). A series of acidobasic STO/SBA15 catalysts were prepared via incipient wetness impregnation by systematically varying the mixed oxide loading and Sr:Ti molar ratio of the catalysts. The STO/SBA15 catalysts exhibited a well-mesostructured order, high dispersion of metal oxides, and good textural properties. The acidic and basic properties of the catalysts were facilely controlled by varying the metal oxide composition and amount of STO loaded onto the SBA15 support. The aldol condensation was carried out batchwise under a pressurized nitrogen atmosphere. The products formed in the reaction comprised 9–18 carbon atoms. The yield and selectivity of α,β-unsaturated C9 ketone with branched molecular structure (C9B) were strongly influenced by the acid–base properties of the catalyst and the reaction conditions. 20STO(2:1)/SBA15 was the suitable catalyst, realizing > 99% furfural conversion and 78.3% C9B yield under the following optimized conditions: 4 wt% catalyst loading, 1:5 furfural:2-butanone molar ratio, 180 °C reaction temperature, and 5 h reaction time. [ABSTRACT FROM AUTHOR]

Mesoporous nanoring-like Zn-Co mixed oxides are synthesized via a simple template-free solvothermal method with a subsequent annealing process. The ring-like nanostructures with hollow interiors are formed under the complexing effects of potassium sodium tartrate. Numerous mesopores are generated after the precursor is annealed at 500 °C. When applied as anode materials, the mesoporous nanoring-like Zn-Co mixed oxides can deliver a high discharge capacity of 1102 mAh g −1 after 200 cycles at 500 mA g −1 . Even when the current density is increased to 2 A g −1 , the mixed oxides can still retain a reversible capacity of 761 mAh g −1 . Such high cycling stability and rate capability are mainly derived from the unique mesoporous ring-like nanostructures and the synergistic effects between Zn and Co based oxides. [ABSTRACT FROM AUTHOR]

In this paper, comparative studies of the structural, mechanical and corrosion properties of TiO 2 -WO 3 thin films, with different contents of WO 3 , have been investigated. The thin films were formed using the electron beam evaporation method, on the Ti6Al4 V surface. The structural characteristics of the thin films obtained, were examined using SEM and XRD measurements. The mechanical properties of the coatings were determined by nanoidentation measurements. The corrosion properties of the thin films were determined by an analysis of the voltammetric curves. The results obtained show that the layer with the highest content of tungsten – (Ti 0.41 W 0.59 )Ox is characterized by the best mechanical and corrosion properties from all tested samples. The hardness obtained for this sample was equal to 3.20 GPa, and was similar to the value obtained for undoped TiO 2 thin film. In addition, the value of corrosion current density for this sample was equal to 3.6∙10 −8 A/cm 2 , and was similar to the value obtained for pure WO 3 thin film. [ABSTRACT FROM AUTHOR]

Multicomponent nanoparticles can be synthesized with either homogeneous or phase-segregated architectures depending on the synthesis conditions and elements incorporated. To understand the parameters that determine their structural fate, multicomponent metal-oxide nanoparticles consisting of combinations of Co, Ni, and Cu were synthesized by using scanning probe block copolymer lithography and characterized using correlated electron microscopy. These studies revealed that the miscibility, ratio of the metallic components, and the synthesis temperature determine the crystal structure and architecture of the nanoparticles. A Co-Ni-O system forms a rock salt structure largely owing to the miscibility of CoO and NiO, while Cu-Ni-O, which has large miscibility gaps, forms either homogeneous oxides, heterojunctions, or alloys depending on the annealing temperature and composition. Moreover, a higher-ordered structure, Co-Ni-Cu-O, was found to follow the behavior of lower ordered systems. [ABSTRACT FROM AUTHOR]

In this work, a novel strategy has been proposed to synthesize a hierarchical Pt@TiO 2 -mSiO 2 yolk@shell nanocatalyst firstly. Inner active sites could be protected by the TiO 2 -mSiO 2 shell. The formation mechanism involves the in-situ growth of TiO 2 nanosheets and simultaneous redeposition of etch-released silica species. TEM images were employed to characterize each step of the synthesis process. During the hydrothermal process, original TiO 2 layer can be converted into a hierarchical structure and the inner SiO 2 sphere was etched out automatically. Furthermore, the reduction of 4-nitrophenol had been used to test the hierarchical Pt@TiO 2 -mSiO 2 yolk@shell nanocatalyst. The mixed oxides shell was constructed with in-situ grown hierarchical TiO 2 nanosheets and redeposited SiO 2 . [ABSTRACT FROM AUTHOR]

Mixed-metal oxides composed of Nb5+(d 0) and Te4+(p -) cations generally exhibit excellent optoelectronic properties due to the stereoactive lone pair of electrons in the structure. In this work, a mixed-metal niobate tellurite Nb 4 TeO 12 was prepared using solid state reaction method. The polycrystalline samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), optical absorption, photoluminescence (PL) and dynamic properties. This sample shows characteristic indirect electronic transitions with an interband energy of 3.01 eV. The bottom of conduction band and the top of valence band are +0.37 eV and +3.38 eV, respectively. Using a Nd:YAG pulsed laser as the excitation light source, the intrinsic luminescence of Nb 4 TeO 12 was investigated over a wide temperature range of T = 10–300 K. The broad band emission peaking at 513 nm corresponds to the self-activating luminescence of the niobate octahedral group [NbO 6 ]7−. The luminescence decay curve did not depend on the laser excitation energy, and it showed a non-exponential characteristic with two decay lifetime components. The experiments also preliminarily studied the performance of the luminescence application of Nb 4 TeO 12. • Mixed-metal niobate tellurite Nb 4 TeO 12 was prepared using solid state reaction. • Nb 4 TeO 12 is an n -type semiconductor (Eg = 3.01 eV) with indirectly allowed transitions. • Nb 4 TeO 12 shows the broad intrinsic luminescence band peaked at 480 nm. • Intrinsic luminescence originates from self-trapped exciton (STE) transitions. [ABSTRACT FROM AUTHOR]

The heterometallic complexes (NH4)2[Co(H2O)6]2[V10O28].4H2O (1) and (NH4)2[Co(H2O)5(β-HAla)]2[V10O28].4H2O (2) have been synthesized and used for the preparation of mixed oxides as catalysts for water oxidation. Thermal decomposition of 1 and 2 at relatively low temperatures (<500 °C) leads to the formation of the solid mixed oxides CoV2O6/V2O5 (3) and Co2V2O7/ V2O5 (4). The complexes (1, 2) and heterogeneous materials (3, 4) act as catalysts for photoinduced water oxidation. A modification of the thermal decomposition procedure allowed the deposition of mixed metal oxides (MMO) on a mesoporous TiO2 film. The electrodes containing Co/V MMOs in TiO2 films were used for electrocatalytic water oxidation and showed good stability and sustained anodic currents of about 5 mAcm-2 at 1.72 V versus relative hydrogen electrode (RHE). This method of functionalizing TiO2 films with MMOs at relatively low temperatures (<500 °C) can be used to produce other oxides with different functionality for applications in, for example, artificial photosynthesis. [ABSTRACT FROM AUTHOR]

Mg-Co-Al mixed oxides were synthesized by the precipitation method and evaluated for dry reforming of methane. The samples were characterized by thermal techniques (TGA/DTA, NH3-TPD, H2-TPR, and TPO), specific surface area, and X-ray diffraction (XRD). Activity runs were conducted at atmospheric pressure, temperatures between 400 and 550°C, a CH4/CO2molar ratio of 1, and a space velocity of 6000 NmL CH4/g/h. The partial substitution of Co with Mg increased the surface area and thermal stability and changed the reducibility and acid-base properties of the samples. These modifications led to a higher activity for dry reforming of methane for the catalyst with Mg/Co = 0.5, primarily due to its enhanced thermal stability. However, its higher activity was followed by higher amounts of coke. The different activation procedures highlighted Co3O4as the main active phase rather than the Co-mixed oxides. Therefore, milder activation temperatures are required to properly reduce the Co3O4phase and avoid sintering. [ABSTRACT FROM PUBLISHER]

In this work, hydrotalcite-like compounds (prepared by a simple and environmentally-friendly method) were evaluated as adsorbent's precursors for arsenic (V) removal in water. Materials were characterized by X-ray powder diffraction, N 2 adsorption-desorption at − 196 °C and thermogravimetric analyses. It was revealed by the XRD characterization that the calcined samples exhibited the characteristic reflections of the MgO and spinel crystalline phases. The thermal treatment increase gave rise to a specific surface area increment achieving a maximum at 550 °C. The effect of adsorbents' activation, reaction time, adsorbent amount, pH and initial arsenic concentrations were evaluated. Results showed that removal efficiency of arsenate increased with the increment of the annealing temperature reaching a maximum removal with the calcined sample at 550 °C. The adsorption isotherms can be well described by Freundlich model and adsorption kinetics of arsenate was adjusted by the pseudo-second-order, indicating that chemisorption was the limit step. It was demonstrated that removal capacity depends on the initial arsenic concentration where more than 98% removal was achieved with initial concentrations below 250 μg/L. [ABSTRACT FROM AUTHOR]

The catalytic performances of Ru and Pt supported on TiO 2 – x wt% CeO 2 were studied in catalytic wet air oxidation (CWAO) of phenol at 160 °C and 20 bar of pure oxygen pressure. Contrary to expectations, improved oxygen storage capacities of the materials prove to be detrimental to catalytic performances since they favor the formation of polymers in solution and the accumulation of adsorbed species. On the opposite, the presence of Lewis acid sites promotes the phenol total oxidation. They would favor the activation of the hydroxyl function, thus promoting the ortho-oxidation of phenol and finally the formation of CO 2 . On the other hand, platinum appears to be more efficient than ruthenium for CWAO of phenol. [ABSTRACT FROM AUTHOR]

The role of the adsorbed reactants and intermediates on the performance and deactivation behavior of Mg Zr mixed oxides as acetone self-condensation catalysts is studied in this work. DRIFT spectroscopy was used for identifying the adsorbed species and following their evolution during both acetone self-condensation reaction and thermo-desorption of pre-adsorbed reactants and products. The evolution of these species and the results of the characterization (nitrogen physisorption, temperature-programmed oxidation, and catalyst leaching) of catalysts samples taken in a continuous reactor at different temperatures (523, 623, and 723 K) and times on stream allow to determine that two concomitant deactivation causes are present in this reaction: the strong adsorption of dimers and trimers on the catalyst surface (especially important at the lowest temperature) and the formation of heavy condensation products physically deposited on the catalyst surface (more relevant at the highest temperature). [ABSTRACT FROM AUTHOR]

Ce–Co and La–Co mixed oxides were synthesized by two different methods: exotemplating and evaporation. The obtained catalysts were evaluated for volatile organic compounds (VOCs) abatement, using toluene as model molecule. The materials were characterized by N 2 adsorption at −196 °C, X-ray diffraction (XRD), scanning electron microscopy (SEM), H 2 temperature-programmed reduction (H 2 -TPR) and NH 3 temperature-programmed desorption (NH 3 -TPD) in order to reveal the structure–activity relationship. The results obtained showed the superiority of mixed oxides compared to single oxides in toluene oxidation. Ce–Co mixed oxides were more active than La–Co samples. For Ce–Co materials, the exotemplating method produced catalysts which were more active than those prepared by the evaporation procedure. The former showed the best catalytic performances, with full conversion of toluene into CO 2 at about 250 °C. Temperatures higher than 320 °C were required with single oxides. Characterization studies revealed strong interactions between Ce (or La) and Co, leading to a fine dispersion of oxide phases in binary systems. As a result, both the surface area and reducibility of the catalysts increase, which can be accounted for the higher performance of the mixed oxides. Furthermore, NH 3 -TPD studies showed a linear relationship between acidity and VOC oxidation activity. In fact, a high concentration of weak acid sites is required for high toluene oxidation activity. The results can be explained in terms of a Mars–van Krevelen type of mechanism, involving the adsorption of toluene and its subsequent oxidation by lattice and/or surface oxygen. [ABSTRACT FROM AUTHOR]

The TiMgAlCu mixed oxides, based on hydrotalcite-like compounds, was developed as novel SOx removal catalysts for FCC (fluid catalytic cracking) process. The mixed oxides were prepared by modified co-precipitation method and estimated for SOx removal under conditions similar to those of FCC units. XRD, TG/DTA and N2 adsorption analysis were performed to investigate the physicochemical and textural properties of the samples. The analysis results indicated that all the samples exhibit good dispersion of metal oxides in the matrix. The SOx adsorption-reduction tests showed that the novel TiMgAlCu catalysts with 15%Ti and 1% Cu had a good performance on SOx removal. Moreover, the particle size had obvious effect on the adsorption activity of sulfur remove catalysts and the best fit particle size is from 100 to 300 µm. [ABSTRACT FROM AUTHOR]

Metal oxides such as Nb2O5, Cr2O3, and especially a ZnIICrIII mixed oxide are demonstrated to be highly active and recyclable heterogeneous catalysts for Prins condensation, which provides a clean, high-yielding route for the synthesis of nopol through the condensation of biorenewable β-pinene with paraformaldehyde. ZnCr mixed oxide with an optimum Zn/Cr atomic ratio of 1:6 gave 100 % nopol selectivity at 97 % β-pinene conversion, with the catalyst easily recovered and recycled. The acid properties of Nb2O5 and ZnCr mixed oxide were characterized by the diffuse reflectance IR Fourier transform spectroscopy of adsorbed pyridine and ammonia adsorption microcalorimetry. An appropriate combination of acid-base properties of ZnCr mixed oxide is believed to be responsible for its efficiency. [ABSTRACT FROM AUTHOR]

The oxidation of CO is the archetypal heterogeneous catalytic reaction and plays a central role in the advancement of fundamental studies, the control of automobile emissions, and industrial oxidation reactions. Copper-based catalysts were the first catalysts that were reported to enable the oxidation of CO at room temperature, but a lack of stability at the elevated reaction temperatures that are used in automobile catalytic converters, in particular the loss of the most reactive Cu+ cations, leads to their deactivation. Using a combined experimental and theoretical approach, it is shown how the incorporation of titanium cations in a Cu2O film leads to the formation of a stable mixed-metal oxide with a Cu+ terminated surface that is highly active for CO oxidation. [ABSTRACT FROM AUTHOR]

Abstract: CuMgAlCe mixed oxides were prepared by a modified coprecipitation–calcination method using CTAB as surfactant template. All the precursors showed hydrotalcite-like layered structure and mixed oxides with mainly periclase phase were obtained after calcination. Catalytic activity for SO2 removal of mixed oxides was examined through adsorption–reduction cycles under the conditions similar to those of FCC units. The results showed that incorporation of both Ce and Cu could improve SO x oxidative chemisorption. CTAB/metal molar ratio during synthesis had a significant influence on the structural properties of mixed oxides. Sample CuMgAlCe-0.1 prepared by CTAB/metal molar ratio of 0.1 had the highest specific area 142.2m2/g and also presented the best SO2 adsorption rate and capacity. This behavior is mainly due to its exposed more adsorption sites provided by high specific surface area, facilitating SO2 diffusion and contact with active components. It still possessed excellent cyclic stability that is beneficial for industrial application. [Copyright &y& Elsevier]

Highlights: [•] La-Cu and La-Co oxides were prepared by exotemplating and evaporation based methods. [•] The materials obtained were tested as catalysts for ethyl acetate oxidation to CO2. [•] La-Co materials were much more active than the individual components. [•] Catalytic activity depends on the amount of Cu or Co and reducibility of the catalyst. [•] The calcination temperature and presence of perovskites also influences activity. [Copyright &y& Elsevier]

Abstract: In the present work, Mg–Al–Fe layered double hydroxides were prepared by coprecipitation reaction with hydrothermal treatment. The characterization of precursors and their corresponding calcinated products (mixed oxides) were carried out by X ray diffraction, X-ray photoelectron spectroscopy (XPS), termogravimetric analysis and differential scanning calorimetry, diffuse reflectance UV–vis spectroscopy, specific surface area, Mössbauaer and magnetic properties. The Fe3+ species were observed in tetrahedrally and octahedrally coordination in brucite layered. The XPS analysis shows that the Fe3+ ions can be found in two coordination environments (tetrahedral and octahedral) as mixed oxides, and as spinel-structure. Oxides show a decrease in the specific surface areas when the iron loading is increased. The magnetic and Mössbauaer response show that MgAlFe mixed oxides are different behaviours such as different population ratios of ferromagnetic, weak-ferromagnetic, paramagnetic and superparamagnetic phases. The better crystallization of spinel structure with increased temperature, is correlated with the improved magnetic properties. [Copyright &y& Elsevier]

Highlights: [•] The Co–Mn–Al LDH precursors were deposited on anodized aluminum foils. [•] The Mn/Co ratio of 4–8 in solutions was favorable for obtaining active catalysts. [•] Supported mixed oxide catalysts were tested in the total oxidation of ethanol. [•] The catalysts specific activity increased with increasing the Mn/Co ratio in solid. [•] Specific activity of supported catalysts was higher than that of the grained one. [Copyright &y& Elsevier]

Highlights: [•] Rare earth cation-containing layered double hydroxides as catalyst precursors. [•] Effective catalysts for methane total oxidation. [•] The Ce-containing catalyst was the most active. [•] The catalytic activity depended on the Ce content. [•] The catalyst reducibility played a key role in the catalytic reaction. [Copyright &y& Elsevier]

Abstract: Solid catalysts comprising Li-based oxides were prepared by LiNO3 impregnation onto supports with different acid/base properties (SiO2, MgO, Al2O3 and Mg(Al)O mixed oxide obtained from hydrotalcite). The materials were characterized by means of XRD, N2 physisorption, ICP–OES, FEG-SEM and TPD of CO2. The oxide reactivities were evaluated using the model transesterification reaction between methyl acetate and ethanol under mild reaction conditions (313K, ethanol/methyl acetate molar ratio=6/1 and 0.2wt.% of catalyst). Lithium impregnation onto silica and γ-alumina yielded inactive catalysts for transesterification. On the other hand, the lithium addition onto MgO produced an active catalyst and remarkably high conversions were obtained for Li/Mg(Al)O. The different supports used considerably affected the base site densities and base strengths of the Li-based catalysts. The base properties thus influenced the catalytic performance of the materials. Stability tests revealed the lithium leaching occurrence which resulted in some homogeneous contribution. [Copyright &y& Elsevier]

Abstract: Pure and mixed oxides (Al2O3, ZrO2, Al2O3–MgO, Al2O3–SiO2, Al2O3–TiO2, and Al2O3–ZrO2) were prepared by homogeneous delayed precipitation. The synthesized supports were impregnated by incipient wetness method to obtain CoMo catalysts. Both supports and catalysts were characterized by N2 physisorption, X-ray diffraction, among other techniques. Acid–base properties were studied with isopropyl alcohol and cumene decomposition. It was possible to assess qualitatively that nature of Al–Si and its respective catalyst was mainly acidic. Conversion of isopropyl alcohol leads to the dehydration products, mostly propylene with a low amount of di-isopropyl ether and acetone. The CoMo/Al2O3–SiO2 catalyst showed the highest conversion during cumene cracking. CoMo/Al2O3–SiO2 catalyst also was the most active during thiophene hydrodesulfurization followed by CoMo/Al2O3–TiO2 catalyst. [Copyright &y& Elsevier]

Abstract: Three new trinuclear symmetric derivatives of formula [Co2M(μ-salenph)2(μ-X)2] (salenph: N,N′-phenylenebis(salicylideniminato); 1, M=Mn, X=CH3COO−; 2, M=Mn, X=Cl−; 3, M=Co, X=CH3COO−), have been obtained by solvothermal reaction between [Co(salenph)] and the corresponding cobalt(II) or manganese(II) salts in ethanol. The complexes have been characterized by X-ray crystallography and magnetic susceptibility measurements. Complexes 1 and 3 are isomorphous and they show the X ligands bridging in opposite sides of the molecule having a trans coordination to the middle metal atom. On the contrary, compound 2 shows an unusual cis coordination of the chloride groups around the central manganese atom. The potential of the new complexes to act as single-source molecular precursors for mixed oxides is considered. The thermal decomposition of the three complexes indicates that they are completely converted to the crystalline spinel like oxides, Co3O4 and Co2MnO4. Magnetic properties of the obtained oxides have been investigated. [Copyright &y& Elsevier]

Abstract: Acido-basic MMgAlO mixed oxide catalysts (M=Mn, Fe, Co, Ni, Cu and Zn) were obtained by thermal decomposition of the corresponding layered double hydroxide (LDH) precursors. They were characterized by XRD, EDX, nitrogen adsorption, TG-DTG, NH3-TPD and CO2-TPD experiments. The cyanoethylation of methanol was used as a model reaction to evaluate the basicity of the LDHs and the corresponding mixed oxides. Mixed oxides were much more active than their LDH precursors, while both were quite selective for β-metoxypropionitrile. A straight correlation between the number of basic sites of the mixed oxides determined by CO2-TPD and their catalytic activity was evidenced. However, the equilibrium between the acid and basic sites is a key factor determining the catalytic activity. [Copyright &y& Elsevier]

Abstract: The effect of zirconium dioxide addition on crystal structure of sol–gel TiO2 mesoporous films and powders has been investigated by means of Raman spectroscopy, X-Ray diffraction, and Atomic force microscopy. Zirconium incorporation (up to 30mol%) into TiO2 lattice resulted in the formation of Ti1−xZrxO2 solid solution with anatase structure for the binary powders has been proved. Appearance of tetragonal ZrO2 phase was observed for the samples with high zirconium content. [Copyright &y& Elsevier]

Abstract: Nanostructured ceria–alumina mixed oxides containing different concentrations of ceria (10 and 30wt.%) were prepared by the sol–gel method using organo-metallic precursors of alumina and ceria. The size of alumina and ceria particles in the prepared Ce–Al–O mixed oxides was smaller than that of pure alumina or ceria. The gold catalysts (3wt.% Au) supported on ceria–alumina mixed oxides by deposition–precipitation (DP) using HAuCl4 and urea were characterized by several techniques: TEM, XPS and UV–vis spectroscopy, and temperature programmed reduction/oxidation (TPR/TPO). The catalytic activity of prepared Au/CeO2–Al2O3 catalysts in CO oxidation was higher than that of Au/Al2O3 and Au/CeO2 catalysts. Nanostructured ceria incorporated into an alumina matrix has been found quite effective for gold species activation in CO oxidation. In fact, transient analysis of CO oxidation provided an estimate of the relative content of (Au–ceria vacancy) active sites in catalysts. Obtained values are in good agreement with the order of activity for tested samples and gold dispersion according to EXAFS data. [Copyright &y& Elsevier]

Abstract: A series of CuMgAl hydrotalcites derived oxides were prepared by co-precipitation and calcination methods and tested for the simultaneous catalytic removal of NOx and soot. The obtained samples were characterized by XRD, N2 adsorption-desorption, H2-TPR and ICP-AES techniques. The crystal phases, porous structures and redox properties of the catalysts were strongly influenced by Cu substitution contents and calcination temperatures. The CuMgAl mixed oxides with mesoporous properties exhibit high activity for the simultaneous NOx-soot removal. Among the tested catalysts, 3.0Cu-800 sample shows the best performance with the ignition temperature of soot=260°C and the total amounts of N2 =6.0×10−5 mol. Based on the experimental work, a primitive kinetics analysis was carried out from the non-steady (dynamic) TPR measurements. Linear Arrhenius plots of rates of CO2, N2 and N2O formation were observed around the onset of formation curves where the substantial amount of the soot still remains in the soot/catalyst mixture and the effective area of the soot/catalyst contact can be regarded as constant. Finally, a compensation effect was found for the formation of CO2, N2 and N2O over CuMgAl mixed oxides with CuO as the predominant phase. [Copyright &y& Elsevier]

Abstract: Supported mixed oxide catalysts of various cation composition were obtained by heating (500°C) of layered double hydroxide (LDH) precursors deposited on Al2O3/Al support (anodized aluminum foil) or grained alumina calcined at various temperatures during hydrothermal reaction in aqueous solutions of Co, Cu, Ni, and Mn nitrates. The MII–(Mn)–Al LDHs (MII =Co, Ni–Co, Ni–Cu, and Co–Cu) with only low Mn content were obtained. NiO-like and spinel-like mixed oxides but no distinct Cu-containing phases were detected in the supported catalysts. A low-temperature peak ascribed to reduction of an amorphous copper oxide was detected in TPR patterns of the supported mixed oxides containing Cu. TPR results indicated reduction of Ni- and Co-containing species at temperatures higher than 400°C; it can be explained by formation of spinel-like phases and high structural ordering of the calcination products. Heating of grained alumina support at high temperatures (>550°C) resulted in substantial decrease in surface area and, consequently, the amount of deposited active species. Among the examined catalysts, the Ni–Cu–(Mn)–Al mixed oxide showed the highest catalytic activity. Slight acetaldehyde formation during ethanol deep oxidation over the supported mixed oxides was observed. [Copyright &y& Elsevier]

Abstract: Structured mixed oxide catalysts were prepared by the calcination of layered double hydroxides (LDHs) deposited on Al2O3/Al supports (anodized aluminum foil). The deposition of LDH precursors on the supports was carried out under hydrothermal conditions at 140°C in aqueous solutions of Ni, Co, Cu, and Mn nitrates. MII-(Mn)-Al LDHs (MII = Ni, Co, Ni-Co, Ni-Cu, and Co-Cu) with only slight Mn contents were obtained. An increased pH of the solutions used for deposition enhanced the formation of LDH phases. After heating at 500°C, spinel-like and/or NiO-like oxides were detected in the supported mixed oxides. Compared to the mixed oxides obtained by calcination of the coprecipitated LDH precursors, the supported mixed oxides exhibited worse reducibility and lower catalytic activity in the total oxidation of ethanol; both the formation of spinel-like phases and high structural ordering of the products deposited on the Al2O3/Al supports could explain the poor reducibility. Among the supported catalysts, the Ni-Cu-(Mn)-Al mixed oxide was the most active in the total oxidation of ethanol. Increasing the pH of solutions used during the hydrothermal deposition of the LDH precursors resulted in improved catalytic activity and selectivity of the supported mixed oxides. [Copyright &y& Elsevier]

Abstract: Ternary mixed oxides of Fe, Co, and Mo with composition FexCo1-xMoO4 (x = 0.25, 0.50 & 0.75) have been prepared by a co-precipitation method and investigated as electrocatalysts for the oxygen evolution reaction (OER) in alkaline solutions. The study indicates that partial replacement of Co by Fe in the CoMoO4 matrix increases the specific surface area as well as the apparent electrocatalytic activity of the oxide; the magnitude of increase being the greatest with x = 0.25. The order for the OER with respect to OH− concentration has been observed to be ∼2 on Fe0.75Co0.25MoO4 and ∼1 on Fe0.25Co0.75MoO4 and Fe0.5Co0.5MoO4. The Tafel slopes at low overpotentials were close to 40 mV with each oxide catalyst. [Copyright &y& Elsevier]

Abstract: Mixed oxides of the Cu/Mn/Mg/Al and Co/Mn/Mg/Al type were obtained by means of the thermal decomposition of hydrotalcites, with manganese as the main active phase and with variations in their content by means of the addition of Cu or Co (molar ratio Cu/Mn or Co/Mn between 0.05 and 0.5). The effect of a second active phase on the material was evaluated in the total oxidation of three volatile organic compounds, VOCs (toluene, ethanol and butanol). The catalysts were characterized by means of X-ray fluorescence (XRF), X-ray diffraction (XRD), temperature-programmed reduction with hydrogen (TPR-H2) and physisorption of nitrogen at 77K. All the solids were active in the oxidation reaction of the VOCs, where the scale of difficulty to oxidize the different organic compounds evaluated was: butanol

Abstract: Heat capacity measurements were carried out on (U1−y La y )O2±x (y =0.2, 0.4, 0.6, and 0.8) using differential scanning calorimeter (DSC) in the temperature range 298–800K. Enthalpy increment measurements were carried out on the above solid solutions using high temperature drop calorimetry in the temperature range 800–1800K. Chemical states of U and La in the solid solutions of mixed oxides were determined using X-ray photoelectron spectroscopy (XPS). Oxygen to metal ratios of (U1−y La y )O2±x were estimated from the ratios of different chemical states of U present in the sample. Anomalous increase in the heat capacity is observed for (U1−y La y )O2±x (y =0.4, 0.6 and 0.8) with onset temperatures in the range of 1000–1200K. The anomalous increase in the heat capacity is attributed to certain thermal excitation process, namely, Frenkel pair defect of oxygen. The heat capacity value of (U1−y La y )O2±x (y =0.2, 0.4, 0.6, and 0.8) at 298K are 65.3, 64.1, 57.7, 51.9JK−1 mol−1, respectively. From the XPS investigations, it was observed that the O/M ratios at the surface are higher than that in the bulk. In uranium rich mixed oxide samples, the surface O/M ratios are greater than 2 whereas that in La rich mixed oxides, they are less than 2, though the bulk O/M in all the samples are less than 2. [ABSTRACT FROM AUTHOR]

Abstract: Catalysts of Pt on Fe2O3 and mixed oxides Fe x Zr(1−x)O2 were prepared for the selective CO+H2 oxidation. X-ray diffraction and Mössbauer spectroscopy showed α-Fe2O3 in pure support, a solid solution for x =0.25 and mixed oxides with segregated phases for higher “x” values. Mössbauer results showed also that with increasing the Zr content Zr4+ ions substitute the Fe3+ ions in the α-Fe2O3 lattice, and also Fe3+ ions diffusing into the zirconia lattice. The Pt/Fe0.25Zr0.75O2(p) exhibited only Fe3+ inside the ZrO2 lattice. After reduction, Fe3O4 was found in the catalysts, which decreased with increasing zirconium loading. It is interesting to note that the corresponding precursor presents 83% of Fe3+ located in the ZrO2 lattice and the remaining 17% corresponds to hematite. Catalytic tests for the preferential oxidation of CO containing H2 showed a maximum CO conversion at different temperatures after reaching total oxygen conversion. The CO conversion decreased with increasing iron content in the mixed oxide. The Pt/Fe2O3 catalyst is the most active compared to the other Pt/mixed oxide and Pt/ZrO2. Results showed the following order: Pt/Fe2O3(c)>Pt/Fe0.75Zr0.25O2(c)>Pt/Fe0.25Zr0.75O2(c)>Pt/ZrO2. The Pt/Fe0.25Zr0.75O2(c) presented high selectivity (56%) at 90°C and is 2-fold higher compared to the Pt/Fe2O3 and Pt/ZrO2 catalyst. [Copyright &y& Elsevier]

Abstract: Mixed xCeO2–Al2O3 oxides with different CeO2 content (x =1–20wt%) were prepared by sol–gel method. The effect of the CeO2 content, atmosphere and temperature treatment during synthesis on the structure and properties of the xCeO2–Al2O3 was investigated. xCeO2–Al2O3 xerogels prepared from aluminum tri-sec-butoxide and Ce(III) nitrates have a pseudo boehmite-like structure. The Ce(III) ions stabilized under a reductive atmosphere randomly occupy vacant sites in tetrahedral and octahedral positions of Al2O3. The crystallization of γ-Al2O3 is suppressed and the textural properties of the mixed xCeO2–Al2O3 oxides are stabilized at high temperature. Conversely, the treatment xCeO2–Al2O3 xerogels in an oxidative atmosphere shows a progressive oxidation of Ce(III) to Ce(IV) with crystallization of γ-Al2O3 and formation of CeO2 with fluorite-like structure as the temperature rises. The effect of CeO2 on the catalytic performance xCeO2–Al2O3-supported Pt catalysts in partial oxidation of methane reaction was tested. The Pt catalysts were obtained by two methods: (i) impregnation of the xCeO2–Al2O3 supports with H2PtCl6·6H2O and (ii) one-step preparation by addition of Pt precursor during the sol–gel synthesis. CeO2-containing catalysts showed higher stability than Pt/Al2O3 catalyst obtained by impregnation method. The effect of the support was less evident when the catalysts were obtained by the one-step method. Pt catalysts based on sol–gel oxides preparation show higher thermal stability and result in higher Pt sintering resistance than conventional ones. [Copyright &y& Elsevier]

Abstract: A series of Ni/Mg/Al/La mixed oxides prepared by thermal decomposition of layered double hydrotalcites (HT) were characterized by XRD, ICP, EXAFS, TGA, TPR-H2, SEM, and N2 adsorption/desorption technique. The results revealed the formation of periclase-type catalysts with mesoporous structure, and the addition of La3+ lowered the phase crystallization with the formation of small oxide particles. Such catalysts had both high activities and stabilities toward partial oxidation of methane (POM). The catalyst containing 6.5 mol.% La3+ showed the highest performance at 1053K with CH4 conversion of 99%, CO selectivity of 93% and H2 selectivity of 96%, which could be attributed to the presence of highly dispersed nickel and then the resistance to coke formation due to the promotion effect of lanthanum. [ABSTRACT FROM AUTHOR]

Abstract: Highly ordered mesoporous titania-alumina mixed oxide thin films are synthesized by using spin-coating method based on solvent evaporation process. The mole ratios of doped alumina are controlled in the range from 0 to 30mol%. In order to achieve a highly ordered mesostructure, a low-temperature and low-humidity aging condition after the spin-coating is applied by means of controlling the hydrolysis and condensation reactions of metal species. During thermal treatment, the Im-3m mesostructure is unidirectionally contracted along the direction perpendicular to the substrates. The mesochannel walls are composed of periodically arranged cages with connecting necks between the neighboring cages. On the top-surface of the films, the uniformly-sized mesopores are observable. By doping alumina species in the pore walls, the thermal stability of the films is enhanced up to 450°C. By finely tuning the amount of the doped alumina species, we can realize the successful anatase crystallization in the frameworks with the retention of the ordered mesoporous structures. The obtained mesoporous titania-alumina mixed oxide films are fully characterized by 2D-grazing-incidence small-angle X-ray scattering (2D-GISAXS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Raman spectroscopy. [Copyright &y& Elsevier]

Abstract: Vapor phase condensation reactions of propanal were investigated over Ce x Zr1−x O2 mixed oxides as a model reaction to produce gasoline range molecules from short aldehydes found in bio-oil mixtures. Several operating parameters were investigated. These included the type of carrier gas used (H2 or He) and the incorporation of acids and water in the feed. Propanal is converted to higher carbon chain oxygenates on Ce x Zr1−x O2 by two pathways, aldol condensation and ketonization. The major products of these condensation reactions include 3-pentanone, 2-methyl-2-pentenal, 2-methylpentanal, 3-heptanone and 4-methyl-3-heptanone. It is proposed that the primary intermediate for the ketonization path is a surface carboxylate. The presence of acids in the feed inhibits the aldol condensation pathway by competitive adsorption that reduces the aldehyde conversion. Water also promotes ketonization and inhibits aldol condensation by increasing the concentration of surface hydroxyl groups that enhance the formation of surface carboxylates with the aldehyde. Hydrogen enhances cracking and production of light oxygenates and hydrocarbons. The light oxygenates may in turn be reincorporated into the reaction path, giving secondary products. However, the hydrocarbons do not react further. Analysis of the fresh and spent catalysts by XPS showed varying degrees of reduction of the oxide under different operating conditions that were consistent with the reaction results. Changing the proportion of the parent oxides showed that increased Zr favored formation of aldol products while increased Ce favored ketonization. This occurs by shifting the balance of the acid–base properties of the active sites. [ABSTRACT FROM AUTHOR]

Abstract: Chromium–titanium mixed oxides with Cr/Ti+Cr molar ratio of 0.1, 0.2, 0.5, and 0.9 were prepared by a direct sol–gel method. The products were characterized by powder XRD, FT-IR spectroscopy, TEM, and N2 adsorption. Starting with 10% Cr3+, Cr/Ti+Cr=0.1, resulted in a complete dispersion of the Cr3+ ions in the titania matrix. On the other hand, a ratio of 0.2 resulted in the formation of traces of segregated α-Cr2O3, besides Cr-doped titania. At higher Cr contents, %Cr of ≥50, crystalline Ti-doped Cr2O3 and an amorphous Cr-doped titania were obtained. Compared with the corresponding one-metal oxides, TiO2 and α-Cr2O3, the mixed oxides showed significantly modified textural properties presented in higher surface areas, larger porosities, and more homogeneous mesoporous structures. In addition, the incorporation of Cr3+ ions in the titania lattice enhanced the thermal stability of the anatase phase against transformation to rutile. [Copyright &y& Elsevier]

Abstract: The preparation of Ce0.80Zr0.20O2 mixed oxides was conducted by coprecipitation, using either Ce(NO3)3·6H2O or (NH4)2Ce(NO3)6 as cerium precursor. Their counterpart pure ceria samples were also prepared for comparative purposes. The samples were characterised by N2 adsorption at −196°C, XRD, Raman spectroscopy, XRF, H2-TPR and XPS, establishing proper comparisons with a commercial catalyst Ce0.80Zr0.20O2, supplied by Rhodia. The use of Ce(NO3)3·6H2O leads to a Ce–Zr mixed oxides with ceria-like structure, Ce-enrichment on the surface and a bi-modal H2-TPR profile, not expected for a true solid solution. On the contrary, a t″ structure was identified when using (NH4)2Ce(NO3)6 as precursor, exhibiting improved oxygen mobility and Zr-enrichment on the particle surface. These findings are in accordance with the solution chemistry of the Ce-species involved. When two pure ceria samples are compared, the most important difference is the very low surface area of CeO2 prepared from the Ce4+ precursor (5m2/g) compared with CeO2 prepared from the Ce3+ precursor (57m2/g). The Ce–Zr mixed oxides prepared from the precursor (NH4)2Ce(NO3)6 shows the highest NO oxidation capacity among the samples prepared in this study. The NO oxidation capacity to NO2 seems to be dependent not only on the BET surface area of the catalyst but also on the Ce/Zr atomic surface ratio and probably, the redox properties of the catalysts, when mixed oxides with the same nominal composition are compared. [Copyright &y& Elsevier]