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CeO2–MnOx mixed oxides supported on different carriers (ZSM-5, TiO2, and SAPO-34) were prepared by the sol-gel combustion method and evaluated for the selective catalytic reduction of NO with NH3. The physicochemical properties of the samples were determined by using XRD, TEM, N2 adsorption (BET method), H2-TPR, and NH3-TPD. The Ce–Mn/TiO2 exhibited a higher NO conversion than Ce–Mn/ZSM-5 in the 100-200°C temperature range, but the NO conversion of Ce–Mn/ZSM-5 increases with reaction temperature (being the N2 selectivity close to 100%) whereas, for Ce–Mn/TiO2, the N2 selectivity extremely decreases. The reducibility and surface acidity of samples seems to explain the catalytic performance. Thus, although the reducibility of Ce–Mn/ZSM-5 and Ce–Mn/TiO2 was similar, the large number of surface acid sites of Ce–Mn/ZSM-5 could be a plausible reason for its excellent SCR activity. In fact, the superior SCR activity of Ce–Mn/ZSM-5 (94% NO conversion and 95% N2 selectivity at 300°C) is related to the presence of well-dispersed Ce–Mn mixed oxide nanoparticles, high reducibility, and a large number of surface acid sites. [ABSTRACT FROM AUTHOR]

Magnesium–aluminum layered double hydroxides and mixed oxides based on them were obtained by high and low supersaturation methods and analyzed. It was shown that the phase composition and formation of nano-sized particles with a large surface area is significantly affected by the rate of introduction of magnesium–aluminum systems into the medium of the precipitated material. All of the obtained samples were studied by thermogravimetric analysis with mass-spectrometric detection, X-ray diffractometry, scanning electron microscopy, energy dispersive X-ray spectroscopy, and infrared spectroscopy. [ABSTRACT FROM AUTHOR]

An efficient organic/inorganic magnetic nanohybrid of MgAl@CuFe2O4-polylysine was successfully synthesized and employed as a suitable adsorbent for removal Cr(VI) and methyl orange from water solution. The prepared nanohybrid was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, vibrating sample magnetometer and thermogravimetric analysis. The nanohybrid of MgAl@CuFe2O4-polylysine was employed to adsorb anionic species, i.e., Cr(VI) and methyl orange through electrostatic attraction, ligand exchange and ion exchange. Multivariate optimization with Box-Behnken design was used to evaluate effective parameters such as dosage of adsorbent, solution pH and contact time on adsorption and their interaction. Results showed that pH, contact time and adsorbent dosage are effective parameters for Cr(VI) adsorption; however, the pH of the solution is the sole effective parameter for methyl orange adsorption. Both analyte adsorptions are fast with adsorption times less than 15 min. Isotherm study revealed that the prepared nanohybrid is a highly efficient adsorbent for methyl orange and Cr(VI) with adsorption capacity of 693.6 and 281.8 mg g−1, respectively. Isotherm study showed that adsorption of both analytes well fitted with the Freundlich adsorption isotherm model, which indicated multilayer adsorption on the heterogeneous surface. The magnetic saturation for the prepared adsorbent was 12.64 emu g−1, which was adequate and suitable for magnetic separation of samples. The prepared adsorbent was regenerated using ethanol-aquaeous NaOH solution as it shows 90% removal efficiency after three cycles. [ABSTRACT FROM AUTHOR]

Oxygen evolution reaction (OER) is the core electrode reaction in energy-related technologies, such as electrolytic water, electrocatalytic carbon dioxide reduction, rechargeable metal-air batteries, and renewable fuel cells. Development of well-stocked, cost-effective, and high-performance OER electrocatalysts is the key to the improvement of energy efficiency and the large-scale commercial implementation of these technologies. Multicomponent transition metal oxides and (oxy)hydroxides are the most promising OER catalysts due to their low cost, adjustable structure, high electrocatalytic activity, and outstanding durability. In this review, a brief overview about the mechanisms of OER is first offered, accompanied with the theory and calculation criteria. Then, the latest advances in the rational design of the related OER electrocatalysts and the modulation of the electronic structure of active sites are comprehensively summarized. Specifically, various strategies (including element doping, defect engineering, and fabrication of binderless catalysts) used to improve the OER performance are detailedly discussed, emphasizing the structure—function relationships. Finally, the challenges and perspectives on this promising field are proposed. [ABSTRACT FROM AUTHOR]

The present work highlights the versatility of a TiO2-Al2O3 mixed oxide bearing highly dispersed gold nanoparticles that was applied in the CO oxidation reaction at room temperature. The TiO2, Al2O3, and TiO2-Al2O3 supports were synthesized by the sol–gel method, while gold nanoparticles were added by the deposition–precipitation with urea method using a theoretical Au loading of 2 wt.%. A promotional effect of the TiO2-Al2O3 support on the activity of gold catalysts with respect to TiO2 and Al2O3 was observed; Au/TiO2-Al2O3 showed outstanding CO oxidation, being active from 0 °C and stable throughout a 24-h test. As for the alumina content (5, 10, and 15 wt.%) in TiO2, it improved the textural properties by retarding the crystal growth and anatase–rutile phase transformation of TiO2, suppressing the deposition of carbon on the catalyst surface and stabilizing the Au nanoparticles even at high temperatures. Gold was highly dispersed with nanoparticle sizes ranging from 1 to 2 nm when H2 was used to treat thermally the Au/TiO2-Al2O3, Au/TiO2, and Au/Al2O3 materials. In addition, the XPS technique helped elicit that Au0 and Au1+ boosted their interaction with the TiO2, Al2O3, and TiO2-Al2O3 supports by means of charge transfer, which resulted in outstanding CO oxidation activity from 0 °C. Likewise, the key factors that control the peculiar catalytic performance in the CO oxidation reaction are discussed, which represents a step forward in the versatility behavior of gold catalysts supported on mixed oxide catalysts. [ABSTRACT FROM AUTHOR]

A ternary oxide of silver, copper, and manganese (Ag2CuMnO4) is prepared by hydrothermal synthesis in an alkaline medium in the presence of sodium peroxodisulfate. The obtained product with the delafossite structure has no admixtures of other crystallized phases and is tested as an ethylene oxidation catalyst. The catalytic properties of the ternary oxide are modified by pretreatments in inert (He, T = 400-600 °C) and reducing (1% CO/He, T = 200 °C) media resulting in partial or complete destruction of the pristine structure. It is established that pre-treatment of the ternary oxide diminishes its catalytic activity in the ethylene oxidation reaction. The main reaction products are ethylene oxide, acetaldehyde, carbon dioxide, and water; their yields depend on the pretreatment type and the changes during the heating–cooling cycle. [ABSTRACT FROM AUTHOR]

The study aimed to develop an electrochemical sensor based on glassy carbon, mixed oxide (SiO2/TiO2/Sb2O5), and carbon black. The material was synthesized, characterized, and used to determine thiamethoxam in raw honey and water. The morphologic structure and electrochemical performance of the sensor was characterized by scanning electron microscopy and cyclic voltammetry. Differential pulse voltammetry with a concentration of 0.1 mol L−1 of Britton-Robinson buffer at pH 7.0 allowed the generation of a method to determine thiamethoxam in a linear range of 0.25 to 100.5 μmol L−1 and with a limit of detection of 0.012 μmol L−1. The system efficiently quantified traces of thiamethoxam in raw honey and tap water samples. The modified sensor did not present interferences of K+, Na+, Ca2+, Mg2+, glyphosate, imidacloprid, and carbendazim. In addition, the device showed good recovery values for thiamethoxam when applied directly to honey and water samples without any treatment, presenting an electrochemical sensor to monitor real-time hazardous substances in environmental and food matrices. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of a novel titania/silica hybrid xerogel subsequently modified with 4-methylpyridine (4-Pic), named TiSi4Pic+Cl− is reported. The physicochemical, structural and thermal properties of TiSi4Pic+Cl− were characterized using several techniques. Anchoring cobalt(II) phthalocyanine (CoTsPc) in TiSi4Pic+Cl− showed greater electroanalytical sensitivity over other sensors built with these materials. A novel electroanalytical method was developed to quantify the noxious biocide pentachlorophenol (PCP) for environmental monitoring. The peak current intensity increased linearly with the analyte concentration in the range between 0.99 and 4.21 μmol L−1, based on the oxidation process (at + 0.81 V, vs. Ag/AgCl) of differential pulse voltammetry (DPV). The estimated limit of detection (LOD) was 29 nmol L˗1. Recovery tests in environmental samples showed a PCP concentration of 2.05 ± 0.03 μmol L−1 (n = 3). The method was statistically validated by comparing the PCP concentrations with those obtained by molecular absorption spectrometry and high-performance liquid chromatography-diode array detection (HPLC–DAD). At a 95% confidence level, no difference between the results was found, therefore confirming the excellent accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

Mixed oxides of Ni0.65Zn0.35Fe2O4 stoichiometry (Ni + Zn/Fe = 1:2) were prepared by citrate and coprecipitation methods, characterized by TGA-TD, XRD, FTIR and SEM, and its catalytic properties were investigated in hydrogenation of 2-nitrophenol (2-NP) to 2-aminophenol (2-AP) counterparts under ambient conditions. The methods of preparation influenced the textural, the structural and the reactivity properties. All the preparations show the presence of mixed phases containing spinel structure and γ-Fe2O3 oxide. The crystallite sizes increase with increasing calcination temperatures due to the coalescence of nanoparticles by solid-state diffusion. All samples exhibited high catalytic activity with first-order kinetic; the sample issued from citrate method and annealed at 800 °C (Ea ~ 31.6 kJ/mol) is the most active system with a high X-ray density and a low force constant at tetrahedral sites. For this catalyst, 99.7% of 2-NP was reduced to 2-AP within 6.5 min and the recycled catalyst shows a very good activity for five catalytic runs. It could remain more than 88% activity after it was used five times. [ABSTRACT FROM AUTHOR]

This study investigates the use of CaO–TiO2 mixed oxides as solid base catalysts to produce biodiesel from cotton oil (Gossypium hirsutism). These CaO–TiO2 mixed-oxide catalysts were prepared in different molar proportions of Ca:Ti (0.75Ca:0.25Ti, 1Ca:1Ti e 0.25Ca:0.75Ti) and characterized by X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TGA), Raman spectroscopy, scanning electron microscopy (SEM) coupled with energy-dispersive X-ray analysis, and Brunauer–Emmett–Teller surface area analysis. The effects of reaction parameters such as the methanol/oil molar ratio, the amount of catalyst amount, and the reaction temperature were also investigated. The process was evaluated by TGA and confirmed by FTIR and GC/MS. The catalysts obtained were tested in the following reaction parameters: 20:1 methanol:oil molar ratio; 10% of catalyst amount; and 60 °C temperature for 5 h. The best catalyst was determined to be 0.25Ca–0.75Ti (calcined at 800 °C), considering its catalytic and anti-leeching abilities, because it obtained the highest yield (92.2%) without leaching calcium. Therefore, CaO–TiO2 catalysts have the potential to be used in biodiesel products. [ABSTRACT FROM AUTHOR]

Co-Fe, Cu-Cr, and Co-Mn mixed oxide catalysts were prepared using a one-pot hard template synthesis method, and their catalytic performance was investigated before and after the rearrangement of the template. To evaluate the structural properties of the catalysts, various analyses were employed, including the BET, XRD, H2-TPR, FE-SEM, EDX, and X-ray digital mapping of the elements. The results indicated that the rearrangement of the catalyst structure had a profound effect on the structural and catalytic properties, so that in all three synthesized catalysts, the specific surface and the reducibility increased significantly, and the crystalline structure and morphology of the catalysts changed remarkably. The specific surface area of the CoFe, CuCr, and CoMn catalysts increased from 3.5, 1.1, and 72.9 m2/g to 151.3, 52.8, and 108.0 m2/g, respectively. These structural changes significantly increased the catalytic performance. The results indicated that the 100% conversion temperature of the CoMn catalyst as the optimal sample after rearrangement was reduced from 250 to 125 °C. Also, the stability of the CoMn catalyst in dry and wet conditions was investigated and the results indicated that the presence of water vapor reduced the activity and stability of the catalyst. The activation energy was also calculated on Co-Mn catalyst (59.5 kJ/mol) and the results confirmed that the most probable mechanism for this reaction was the MVK mechanism. [ABSTRACT FROM AUTHOR]

Two types of mixed oxides of B2O3 and Al2O3 were prepared. Aluminum borates (ABx, x represents the B/(B + Al) ratio) were prepared by low-temperature thermal decomposition of aluminum nitrate and H3BO3 sustained by the simultaneous oxidation of an organic agent (glycerol), while B2O3-Al2O3 with B/(B + Al) ratio of 0.3 was obtained by incipient wetness impregnation of H3BO3 on a commercial γ-Al2O3 support. Tetrahedrally, pentahedrally, and octahedrally coordinated Al3+ cations were all present in AB0.3 with ratios of 10.9/21.3/67.8, while no pentahedrally coordinated Al3+ was observed in B2O3-Al2O3. B2O3 was enriched in the surface of AB0.3. The Ni2P phase was obtained by temperature-programmed reduction of a phosphate precursor with a P/Ni ratio as low as 1.2 supported over both AB0.3 (Ni-P(1.2)/AB0.3) and B2O3-Al2O3 (Ni-P(1.2)/B2O3-Al2O3). This suggests that the surface B2O3 inhibits the reaction between nickel phosphates and Al2O3, and thus facilitates the formation of Ni2P. The hydrodesulfurization (HDS) of dibenzothiophene (DBT) over the supported Ni2P catalysts occurred mainly by the direct desulfurization pathway, and Ni-P(1.2)/B2O3-Al2O3 was much more active than Ni-P(1.2)/AB0.3. These features make B2O3-Al2O3 a promising support for Ni2P catalysts. The HDS of DBT followed a pseudo-first-order kinetics over Ni-P(1.2)/B2O3-Al2O3, whereas over Ni-P(1.2)/AB0.3 it can be described by pseudo-zero-order kinetics. The pseudo-zero-order kinetics suggests a strong adsorption of DBT on Ni-P(1.2)/AB0.3, which could be responsible for its lower activity. [ABSTRACT FROM AUTHOR]

A non-destructive wavelength dispersive X-ray fluorescence (WDXRF) spectrometric method for direct determination of uranium and plutonium in as fabricated annular sintered (U, Pu)O2 mixed oxide (MOX) pellets avoiding the traditional cumbersome sample preparation involving dissolution or comminution–pelletization of sample has been developed. Sintered (U, Pu)O2 MOX pellets were directly analyzed using this method by taking the sample pellets inside an indigenously developed special collet which was loaded in the spectrometer for WDXRF measurements. The developed methodology has the utility for regular analysis of samples in fuel fabrication facilities. The relative standard deviation of the analytical results for U and Pu using WDXRF were found to be better than ± 0.13% and ± 0.31% (n = 10) respectively and equivalent plutonium content obtained are in close agreement with the standard titrimetric methods. [ABSTRACT FROM AUTHOR]

In the present work, appropriate reaction conditions were found to control the catalyst deactivation in the CO2 reforming of methane over Ni–Mg–Al catalyst. Experiments with variable CO2/CH4 ratio showed that the carbon deposition and the sintering of the catalyst decrease with increasing CO2/CH4 ratio. The carbon deposition was controlled at CO2/CH4 = 2, whereas a strong deactivation was observed for a ratio of CO2/CH4 < 1. The experiments with variable space time and fixed CO2/CH4 ratio showed that a shorter space time favors both the carbon deposition control and enhances the resistance of the catalyst to sintering. These results are supported by XRD, TPO and Raman Spectroscopy analyses. Catalyst presented high stability with the time-on-stream in the reaction at 700 °C, CO2/CH4 = 2, and space time of 1.2 g h/mol. The proper reaction conditions are suitable for high CO2 content feed. [ABSTRACT FROM AUTHOR]

A low-cost Cr(III)-incorporated Zr(IV) bimetallic oxide (CZ) was synthesized by simple chemical precipitation method for removal of fluoride from contaminated water. The physicochemical properties of CZ before and after fluoride removal were established with several instrumental techniques such as TEM with elemental mapping, SEM with EDX, XRD, IR, XPS, zeta potential measurement, etc. Batch adsorption technique were carried out to understand the factors affecting fluoride adsorption, such as effects of initial pH, adsorbent dose, co-occurring ions, contact time, and temperature. The maximum adsorption capacity observed at pH between 5 and 7. The fluoride adsorption processes on CZ obeyed the pseudo-second-order rate equations and both Freundlich and DR isotherm models. The maximum adsorption capacity of 90.67 mg g−1 was obtained. The thermodynamic parameters ΔH0 (positive), ΔS0 (positive), and ΔG0 (negative) indicating the fluoride sorption system was endothermic, spontaneous, and feasible. The CZ also successfully used as fluoride adsorbent for real field contaminated water collected from the Machatora district, Bankura, West Bengal, India. [ABSTRACT FROM AUTHOR]

In this work, three novel catalysts were prepared by 2.5, 5.0, and 10.0 wt.% facile impregnation with an iron and molybdenum mixed oxide (Fe/Mo) on an aluminum pillared clay (Al-PILC) support. These materials were characterized by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD), temperature programed reduction (TPR), and nitrogen (N2) physisorption at 77 K. Characterizations indicated that the metal particles were dispersed on the surface of the three catalysts, and the interlayer d001 spacing of the pillared material remained unchanged after the impregnation process. The catalytic tests showed good results for DBT oxidation using the synthesized catalysts, with high turnover frequency (TOF) values, particularly for the material with 5.0 wt.% Fe/Mo. Theoretical calculations were carried out at the density functional theory (DFT) level, to investigate how the DBT molecules were adsorbed onto the surface of the mixed oxide. The lowest energy proposal was obtained when both Fe and Mo were present at the active sites, indicating a possible synergistic effect of the metals on catalyst activity. Reuse tests indicated that the catalysts could be employed effectively for up to 3 cycles in a row, then a decrease in activity occurred and the active sites needed to be regenerated. [ABSTRACT FROM AUTHOR]

Different MgAl mixed oxides with a Mg/Al ratio of 2 were obtained through calcination of the corresponding hydrotalcites at 450 °C and tested for MPV reaction of benzaldehyde with 2-butanol. The influence of several synthetic parameters (such as co-precipitation in the presence of Pluronic P123 or homogeneous precipitation in the presence of urea in the medium) on catalytic performance was studied. The use of urea led to a decrease in surface area as compared to conventional precipitation method (125 m2/g and 201 m2/g, respectively) but an increase in surface basicity (7.3 µmol CO2/m2 and 4.3 µmol CO2/m2, respectively). Utilization of Pluronic 123 increases surface area (183 m2/g) though basicity is hardly affected (4.2 µmol CO2/m2). All the catalysts showed a high conversion and high selective to the desired product, observing a relationship between the density of basic sites and the catalytic activity. All in all, the solid exhibiting the highest benzyl alcohol yield was that synthesized in the presence of urea (labelled as HT-U-450), with a rate of 2.05 mmol benzyl alcohol/gcat × min. [ABSTRACT FROM AUTHOR]

A series of MnCoOx flower-like hollow microspheres with various molecular proportions of reactant were prepared through simple solvothermal method for the ammonia selective catalytic reduction (SCR) at low temperatures. The as-prepared samples have been applied by various characterization techniques to explore the formation process of the morphology and physicochemical properties. The Mn(1)Co(1)Ox presented the optimal intrinsic catalytic performance (95% NOx conversion at 75 °C), favorable thermal stability, and strong SO2 resistance. The excellent properties mainly related to its higher specific surface area and abundant active sites originated from hollow microsphere special structure consists of abundant nanosheets, robust redox properties beneficial for the strong interaction between the manganese and cobalt, larger number of acidic sites and stronger acid strength, etc., which collaboratively dominate its catalytic properties of NH3-SCR at low temperatures. [ABSTRACT FROM AUTHOR]

Tin and molybdenum oxide catalytic systems were employed in transesterification and esterification reactions using methanol. In the presence of the molybdenum-based catalysts, low activity was observed in the methanolysis of soybean oil. However, high activity was attained in the case of ethyl acetate transesterification (conversion of 75% at 1 h, using SnMo50 as catalyst) and oleic or propionic acid esterification (conversion of 48% at 1 h, in the case of propionic acid, using SnMo50 as catalyst). This result may be associated with the formation of molybdenum carboxylates that are soluble in more polar media and are responsible for the catalytic activity. These results suggest that the conversions observed with these systems can be related to the formation of homogeneous catalytic complexes, promoting better diffusion of the substrate and the acid sites of these systems. [ABSTRACT FROM AUTHOR]

Effect of mixed Mg–Al oxides contained in catalysts on the distribution of target products formed in cracking of a mixture of vacuum gas oil with sunflower oil was examined. It was found that the process of deoxygenation of oxygen-containing compounds can be controlled by varying the molar ratio between magnesium and aluminum in the mixed oxides. For catalyst samples containing mixed oxides with large Mg: Al molar ratios, the content of carbon dioxide in inorganic products grows, which is indicative of the increased activity of the decarboxylation reaction. In addition, the results of catalytic tests demonstrate that the highest conversion and yield of the benzine fraction are observed for catalyst samples containing mixed oxides with small magnesium-to-aluminum ratios of 0.32: 1 and 0.49: 1. A high activity of hydrogen-transfer reactions is observed for these samples, which leads to a decrease in the yield of light olefins. Thus, it is advisable, for obtaining an increased yield of C3 and C4 olefins, to include into the composition of the catalysts mixed oxides with increased content of magnesium, with Mg: Al ratios of 1.90: 1 and more. [ABSTRACT FROM AUTHOR]

Currently, production of high-purity hydrogen (H2) in a viable and sustainable manner is highly sought. H2 generation is possible by water splitting or biomass conversion as renewable resources. Bio-based n-butanol is a potential candidate for H2 production via catalytic steam reforming (SR) which is both of industrial and scientific significance. In the current work, a new catalyst is developed using La–Mg-based mixed metal oxide as support loaded with Ni–Cu as metals promoted by a suitable noble metal from Pt, Ru and Pd for steam reforming of n-butanol (SRB) in a fixed bed reactor. The effects of temperature, steam to carbon (S/C) ratio and gas hourly space velocity on hydrogen production from n-butanol were studied systematically. High n-butanol conversion (> 75%) and H2 yield (> 70%) were obtained. Particularly, the promotion with Pt resulted in the highest H2 concentration (> 90 mol%) with long-term stability of 25 h. The process optimization studies revealed that at T = 773 K, steam/carbon ratio (S/C) = 6 mol/mol and GHSV = 3120 h−1, maximum H2 concentration was obtained. The promotion with noble metals was further justified by the absence of coke formation and minimal metal sintering because noble metals help avert oxidation of Ni and Cu maintaining their active form. It was further bolstered through the cyclic stability studies which demonstrated that all catalysts remained stable for longer periods. A possible reaction mechanism on the synthesized catalysts is proposed in consonance with experimental data. [ABSTRACT FROM AUTHOR]

Delafossite mixed metal oxides of the form BaCuO2 and BaCu1M1−xO2 (M = Ni, Fe and Co) were successfully synthesized following a sol–gel citrate method. The products, obtained after heat treatment under N2 at 800 °C, were characterized using several techniques such as: thermogravimetric analysis (TG), inductively coupled plasma atomic emission spectroscopy (ICP), X-ray diffraction (XRD) spectroscopy, Brunauer–Emmett–Teller (BET) surface area analysis, Fourier transform infrared (FTIR) spectroscopy and temperature-programmed reduction (TPR). The formation of the delafossite oxide structure for all solid powders was confirmed by XRD. The BET surface area of all catalysts was lower than 10 m2 g−1. The catalytic performance of the synthesized catalysts was evaluated in the vapor-phase hydrogenation of benzaldehyde. Benzyl alcohol and toluene were obtained through consecutive hydrogenation/hydrogenolysis reactions, while benzene was formed via a concomitant hydrogenolysis reaction. BaCuO.47Ni0.51O2 catalyst showed better activity at 250 °C with 98% benzaldehyde conversion. Under the same conditions, BaCuO.52Fe0.48O2 catalyst showed the highest selectivity for benzyl alcohol (84% at 20% of conversion). [ABSTRACT FROM AUTHOR]

Additives for diminishing the content of carbon monoxide in gases formed in regeneration of the cracking catalyst without noble metals were synthesized and tested. As additives of this kind can serve mixed oxides based on copper, cerium, magnesium, and aluminum and manganese oxide supported by gamma aluminum oxide. Additives based on mixed oxides possess a high acidity and do not impair the activity of the catalytic system in the cracking reactions. In the efficiency (89.7–95.5%) in lowering the content of carbon monoxide, mixed oxides based on copper and cerium are comparable with the platinum-based additive KO-10 (96.8%). The activity of the additive based on manganese oxide depends on the sample calcination temperature, with the maximum efficiency in lowering the content of carbon monoxide (88.0%) reached at temperatures of 850–920°C. [ABSTRACT FROM AUTHOR]

VOC and CO constitute the principal emission during cold-start of vehicles. In order to decrease this emission at low temperature, this study focuses on the development of new catalysts: MgAlCe mixed oxides issued from the calcination of hydrotalcite precursors. Addition of cerium on the MgAl solid increase the reducibility of catalysts inducing a better catalytic reactivity for the CO and toluene total oxidation. Moreover, toluene oxidation is facilitated at low temperature due to a beneficial effect of CO in the reaction mixture. [ABSTRACT FROM AUTHOR]

In this work, different materials of Nd2CuO4 and K2NiF4 Ruddlesden-Popper structure have been prepared by solid-state reaction in air and high temperatures. The powders of mixed oxides, of general formula La2Li0.5M0.5 − xAuxO4 (M = Cu, Ni), were prepared from [Au(NH3)4](NO3)3 as gold source. The stoichiometric proportions of the all reagents (including La2O3, NiCO3, CuO) were grounded with a LiOH excess as mineralizer, pressed to form into pellets and heated in static air at temperatures between 750 and 850 °C for several hours. Structural characterization of the synthesized oxides using X-ray diffraction (XRD) are presented. La2Li0.5Au0.5O4, La2Li0.5Cu0.5O4, and La2Li0.5Ni0.5O4, three previously known oxides, were obtained. As expected, La2Li0.5Ni0.5O4 and La2Li0.5Cu0.5O4 consist of an ordered K2NiF4 Ruddlesden-Popper structure, while the La2Li0.5Au0.5O4 compound exhibits a Nd2CuO4 type structure. On the other hand, the preparation of the new proposed group La2Li0.5M0.5 − xAuxO4 (x = 0.0125-0.5) containing gold and nickel/copper simultaneously, under the studied conditions, was not possible. The experimental results revealed that the host structures are intolerant with respect to M (Cu or Ni) and Au cation double substitution. The difficulty to obtain the new phases is discussed regarding the exceptional instability displayed by the trivalent state of gold ion (Au3+) and the soft interactions of this specie with the lithium cation. Finally, the monophasic oxides, more interesting in terms of catalytic activity, were analyzed by temperature-programmed reduction (TPR-H2). [ABSTRACT FROM AUTHOR]

UO2 pellets doped with 1, 5 and 10 mol% Th before and after oxidation were analyzed by using Raman spectroscopy to investigate the Th doping effect on the structural changes during oxidation of UO2. While the Raman spectra of all sample pellets showed a close-to-perfect fluorite structure before oxidation, those of oxidized (U1−yThy)O2+x (0.03 ≤ x ≤ 0.06) pellets showed distinct defect structures after oxidation at 1150 °C with CO/CO2 = 0.001. The increasing relative ratio of first-order longitudinal optical modes of (U1−yThy)O2+x with increasing doping levels should represent the defect structure due to the Th doping effect. [ABSTRACT FROM AUTHOR]

We present a simple route to prepare mesoporous hollow silica particles containing an Au core, i.e., yolk/shell particles, by sol-gel and selective etching processes. Using tetraethoxysilane as a silica precursor, zinc acetate as a base catalyst, and cetyltrimethylammonium chloride as a soft template in the presence of Au nanoparticles, double-layered mesoporous shells were produced in one step. Elemental analysis showed that the inner shell consists of zinc silicate and the outer shell is pure silica. Au/mesoporous silica yolk/shell nanoparticles were obtained by selective etching of the zinc oxide phase with citrate buffer. The particle structure and composition were studied by transmission electron microscopy with energy disperse spectroscopy, UV-vis spectroscopy, X-ray diffraction, and nitrogen sorption experiments. Formation of double shells on the Au core in a single step was explained by a difference in the formation rates of the silica and zinc silicate phases. Au/mesoporous yolk/shell particles showed a high catalytic activity for reduction of 4-nitrophenol. [ABSTRACT FROM AUTHOR]

In this study, the photocatalytic removal of an emerging contaminant, diclofenac (DCF) sodium, was performed using the nitrogen-doped WO/TiO-coupled oxide catalyst (WO/TiO-N). The catalyst synthesis was accomplished by a sol-gel method using tetrabutyl orthotitanate (CHOTi), ammonium p-tungstate [(NH)HWO·4HO] and ammonium nitrate (NHNO) as the nitrogen source. For comparison, TiO and WO/TiO were also prepared under similar conditions. Analysis by X-ray diffraction (XRD), N adsorption-desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance UV-Vis spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS) were conducted to characterize the synthesized materials. The photocatalytic efficiency of the semiconductors was determined in a batch reactor irradiated with simulated solar light. Residual and mineralized DCF were quantified by high-performance liquid chromatography, total organic carbon analysis and ion exchange chromatography. The results indicated that the tungsten atoms were dispersed on the surface of TiO as WO. The partial substitution of oxygen by nitrogen atoms into the lattice of TiO was an important factor to improve the photocatalytic efficiency of WO/TiO. Therefore, the best photocatalytic activity was obtained with the WO/TiO-N catalyst, reaching 100% DCF transformation at 250 kJ m and complete mineralization at 400 kJ m of solar-accumulated energy. [ABSTRACT FROM AUTHOR]

The partial oxidation of unsaturated aldehydes such as acrolein and methacrolein to the corresponding carboxylic acids is of big importance for the chemical industry. The heart of these production plants is the oxidation catalyst. Acrylic acid is produced via the selective oxidation of acrolein on Mo/V/W mixed oxides with an excellent catalytic performance (S > 90 %, X > 95 %, life time >3 a). Under the same conditions the conversion of methacrolein to methacrylic acid has a poor catalytic performance (S < 35 %, X ≈ 40 %). To this day the reason for this is unclear. Hence, for the partial oxidation of methacrolein a heteropoly acid catalyst is used with a good performance (S ≈ 88 %, X ≈ 62 %), but unfortunately the lifetime is unsatisfactory (<1 a). Therefore, we have studied the gas and surface mechanism of the partial oxidation of acrolein to acrylic acid on mixed oxides with the help of in-situ experiments. The learning outcome of this study will help us to find a rational way to come up with a new catalytic system for the unsatisfactory partial oxidation of methacrolein to methacrylic acid and are summarised in a new extended mechanism. [ABSTRACT FROM AUTHOR]

Aerogel sulfated ZrO-SiO mixed oxide solid acid catalyst was prepared by sol-gel method followed by supercritical drying (SCD) in n-propanol solvent, which resulted into higher surface area (170 m/g), pore volume (0.31 cm/g) and pore diameter (7.2 nm) having ordered mesoporous structure as well as more number of Brönsted and Lewis acid sites available on larger surface area. The catalyst exhibited 91 % yield of methyl stearate at 60 °C in 7 h, which increased from 71 to 91 % with an increase in the Zr to Si ratio from 1:2 to 2:1 due to increase in acid site concentration. The reaction followed pseudo-first order kinetics under the optimized reaction conditions with a reaction rate of 1.15 mmol h, rate constant of 2.7 × 10 h and turn over frequency of 9.68 h. The catalyst displayed higher activity (91 %) compared to ion exchange resins (44-68 %), Nafion (58 %), acid clay (61 %) and pure sulfated zirconia (78 %), and was slightly lower as compared to HSO (97 %). The study clearly reveals the improved structural, textural and acidic properties of ZrO-SiO mixed oxide aerogel prepared via SCD technique. [ABSTRACT FROM AUTHOR]

The poly(vinyl alcohol) (PVA) influence on the adsorption and electrokinetic properties of the mixed oxide MnO-SiO/polymer solution system was examined. Three oxides differing with the MnO contents were applied (0.2; 1 and 3 mmol/g SiO, respectively). The PVA with the molecular weight 100 kDa was characterized with the acetate groups content equal to 14 %. Adsorption, solid surface charge and zeta potential measurements were made as a function of solution pH (3-10). The obtained results showed that the PVA adsorption amount strongly depends on not only the solution pH, but also manganese oxide content on the mixed oxide surface. The higher solution pH value (or MnO content) is, the higher polymer adsorption is obtained. The PVA addition to the solid suspension causes minimal changes of the mixed oxide surface charge density, whereas the zeta potential of solid particles increases significantly in the polymer presence. [ABSTRACT FROM AUTHOR]

The following investigation reports the synthesis of novel complex [Fe(opd)][Ba(CN)] and preparation of BaFeO nanoparticles through thermal decomposition without using any surfactant. The complex was characterized via Furrier transform infrared spectroscopy (FT-IR), ultra violet-visible spectroscopy (UV-vis), conductivity measurement and elemental analysis. The synthesized crystals of inorganic precursor complex was transferred to furnace, where they were calcined under normal atmosphere condition at 900 °C for 4 h. Formation of BaFeO was supported by FT-IR and energy-dispersive X-ray analysis. Hexagonal structure of nano-oxide was confirmed on powder X-ray diffraction. Furthermore, uniform morphology of nanocrystals were reported by scanning electron microscopy. The saturation magnetization (22 emu/g), remanent magnetization (6 emu/g) and coercivity (400 Oe) reported on vibrating sample magnetometer curve illustrates the promising industrial and medicinal applications of prepared mixed oxide. [ABSTRACT FROM AUTHOR]

Layered double hydroxides of the hydrotalcite (HT)-type materials have been considered as promising supports for Co-based Fischer-Tropsch synthesis (FTS) catalysts. In this work the effect of the Mg/Al ratio on the catalytic behavior of cobalt-based catalysts obtained from HTs precursors have been studied. Cobalt supported on Mg-Al oxides obtained from HTs Mg-Al precursors were prepared by wet impregnation method and calcined at 300 °C. The textural, structural and reducibility properties of the samples were characterized using different techniques. FTS was evaluated in a down-flow fixed-bed reactor at 20 bar, 250 °C and H/CO ≈ 2 molar ratio. All catalysts were active and stable during 72 h testing time. The stability was improved by the presence of magnesium in the alumina support; however the CO conversion was negatively affected by increasing the Mg/Al ratio. The reducibility of cobalt decreased as the Mg/Al ratio increased, probably due to the strong Co-O-Mg interaction as evidenced by the formation of CoO-MgO mixed oxide. Furthermore, the activity of the catalysts was correlated with the H-chemisorption measurements. The results suggest that HTs as Co-based catalysts were highly stable in FTS. [ABSTRACT FROM AUTHOR]

In the base catalyzed ethanol condensation reactions, the calcined MgO-AlO derived hydrotalcites used broadly as catalytic material and the calcination temperature plays a big role in determining the catalytic activity. The characteristics of the hydrotalcite material treated between catalytically relevant temperatures 450 and 800 °C have been studied with respect to the physical, chemical, and structural properties and compared with catalytic activity testing. With the increasing calcination temperature, the total measured catalytic basicity dropped linearly with the calcination temperature and the total measured acidity stayed the same for all the calcination temperatures except 800 °C. However, the catalyst activity testing does not show any direct correlation between the measured catalytic basicity and the catalyst activity to the ethanol condensation reaction to form 1-butanol. The highest ethanol conversion of 44 % with 1-butanol selectivity of 50 % was achieved for the 600 °C calcined hydrotalcite material. [ABSTRACT FROM AUTHOR]

Two novel catalysts of nano-hybridized Ni-Mo over AlO/TiO and AlO/ZrO were synthesized through a newly designed procedure by using ultrasonic irradiation and characterized by X-ray diffraction, UV-Vis diffuse reflectance spectra, FT-IR, energy dispersive X-ray spectroscopy and transmission electron microscopy. Then, the catalytic activities of these catalysts were examined in the oxidation of toluene by Oin various conditions of pressure, time and temperature. The products were analyzed by GC and GC-MS. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The analysis of the literature data reveals that, as a rule, layered double hydroxides prepared by co-precipitation have an imperfect structure; however, there are different viewpoints on the type of the defects. Thermal decomposition of Mg-Al, Mg-Ga, and Ni-Al hydroxides occurs through dehydration, dehydroxylation, and decarbonization. The first stage affords a layered dehydrated phase with a strongly disordered structure, which is a subject of controversy. Also, the question on the diffusion of cations during thermolysis is still open, i.e., whether the Mg-Al, Mg-Ga and Ni-Al systems degrade with the development of a nanoheterogenous oxide systems or a single-phase mixed oxide, but with very defective structure, is formed. [ABSTRACT FROM AUTHOR]

Silica-titania mixed oxide were prepared by sol-gel method from tetraethylorthosilicate and titanium (IV) isopropoxide as precursors in the presence of room temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [CMIm][NTf]. The effects of [CMIm][NTf] on the structural and textural characteristics of silica-titania matrix are investigated in this paper. The materials obtained were well characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis X-ray powder diffraction (XRPD), field emission scanning electron microscope (FESEM) and N adsorption-desorption analysis. It is believed that the [CMIm][NTf] plays an important role as a template and the high surface area of the samples is thought to mainly attribute to the formation of microporous in the reaction. The synthesized materials showed the presence of C-N groups in the FTIR spectrum which indicates the presence of RTIL in the silica-titania matrix. XRPD, FESEM and N adsorption-desorption analysis results indicated that the composite materials possessed good microporous character. The subsequent material displayed average pore diameter of 1.70-2.12 nm, pore volume of 0.08-0.19 cm/g and BET surface area of 191-386 m/g. Increasing the content of RTIL resulted in an increase of the average pore diameter of the silica-titania gel. [ABSTRACT FROM AUTHOR]

One of the primary aims of the actinide community within nanoscience is to develop a good understanding similar to what is currently the case for stable elements. As a consequence, efficient, reliable and versatile synthesis techniques dedicated to the formation of new actinide-based nano-objects (e.g. nanocrystals) are necessary. Hence, a 'library' dedicated to the preparation of various actinidebased nanoscale building blocks is currently being developed. Nanoscale building blocks with tunable sizes, shapes and compositions are of prime importance. So far, the non-aqueous synthesis method in highly coordinating organic media is the only approach which has demonstrated the capability to provide size and shape control of actinide-based nanocrystals (both for thorium and uranium, and recently extended to neptunium and plutonium). In this paper, we demonstrate that the non-aqueous approach is also well adapted to control the chemical composition of the nanocrystals obtained when mixing two different actinides. Indeed, the controlled hot co-injection of thorium acetylacetonate and uranyl acetate (together with additional capping agents) into benzyl ether can be used to synthesize thorium/uranium mixed oxide nanocrystals covering the full compositional spectrum. Additionally, we found that both size and shape are modified as a function of the thorium:uranium ratio. Finally, the magnetic properties of the different thorium/uranium mixed oxide nanocrystals were investigated. Contrary to several reports, we did not observe any ferromagnetic behavior. As a consequence, ferromagnetism cannot be described as a universal feature of nanocrystals of non-magnetic oxides as recently claimed in the literature. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

As traditional sources of energy become depleted, significant research interest has gone into conversion of biomass into renewable fuels. Biomass-derived synthesis gas typically contains concentrations ranging from ~30 to 600 ppm HS. HS is a catalyst poison which adversely impacts downstream processing of hydrogen for gas-to-liquid plants and the deactivation of water-gas shift catalysts by sulfur is typical. Novel catalysts are needed to remain active in the presence of sulfur in order to boost efficiency and mitigate costs. Previous studies have shown molybdenum to be active in concentrations of sulfur >300 ppm. Cobalt has been shown to be active as a spinel in concentrations of sulfur <240 ppm. Ceria has received attention as a catalyst due to its oxygen donating properties. In this study, mixed oxide catalysts were synthesized via Pechini's method into various blends of metal oxide solutions. Activity testing at low steam-to-carbon ratios (1:1) produced near equilibrium conversions at a GHSV of 6,300 h and over a temperature range of 350-400 °C for a Ce-Co mixed oxide even after an 800 ppm sulfur treatment. The addition of molybdenum to the Ce-Co base had little effect on sulfur tolerance, but it did lead to a reduction in selectivity for methanation. Specific surface areas generally increased following the sulfur treatments and X-ray diffraction patterns confirmed that bulk sulfiding did not occur. [ABSTRACT FROM AUTHOR]

A study was carried out on the acetylation of methyl tert-butyl ether (MTBE) by acetic anhydride on Amberlist 15 and acid ZrO 2-SiO 2 oxide in a flow system. The reaction products are tert-butyl acetate and methyl acetate, which are formed with 40 %-45 % selectivity at 40-50 °C. The most selective and stable ZiO 2-SiO 2 catalyst provides for 95 % conversion of MTBE and 45 % yield of tert-butyl acetate (LHSV = 3.9 h –1). Isobutylene and 2,4,4-trimethyl-1-pentene are the side-products. [ABSTRACT FROM AUTHOR]

The system of VO-TiO catalysts with VO contents from 5 to 20 wt% were prepared by the sol-gel route and calcined at 500 °C. The mixed oxide series presented the crystalline structure of TiO anatase phase. BET analysis showed a medium surface area decreasing from 73 to 19 m g when VO content rose from 5 to 20 wt%. The results of pyridine adsorption followed by FT-IR indicate that the catalysts display identical surface acid densities, independently of the VO content, and both Brønsted and Lewis acid sites are present on their surfaces. The VO system presents an activity and selectivity during the cyclohexene oxidation reaction. The presence of VO increases the catalyst efficiency and leads to a selectivity change from cyclohexenol (blank test) to epoxide, with a maximum for 15 wt% VO. The conversion of cyclohexene was 46 % while the selectivity to epoxide was higher (75 %). [ABSTRACT FROM AUTHOR]

Processing the aerosol of metal salts in non-equilibrium plasma represents a promising technique that combines the advantages of spray pyrolysis with the high reactivity of plasmas at nearlaboratory temperature in order to produce mixed-oxides and perovskite materials. The aim of this paper is to describe the principles of this new technique and to present the various applications and latest developments. This technique's capacity to deposit various mixed metal oxides with precise stoichiometry is demonstrated. It is shown that oxidant plasma species play a key role in the chemical transformation of starting materials into oxides at laboratory temperature, while the configuration of the reactor determines the morphology and texture of the deposited layers. Two different reactor configurations are presented. The porous layers of LaSrMnO as the cathode for fuel cells were synthesised in a wave shock reactor configuration, while nanostructured ZnO-Al layers to form a transparent conductive cathode for photovoltaic cells were deposited in the spray plasma reactor of the latest generation for this technique. The experimental results emphasise the role of plasma species in the rate of chemical reactions and in the chemical composition of the deposited layers. [ABSTRACT FROM AUTHOR]

MgAl hydrotalcite was synthesized and used as support for Li impregnation. MgAlLi oxides were obtained from heat treatment of the Li/MgAl hydrotalcite. These materials were characterized and evaluated as catalysts for model transesterification reactions. MgAl showed negligible activity under mild reaction conditions (50 °C and 0.5 h) whereas Li incorporation greatly increased the activity. The activities were correlated to their basicity determined by TPD of CO. Reuse tests showed catalyst deactivation after the third cycle, probably due to lithium leaching. However, the contribution to a homogeneous reaction has been dismissed. MgAlLi revealed to be a promising catalysts for transesterification reaction and thus for biodiesel production. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

In this work is reported the synthesis of nanotubes and nanoribbons from mixed oxides (TiZrO· nHO), employing hydrothermal treatment in a highly alkaline medium. The morphology and crystal structure of the products obtained via hydrothermal treatment depend on the value of x. For example, for x equal to 0 and 0.50 were observed the presence of nanotubes (diameter around 9 nm) and nanoribbons (diameter around 200 nm), respectively. However, for x values above 0.50, there was no morphological change. Regarding the crystalline structure of these samples, for x equal to 0 was observed the sodium titanate phase; already for x values up to 0.50, we observed the presence of two crystalline phases: sodium titanate and tetragonal ZrO. For x values above 0.50, only tetragonal ZrO was observed. Furthermore, only the product obtained from x equal to 0.15 was observed the presence of three-dimensional flower-like arrangements. The results obtained by the characterization techniques showed the segregation of zirconium after hydrothermal treatment of precursors with x less or equal to 0.50. Thus, we describe the important role that Ti/Zr molar ratio of the precursor plays on the morphology and crystalline phase of the products formed by hydrothermal treatment. [ABSTRACT FROM AUTHOR]

Eighteen Ce0.76Zr0.24O2 samples have been prepared by different procedures and characterised by N2 adsorption at –196 °C, XRD, Raman spectroscopy, H2-TPR and XPS. The catalytic activity for soot combustion depends both on the BET surface area and on the Ce/Zr atomic surface ratio, which strongly depends on the preparation procedure. [ABSTRACT FROM AUTHOR]

Eighteen Ce0.76Zr0.24O2 samples have been prepared by different procedures and characterised by N2 adsorption at –196 °C, XRD, Raman spectroscopy, H2-TPR and XPS. The catalytic activity for soot combustion depends both on the BET surface area and on the Ce/Zr atomic surface ratio, which strongly depends on the preparation procedure. [ABSTRACT FROM AUTHOR]

A series of Al–Zr mixed oxides with different molar ratios was prepared by coprecipitation method and characterized by N2 physiorption, XRD, NH3-TPD and CO2-TPD. Solid solution is formed in the mixed oxides. And the composition of the mixed oxides has significant influence on their acid–base properties. The catalysts were examined with glucose reaction in hot compressed water at 180 °C. The prepared oxides exhibit very good catalytic activity and glucose conversion can be increased from 46.6 to 85%. The products distribution is related with the acid–base property of the oxide. [ABSTRACT FROM AUTHOR]

The catalytic activity of Pd-supported catalysts over Ce0.39Zr0.61O x/SiO2 was studied by using methane combustion reaction. UV–visible and TPR results showed the presence of large PdO particles. CO/Pd ratio decreased with the increase of metal load. The light-off temperatures indicated that high Pd loading favored the reaction. The reduction treatment decreased the activity suggesting loss of the active phase. [ABSTRACT FROM AUTHOR]

The catalytic activity of Pd-supported catalysts over Ce0.39Zr0.61O x/SiO2 was studied by using methane combustion reaction. UV–visible and TPR results showed the presence of large PdO particles. CO/Pd ratio decreased with the increase of metal load. The light-off temperatures indicated that high Pd loading favored the reaction. The reduction treatment decreased the activity suggesting loss of the active phase. [ABSTRACT FROM AUTHOR]