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Nanocrystalline materials with the composition of (Cu0.5Ni0.5)yFe3−yO4 and a spinel structure were synthesized by the auto-combustion sol–gel method. The materials were characterized by powder X-ray diffraction, Mössbauer spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and N2 physisorption. A decrease in the unit cell parameter and increase in the crystallite size with a decrease in the copper and nickel content in ferrites were evidenced. Mössbauer analysis determined that iron ions are in the 3+ states in all compositions. Transmission electron microscopy showed that synthesized ferrite materials consisted of nanoparticles with narrow size distributions. The catalytic properties of synthesized ferrites were studied in the reaction of ethyl acetate oxidation and methanol decomposition. The conversion of ethyl acetate and CO2 selectivity increased with temperature, and this effect was most pronounced for (Cu0.5Ni0.5)0.5Fe2.5O4, for which the main part of the particles possessed sizes below 10 nm, and the mean diameter was calculated to be 4.3 nm. The catalytic activity in the reaction of methanol decomposition was the highest for (Cu0.5Ni0.5)0.25Fe2.75O4, and it decreased with the increase in Cu and Ni content in the samples. The analysis of the samples after the catalytic test indicated significant reduction transformations within the catalysts. Under the reaction medium, the spinel phase decomposed through the formation of Hägg carbide. [ABSTRACT FROM AUTHOR]

Pt nanoparticles and a CeMnOx composite were loaded on the surface of the natural diatomite material to generate the Pt/CeMnOx/diatomite using the redox precipitation and impregnation methods. The physicochemical properties of the catalysts were characterized by means of various techniques. The catalytic properties and resistance to H2O and SO2 of the catalysts were measured for the oxidation of typical volatile organic compounds (i.e., toluene and ethyl acetate). Among all of the as-prepared samples, Pt/CeMnOx/diatomite exhibited the highest catalytic activity: the temperatures (T90%) at a toluene or ethyl acetate conversion of 90% were 230 and 210 °C at a space velocity (SV) of 20,000 mL g−1 h−1, respectively, and the turnover frequency (TOFPt) at 220 °C was 1.04 μmol/(gcat s) for ethyl acetate oxidation and 1.56 μmol/(gcat s) for toluene oxidation. In particular, this sample showed a superior catalytic activity for ethyl acetate oxidation at low temperatures, with its T50% being 185 °C at SV = 20,000 mL g−1 h−1. In addition, the Pt/CeMnOx/diatomite sample possessed good sulfur dioxide resistance during the toluene oxidation process. In the presence of SO2, some of the SO2 molecules were adsorbed on diatomite, which protected the active sites from being poisoned by SO2 to a certain extent. The pathways of ethyl acetate and toluene oxidation over Pt/CeMnOx/diatomite or Pt/CeMnOx were as follows: The C–C and C–O bonds in ethyl acetate are first broken to form the CH3CH2O* and CH3CO* species or toluene is first oxidized to benzaldehyde and benzoic acid, and all of these intermediates are then converted to CO2 and H2O. This work can provide a strategy to develop efficient catalysts with high catalytic activity, durability, low cost, and easy availability under actual working conditions. [ABSTRACT FROM AUTHOR]

The development of efficient and stable catalysts is of great importance for the elimination of volatile organic pollutants (VOCs). In this work, AuPdx nanoparticles (NPs) were loaded on TiO2 through the electrostatic adsorption approach to generate the yAuPdx/TiO2 (i.e., 0.35AuPd0.46/TiO2, 0.34AuPd2.09/TiO2, and 0.37AuPd2.72/TiO2; x and y are Pd/Au molar ratio and AuPdx loading, respectively; x = 0.46–2.72; and y = 0.34–0.37 wt%) catalysts, and their catalytic activities for the oxidation of ethyl acetate were determined. The results showed that the 0.37AuPd2.72/TiO2 sample exhibited the best activity (T50% = 217 °C and T90% = 239 °C at SV = 40,000 mL/(g h), Ea = 37 kJ/mol, specific reaction rate at 220 °C = 113.8 µmol/(gPd s), and turnover frequency (TOFNoble metal) at 220 °C = 109.7 × 10−3 s−1). The high catalytic performance of the 0.37AuPd2.72/TiO2 sample was attributed to the good dispersion of AuPd2.72 NPs, the strong redox ability, the large ethyl acetate adsorption capacity, and the strong interaction between AuPdx and TiO2. Acetaldehyde, ethanol, and acetic acid are the main intermediates in the oxidation of ethyl acetate, and the loading of AuPdx NPs effectively reduces the formation of the toxic by-product acetaldehyde. The oxidation of ethyl acetate over the 0.34AuPd2.09/TiO2 sample might occur via the pathway of ethyl acetate → ethanol → acetic acid → acetate → CO2 and H2O. We believe that the obtained results may provide a useful idea for the design of bimetallic catalysts under industrial conditions and for understanding the VOCs oxidation mechanisms. [ABSTRACT FROM AUTHOR]

Nanocrystalline materials with the composition of (Cu0.5Ni0.5)yFe3−yO4 and a spinel structure were synthesized by the auto-combustion sol–gel method. The materials were characterized by powder X-ray diffraction, Mössbauer spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and N2 physisorption. A decrease in the unit cell parameter and increase in the crystallite size with a decrease in the copper and nickel content in ferrites were evidenced. Mössbauer analysis determined that iron ions are in the 3+ states in all compositions. Transmission electron microscopy showed that synthesized ferrite materials consisted of nanoparticles with narrow size distributions. The catalytic properties of synthesized ferrites were studied in the reaction of ethyl acetate oxidation and methanol decomposition. The conversion of ethyl acetate and CO2 selectivity increased with temperature, and this effect was most pronounced for (Cu0.5Ni0.5)0.5Fe2.5O4, for which the main part of the particles possessed sizes below 10 nm, and the mean diameter was calculated to be 4.3 nm. The catalytic activity in the reaction of methanol decomposition was the highest for (Cu0.5Ni0.5)0.25Fe2.75O4, and it decreased with the increase in Cu and Ni content in the samples. The analysis of the samples after the catalytic test indicated significant reduction transformations within the catalysts. Under the reaction medium, the spinel phase decomposed through the formation of Hägg carbide.

This study is focused on the design control of Cu–Zr–Ti oxide composites by the variation of the Zr/Ti ratio and the copper deposition procedure used. For the first time, these ternary composites were obtained by a combination of template-assisted hydrothermal techniques for the preparation of mesoporous ZrO2–TiO2 mixed oxides with diverse compositions, followed by the consecutive chemisorption and hydrolysis of copper ammonia complexes on them. The nitrogen physisorption, XRD, SEM, HRTEM, TPR, XPS, UV-Vis, and Raman spectroscopies were applied for the catalysts' characterization. Methanol decomposition and the total oxidation of ethyl acetate, both of which with potential for sustainable environmental protection, were used as catalytic tests. The complex relationship between the phase composition, structure, and morphology of titania–zirconia mixed oxides and the state and catalytic behavior of the copper oxide species supported on them was investigated. In comparison with the conventional impregnation technique, the novel preparation procedure revealed the generation of more uniform and homogeneously dispersed needle-like copper oxide crystallites in the mesoporous TiO2–ZrO2 host matrix, which typically ensure improved catalytic performance. The synergistic activity between the loaded copper species and TiO2–ZrO2 support was discussed. All ternary composites exhibited superior catalytic activity in total oxidation of ethyl acetate. The specific behavior of the catalysts in methanol decomposition was related to the irreversible phase transformations by the influence of the reaction medium. [ABSTRACT FROM AUTHOR]

The octahedral molecular sieve (OMS-2)-supported Ag samples were prepared by the pre-incorporation, ion exchange, and polyvinyl alcohol (PVA)-protecting methods, respectively. The XRD, TEM, BET, H2-TPR, O2-TPD, and FT-IR techniques were used to investigate effects of the preparation method on physicochemical property of the samples, over which oxidation of ethyl acetate and formaldehyde was used as probe reactions. It is found that catalytic activity was dependent on physicochemical property of the sample, and decreased in the order of Ag/OMS-2-PI > Ag/OMS-2-IE > Ag/OMS-2-PVA > OMS-2. The Ag/OMS-2-PI sample performed the best: the T90 for ethyl acetate and formaldehyde oxidation was 200 and 170 °C, respectively. The Ag species in Ag/OMS-2-PI were uniformly distributed in the pores and channels of the OMS-2 support. The characterization results indicate that the outstanding catalytic activity of Ag/OMS-2-PI was due to its high surface Mn3+ and adsorbed oxygen species concentrations, good low-temperature reducibility, and the largest surface area. [ABSTRACT FROM AUTHOR]

Materials with nominal composition Cu0.5Ni0.5Fe2O4 were prepared by sol-gel auto-combustion technique using corresponding metal nitrates and citric acid as complexating agent/fuel agent. Different ratios between citric acid and metal ions were used to control the combustion reaction. For comparison, Cu0.5Ni0.5Fe2O4 ferrite was also synthesised by co-precipitation. Mössbauer spectroscopy was used for analysis of synthesised samples both at room temperature and liquid nitrogen boiling temperature. Iron distribution in tetrahedral and octahedral positions of spinel lattice was determined. Different degrees of agglomeration of the ferrite phase were estimated by super-paramagnetic behaviour of samples. In addition, methods of X-Ray Diffraction, UV-Vis, FTIR, nitrogen physisorption, TPR with hydrogen were applied for structural characterization of the materials. Some quantities of secondary phases (Cu, Cu-Ni alloy and hematite) were found out in samples prepared by auto-combustion method. The catalytic activities of the samples in ethyl acetate oxidation reaction strongly depended on the variations in the structural and texture characteristics of the samples. The sample synthesized at the highest ratio of citric acid to metal ions is characterized by the smallest ferrite crystallite size, the higher surface area and the best catalytic activity. [ABSTRACT FROM AUTHOR]

• MnO x -CeO 2 catalyst was successfully synthesized by sacrificial template method. • MOF-derived catalyst exhibited the best ethyl acetate catalytic activity. • Frankel-type oxygen vacancies are the active sites in ethyl acetate oxidation. • MOF-derived catalyst has higher oxygen vacancies recovery potential. Industrial volatile organic compounds (VOCs) are harmful to the environment and human health. Catalytic oxidation is the most effective method for end-of-pipe control. The challenges of VOC catalytic oxidation are the high space velocities and low oxidation temperatures. In this work, Mn cations were introduced into Ce-BTC supports by an impregnation method, after which the mixture was calcined. The as-synthesized CeO 2 -supported Mn catalyst MnO x -CeO 2 -s exhibited an outstanding activity for ethyl acetate (EtOAc) catalytic oxidation, which reached complete conversion at 210 °C (T 99 = 210 °C), even at a high space velocity (WHSV = 60,000 mL g−1 h−1). With in situ UV Raman and other characterization methods, the Frankel oxygen vacancy (F-OV) was determined to be the crucial active site for EtOAc catalytic oxidation. The excellent low temperature activity of MnO x -CeO 2 -s benefited from the enhanced F-OVs concentration. The high temperature stability was attributed to the stable F-OVs recovery potential of the Ce-BTC-derived CeO 2 support. The durability at a high space velocity was the result of the unique crossed channel structure inherited from Ce-BTC. These findings unraveled the crucial role of F-OVs in the EtOAc catalytic oxidation and the value of MOF-derived materials, which highlighted a feasible approach for the design of VOC-removal catalysts. [ABSTRACT FROM AUTHOR]

Abstract A series of titania-tin oxide binary nanosized mesoporous materials with various composition were successfully obtained by template assisted hydrothermal technique. They were characterized by nitrogen physisorption, XRD, TEM, XPS, UV-Vis, FTIR of adsorbed pyridine and Raman spectroscopes. The reduction properties of the composites were studied by TPR with hydrogen. Two environmental feasible processes, such as total oxidation of ethyl acetate as representative VOCs and decomposition of methanol as hydrogen source, which are also sensitive both to the surface and redox properties of the solids, were used as catalytic tests. On the base of detailed analyses of the data from the complex physicochemical study and comparison with the reference samples, obtained by homogeneous precipitation with urea, a possible mechanism of the formation of TiO 2 -SnO 2 binary materials was proposed and discussed in a view of catalyst design control. Graphical abstract Image 1 Highlights • Template assisted hydrothermal vs urea precipitation methods for SnO 2 -TiO 2 preparation. • Improved dispersion and surface area, but low specific catalytic activity of SnO 2 -TiO 2. • Possible mechanism of SnO 2 -TiO 2 formation and application for catalysts design control. [ABSTRACT FROM AUTHOR]

Template assisted hydrothermal and homogeneous precipitation with urea techniques were used for the preparation of TiO 2 -ZrO 2 binary oxides with wide range variation of their composition. Low temperature nitrogen physisorption, XRD, SEM, HRTEM, XPS, UV–vis, FTIR, FTIR of adsorbed pyridine and Raman spectroscopy were used for the characterization of the obtained samples. Their catalytic properties were tested in total oxidation of ethyl acetate as a representative VOCs and methanol decomposition as hydrogen carrier. It was established that the template assisted hydrothermal technique provoked preparation of materials with good crystallinity, high BET surface area and well developed mesoporous structure, while the homogeneous precipitation with urea method facilitated the formation of more highly dispersed in wide Zr/Ti region samples. The degree of incorporation of Zr 4+ ions into titania lattice could be controlled by the samples composition and the preparation method used, which revealed good opportunity for effective and simple regulation of their catalytic properties. [ABSTRACT FROM AUTHOR]

Schematic. Possible synergistic mechanism of CuO and Cu-O-Ce structures. [Display omitted] • A modified impregnation method to synthesize CuO/CeO 2 catalysts was developed. • The synergy between the Cu-O-Ce and the CuO species is vital for catalytic oxidation. • The roles of CuO species and Cu-O-Ce in the catalytic oxidation reaction were distinguished. • The active sites and the structure–activity relationship were proposed. The impregnation method is one of the most popular methods for preparing various types of supported catalysts. However, the preparation of highly active catalysts by the conventional impregnation method is still a great challenge. In this paper, a modified impregnation method (MI) was developed to prepare CuO/CeO 2 catalysts for the catalytic oxidation of ethyl acetate (EA). It was found that the 5 %CuO/CeO 2 catalyst (5-MI-500) prepared by MI method achieves 100% EA conversion at a low temperature of 200 °C. However, the temperature for 100% EA conversion over the 5 %CuO/CeO 2 catalyst prepared by the conventional method is as high as 300 °C. Notably, the 5-MI-500 catalyst exhibits the highest proportion of well-dispersed CuO and Cu-O-Ce structures, which synergistically enhance catalyst activity. The well-dispersed CuO particles enhance the redox ability of the catalyst, while the Cu-O-Ce structure provides high activated oxygen via oxygen vacancy and better thermal stability during catalytic reaction. Accordingly, the possible reaction mechanism over the 5-MI-500 catalyst for EA oxidation was proposed. This study demonstrates that the MI method reported in this paper can provide a feasible methodology to prepare highly active catalysts with unique structures. [ABSTRACT FROM AUTHOR]

Cobalt-cerium mixed oxides were prepared by the wet impregnation method and evaluated for volatile organic compounds (VOCs) abatement, using ethyl acetate (EtAc) as model molecule. The impact of Co content on the physicochemical characteristics of catalysts and EtAc conversion was investigated. The materials were characterized by various techniques, including N 2 adsorption at −196 °C, scanning electron microscopy (SEM), X-ray diffraction (XRD), H 2 -temperature programmed reduction (H 2 -TPR) and X-ray photoelectron spectroscopy (XPS) to reveal the structure–activity relationship. The obtained results showed the superiority of mixed oxides compared to bare CeO 2 and Co 3 O 4 , demonstrating a synergistic effect. The optimum oxidation performance was achieved with the sample containing 20 wt.% Co (Co/Ce atomic ratio of ca. 0.75), in which complete conversion of EtAc was attained at 260 °C. In contrast, temperatures above 300 °C were required to achieve 100% conversion over the single oxides. Notably, a strong relationship between both the: (i) relative population, and (ii) facile reduction of lattice oxygen with the ethyl acetate oxidation activity was found, highlighting the key role of loosely bound oxygen species on VOCs oxidation. A synergistic Co-Ce interaction can be accounted for the enhanced reducibility of mixed oxides, linked with the increased mobility of lattice oxygen. [ABSTRACT FROM AUTHOR]

[Display omitted] • Highly efficient catalytic ethyl acetate abatement are achieved on La-doped OMS-2 even with IR illumination. • La-doping dramatically promotes catalytic performance of OMS-2. • A novel photoactivation is discovered to substantially promote catalytic performance. • The origin of the La-doping-induced catalytic promotion and photoactivation is revealed. La-doped manganese oxide catalysts with nanorod morphology, cryptomelane octahedral molecular sieve structure (OMS-2) and La/Mn atomic ratios of 0.0045, 0.0097, and 0.0459 (denoted as La-OMS-2-A, La-OMS-2-B, and La-OMS-2-C) were synthesized with the reaction among KMnO 4 , La(NO 3) 3 , and Mn(NO 3) 2 at 90 °C. They were used for photothermocatalytic oxidation of ethyl acetate (typical organic pollutant) merely with UV–visible-infrared (UV–vis-IR) illumination. An appropriate amount of La doping was found to dramatically enhance photothermocatalytic activity and diminish the selectivity of more toxic by-product acetaldehyde. The optimal La-OMS-2-B demonstrated exceptionally large photothermocatalytic activity, low acetaldehyde selectivity, and good catalytic stability. Within initial five minutes, its CO 2 formation rate (r CO2) was exceptionally high (1362.0 μmol g−1 min−1), a 67-fold increase as compared to pure OMS-2, while its acetaldehyde selectivity was very low (1.9%), a 37-fold decrease as compared to pure OMS-2. Even with λ > 830 nm IR illumination, it still possessed good photothermocatalytic performance. The photothermocatalytic oxidation abided by a light-driven thermocatalysis mechanism. The dramatic catalytic enhancement by the La-doping arose from a considerable promoted thermocatalytic activity due to the oxygen activity of OMS-2 being substantially improved with La-doping. A photoactivation on La-OMS-2-B, quite unlike photocatalysis on semiconductor photocatalysts, was discovered that further substantially improved catalytic activity and decreased acetaldehyde selectivity due to the oxygen activity of OMS-2 being considerably promoted with UV–vis-IR illumination. [ABSTRACT FROM AUTHOR]

A synthetic strategy for Co -MOF-74-derived Co 3 O 4 -based materials (polyhedral prism, hexagonal-prism spindle and prism-assembly 3D microspheres with different surface dense degrees) with atomic p-n homojunctions were proposed by introducing a dual-ligand (2,5-dihydroxyterephthalic acid and 2-methylimidazole) approach in the hydrothermal process. Among these Co 3 O 4 -based catalysts, the Co 3 O 4 -M-3 catalyst with 3D prism-assembly microsphere exhibited the greatest photothermal catalytic activity for ethyl acetate oxidation (around 92%) under the visible-IR light intensity of 480 mW/cm2 (λ > 420 nm). The smart modulation of dual-ligand approach could effectively improve the oxygen storage capacity, abundant oxygen vacancies and outstanding reductive ability over the Co 3 O 4 -M-3 catalyst. In addition, Mott-Schottky plot characterization verified the formation of p-n homojunction over the Co 3 O 4 -M-3, and its suitable energy band level and Z -scheme charge transfer pathway effectively improved visible-light absorption capacity, accelerated charge pairs transportation and restrained photogenerated electron-hole recombination. Finally, in situ DRIFTS results demonstrated that the adsorbed oxygen and lattice oxygen would participate in the photothermal catalytic reaction. Ethanol and acetic acid were considered as a main reaction pathway, whereas methyl ethyl ketone as no-critical intermediate was generated in the strict condition with exclusive active lattice oxygen of catalyst and light irradiation. [Display omitted] • 3D Co-MOF-74-derived Co 3 O 4 -based materials with atomic p-n homojunctions were synthesized by introducing a dual-ligand strategy. • Z -scheme charge transfer pathway effectively charge pairs transportation and restrained photogenerated electron-hole recombination. • DRIFTS revealed that adsorbed oxygen and lattice oxygen would participate in the photothermal catalytic reaction. • Methyl ethyl ketone was generated in the strict condition with both exclusive active lattice oxygen of catalyst and light irradiation. [ABSTRACT FROM AUTHOR]

High surface area mesoporous ceria-titania binary materials with high Lewis acidity and improved reduction properties were synthesized using template assisted hydrothermal technique. The obtained materials were characterized by low temperature nitrogen physisorption, XRD, SEM, TEM, Raman, UV–vis, XPS, FTIR, FTIR of adsorbed pyridine and thermo-programmed reduction with hydrogen. Their catalytic activity was tested in total oxidation of ethyl acetate and methanol decomposition to CO and hydrogen with a potential application in VOCs elimination and alternative fuels, respectively. The structural changes in the binary materials, which could be tuned by the variation in the Ce/Ti ratio and the temperature of hydrothermal treatment, provoked significant changes in their textural, surface and redox properties, which is in close relation to the catalytic activity and selectivity in various catalytic processes. The intimate contact between the individual oxides results in the formation of different catalytic active sites and their role in the studied catalytic reactions was discussed in details. [ABSTRACT FROM AUTHOR]

Different lanthanide (Ln)-doped cerium oxides (Ce0.5Ln0.5O1.75, where Ln: Gd, La, Pr, Nd, Sm) were loaded with Cu (20 wt. %) and used as catalysts for the oxidation of ethyl acetate (EtOAc), a common volatile organic compound (VOC). For comparison, both Cu-free (Ce-Ln) and supported Cu (Cu/Ce-Ln) samples were characterized by N2 adsorption at −196 °C, scanning/transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and temperature programmed reduction in H2. The following activity sequence, in terms of EtOAc conversion, was found for bare supports: CeO2 ≈ Ce0.5Pr0.5O1.75 > Ce0.5Sm0.5O1.75 > Ce0.5Gd0.5O1.75 > Ce0.5Nd0.5O1.75 > Ce0.5La0.5O1.75. Cu addition improved the catalytic performance, without affecting the activity order. The best catalytic performance was obtained for Cu/CeO2 and Cu/Ce0.5Pr0.5O1.75 samples, both achieving complete EtOAc conversion below ca. 290 °C. A strong correlation was revealed between the catalytic performance and the redox properties of the samples, in terms of reducibility and lattice oxygen availability. Νo particular correlation between the VOC oxidation performance and textural characteristics was found. The obtained results can be explained in terms of a Mars-van Krevelen type redox mechanism involving the participation of weakly bound (easily reduced) lattice oxygen and its consequent replenishment by gas phase oxygen. [ABSTRACT FROM AUTHOR]

A series of CeO 2 –CoO x nanocatalysts have been synthesized by a facile surfactant-free hydrothermal method and investigated for the oxidative degradation of ethyl acetate (EA) at exceptionally low temperature. The combination of various techniques, such as H 2 -TPR, XRD, XPS and HRTEM provides insights to the effect of various factors including redox properties, enhanced lattice oxygen and its mobility etc . on catalysis performance. The results demonstrate that the enriched lattice oxygen is the dominant factor for the low-temperature degradation of EA due to the interaction between lattice-mixed Ce and Co ions, which can be used to design the catalysts for removing VOCs with improved performance. [ABSTRACT FROM AUTHOR]

Two series of ceria–zirconia mixed oxide samples with wide variation in the composition were synthesized using homogeneous precipitation with urea and template-assisted hydrothermal procedures. The samples were characterized by nitrogen physisorption, XRD, SEM, Raman, XPS, UV–vis, FTIR, pyridine-FTIR and TPR techniques. The catalytic activity in ethyl acetate total oxidation as a representative of VOCs was tested. The effect of preparation procedure on the texture, structure, morphology, acidic and redox properties was discussed in details in close relation with mixed oxides composition and possibilities for fine tuning of their catalytic activity. As compared to urea procedure, the hydrothermal treatment provides more homogeneous insertion of Zr ions within cubic ceria lattice even at high Zr content. As a result higher degree of distortion of the cubic lattice, creation of Ce 3+ and oxygen vacancies and an increase in both Lewis acidity and redox ability is observed and these properties are not affected by the presence of template during the synthesis. The differences in the redox and surface acidic properties of both series of materials probably promote the realization of the catalytic process by various reaction pathways and thus influence in a complex way the catalytic activity and selectivity. [ABSTRACT FROM AUTHOR]

The layered manganese oxide (δ -MnO 2)-supported reduced graphene oxide (rGO)-promoted silver catalysts (x Ag− y rGO/ δ -MnO 2 ; x and y are the Ag and rGO contents (wt%), respectively) were prepared via a polyvinyl alcohol-protected reduction route. Physicochemical properties of these materials were determined using the numerous techniques, and their catalytic activities were evaluated for the oxidation of CO and ethyl acetate. It is found that the loading of rGO as an electron transfer promoter could significantly strengthen the metal−support interaction (SMSI) between Ag and δ -MnO 2 and increase specific surface area of the sample, hence improving catalytic performance of the sample. Activity evaluation reveals that 1Ag− 1.0rGO/ δ -MnO 2 showed the best catalytic activity and the lowest apparent activation energy (E a), giving a T 90% of 140 °C and an E a of 42.7 kJ/mol for CO oxidation, and a T 90% of 160 °C and an E a of 39.8 kJ/mol for ethyl acetate oxidation at space velocity (SV) = 60,000 mL/(g h). The good performance of 1Ag− 1.0rGO/ δ -MnO 2 was associated with its high Mn3+/Mn4+ or O ads /O latt molar ratio, good low-temperature reducibility, and strong SMSI between Ag and δ -MnO 2. The in situ DRIFTS characterization demonstrates that the carbonate and acetate species were the main intermediate products in CO and ethyl acetate oxidation over 1Ag− 1.0rGO/ δ -MnO 2 , respectively. The 1Ag− 1.0rGO/ δ -MnO 2 sample was not significantly altered in physicochemical property after 55 h of stability test, but its activity decreased in the presence of water vapor, especially such an effect on ethyl acetate oxidation was more obvious, which was possibly due to the competitive adsorption of water and reactants on the catalyst surface. Our present research work promotes the technological innovation and progress in the highly efficient elimination of industrially emitted CO and VOCs, which is of important theoretical and practical significance. Therefore, such an exciting work is worthy for publication in your journal, and is of general interest to readerships from different disciplines and those working in the related fields including but not limited to environmental science, catalysis, and nanotechnology. [Display omitted] • Reduced graphene oxide (rGO)-promoted Ag/ δ -MnO 2 catalysts are prepared using the PVA-protected reduction method. • rGO loading promotes the effective electron transfer and favors the increases in O ads and Mn3+ concentrations. • Loading of rGO significantly improves the catalytic activity of Ag/ δ -MnO 2 for CO and ethyl acetate oxidation. • 1Ag− 1.0rGO/ δ -MnO 2 exhibits good catalytic stability and moisture resistance. [ABSTRACT FROM AUTHOR]

A series of copper and manganese oxides modified SBA-15 mesoporous silicas with different composition was prepared by incipient wetness impregnation with the corresponding nitrate precursors and compared with the analogous materials supported on conventional SiO. Nitrogen physisorption, XDR, FTIR, UV-Vis and temperature programmed reduction with hydrogen were used for samples characterization. Their catalytic activity was tested in ethyl acetate oxidation and methanol decomposition. The ordered porous structure of the support facilitates the interaction between different metal oxide nanoparticles and increases their dispersion due to the formation of mixed oxide phase. The ethyl acetate oxidation on SBA-15 binary materials is suppressed due to the lower accessibility of the metal oxide particles, located deeply into the micro-meso pores of the support. The reaction medium which forms during the methanol decomposition provides the reduction/decomposition transformations with the mixed oxide phase. The final phase composition of finely dispersed Cu/CuO and MnO particles stabilizes in a highly dispersed state into the porous matrix of SBA-15 support and increases the catalytic activity in methanol decomposition due to the appearance of synergistic effect between them. [ABSTRACT FROM AUTHOR]

Highlights: [•] Copper–ceria interaction promotes the formation of highly active catalysts. [•] Different model of active sites formation on silica support. [•] Supported bi-component catalysts exhibit high activity even at low Cu/Ce ratio. [ABSTRACT FROM AUTHOR]

Abstract: The use of austenitic stainless steel (AISI 304) as metallic substrate for catalytic devices is explored in this work as well as an alternative procedure to the washcoating of the active phase. Catalyst deposition on austenitic stainless steel takes advantage of the manganese concentration of this alloy by direct growing of the new catalytic phase on the monolith surface during the synthesis. Manganese oxide (OMS) is chosen as active phase and VOC abatement by total oxidation as catalytic test. It is possible to coat metallic monoliths by growing the catalytic phase, manganese oxide (OMS), in situ during the reflux synthesis of cryptomelane. This preparation strategy needs a proper metal surface modification but is possible to deposit a large amount of catalyst in a very adherent form. The metallic coating shows similar adherences to those found using Fecralloy substrates even thought, in the case of the monolith prepared by repeated washcoating on AISI 304, new phases seem to be produced showing quite higher activity in total oxidation of ethyl acetate. [Copyright &y& Elsevier]

Abstract: The catalytic behavior of two mixed-valence borates was studied in ethyl acetate oxidation in respect to their different electronic structure. The studied compounds ferroferriborate (Fe3BO5) and magnesium ferroferriborate (Fe2MgBO5) are members of a solid solution series, which allows to synthesize samples with different mixed valence ions content. A number of methods, such as XRD, ISP, krypton adsorption, XPS and Moessbauer spectroscopy are used for sample characterisation. The catalytic experiments, as well as in situ Moessbauer investigation of the studied oxides in the course of ethyl acetate oxidation are also performed. It is established that ferroferriborate having higher mixed valence cations content shows higher catalytic activity. It is observed, that electron exchange (EE) in mixed valence metal oxide catalyst provides optimal conditions for ethyl acetate total oxidation. However, in respect to the observed selectivity against by-products formation, the electron delocalization (ED) should be located in a limited range. A partial oxidation of iron ions in the studied compounds, mainly in their surface, is observed after catalytic tests. [Copyright &y& Elsevier]

The deactivation of alumina supported platinum and iron catalysts by hexamethyldisiloxane (HMDS) exposure has been investigated. Three catalysts (Pt/Al2O3, Fe/Al2O3 and Fe/Pt/Al2O3) were prepared and the influence of short- and long-term deactivation on the activity for oxidation of ethyl acetate was studied. The catalysts were characterized using BET, ICP-AES, XPS, SEM and CO chemisorption. The deactivation was found to proceed by deposition of silicon-species in form of silicate (SixOy) that block the active sites on the surface of the catalysts. The silicon seems to rather attach to platinum and iron sites than to the alumina surface. The Pt/Al2O3 catalyst was moderately deactivated by HMDS even though the silicate was blocking almost the entire platinum surface. Adding iron to the catalyst increased the tolerance towards HMDS as fewer Pt sites were blocked for the Fe/Pt/Al2O3 sample. The deactivation of the two platinum containing samples was reversible since the silicate could partly be removed from the Pt sites by regeneration whereby most of the activity was restored. However, for the Fe/Al2O3 sample the deactivation was more severe and irreversible. [Copyright &y& Elsevier]

[Display omitted] • A series of transition metal cordierite-based monolithic catalysts were prepared. • Mn/Al 2 O 3 /COR shows excellent ethyl acetate (EA) oxidation activity and water resistance. • Surface oxygen species (O β) play vital roles in EA activation and intermediate generation. • Low content water vapor (≤1 vol%) promotes EA activation and ethanol formation. • Water vapor leads to the decline of O β and formation of large-size hard coke. The reduction and control of VOCs from anthropogenic sources becomes a research hotspot due to their tremendous environment hazards. Fabricating efficient and applicable noble-metal-free monolithic catalysts is still a great challenge for industrial VOC economical removal. In this work, cordierite-based honeycomb monolithic catalysts (M/Al 2 O 3 /COR; M = Cr, Mn, Fe, Co, Ni and Cu) were synthesized by a versatile and scalable wash-coating method and adopted for ethyl acetate (EA) catalytic oxidation. Mn/Al 2 O 3 /COR possesses remarkable activity with 90% of ethyl acetate (EA) oxidized at 236 °C owing to abundant surface active oxygen species. Moreover, excellent stability and water resistance of Mn/Al 2 O 3 /COR were observed during long-term successive reaction. In situ DRIFTS results reveal that the decomposition of EA to ethanol is the main pathway under humid conditions, and the presence of low content water vapor (≤1 vol%) promotes EA conversion ascribed to the presence of abundant OH derived from H 2 O dissociation; however, further increasing of water concentration inhibits EA conversion. The adsorption of OH over oxygen vacancies inhibits the generation of surface oxygen species and blocks further oxidation of intermediates to form acetate, leading to the reduction of CO 2 yield and formation of coke aggregates. This work will provide instructive and feasible references for designing of VOC oxidation catalysts under practical reaction conditions. [ABSTRACT FROM AUTHOR]

The Ni-loaded cryptomelane-type manganese oxide octahedral molecular sieve (OMS-2) catalysts (xNi/OMS-2: x = 1, 3, 5, and 10 wt%) were prepared by a pre-incorporation method. Physicochemical properties of the as-synthesized materials were characterized by means of various techniques, and their catalytic activities for CO, ethyl acetate, and toluene oxidation were evaluated.The loading of Ni played an important role in improving physicochemical propertiesof OMS-2. Among all of the samples, 5Ni/OMS-2 exhibited the best catalytic activity, with the T90 being 155 °C for CO oxidation at a space velocity (SV) of 60,000 mL/(g·h), 225 °C for ethyl acetate oxidation at an SV of 240,000 mL/(g·h), and 300 °C for toluene oxidation at an SV of 240,000 mL/(g·h), which was due to its high Mn3+ content and Oads concentration, good low-temperature reducibility and lattice oxygen mobility, and strong interaction between the Ni species and the OMS-2 support. In addition, catalytic mechanisms of the oxidation of three pollutants over 5Ni/OMS-2 were also studied. The oxidation of CO, ethyl acetate, and toluene over the catalysts took place first via the activated adsorption, then intermediates formation, and finally complete conversion of the formed intermediates to CO2 and H2O. [ABSTRACT FROM AUTHOR]

• CuO-CeO2-TiO2 catalyst with superior activity in VOCs elimination and methanol decomposition. • Finely dispersed CuO and "conjugated" Ti-Ce-Cu centres ensures the catalytic activity • The mechanism of the formation of the interface layer is controlled by preparation procedure used. Hydrothermally obtained mesoporous ceria-titania mixed oxides with different composition are modified with copper using incipient wetness impregnation and "chemisorption-hydrolysis" techniques. Their catalytic properties in methanol decomposition as a source of hydrogen and total oxidation of ethyl acetate as representative volatile organic pollutant are investigated. The effect of support composition and modification method on the formation of catalytic active sites is studied. The obtained results show that the catalytic behavior is determined by the activity of finely dispersed CuO crystallites and facile electron transfer in the "conjugated" Ti Ce Cu redox centres in the interface layer. The mechanism of the formation of the interface layer and the growth of CuO crystallites during different modification procedures are discussed in details. The mesoporous Cu Ce Ti oxides demonstrate excellent catalytic activity in total oxidation of ethyl acetate. Their catalytic behavior in methanol decomposition is strongly influenced by the reductive transformations, which are provoked by the reaction medium. [ABSTRACT FROM AUTHOR]

A series of mesoporous cerium-iron binary oxides was prepared by a hydrothermal technique using CTAB as a template. The influence of the Fe/Ce ratio and the variations in the preparation techniques such as the type of solvent and the precipitation agent, the approach of the template release, and the temperature of calcination on the phase composition, textural, structural, surface, and redox properties of the obtained materials was studied in details by XRD, nitrogen physisorption, TPR, FTIR, UV-vis, XPS, Raman, and Moessbauer spectroscopies. The materials were tested as catalysts in methanol decomposition and total oxidation of ethyl acetate. It was assumed that the binary materials represented a complex mixture of differently substituted ceria- and hematite-like phases. Critical assessment of their formation on the base of a common mechanism scheme was proposed. This scheme declares the key role of the formation of shared Ce-O-Fe structures by insertion of Fe 3+ in the ceria lattice and further competitive compensation of the lattice charge balance by the existing in the system ions, which could be controlled by the Fe/Ce ratio and the hydrothermal synthesis procedure used. This mechanism provides proper understanding and regulation of the catalytic behavior of cerium-iron oxide composites in methanol decomposition with a potential for hydrogen production and total oxidation of ethyl acetate as a model of VOCs.