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The development of efficient method for preparation of well-performed catalyst is an attractive topic in heterogeneous catalysis. Conventional route to obtaining mixed oxide catalysts is based on wet chemical methods. In the present study, a novel solid state method was proposed to fabricate NiO-CeO 2 catalyst by directly mixing metal precursors (nickel nitrate hydrate and cerium nitrate hydrate) and the subsequent calcination, omitting the common drying procedure in wet preparations. The preparation process was tracked by thermogravimetry-differential thermal analysis (TG-DTA) and obtained catalyst was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), N 2 physisorption, powder X-ray diffraction (XRD), Raman spectroscopy, H 2 temperature programmed reduction (H 2 -TPR) and tested in the model reaction of NO reduction by CO. Results showed that simultaneous decomposition of the mixed nitrates was occurred, suggesting cooperative interaction between the precursors. Moreover, in comparison with wet impregnation method, the catalyst from solid state preparation displayed not only improved textual properties (larger surface area and enriched porous structure), but also enhanced interfacial interactions between nickel and ceria, which promoted the bulk doping, surface dispersion of nickel species and the reduction of surface oxygen species. As a result, the catalytic performance in NO + CO reaction was significantly upgraded. Based on the preliminary results of this study, it is supposed the solid state preparation may open a convenient and versatile pathway to fabricate mixed oxide catalysts. [ABSTRACT FROM AUTHOR]

Ceria-based solid solutions were synthesized and used as supports to prepare MnO x /Ce 0.8 Ti 0.2 O 2 and MnO x /Ce 0.8 Sn 0.2 O 2 catalysts (Mn/CeTi and Mn/CeSn) for low temperature selective catalytic reduction of NO by NH 3 . The effects of Ti or Sn doping on the catalytic performance of MnO x /CeO 2 catalyst were investigated. Experimental results show that doping of Ti or Sn increases the NO removal efficiency of MnO x /CeO 2 . The NO conversion of Mn/CeTi catalyst is more than 90% at temperature window of 175–300 °C under a gas hour space velocity of 60,000 mL g −1 h −1 . Modified catalysts are also found to exhibit greatly improved resistance to sulfur-poisoning. Characterization results indicate that doping of Ti or Sn brings about catalysts with higher BET surface area, enhanced oxygen storage capacity and increased surface acidity. X-ray photoelectron spectroscopy (XPS) analysis of spent catalysts following SCR reaction in the presence of SO 2 verify that the loss of surface Mn species was inhibited by doping of Ti, which contributes to extend the sulfur durability. The SCR activity is considered as well to be promoted by the dual redox cycles in Mn/CeTi (Mn 4+ + Ce 3+ ↔ Mn 3+ + Ce 4+ , Ce 4+ + Ti 3+ ↔ Ce 3+ + Ti 4+ ) and Mn/CeSn (Mn 4+ + Ce 3+ ↔ Mn 3+ + Ce 4+ , 2Ce 4+ + Sn 2+ ↔ 2Ce 3+ + Sn 4+ ) catalysts. [ABSTRACT FROM AUTHOR]

Highlights: [•] CuO-CeO2/SBA-15 catalysts were prepared by a novel solid state impregnation method. [•] Both copper species and ceria can be well dispersed. [•] In comparison with wet impregnation, the solid state impregnation derived catalyst owns increased interfacial CuO-CeO2 entities and enhanced interfacial interactions. [•] CuO-CeO2/SBA-15 catalyst from solid state impregnation shows enhanced CO-PROX activity and good tolerance to CO2 and H2O. [Copyright &y& Elsevier]

Abstract: This work investigated influence of cerium modification methods (impregnation and ion-exchange) on the gold dispersion, surface chemical states, synergistic effect between gold and cerium and CO oxidation activity of Au catalysts supported on Ce modified mordenites. The supports and catalysts were characterized by XRF, ICP, XRD, N2 adsorption–desorption, UV–vis spectroscopy, HRTEM, in situ FT-IR and XPS. In general, Ce-containing Au catalysts were found to be more active in CO oxidation than the Ce-free counterpart, with the impregnation method of cerium modification being more effective than the ion exchange method. The different catalytic performance of Ce-containing catalysts was related to multiple factors: (1) the impregnation method of cerium modification was more favorable to form Au particles with smaller mean size than the ion-exchange method, due to the higher ratio of surface Lewis acid sites; (2) the interface between Au and CeO2 particles produced by impregnation method was more beneficial for the redox equilibrium of Au0 +Ce4+ ↔Au3+ +Ce3+ to shift to right to form more active Au3+ species than the interface between Au particles and Ce cations produced by ion-exchange method, which enhanced the synergistic effect between gold and cerium and the catalytic performance of CO oxidation. [Copyright &y& Elsevier]

Abstract: A series of copper-containing SBA-15 samples were successfully synthesized via evaporation-induced self-assembly route. The resulting materials were characterized by X-ray diffraction (XRD), 29Si MAS NMR spectroscopy, transmission electron microscopy (TEM), N2 sorption, inductively coupling plasma-atomic emission spectrometer (ICP-AES), thermogravimetry, and differential thermal analysis (TG–DTA), Fourier-transform infrared spectroscopy (FT-IR), UV–vis diffuse reflectance spectra (UV–vis) and X-ray photoelectron spectroscopy (XPS). The results indicated that: (1) all the samples exhibited typical hexagonal arrangement of mesoporous structure; (2) copper ions could be incorporated into the framework of SBA-15; (3) the addition of urea in the hydrothermal stage efficiently reduced the leaching of copper and improved the thermal stability of the mesoporous materials. Catalytic performances of the obtained materials were evaluated in the hydroxylation of phenol with H2O2. The catalytic tests showed that the synthesized materials exhibited high activity for this reaction and copper ions in the framework were more active than copper species in the extra-framework position. The nitric acid treatment on the samples removed the bulk CuO species, which resulted in a dramatic increase in the catalytic activity. [Copyright &y& Elsevier]

Abstract: A series of bimetallic Fe–Mo-SBA-15 materials were synthesized through direct synthetic strategy and comprehensively characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 sorption, inductively coupled plasma (ICP), thermogravimetry and differential thermal analysis (TG–DTA), Fourier-transform infrared spectroscopy (FT-IR), UV–vis spectroscopy (UV–vis), temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), in situ NH3-adsorbed FT-IR (NH3-IR) and temperature-programmed desorption of NH3 (NH3-TPD). The results indicated that: (1) all the samples exhibited typical hexagonal arrangement of mesoporous structure; (2) the incorporation of Fe could efficiently promote the incorporation/dispersion behavior of Mo in SBA-15; (3) the addition of Mo species could enhance the structural ordering of mesoporous materials. Moreover, the prepared materials were evaluated in the selective catalytic reduction (SCR) of NO with NH3. The results showed that the materials containing Fe and Mo exhibited higher catalytic activity than monometallic modified SBA-15 due to the increased intensity and quantity of surface acidity with the addition of Mo species. [Copyright &y& Elsevier]

Abstract: A family of metal oxides (Co3O4, NiO and CeO2) confined in SBA-15 with high loadings (≥20wt%) was prepared through a solvent-free method. Characterizations of X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that aggregation-free nanoparticles were obtained and N2 physisorption confirmed they were studded in mesopores. It was proposed that the intermediate molten salt phases ensured successful encapsulation and homogeneous dispersion of metal oxides. Lastly, the importance of the strategy was exemplified by NiO, and the high thermal stability together with superior performance in hydrodechlorination of chlorobenzene suggested great potential of these samples in heterogeneous catalysis. [Copyright &y& Elsevier]

[Display omitted] • The CeCoMnO x spinel-type catalyst prepared using oxalic acid precipitant has a more favorable physicochemical structure for NO conversion than that prepared using alkaline precipitant. • 400 °C is the optimum calcination temperature for oxalic acid precipitated CeCoMnO x spinel for NH 3 -SCR reaction. • The oxalic acid precipitated CeCoMnO x calcined at 400 °C has nearly 100 % NO conversion at 100–200 °C at GHSV = 15,000 mL·g−1·h−1. • An interface-enhanced redox macrocycle mechanism incorporating acid cycling is proposed for oxalic acid precipitated CeCoMnO x catalysts. CeCoMnO x spinel-type catalysts for the selective catalytic reduction of NO using NH 3 (NH 3 -SCR) are usually prepared by alkaline co-precipitation. In this paper, a series of CeCoMnO x spinel-type catalysts with different calcination temperatures were prepared by acidic oxalate co-precipitation. The physicochemical structures and NH 3 -SCR activities of the CeCoMnO x spinel-type catalysts prepared by oxalate co-precipitation and conventional ammonia co-precipitation were systematically compared. The results show that the CeCoMnO x spinel-type catalysts prepared by the oxalate precipitation method (CeCoMnO x -C) have larger specific surface area, more mesopores and surface active sites, stronger redox properties and adsorption activation properties than those prepared by the traditional ammonia co-precipitation method at 400 °C (CeCoMnO x -N-400), and thus CeCoMnO x -C have better low-temperature NH 3 -SCR performance. At the same calcination temperature of 400 °C, the NO conversion of CeCoMnO x -C-400 exceeds 89 % and approaches 100 % within the reaction temperature of 100–125 °C, which is 14.8 %-2.5 % higher than that of CeCoMnO x -N-400 at 100–125 °C. In addition, the enhanced redox and acid cycle matching mechanisms on the CeCoMnO x -C surface, as well as the enhanced monoadsorption Eley-Rideal (E-R) and double adsorption Langmuir-Hinshelwood (L-H) reaction mechanisms, are also derived from XPS and in situ DRIFTS characterization. [ABSTRACT FROM AUTHOR]

Herein, two CeO2 samples dominantly decorated with surface and bulk sulfates were constructed and their distinct effects on high-temperature NH3-SCR were investigated by strictly controlling the sulfate content at a comparable level. The obtainment of surface and bulk sulfates was revealed using a designed leaching experiment, and further evidenced by the characterization results from XPS and H2-TPR. In comparison with CeO2 modified with bulk sulfates (B-CeS), sufficient acid sites with strong intensity were generated on CeO2 modified with surface sulfates (S-CeS). In addition, due to electron-withdrawing effect from S=O in sulfate species, NH3 oxidation over S-CeS was greatly suppressed, providing an additional contribution to enhanced performance in high-temperature NH3-SCR. [ABSTRACT FROM AUTHOR]

A series of ceria modified CuO/γ-Al 2 O 3 (CuO-CeO 2 /γ-Al 2 O 3 ) catalysts were prepared via stepwise impregnation (CuCeAl-SI) and co-impregnation (CuCeAl-CI) method and tested in the model reaction of NO reduction by CO. It was found that the influence of impregnation modes on the catalytic properties of CuCeAl samples mainly lies on the control of ceria particle sizes and modulation of the distribution of various copper species. In both impregnation modes, ceria was mainly spread on γ-Al 2 O 3 as small particles while copper species were highly dispersed. A quantitative estimation of copper species was tentatively provided via a combined surface acid leaching experiment and H 2 -TPR characterization for the first time. The results showed that for CuCeAl-CI catalyst, about 55% and 25% copper species were dispersed on γ-Al 2 O 3 and nanosized ceria, respectively, while about 20% was migrated into ceria lattice during the calcination process. In contrast, in CuCeAl-SI sample, the corresponding values changed to about 25%, 70% and 5%, respectively. The synergistic effect between copper species and ceria can promote the improvement of catalytic performance, which results in higher activity of CuCeAl-SI than that of CuCeAl-CI catalyst. [ABSTRACT FROM AUTHOR]

The application of iron oxide to NH3-SCR is attractive but largely hindered by its poor acid properties, and surface sulfation is proven to be a prominent way of enhancing the acidity. As such, the method of enriching the sulfate species on iron oxide is crucial for improving the NH3-SCR performance. In the present study, by employing ammonium bisulfate (ABS) as the source of gaseous SO2 for the purpose of trapping, we reported an effective strategy for enhancing the SO42− immobilization on α-Fe2O3 catalyst via spatial confinement in a mesoporous SBA-15 framework. Interestingly, although the presence of the mesopore channel had an adverse effect on the ABS decomposition, which was expected to produce less available SO2, the measured SO42− immobilized on α-Fe2O3 in the mesoporous SBA-15 system was significantly greater than that of the regular SiO2, demonstrating the promoting effect of the spatial confinement on the SO42− enrichment. Further characterizations of the NH3-TPD, NO oxidation, and NH3-SCR performance tests proved that, as a result of the enhanced acidity, the enrichment of SO42− on α-Fe2O3 displayed a clear correlation with the SCR activity. The results of the present study provide an effective strategy for boosting the catalytic performance of iron oxide in NH3-SCR via SO42− enrichment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Quantitative analysis based on the number of active sites disclosed the reaction rates for different copper species actually followed the order of highly dispersed CuO > bulk CuO > clustered CuO. • Highly dispersed CuO was advantageous to enhance NH 3 adsorption and NO x activation via weakly bonded NO x species, which accelerated the reaction via both L-H and E-R pathways. • The presence of clustered CuO induced the formation of stable NO x species and aggravation of NH 3 oxidation. Cu-based catalysts are attractive for selective catalytic reduction of NO with NH 3 (NH 3 -SCR). However, the inherent contribution from different copper species is still elusive. Herein, by adopting a novel solvent-free preparation, CuO/SiO 2 catalysts with controlled copper species (highly dispersed CuO, clustered CuO and bulk CuO) were constructed for investigation. Evidence for the presence of distinct copper species was provided by diverse characterizations like XRD, N 2 sorption, TEM and XPS. Quantitative analysis based on the number of active sites disclosed the reaction rates for different copper species actually followed the order of highly dispersed CuO (0.19–0.3 min−1) > bulk CuO (0.14 min−1) > clustered CuO (0.03 min−1). Regarding the crucial information of activity contribution and reaction mechanism, results from NO/NH 3 -TPD, kinetics measurement and in situ DRIFTS conveyed that despite with the unique feature of more NO 2 generation, the presence of clustered CuO induced the formation of stable NO x species and aggravation of NH 3 oxidation, delivering a detrimental effect on NO conversion. As a contrast, the formation of highly dispersed CuO was advantageous to enhance NH 3 adsorption and NO x activation via weakly bonded NO x species, which accelerated the reaction via both L-H and E-R pathways. [ABSTRACT FROM AUTHOR]

Manganese oxide-based catalysts exhibit excellent low-temperature denitration efficiency, making them potential candidates for application. Herein, the relationship between reaction stability and phase structure for MnO 2 , Mn 2 O 3 and Mn 3 O 4 was disclosed. The NO conversion for Mn 2 O 3 drastically reduced after 120 h reaction, while minor decline was detected for MnO 2 and Mn 3 O 4. Based on dedicate qualitative and quantitative analyses on the deposits over catalyst surface, deactivation trigged by ammonium nitrate (AN) deposition was confirmed. Different from penta-coordinated Mn4+ on MnO 2 (110) and tri-coordinated Mn2+, penta-coordinated Mn4+ on Mn 3 O 4 (101), the unique tetra-coordinated Mn3+ on Mn 2 O 3 (200) could stabilize the nitrates and make it difficult to be removed via decomposition or reaction and accumulate continuously, which resulted in the significant deactivation. This research could not only unveil the poisoning mechanism of MnO x based catalysts, but also provide new insights into the relationship between the catalytic stability and surface Mn-O microstructure. [Display omitted] • The relationship between reaction stability and MnO x phase structure was disclosed. • The texture property and Mn valence had finite effect on reaction stability. • The ammonium nitrates (AN) deposition could induce deactivation of catalysts. • A model was proposed to describe the stability of nitrates in AN. [ABSTRACT FROM AUTHOR]

[Display omitted] This work investigated the influence of introduction methods of cerium and tin on the physicochemical properties as well as the activity and durability of titanium-based catalysts for the selective catalytic reduction of NO by NH 3 (NH 3 -SCR). Precipitation and impregnation methods were adopted to synthesize a series of cerium-tin-titanium catalysts. These catalysts were characterized by XRD, Raman, N 2 adsorption–desorption, HRTEM, EDS mapping, XPS, H 2 -TPR, NH 3 -TPD and in situ DRIFT. Notably, Ce/Sn/Ti(imp) catalyst prepared by stepwise-impregnation method could provide an interface between Ce and Sn for more facile electron transfer than Sn/Ce-Ti(co), Ce/Sn-Ti(co) and Sn/Ce/Ti(imp) catalysts. It promoted the redox equilibrium of Ce4+ + Sn2+ ↔ Ce3+ + Sn4+ shifting to right to produce adequate Ce3+ and surface adsorbed oxygen, resulting in optimal reducibility and surface acidity of Ce/Sn/Ti(imp) catalyst. Besides, the activation of NH 3 and desorption of NO x readily occurred on the surface of Ce/Sn/Ti(imp), which were favorable for the proceeding of subsequent reactions and excellent performance of NH 3 -SCR. [ABSTRACT FROM AUTHOR]

Abstract: High surface area Ti0.5Sn0.5O2 mixed oxide with rutile phase was prepared by a coprecipitation method. The surface area of Ti0.5Sn0.5O2 sample is 76.7m2 g−1, and VO x /Ti0.5Sn0.5O2 catalysts were prepared using the mixed oxide as support. Characterizations using XRD, FT-IR, LRS, EPR, UV–vis, and TEM demonstrated that vanadium oxide species are highly dispersed on the surface of Ti0.5Sn0.5O2 support when the loading amount of vanadium oxide is ≤1.5mmolV/100m2 Ti0.5Sn0.5O2. The dispersed vanadium oxide species form epitaxial-growth layer on the support. In situ FT-IR (NH3 adsorption), combined with NH3-TPD, indicate that the catalyst with vanadium loading amount of 1.5mmolV/100m2 Ti0.5Sn0.5O2, which equals to the dispersion capability, possesses a maximum amount of Brønsted acid sites. The 1.5V/Ti0.5Sn0.5O2 catalyst exhibits the best catalytic performance and good resistance to water vapor poison for the “NO+NH3 +O2” reaction, indicating that surface dispersed polymeric vanadium oxide species are the primary active species. A possible reaction mechanism is proposed on the basis of in situ FT-IR results. [Copyright &y& Elsevier]

Abstract: The present work focuses on the combination of ceria with another oxide of different ionic valences from period 3 (Mg2+, Al3+, and Si4+) using coprecipitation method, followed by calcination at 450 and 750°C, respectively. The textural, structural, morphological and redox properties of nanosized ceria–magnesia, ceria–alumina and ceria–silica mixed oxides have been investigated by means of N2 physisorption, XRD, Raman, HRTEM, DRS, FT-IR, and H2-TPR technologies. XRD results of these mixed oxides reveal that only nanocrystalline ceria (ca. 3–6nm for the 450°C calcined samples) could be observed. The grain size of ceria increases with the increasing calcination temperature from 450 to 750°C due to sintering effect. The highest specific surface area is obtained at CeO2–Al2O3 mixed oxides when calcination temperature reaches 750°C. Raman spectra display the cubic fluorite structure of ceria and the existence of oxygen vacancies, and displacement of oxygen ions from their normal lattice positions in the ceria-based mixed oxides. DRS measurements confirm that the smaller the grain size of the ceria, the higher indirect band gap energy. H2-TPR results suggest that the reductions of surface and bulk oxygen of ceria were predominant at low and high calcination temperature, respectively. Finally, CO oxidation were performed over these ceria-based mixed oxides, and the combination of CeO2–Al2O3 exhibited highest activity irrespective of calcination temperature, which may due to excellent textural/structural properties, good homogeneity, and redox abilities. [Copyright &y& Elsevier]

The introduction of WO 3 species on to FeTiO x catalysts led to the formation of Fe(3+n)+-O-W(6−n)+ and Ti(4+n)+-O-W(6−n)+ structures, increasing the ratio of chemical adsorbed oxygen, surface W-OH species, which were beneficial to the NH 3 -SCR reaction. [Display omitted] • The catalytic activity of FeTiO x was improved after the loading of WO 3 species. • The amount and strength of Brønsted acid sites was enhanced. • Fe(3+n)+-O-W(6−n)+ raised the count of chemical adsorbed oxygen, surface W-OH species. A series of WO 3 modified iron-titanate mixed metal oxides catalysts (the molar ratio of Fe/Ti = 4:1) were synthesized by conventional impregnation method and tested for selective catalytic reduction of NO x by NH 3. The addition of WO 3 species could enhance the catalytic performance of FeTiO x and 6 W/FeTiO x showed optimal activity with above 80 % NO conversion under a wide operating temperature window of 200–400 °C. It also exhibited excellent stability in the presence of H 2 O and SO 2 at 250 °C, even as low as 225 °C, which provided a suitable deNO x candidate for stationary sources. The characterization methods including XRD, BET, XPS, H 2 -TPR, NH 3 -TPD, NO-TPD and in situ DRIFTs were used to investigate the structure and surface properties of catalysts and their influence on the catalytic activity. The results demonstrated that the impregnation of WO 3 species led to the strong electronic inductive effects between Fe3+and W6+, Ti4+ and W6+ in the forms of Fe(3+n)+-O-W(6−n)+ and Ti(4+n)+-O-W(6−n)+ structures, increasing the ratio of chemical adsorbed oxygen species, surface OH-, which were stimulative to low-temperature NH 3 -SCR reaction. The increased amount of surface Brønsted acid sites mainly came from W-OH species. Besides, the reaction pathway over 6 W/FeTiO x mainly followed Eley-Rideal mechanism at 225 °C through the reaction between gaseous NO and adsorbed NH 3 species. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel effect of strong acid-redox interface hinders NH 3 -SCR activity is reported. • Three Ce 2 (SO 4) 3 -CeO 2 catalysts with distinct interfaces are constructed. • NO adsorption and oxygen vacancy formation are limited after Ce 2 (SO 4) 3 addition. • Weak interface promotes NO activation and the formation of active nitrites. The occurrence of NH 3 -SCR (selective catalytic reduction of NO with NH 3) reaction on catalyst surface typically requires acid and redox sites. However, the role of acid-redox interaction on NH 3 -SCR performance is still obscure due to complex acidities and entangled acid-redox sites. Herein, three types of model Ce 2 (SO 4) 3 -CeO 2 catalysts with distinct interfaces are constructed to reveal the effect of acid-redox interaction on NH 3 -SCR performance. That is, SO 4 2-/CeO 2 -VS (vapor sulfation of ceria) with strong acid-redox interfacial contact, SO 4 2-/CeO 2 -WI (wet impregnation), and SO 4 2-/CeO 2 -SG (solid grinding) with limited interfaces. It is found the redox property is significantly disturbed as a result of the electron-withdrawing effect from the sulfate. Theoretical result unravels that the introduction of Ce 2 (SO 4) 3 retards the oxygen vacancy formation over CeO 2. Due to restricted interfaces in SO 4 2-/CeO 2 -SG, the negative influence from acid sites is greatly alleviated. Further mechanism study discloses the weakened acid-redox interaction actually changes the nature of surface NO x species, resulting in the generation of reactive species (*O-N-O* and cis -N 2 O 2 2-) and the promotion of surface reaction via Langmuir-Hinshelwood (L-H) mechanism. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hierarchical ordered MnFe 1-δ Co δ O x ternary oxide catalysts were prepared. • Co doping can enhance the low-temperature performance of the NH 3 -SCR reaction. • The enhanced performance depends on the increased acidity and redox of Hierc-MnFe 1-δ Co δ O x. • Co doping can retard the sulfuration rates of Hierc-MnFe 1-δ Co δ O x catalysts. Manganese (Mn)-based mixed oxides are considered the most efficient catalysts for low-temperature ammonia selective catalytic reduction of nitrogen oxides (NO x) (NH 3 -SCR of NO x). Water resistance and sulfur tolerance, especially the SO 2 tolerance of Mn-based catalysts, are the main obstacles preventing their practical application. Therefore, in this study, a series of cobalt (Co)-doped MnFeO x ternary mixed oxides catalysts with a hierarchically ordered structure (Hierc-MnFe 1-δ Co δ O x , δ = 0.2, 0.4 and 0.6) were developed and applied for NH 3 -SCR of NO x at low temperature. Compared with Hierc-MnFeO x , Hierc-MnFe 1-δ Co δ O x catalyst exhibited enhanced low-temperature activity and a broadened temperature window (NO x conversion above 80% was between 90 and 343 °C over Hierc-MnFe 0.6 Co 0.4 O x), as well as better H 2 O resistance and SO 2 tolerance. The enhanced low-temperature activity was attributed to a larger amount of active oxygen species, a higher proportion of Mn4+, Fe3+ and Co3+ content, and the improvement of surface acidity, which can facilitate the adsorption and activation of NO and NH 3. Additionally, the Hierc-MnFe 0.6 Co 0.4 O x catalyst exhibited superior soot tolerance due to its special hierarchically ordered architecture. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) revealed that the Co-modified Hierc-MnFe 1-δ Co δ O x ternary oxide catalyst could efficiently protect nitrate species on Hierc-MnFe 0.6 Co 0.4 O x from the poisoning effect of SO 2 , thereby boosting its SO 2 tolerance. This study provides a good candidate for low-temperature de NO x application with enhanced SO 2 and soot tolerance. [ABSTRACT FROM AUTHOR]

A series of mesoporous alumina (MA) doped with acidic (Ti, W) or alkaline earth (Ba, Mg) elements were prepared. They were used as the supports for Pd catalysts. These catalysts were characterized by N2 sorption, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, infrared spectroscopy of CO adsorption and temperature-programmed reduction. Complete oxidation of toluene on these catalysts was tested in a fixed-bed micro-reactor. The results of in situ IR of CO adsorption indicated that the doping of basic element was beneficial for the dispersion of PdO particles, while the doping of acid element suppressed the dispersion of PdO particles. The binding energy of Pd in Pd/Ba-MA shifted to high energy, indicating that the interaction between PdO and support was enhanced. The results of H2-TPR showed that the reducibility of PdO doped with alkaline element was stronger than those of catalysts doped with acidic element. The doping of basic elements promoted the dispersion of PdO particles, changed the electronic state of Pd and enhanced the reducibility of PdO, which led to its high activity. The catalysts doped with the basic elements had higher activities than those doped with acidic elements, among which the Pd/Ba-MA catalyst had the highest activity among all catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • The immobilization efficiency of sulfate species in ABS/FeSi catalyst exhibits a distinct atmosphere-dependent feature. • ABS/FeSi-NO displays the most remarkable activity enhancement due to the accelerated depletion of NH 4 +. • NH 3 treatment inhibits ABS decomposition and results in less SO 4 2- immobilization. • NH 3 treatment brings addition effect of α-Fe 2 O 3 disintegration, which was detrimental to activity enhancement. SO 4 2- immobilization is pivotal for boosting the catalytic performance of iron oxides in NH 3 -SCR. However, the critical issue related to sulfate species enrichment on α-Fe 2 O 3 is still elusive. Herein, by employing ammonium bisulfate (ABS) as the source of SO 4 2-, we conducted a detailed investigation on the effect of reaction atmospheres (NH 3 , NO + O 2 and NH 3 + NO + O 2) on the immobilization of sulfate species and their consequence for ABS poisoned Fe 2 O 3 /SiO 2 (ABS/FeSi) catalysts in NH 3 -SCR. Results showed sulfate group could be transferred from ABS to FeSi under thermal treatment and the efficiency actually exhibited an atmosphere-dependent feature. The promotion effect from NO/O 2 was most prominent due to accelerated consumption of NH 4 +, whereas NH 3 treatment retarded ABS pyrolysis, resulting in reduced sulfate immobilization on FeSi surface. Besides, an unexpected effect on Fe 2 O 3 disintegration was exhibited by NH 3 , which was detrimental to activity enhancement due to disruption of electronic property. By correlating catalytic performance with adsorption feature, we propose the occurrence of reaction via E-R pathway over sulfated FeSi catalysts. The result of present study can enrich our understanding on the controlled sulfate immobilization for robust SCR denitration. [ABSTRACT FROM AUTHOR]

• The influence of surface configuration over FeCe/Al catalysts was studied. • The existence states and content for each coordinated FeO x species was determined. • Clustered FeO x was identified as the main active species for CO oxidation. The surface configuration of a catalyst, including the present state, coordination environment and related content of the active and additive species, has dominant effect on its physicochemical properties and catalytic performance. Herein, two types of FeCe/Al catalysts with different surface configurations, FeCe/Al-CI (co-impregnation) and FeCe/Al-SI (stepwise impregnation) were synthesized by adjusting the preparation conditions. Both catalysts together with the reference sample Fe/Al and Ce/Al were characterized by means of XRD, BET, TEM, EPR, UV–vis, Mössbauer spectra, H 2 -TPR and XPS. The results showed that (1) in both impregnation modes, ceria presented as small particles, while the iron species existed in two forms: the isolate state (tetrahedral coordination), cluster state (octahedral coordination); (2) iron species in different existence state can be characterized qualitatively or quantitatively via EPR, UV–vis and Mössbauer spectra, and the contents of FeO x clusters follows: FeCe/Al-SI < FeCe/Al-CI < Fe/Al. (3) With the help of HNO 3 leaching operation, FeO x clusters were identified as the main active species for CO oxidation. Although Fe/Al sample contained the highest concentration of active cluster FeO x species, the deficiency of Fe-O-Ce structures led to the lowest number of surface oxygen, Ce3+ and Fe2+ species, which resulted in poor CO oxidation activity for Fe/Al catalyst. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Defective LaNi 0.5 M 0.5 O 3 perovskites are synthesized by improved sol–gel method. • Doping M ions into LaNiO 3 leads to modified activity of NO + CO reaction. • The LaNi 0.5 Cu 0.5 O 3 catalyst exhibits optimized N 2 selectivity. • The improvement is attributed to surface amorphous CuO and oxygen vacancy. • The catalytic mechanism of LaNi 0.5 Cu 0.5 O 3 conforms to L-H mechanism. Abstract Catalytic removal of NO by CO has been studied over a series of LaNi 0.5 M 0.5 O 3 (M = Co, Mn, Cu) perovskite oxide catalysts were synthetized via an improved sol–gel method. The effects of M-doped on physicochemical properties of LaNiO 3 were systemic characterized by XRD, BET, SEM, ICP-AES, XPS, H 2 -TPR and O 2 -TPD techniques. The possible catalytic mechanism for NO + CO model reaction was also tentatively proposed with the help of the in situ DRIFTS technique. The M-doped samples remained pure perovskite structure and exhibited modified activity, among which the LaNi 0.5 Cu 0.5 O 3 possessed optimized catalytic performance, especially superior N 2 selectivity. It is confirmed that the amorphous CuO highly dispersed on Cu-doped defective perovskite oxide, the reduction of Cu2+ to Cu+ is vital for the chemisorption of CO, a large amount of oxygen vacancies accelerated the dissociation of NO and N 2 O. Hence, adsorbed CO can fast react with N and O at lower temperature, afterwards N 2 O was converted to N 2 fleetly, leading the improvement of activity/selectivity toward NO + CO reaction. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The addition of TiO 2 improves the physicochemical property of Mn/CZ-NR catalyst. • Catalytic activity of Mn/CZ-NR catalyst is obviously enhanced by TiO 2 modification. • TiO 2 modification can inhibit the generation of N 2 O over Mn/CZ-NR catalyst. • Mn-Ti/CZ-NR catalyst exhibits excellent H 2 O + SO 2 tolerance in NH 3 -SCR reaction. Abstract In the present work, we chose MnO x /CeO 2 -ZrO 2 nanorod (i.e. , Mn/CZ-NR) as a benchmark catalyst, and used TiO 2 as a modifier with the purpose of inhibiting the formation of N 2 O (by-product) as well as further enhancing the catalytic activity and H 2 O + SO 2 tolerance of Mn/CZ-NR catalyst. These samples were characterized by TEM, HRTEM, XRD, Raman, H 2 -TPR, XPS, NH 3 -TPD, and in situ DRIFTS. De NO x performance and H 2 O + SO 2 tolerance of these samples were evaluated by low-temperature NH 3 -SCR reaction. The obtained results show that the TiO 2 modified catalyst (i.e. , Mn-Ti/CZ-NR) exhibits higher catalytic activity than Mn/CZ-NR catalyst due to larger amount of oxygen vacancy accompanied with more Ce3+, higher ratios of Mn4+ and surface adsorbed oxygen species, as well as the improvement of surface acidity. Furthermore, TiO 2 modification effectively inhibits the non-selective oxidation of NH 3 to N 2 O through appropriately weakening the redox property of Mn/CZ-NR catalyst, which is beneficial to the enhancement of N 2 selectivity. Finally, Mn-Ti/CZ-NR catalyst exhibits excellent H 2 O + SO 2 tolerance, which indicates that it has the potential to be used for practical low-temperature de NO x application. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Ti4+ and Sn4+ co-incorporation enhanced the catalytic performance of Ce-Mn catalyst. • N 2 O formation is suppressed remarkably over Ce-Mn-Ti-Sn catalyst. • NH 3 -SCR reaction over Ce-Mn-Ti-Sn catalyst follows an L-H mechanism. Abstract A novel Ti4+ and Sn4+ co-incorporated CeO 2 -MnO x based catalyst was synthesized by an inverse co-precipitation method with the purpose of inhibiting the formation of N 2 O and enhancing the NO x conversion of CeO 2 -MnO x catalyst for NH 3 -SCR at low temperature. The obtained catalysts were characterized by a series of XRD, Raman, N 2 -physisorption, NH 3 -TPD, H 2 -TPR, XPS, and in situ DRIFTS techniques in details. The experiment results suggested that CeO 2 -MnO x -TiO 2 -SnO 2 (Ce-Mn-Ti-Sn) catalyst displayed the optimal catalytic performance with an enhancement of 30% compared with CeO 2 -MnO x (Ce-Mn) in the range of 225–275 °C. Moreover, the N 2 O formation was inhibited remarkably compared to Ce-Mn (152 ppm), and there was no N 2 O (0 ppm) detected even at 250 °C. This is linked to moderate weakening of redox property, more generation of acid sites, enhancement of acidic strength, as well as large amount of Ce3+, oxygen vacancies, and absorbed oxygen species, which are contributed to improving the chemical property of Ce-Mn-Ti-Sn catalyst, and further enhancing the catalytic performance and inhibiting the generation of N 2 O. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Sm doped CeO 2 -TiO 2 catalyst presents excellent NH 3 -SCR activity in range of 250–425 °C. • The acidity and redox property are adjusted with appropriate balance by Sm doping. • Redox cycle of Ce4++Sm2+⇌Ce3++Sm3+ is responsible for the good SO 2 tolerance. Abstract The Sm doped CeO 2 -TiO 2 mixed oxide catalyst, which exhibited excellent activity and tolerance to H 2 O and SO 2 in the NH 3 -SCR reaction, was synthesized. The reasons for the high activity and SO 2 resistance of the catalyst were investigated by a series of characterization. The H 2 -TPR and O 2 -TPD results suggested that the reducibility and oxygen storage capacity (OSC) of CeTi catalyst were promoted by the addition of Sm species, which was beneficial for improving the activity of catalyst. The in situ DRIFTS results revealed that the adsorptive ability of NO x species and activation ability of NH 3 were enhanced by Sm doping, which was also propitious to enhance the activity. XPS combined with DFT calculated results confirmed that the transfer of electron by Sm2++Ce4+⇌Sm3++Ce3+ circles occurred in the SmCeTi catalyst. The redox circles may be the reason of the good SO 2 tolerance of the SmCeTi catalyst, for which suppressed the electron transferring from adsorbed SO 2 to Ce4+. Through in situ DRIFTS and TG-DSC results, it can be concluded that the sulphation of catalyst was lowered by samarium doping into CeTi catalyst. Consequently, the SmCeTi catalyst exhibited significant SO 2 tolerance ability. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • CC systems exhibited excellent SO 2 and H 2 O tolerance at low temperature. • SO 2 was totally removed on Mn oxides bed and Al 2 O 3 buffer layer. • The deSO x process on Mn oxides was revealed. • Mn oxides were not consumed in the deSOx process. Abstract Mn-based catalysts were believed to be promoting low temperature NH 3 -SCR catalysts for their satisfactory catalytic activity, whereas their poor SO 2 and H 2 O tolerance inhibited their applications. In this work, utilizing poor SO 2 tolerance of Mn oxides, composite catalytic systems containing Mn oxides as deSO x catalyst was designed and synthesized, which exhibited excellent low temperature NH 3 -SCR performance in the presence of SO 2 and H 2 O. The deSO x mechanism of Mn oxides was systematically investigated. In results, SO 2 was catalytic oxidized on the surface of Mn oxides. Oxidized sulfur species could flow away from Mn oxides surface through feed gas flow or form MnSO 4. When NH 3 and H 2 O were introduced into the feed gas, the oxidized sulfur species were completely deposited as NH 4 HSO 4 instead of forming MnSO 4. Thus, SO 2 was removed from feed gas entirely resulting in the superb low temperature NH 3 -SCR performances. This work provided a general strategy to enhance SO 2 and H 2 O tolerance of NH 3 -SCR catalysts at low temperature by removing SO 2 using NH 3 and H 2 O who existed in the exhaust gas from stationary sources. [ABSTRACT FROM AUTHOR]

Abstract We first present preparation of MnO x –CeO 2 –Al 2 O 3 catalysts with varying Mn contents through a self-propagating high-temperature synthesis (SHS) method, and studied the application of these catalysts to the selective catalytic reduction of NO x with NH 3 (NH 3 -SCR). Using the catalyst with 18 wt.% Mn (18MnCe1Al2), 100% NO conversion was achieved at 200°C and a gas hourly space velocity of 15384 hr− 1, and the high-efficiency SCR temperature window, where NO conversion is greater than 90%, was widened to a temperature range of 150–300°C. 18MnCe1Al2 showed great resistance to SO 2 (100 ppm) and H 2 O (5%) at 200°C. The catalysts were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller (BET) analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and H 2 temperature programmed reduction. The characterization results showed that the surface atomic concentration of Mn increased with increasing Mn content, which led to synergism between Mn and Ce and improved the activity in the SCR reaction. 18MnCe1Al2 has an extensive pore structure, with a BET surface area of approximately 135.4 m2/g, a pore volume of approximately 0.16 cm3/g, and an average pore diameter of approximately 4.6 nm. The SCR reaction on 18MnCe1Al2 mainly followed the Eley-Rideal mechanism. The performances of the MnO x –CeO 2 –Al 2 O 3 catalysts were good, and because of the simplicity of the preparation process, the SHS method is applicable to their industrial-scale manufacture. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

A novel CeO 2 /TiO 2 -MoO 3 (Ce/TM) catalyst was synthesized by using of Mo as a bulk dopant to boost the NH 3 -SCR performance of CeO 2 /TiO 2 catalyst. It displayed 100% NO conversion at 200–350 °C under 60,000 mlg −1  h −1 and high tolerance to H 2 O and SO 2 at 250 °C. Characterization results manifested that the doping of Mo not only resulted in more Brønsted acid and Lewis acid sites formed on the Ce/TM surface, but also increased the specific surface area and redox ability of the catalyst, all of which account for the enhanced NH 3 -SCR activity. [ABSTRACT FROM AUTHOR]

• Three MnOx-CeO 2 catalysts with controlled surface and interfacial properties are prepared for investigation. • Strong interface between dispersed MnOx and CeO 2 does not show the best NH 3 -SCR performance. • The unique role of crystalline Mn 3 O 4 in promoting NH 3 activation is revealed. • The catalytic performance can be considerably improved by the synergistic interaction between crystalline Mn 3 O 4 and CeO 2. MnOx-CeO 2 catalysts have been widely investigated in the reaction of selective catalytic reduction of NO with NH 3 (NH 3 -SCR). However, the existence of diverse Mn species together with multiple interfaces between MnOx and CeO 2 precludes clear understanding of the synergy. Herein, by constructing MnOx-CeO 2 catalysts with controlled dispersion and interface properties, the significant promotion effect of interfacial contact between CeO 2 and crystalline Mn 3 O 4 in NH 3 -SCR was revealed. Although dispersed MnOx exhibited the combined merits of strong interaction with CeO 2 , improved textural property and abundant adsorption sites for NO/NH 3 , the catalytic performance was still not superior. With advent of Mn 3 O 4 crystallites, the NO conversion was much enhanced, demonstrating essential role of crystalline MnOx. Notably, loss of activity was also observed when apparent phase segregation between ceria and crystalline Mn 3 O 4 occurred, emphasizing the importance of Mn 3 O 4 /CeO 2 boundary. Further mechanism analyses from in situ NH 3 -DRIFTS, quantitative titration of surface NOx with NH 3 and kinetics measurement disclosed the crucial role of crystalline Mn 3 O 4 in activating NH 3 for reaction with NOx anchored on ceria, greatly boosting the catalytic performance. The result of present study enriches our understanding on the synergism between MnOx and ceria in NH 3 -SCR. [ABSTRACT FROM AUTHOR]

Understanding how H 2 O affects SO 2 tolerance of SCR catalysts at different working temperatures is of great importance. Herein, we reported that H 2 O addition at ultra-low temperature of 100 °C induced a significant promotion on SO 2 tolerance of MnO x -CeO 2 catalysts. Sole SO 2 led to serious activity loss from 100% to 20%, while H 2 O coexistence alleviated the deactivation and an admirable activity of 60% was reserved. Combining experimental characterizations with DFT calculation, we demonstrated that H 2 O promoted hydroxyl formed on defect sites, which promoted more sulfite formation and retarded sulfates with strong electron-withdrawing capacity disturbing active Mn sites. In comparison with sulfates, sulfites exhibited less interference in adsorbed species, ensuring the occurrence of Eley-Rideal and Langmuir-Hinshelwood mechanisms. The present study discloses the unique temperature-dependent effect of H 2 O on SO 2 tolerance, which is expected to deepen our understanding on the role of H 2 O in modulating surface species and catalytic behaviors of SCR catalysts. [Display omitted] • Unusual temperature-dependent H 2 O promotion effect on SO 2 tolerance of SCR catalysts was reported. • The addition of H 2 O greatly alleviated the SO 2 poisoning of MnO x -CeO 2 catalysts at ultra-low temperature of 100 °C. • Hydroxyl group derived from H 2 O disassociation restricted the electron interaction between sulfur species and Mn sites, protecting active Mn via more sulfites forming. • Sulfites showed less interference on surface active adsorbed species and ensured the occurrence of both L-H and E-R mechanism over MnCe-SO 2 +H 2 O catalyst. [ABSTRACT FROM AUTHOR]

Catalytic reduction of NO by CO was studied over a series of CuO-CoO x /γ-Al 2 O 3 catalysts prepared by co-impregnation with different copper and cobalt precursors (acetate and nitrate) to evaluate the structure–activity relationship. The obtained samples were characterized in detail by means of XRD, LRS, XPS, H 2 -TPR and in situ FT-IR technologies. Results indicate that copper oxide is agglomerated while cobalt oxide is dispersed on γ-Al 2 O 3 for the catalyst prepared from copper acetate and cobalt acetate precursors (CuACoA); Cu x Co 3-x O 4 spinel is formed and agglomerated on the catalyst prepared from copper nitrate and cobalt nitrate precursors (CuNCoN); while both copper oxide and cobalt oxide could be homogeneously dispersed for the catalyst prepared from copper nitrate and cobalt acetate precursors (CuNCoA), which exhibits the best activity for NO reduction by CO. Probably the synergistic effect between dispersed copper oxide and cobalt oxide is propitious to the oxygen transfer, which could be the reason for its high activities. Finally, a possible reaction mechanism was tentatively proposed to explore the different catalytic performances in NO reduction by CO model reaction. [ABSTRACT FROM AUTHOR]

In this work, CeO 2 nanocubes hybridized g-C 3 N 4 composites had been facilely synthesized to investigate the interfacial effects on photocatalytic water splitting. The c-CeO 2 /g-C 3 N 4 composites exhibited the superior photocatalytic hydrogen evolution under visible light irradiation. The optimal c-CeO 2 loading content was 5 wt%, with the H 2 evolution of 4300 μmol g −1 for 5 h illumination, higher than that of pristine CeO 2 , g-C 3 N 4 and irregular CeO 2 nanoparticles/g-C 3 N 4 . Moreover, UV–vis DRS, PL spectra and photoelectrochemical measurements demonstrated that 5 wt% c-CeO 2 /g-C 3 N 4 composite possessed more visible light adsorption and faster charge transfer, which was attributed to the stronger interfacial effects through the presence of the hydrogen bond and p-π hybrid between c-CeO 2 {100} and g-C 3 N 4 , revealed by the FT-IR and XPS results. The work suggested that engineering the structures of the CeO 2 and g-C 3 N 4 interface could be an effective strategy to obtain excellent photocatalysts. [ABSTRACT FROM AUTHOR]

A novel MnO x -CeO 2 nanosphere catalyst with assembled structure from tiny particles was prepared and tested towards low-temperature NH 3 -SCR. A superior deNO x performance compared to that obtained over the catalyst composed of MnO x supported on CeO 2 was obtained. A good resistance to high space velocity and SO 2 present in the feed and an excellent stability (no deactivation was observed during 100-h of testing at 150 °C) were obtained. The characterization results suggested that the higher specific surface area, better redox behavior and larger concentration of surface active oxygen species were responsible for the above mentioned excellent performance. The results of the present study suggest that control of catalyst morphology can be an effective strategy to upgrade low-temperature NH 3 -SCR performance. [ABSTRACT FROM AUTHOR]

A series of ultra-low content copper-modified TiO 2 /CeO 2 catalysts were prepared by wet impregnation method and tested for selective catalytic reduction of NO by NH 3 . The catalyst with a Cu/Ce molar ratio of 0.005 showed the best low-temperature activity and excellent sulfur-poisoning resistance. It was worth noting that the very small amounts of copper addition can lead to three times the activity at low temperature. The prepared catalysts were characterized by XRD, BET, Raman, XPS, NH 3 -TPD and the results revealed that the introduction of copper increased the amount of surface adsorbed oxygen and Ce 3+ species on the catalyst surface and generated more Brønsted acid sites. The redox and surface acidic properties were also improved by the addition of Cu. All these factors played important roles in enhancing NH 3 -SCR performance of TiO 2 -CuO/CeO 2 catalysts. Furthermore, in situ DRIFT experiments demonstrated that Cu doping enhanced the adsorption capacity of NH 3 while the appearance of CuO weakened the adsorption ability of bridging nitrates, both the two factors synergistically facilitated the NH 3 -SCR reaction proceed smoothly via the Eley-Rideal pathway. [ABSTRACT FROM AUTHOR]

Water tolerance is an important topic for low temperature NH 3 -SCR, because of the inevitable deactivation of the catalyst in the presence of water. In this work, it was found that by depositing trace SiO 2 onto the surface of Mn 0.2 Ti 0.8 O 2 catalyst, the catalysts displayed enhanced water-tolerance with no compromise of its initial activity. Furthermore, NH 3 -TPD, H 2 -TPR, and XPS results indicated that deposition of SiO 2 tuned the pore sizes of the catalysts without modifying their chemical properties, and controlled the inherent capillarity property that led to the improved anti-water performance. This result sheds light on the rational design of NH 3 -SCR catalysts with enhanced water-tolerance. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel hybrid strategy is employed to design catalysts with superior K resistance. • The main reason for CeMn deactivation is cut-off of L-H mechanism resulting from the formation of stable nitrates. • The addition of ZSM-5 can re-activate the inert nitrates. • Alkali metals poisoned catalysts can be regenerated by ZSM-5 hybridization. The application of cerium-manganese oxides (CeMn) in controlling exhaust gas from biomass combustion is greatly inhibited due to poor resistance to alkali metals. Herein, we report a smart strategy to circumvent the K poisoning problem of CeMn by physically coupling with ZSM-5, which exhibited almost no activity loss even under a high loading of 2 wt % K 2 O. Results showed that in contrast to the conventionally believed disturbance of redox property and reduction of acid sites, the dominant effect from K loading on the deactivation of CeMn catalysts lies on the formation of chemically inert nitrates, which significantly restrains the reaction cycle via Langmuir-Hinshelwood route. With ZSM-5 hybridization, the stable nitrates over CeMn can be facilely activated and consumed by NH 4 + species introduced by ZSM-5, thus transforming poisoning sites into active sites and ensuring superior catalytic performance. The study presenting here not only provides an efficient strategy for fabricating NH 3 -SCR catalysts with superior K resistance but also sheds new light on the deactivation mechanism of K over CeMn catalysts. [ABSTRACT FROM AUTHOR]

In this work, Cu 2 O–reduced graphene oxide (rGO) composites were synthesized with tunable Cu 2 O crystal facets ({1 1 1}, {1 1 0} and {1 0 0} facets). The degradation performance of methylene blue under visible light was ranked: o-Cu 2 O{1 1 1}–rGO > d-Cu 2 O{1 1 0}–rGO > c-Cu 2 O{1 0 0}–rGO. UV–vis diffuse reflectance and photoluminescence spectra showed that o-Cu 2 O–rGO exhibited the enhanced visible-light absorption and the faster charge-transfer rate. Furthermore, X-ray photoelectron spectroscopy and Raman characterizations showed that o-Cu 2 O–rGO was beneficial for the stabilization of Cu + species and the formation of oxygen defects. With the help of in-situ electron spin resonance (ESR), more superoxide radicals were detected over o-Cu 2 O–rGO, which promoted organic pollutants degradation. The above results confirmed that the catalytic behaviors of three Cu 2 O–rGO composites were related to the electronic structures and interfacial connections. The o-Cu 2 O{1 1 1}–rGO displayed the superior performance, for the highly-active coordinated unsaturated Cu and the intensive interfacial connection, which was beneficial for the rapid the photo-generated electron transfer and the formed active superoxide species. This study showed that engineering the interfacial structures could provide a scientific basis for the design of efficient photo-catalysts. [ABSTRACT FROM AUTHOR]

Ti x Sn 1 − x O 2 mixed oxides were synthesized by the coprecipitation method. CuO/Ti x Sn 1 − x O 2 catalysts were then prepared by wetness impregnation of the mixed oxides with Cu(NO 3 ) 2 . These catalysts were characterized using X-ray diffraction (XRD), laser Raman spectroscopy (LRS), H 2 -temperature-programmed reduction (TPR), O 2 -temperature-programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), and in situ Fourier transform infrared (FT-IR) techniques. The activities of the catalysts during CO oxidation were evaluated. The following observations were made: (1) CuO species can be highly dispersed on the Ti x Sn 1 − x O 2 supports, such that several surface Cu + ions and oxygen vacancies are formed. (2) Among the prepared catalysts, the 5CuO/Ti 0.75 Sn 0.25 O 2 -600 °C catalyst exhibits the highest reducing property, which arises from the difference in electronegativity between Ti and Sn. (3) The CO species can adsorb on Cu + and O 2 on the oxygen vacancy, which forms O 2 − species. The in situ FT-IR results show that the Cu + –(CO) 2 species and O 2 − adsorbed on the catalyst play a key role in CO oxidation. (4) The resistance of the catalysts to H 2 O is related to the Brunauer–Emmett–Teller (BET) surface area and the H 2 O adsorption on the catalyst surface. Furthermore, a possible reaction mechanism is tentatively proposed to understand this reaction. [ABSTRACT FROM AUTHOR]

A series of FeMnTiO x mixed oxides catalysts, which were synthesized by a CTAB-assisted co-precipitation process and calcined at different temperatures, were investigated for selective catalytic reduction of NO with NH 3 in the presence of excess O 2 . The samples were characterized by means of N 2 -physisorption, XRD, TEM, H 2 -TPR, XPS, NH 3 -TPD, and in situ DRIFTS technologies. The results indicated that the activities of samples were not predominately determined by BET specific surface area. Compared with amorphous TiO 2 , the anatase TiO 2 crystalline phase was more conducive to enhance the electron interaction between manganese species and support: Mn 4+ + Ti 3+ ↔ Mn 3+ + Ti 4+ ·NH 3 was easier to be activated on the surface of samples which had lower binding energy of lattice oxygen in selective catalytic reduction of NO with NH 3 . The addition of CTAB not only promoted the formation of anatase TiO 2 crystalline phase and Lewis acid sites, but also improved the dispersion extent of active phase on the surface of samples. Thus, it enhanced the catalytic performance of samples. In addition, calcination temperature had an important influence on the valence state of manganese species, as well as the dispersion extent of active phase and the crystal phase structure of support. The sample calcined at 400 °C showed excellent low-temperature activity and mid-temperature N 2 selectivity. The NO conversion and N 2 selectivity of this sample were above 90% in the range of 150–350 °C at a space velocity of 30,000 mL g −1 h −1 . Furthermore, it exhibited sulfur tolerance and water resistance to a certain extent. [ABSTRACT FROM AUTHOR]

In this work, Cu 2 O rhombic dodecahedrons {1 1 0}, octahedrons {1 1 1} and cubes {1 0 0} were synthesized to study the crystal-plane effects on surfaces and catalytic properties in NO + CO reaction. TPR results demonstrated the reducibility was ranked by {1 1 0} > {1 1 1} > {1 0 0}. Interestingly, the activity order in NO + CO reaction was well consistent with the reducibility order. Moreover, the in-situ formed metallic Cu nanoparticles affected by Cu 2 O exposed crystal planes were found on surfaces during the process. In-situ diffuse reflectance infrared Fourier transform spectra (DRIFTS) studies revealed that the Mars van Krevelen mechanism worked in this system and the adsorption/dissociation of NO was the key step. Dodecahedral Cu 2 O {1 1 0} with better reducibility was more sensitive to the NO + CO reaction, and the generated interface between Cu 0 and Cu 2 O{1 1 0} was beneficial to the effective decomposition of adsorbed NO species. This work provided the scientific basis over Cu-based catalysts. [ABSTRACT FROM AUTHOR]

A series of inverse TiO 2 /CeO 2 catalysts were prepared by the impregnation method and their catalytic performances for the selective catalytic reduction of NO by NH 3 have been tested with and without SO 2 and/or H 2 O. Compared with the normally discussed CeO 2 /TiO 2 catalyst, the advantage of inverse TiO 2 /CeO 2 catalyst was not only shown a good low temperature catalytic activity (150–250 °C), but also exhibited much better SO 2 resistance performances with the existence of 200 ppm SO 2 and/or 5 vol.% H 2 O at 300 °C. Furthermore, SO 2 had more significant inhibitory effect on catalytic activity than H 2 O based on the configuration differences of Ce–Ti-based catalysts. These catalysts were investigated by means of TG-DTA, XRD, BET, in situ DRIFT, XPS and H 2 -TPR. The results demonstrated that the sulfation of these samples under reactive conditions mainly generated three different kinds of sulfate species including NH 4 HSO 4 , surface and bulk-like metal sulfates (mainly interacted with cerium species). The formed metal sulfates blocked the active sites of Ce–O–Ti and resulted in the deactivation of CeO 2 /TiO 2 . Although metal sulfates were also formed over TiO 2 /CeO 2 , NH 3 -SCR could still proceed and that was similar as the reaction system with the use of sulfated CeO 2 as the catalyst. Meanwhile, the interactions between SO 2 and Ce–Ti-based catalysts were discussed in detail and an adsorption model of SO 2 was proposed. [ABSTRACT FROM AUTHOR]

FeMnTiOx mixed oxide is prepared by the CTAB-assisted co-precipitation method, and the transformation of anatase into rutile is inhibited by CTAB to some extent. The catalyst obtained in the present work shows nearly 100% NO conversion at 100–350 °C, more than 80% N2 selectivity at 75–200 °C, and excellent H2O durability for the selective catalytic reduction of NO by NH3 with a space velocity of 30 000 mL g−1 h−1. [ABSTRACT FROM AUTHOR]

Abstract: Acetic acid (HAc) aqueous was used as solvent in wetness impregnation to prepare CeO2-modified γ-Al2O3 support. With the help of HAc, the dispersion of CeO2 on γ-Al2O3 is significantly improved and the size of CeO2 nanoparticles can be controlled through tuning the concentration of HAc aqueous. XPS analysis shows that the percentages of Ce3+ in CeO2 nanoparticles will vary with the size. Then we load CuO on the as-prepared CeO2-modified γ-Al2O3 support and choose NO reduction with CO as a probe reaction to investigate the influences of impregnation solvent on the catalytic properties. The results demonstrate that the CuO/CeO2/γ-Al2O3 prepared in the solvent with volume ratio of 20:1 (H2O:HAc) has the highest activity in NO+CO reaction. Combing the structural characterizations and catalytic performances, we think that the size of the CeO2 nanoparticles should be a key factor that affects the activities of CuO/CeO2/γ-Al2O3. Furthermore, CuO dispersed on CeO2 nanoparticles with an average size of ca. 5nm should be the highest active sites for NO+CO reaction. [Copyright &y& Elsevier]

Highlights: [•] Ce4+ has been successfully incorporated into the lattice of anatase TiO2 to form uniform Ti0.95Ce0.05O2 solid solution. [•] The coordination status of Cu2+ in CuO/Ti0.95Ce0.05O2 catalyst is an unstable distorted octahedral coordination structure. [•] The redox cycles of Cu2+ +Ce3+ ↔Cu+ +Ce4+ and Cu2+ +Ti3+ ↔Cu+ +Ti4+ may be established in CuO/Ti0.95Ce0.05O2 catalyst. [•] Lewis acid site plays an important role in NO+NH3 +O2 model reaction. [ABSTRACT FROM AUTHOR]

Highlights: [•] Sn4+ can be incorporated into the lattice of CeO2 to form uniform Ce x Sn1–x O2 solid solution when the mole ratio of Ce:Sn is not less than 2:1. [•] The incorporation of Sn4+ into the lattice of CeO2 is conducive to the decrease of crystallite size, the increase of lattice strain and the improvement of reduction behavior, which further promote the enhancement of catalytic performance. [•] The catalytic domain (CD, -Ce3+-□-Sn2+- species) in these Ce x Sn1–x O2 mixed oxides plays a key role in NO reduction by CO model reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Research progress on ABS poisoning NH 3 -SCR catalysts are comprehensively reviewed for the first time. • General characterization methods for ABS on catalysts are collected. • Reported strategies for controlling ABS formation and decomposition are presented. • Future effort on addressing the problem of ABS poisoning is prospected. The urgent need for the treatment of flue gas from non-electric industries has stimulated great interest in developing NH 3 -SCR (selective catalytic reduction of NO with NH 3) catalysts that can work stably at low temperatures (< 300 °C). However, the performance of low-temperature NH 3 -SCR catalysts is expected to be largely hindered by surface accumulation of ammonium bisulfate (ABS), which inclines to induce significant deactivation of NH 3 -SCR catalysts due to active sites blocking. As such, how to solve the problem of ABS poisoning becomes a timely research topic. Herein, we focus on the recent progress on controlling ABS deposition/decomposition during the NH 3 -SCR process for sustainable denitration. The review starts with a brief introduction on physicochemical properties of ABS, then the common methods used for qualitative and quantitative analysis of ABS on catalyst surface are introduced. Afterwards, recent developed strategies on restraining ABS formation and accelerating ABS decomposition are reviewed. Lastly, some suggestions for the future study of ABS poisoning are prospected. We hope that this review can provide helpful guidance for designing NH 3 -SCR catalysts with great tolerance to ABS poisoning. [ABSTRACT FROM AUTHOR]

Abstract: A series of ceria-based solid solutions (Ce0.67Zr0.33O2, Ce0.67Sn0.33O2, Ce0.67Ti0.33O2) were synthesized by inverse co-precipitation, and then used as supports to prepare CuO/Ce0.67M0.33O2 (M=Zr4+, Sn4+, Ti4+) catalysts through wetness impregnation method. The obtained samples were investigated in detail by means of XRD, LRS, N2-physisorption, H2-TPR, XRF, XPS and in situ FT-IR techniques. The catalytic reduction of NO by CO as a model reaction was chosen to evaluate the catalytic performance of these samples. These results suggest that: (1) the reduction of CuO/Ce0.67Zr0.33O2 is easier than CuO/Ce0.67Sn0.33O2 and CuO/Ce0.67Ti0.33O2 catalysts, which may be attributed to the difference in the electronegativity of dopant; (2) the reduced state Cu+ is present in CuO/Ce0.67Zr0.33O2 at ambient temperature due to the shifting of redox equilibrium (Cu2+ +Ce3+ ↔ Cu+ +Ce4+) to right; (3) the adsorbed NO species on CuO/Ce0.67Zr0.33O2 are more liable to desorb/transform/decompose than those on CuO/Ce0.67Sn0.33O2 and CuO/Ce0.67Ti0.33O2 samples. The results of catalytic performance show that Cu+/Cu0 species play a key role in NO reduction by CO, and the activity is mainly related to the electronegativity of dopant, the reduction and adsorption behaviors of these catalysts. Furthermore, a possible reaction mechanism (schematic diagram) is tentatively proposed to understand this reaction. [Copyright &y& Elsevier]

Abstract: This work investigated the effects of cerium precursors [Ce(NO3)3 and (NH4)2Ce(NO3)6] on the structure, surface state, reducibility and CO oxidation activity of mesoporous CuO-CeO2 catalysts. The catalysts were characterized by TG–DTA, XRD, LRS, N2 adsorption–desorption, HRTEM, XPS, H2-TPR and in situ FT-IR. The obtained results suggested that the precursors exerted a great influence on the properties of CuO-CeO2 catalysts: (1) compared with the catalysts from Ce(III) precursor, the derived Ce(IV) precursor catalysts showed smaller grain size, higher BET surface area, narrower pore size distribution, whereas their reducibility and activities were not enhanced. (2) In contrast, the catalysts from Ce(III) precursor without excellent texture displayed high reducibility and activities for CO oxidation due to the high content of Ce3+, following the redox equilibrium of Cu2+ +Ce3+ ↔Cu+ +Ce4+ shifting to right to form more stable Cu+ species, which was the origin of synergistic effect. The synergistic effect between copper and cerium was the predominant contributor to the improved catalytic activities of CuO-CeO2 catalysts, instead of structural properties. [Copyright &y& Elsevier]

Abstract: Titania hollow spheres were synthesized via the styrene-methyl methacrylate copolymer (PSMMA) spheres as templates in conjunction with the sol–gel method without any surfactant or polyelectrolyte. Uniform TiO2 hollow spheres were made up of loosely aggregated anatase-phase nanoparticles. Compared to TiO2 nanoparticles (NPs), TiO2 hollow spheres exhibited a higher photocatalytic activity for the degradation of methyl orange (MO), which may be attributed to their larger specific surface area, more abundant porous structure and larger band-gap energy. In addition, the hollow spheres catalysts can be recycled. [Copyright &y& Elsevier]