Search

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]

In this work, TiO2 (B) nano-belts were synthesized by hydrothermal method under stirring, and static conditions and preparation conditions were optimized. The prepared materials were characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), photoluminescence spectroscopy (PL), and N2 adsorption/desorption measurement. The photocatalytic performance was evaluated by removing synthetic estrogen 17α-ethynylestradiol (EE2), which is the most potent endocrine-disrupting chemical. The results show that the TiO2 nano-belt possesses pure metastable monoclinic TiO2 (B) and has uniform nano-belt shape with 80~120-nm diameters and 62.904 m2 g−1 of specific surface area. Under the best optimal preparation conditions (0.5 g P25, 20 mL 10 mol L−1 NaOH, hydrothermal temperature 180 °C for 18 h under stirring, 400 °C calcination for 2 h), the TiO2 (B) has better catalytic activity with 100.00% removal rate towards 3 mg L−1 EE2 in 120 min. The removal rates of EE2 over catalyst which was prepared under static condition and P25 are 74.66% and 70.71%, respectively. The photocatalytic degradation rate constant of TiO2 (B) prepared under stirring condition (0.0379 min−1) is 4.51 times and 8.42 times than those of TiO2 prepared under static condition (0.0084 min−1) and P25 (0.0045 min−1). The excellent photocatalytic activity is mainly ascribed to longer one-dimensional nano-belt structure and effective suppression of photo-produced electron-hole. [ABSTRACT FROM AUTHOR]

A copper-catalyzed condensation reaction of oxime acetates and α,β-unsaturated ketimines to give pyridine derivatives is reported. The reaction features mild conditions, high functional-group compatibility, and high regioselectivity with respect to unsymmetrical oxime acetates, thus allowing the preparation of a wide range of polysubstituted pyridines, many of which are not readily accessible by conventional condensation methods. [ABSTRACT FROM AUTHOR]

Developing cost-effective, but efficient and stable trifunctional catalysts synchronously for oxygen reduction (ORR), oxygen evolution (OER) and hydrogen evolution reaction (HER) under same electrolytes is essential for the real application of renewable energy systems. Herein, we report the synthesis of a cheap and high-efficiency electro-catalyst based on Co 9 S 8 nanoparticles decorated with Co-N-C sites well anchored to metal-porous organic polymer (MPOP)-derived N, S-codoped carbon (Co-IM-POP-1000), which exhibits pronounced trifunctional electrocatalytic activity for ORR, OER and HER, simultaneously, in alkaline media. Consequently, breathing Zn–air batteries (ZABs) employing Co-IM-POP-1000 as the sole catalysts present prominent performance, i. e., the charge/discharge voltage, power and energy density, specific capacity, rate performance as well as the lifetime, outperforming that of Pt/C 20% + RuO 2 counterparts, which could be regenerated and maintained at the same performance level for subsequent runs by simply replenishing the Zn anode and electrolyte. An alkaline water splitting system using the IM-POP-Co-1000 as catalyst for overall water splitting affords a cell voltage as low as 1.60 V at 10 mA cm−2. A self-driven water splitting system powered by the home-made ZABs is demonstrated using IM-POP-Co-1000 as the sole catalyst in 0.1 M KOH, giving a high H 2 evolution rate of 0.244 mmol h−1. These novel metal-POPs provides an effective strategy to prepare high-performance POPs for special applications. Therefore, this study shows a promising approach for the utilization of low cost and massive producible POPs as precursor for the preparation of stable and efficient trifunctional electro-catalyst toward clear energy applications. [Display omitted] • Easily scalable metal-coordinated imidazole porous organic polymers were prepared. • IM-POP realizes the finely control of metal species and contents in porous skeleton. • IM-POP-Co was pyrolyzed to N, S-doped porous carbon with encapsulated Co 9 S 8 and CoNx. • IM-POP-Co-1000 shows excellent catalytic activity synchronously for ORR, OER and HER. [ABSTRACT FROM AUTHOR]

• The competitive adsorption between SO 2 and NO x is the main reason for the decrease of activity in low temperature. • The formation and consumption of ABS reach a dynamic equilibrium, making the negative effect on the SCR activity limited. • The accumulation of ferric sulfate species enhances the surface acidity and promotes E-R pathway, further facilitating the activity. • The higher the temperature, the more SO 4 2− accumulated, and the rapider climbing rate of the catalytic activity. SO 2 poisoning of NH 3 -SCR catalysts at low temperature (< 300 °C) is still an austere challenge. In this work, γ-Fe 2 O 3 was taken as a model catalyst and the effect of reaction temperature on the catalytic activity in the presence of SO 2 were fully revealed. SO 2 introduction has no negative effect on the activity at 300 °C, which gradually improves with the extension of time. While for 225−275 °C, the activity decreases firstly and then increases slowly. The formatted sulfate species inhibits the adsorption of NO x , cuts off L-H reaction pathway and leads to the initial decline. While the deposited ammonium bisulfate (ABS) can be consumed continuously by NO + O 2 , implying the formation and consumption of ABS have reached a dynamic equilibrium. Moreover, the formation of ferric sulfate species results in the enhancement of surface acidity, which leads to the promotion of the E-R reaction pathway and further facilitates the increase of activity. [ABSTRACT FROM AUTHOR]

Abstract: Magnetite catalysts doped by five common transition metals (Ti, Cr, Mn, Co and Ni) on a similar level were prepared by a precipitation–oxidation method and characterized by chemical analysis, XRD, TG-DSC, BET surface area and XANES. The effects of substituting metal species on the photocatalytic performance of magnetite were investigated and compared through the UV/Fenton degradation of tetrabromobisphenol A (TBBPA). The substitution of above metals improved the heterogeneous UV/Fenton degradation of TBBPA, and the improvement extent increased in the following order: Co

Highlights: [•] The •OH radicals in Fenton and UV/Fenton processes were analyzed quantitatively. [•] The substitutions affected the catalytic activity of magnetite in •OH generation. [•] Cr substituted magnetite displayed the best catalytic activity in •OH generation. [•] The relationship between •OH generation and pollutant degradation was discussed. [•] Multivariate analyses were carried out to interpret the main influence factors. [ABSTRACT FROM AUTHOR]

Abstract: Recently, growing interest has been evoked in the application of transition metal substituted magnetite as heterogeneous Fenton catalyst in the degradation of organic pollutants. In the present study, the effect of substitution on the heterogeneous Fenton catalytic activity of magnetite was investigated in interfacial view. The substitution of transition metals improved the degradation of organic pollutants by accelerating the OH free radical generation and enhancing the adsorption of pollutant and H2O2. As the octahedral sites were exclusively exposed at magnetite surface, V3+ and Cr3+ occupying the octahedral sites not only participated in H2O2 decomposition to produce OH, but also quickened the electron transfer in the inverse spinel structure to reduce Fe3+ to Fe2+ with higher Fenton activity. Ti4+ , V3+ and Cr3+ increased the specific surface area and surface hydroxyl amount of magnetite, resulting in larger adsorption of methylene blue (MB) and H2O2 and accordingly faster degradation. In Ti-V co-doped magnetite, though Ti4+ was thermodynamically unfavorable for OH generation, Ti4+ showed a more prominent effect than V3+ on improving catalytic activity of magnetite, ascribed to its more significant effect on the increase of specific surface area and surface hydroxyl amount of magnetite. The catalytic efficiency was closely related to not only the nature of substituting metals, but also the pollutant characters. Due to the different adsorption behaviors, the degradation MB and acid orange II followed different degradation mechanism and was also described by different kinetics. The above results will be benefit for the application of transition metal substituted magnetite in environmental engineering. [Copyright &y& Elsevier]