Search

Extraction of Mn from manganese oxide ore via sulfur-based reduction followed by acid leaching has received much attention. In this study, the mechanism on reducing manganese oxide ore with elemental sulfur was investigated. The reduction of manganese dioxide by sulfur is feasible thermodynamically, and the experimental validation proved that manganese dioxide was reduced stepwise to low-valence state in the order of MnO 2  → Mn 2 O 3  → Mn 3 O 4 (together with MnSO 4 or SO 2 ). Subsequently, Mn 3 O 4 would be reduced to form MnS or MnO, and the tendency of forming MnO was enhanced with increase in the temperature. Manganese oxide (MnO) will further react with excessive sulfur forming MnS and MnSO 4 . However, the formed MnS on the surface of the particles would inhibit further reduction or sulfidation. During the reductive roasting process, MnSO 4 as well as gaseous SO 2 were simultaneously generated. The reaction between MnS and Mn 3 O 4 occurred at temperatures over 500 °C, which facilitated producing MnO and SO 2 . The roasted product contained MnS, MnSO 4 , MnO and unreacted Mn 3 O 4 at lower temperature (<500 °C), whereas the main products were MnO and MnSO 4 at higher temperature (≥500 °C). The content of MnO increased gradually while that of MnS was decreased by increasing the roasting temperature. [ABSTRACT FROM AUTHOR]

Manganese oxide ore is one of the most important resources. Owing to the depletion of high-grade ores, attention has turned to low-grade ones containing multiple elements such as iron, silicon, and aluminum. Conventional processes for extracting manganese are characterized by high production costs, intensive energy consumption, heavy environmental issues, or high co-leaching of impurities. In this study, selective sulfation roasting–water leaching is proposed for recovering manganese from iron rich low-grade manganese oxide ores using SO 2 as reductant. Thermodynamic analysis indicated that manganese dioxide is readily transformed to sulfate. However, the sulfation of ferric oxide only occurs in the presence of both SO 2 and O 2 . The thermodynamic stability region for MnSO 4 and Fe 2 O 3 demonstrated selective sulfation of manganese dioxide is feasible. The experimental validation for sulfation roasting and water leaching revealed that 90.6% of manganese and only 3.5% of iron were extracted when sulfation roasting was conducted at 500 °C for 60 min with SO 2 partial pressure (SO 2 / (SO 2 + N 2 )) of 0.5%–1.0% (Vol.), and the leaching process was performed at 50 °C for 15 min with liquid-to-solid ratio of 5. This process is able to recover manganese from various low-grade manganese oxide ores. [ABSTRACT FROM AUTHOR]

Mesostructured MnOx–Cs2O–Al2O3 nanocomposites have been synthesized by reverse microemulsion method combined with hydrothermal treatment and then applied to the catalytic combustion of methane. Compared to impregnation-derived conventional MnOx/Cs2O/Com-Al2O3 catalyst, the microemulsion-derived catalyst showed higher activity and stability for methane combustion. The T10% of the fresh and of the 72 h aged MnxO–Cs2O–Al2O3 were ∼475 and 490 °C, respectively, recommending it as a potential candidate catalyst for application in hybrid gas turbines. The homogeneous composition of the microemulsion-derived nanocomposite catalyst can hinder the loss of Cs+ and accelerate the formation of Cs–β-alumina phase, ensuring thus higher activity and stability for methane combustion. [Copyright &y& Elsevier]

Recently, lattice defects (hydrogen vacancies, oxygen vacancies and nitrogen vacancies) have attracted significant attention due to their promoted activity of ammonia synthesis. Here, composites of CaBTO were prepared via treatment of Ba 5 Ta 4 O 15 –CaH 2 mixture in a flow of H 2 /N 2 at 600 °C for 16 h. It was found that the reduction of Ba 5 Ta 4 O 15 by CaH 2 significantly promoted the ammonia synthesis activity of Ru/Ba 5 Ta 4 O 15. The oxygen vacancies (O v) with trapped electrons were formed in CaBTO. Various characterizations and kinetic experiments indicated that O v donated electrons to Ru particles to promote the activation and dissociation of N 2 , and accepted the hydrogen atoms from Ru surface to suppress hydrogen poisoning. The lattice N3− and H− in CaBTO could also accept hydrogen or nitrogen atoms to form NH 3 , which provided more reaction pathways for ammonia synthesis and further improved the rate of ammonia synthesis. [Display omitted] • N3−, H− and O V were introduced in Ba 5 Ta 4 O 15 by reduction of Ba 5 Ta 4 O 15 with CaH 2. • Hydrogen poisoning of Ru species was alleviated through hydrogen spillover. • NH x (x = 1–3) species could form on the Ru surface and CaBTO600. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the non-isothermal reduction kinetics of nickel laterite with graphite was investigated under argon atmosphere. The reduction of nickel laterite was carried out at different heating rates (10, 15 and 20 K/min) and the evolved gas was detected by mass spectrometer in real time. The activation energies were determined by Kissinger-Akahira-Sunose (KAS) method and the reaction kinetics were determined by model-fitting (Coats-Redfern) method. The results showed that the reduction process can be divided into three stages according to the conversion degree (α): α = 0–0.45, α = 0.45–0.75, and α = 0.75–1.0, respectively. In the first stage, the average activation energy was 351.03 kJ/mol and the kinetic model fitted the two-dimensional diffusion function. In the second stage, the model of three-dimensional diffusion function was determined as the kinetic function and the average activation energy was 322.89 kJ/mol. In the third stage, the average activation energy was 341.45 kJ/mol and the kinetic model was in accordance with the chemical reaction function. The phase transformation as well as reaction mechanism during reduction were also analyzed which explained the reduction kinetics of nickel laterite. Graphical abstract Unlabelled Image Highlights • The non-isothermal reduction kinetics of nickel laterite with graphite was studied. • The reduction process can be divided into three stages according to the conversion degree. • The activation energy was calculated by Kissinger-Akahira-Sunose (KAS) method. • The model of reaction kinetics was determined by model-fitting (Coats-Redfern) method. [ABSTRACT FROM AUTHOR]

The radiation performance of acoustically actuated magnetoelectric (ME) antennas is originated from converse magnetoelectric (CME) effect that converts the electric field to magnetic field due to strain coupling. This paper presents a two-dimensional model for the CME effect of ME antennas with considering a fully magneto-elastic coupled characteristic of magnetostrictive materials. The nonlinear magnetostrictive relation is equivalent to a linear-like form using the equivalent parameter method. The coupled effects of magnetic bias and pre-stress on the CME coupling are discussed. The prediction for the CME coefficient shows a good agreement with the experimental data. The results indicate that pre-stress and magnetic bias have a strong-coupled effect on the CME effect. In addition, optimal loading modes are obtained for improving the CME effect. The radiations of ME antennas have not yet been obtained. Nevertheless, the results in this work may provide a basis for further investigation on the radiations. • A two-dimensional multi-field coupling model for the CME effect is proposed. • The linear-like magnetostrictive relation is derived using equivalent parameters. • The coupled effect of magnetic bias and pre-stress is discussed in detail. • The influence of the loading directions of the external stimuli is analyzed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A nanocube structure anatase-TiO 2 has been prepared by an ion exchange reaction between F- and H+. • The TiO 2 has an approximate amount of oxygen vacancies as Degussa-P25. • The surface of TiO 2 contains abundant hydroxyl to the extent that it changes the reaction pathway of CO 2 methanation. • The CO 2 conversion of Ru/TiO 2 catalyst could exceed that of Ru/Deggusa-P25 by 38% and the CH 4 formation rate of Ru/TiO 2 catalyst could exceed that of Ru/Deggusa-P25 by 35%. In the present study, an anatase-TiO 2 abundant in oxygen vacancies and hydroxyl was successfully designed and synthesized by introducing NaBH 4 , and loading Ru on it for application of CO 2 hydrogenation to CH 4. Compared with the conventional cascade of CO-mediated reactions of traditional Ru/TiO 2 , the Ru/TiO 2 we prepared changes the reaction pathway of CO 2 hydrogenation through abundant hydroxyl on the surface of underlying TiO 2. The hydroxyl was formed by ion exchange of F- in TiOF 2 and H- in NaBH 4 , and was a key factor in the CO 2 methanation activity of the Ru/TiO 2 we prepared beyond that of Ru/Deggusa-P25. The CO 2 conversion of the Ru/TiO 2 we prepared exceeded that of Ru/Deggusa-P25 by 38% and the CH 4 formation rate of the Ru/TiO 2 we prepared exceeded that of Ru/Deggusa-P25 by 35% at 300 °C. [ABSTRACT FROM AUTHOR]

• This work revealed the law of gas sulfides release during the reduction process of blast furnace raw materials. • The precipitation of sulfur during the reaction of coke and sinter in reducing atmosphere was divided into two stages. • Low temperatures favored the generation of H 2 S, while high temperatures promoted the generation of COS. Understanding the transformation behavior of sulfides in the blast furnace raw materials during the ironmaking process is crucial for controlling the form and emission of gaseous sulfides in the blast furnace top gas. This study investigates the reactions of coke and sinter at different reducing atmosphere ranging from 200 °C to 1000 °C by using of thermogravimetry and mass spectrometry (TG-MS). Additionally, thermodynamic theoretical calculations were performed to enhance the understanding of the reaction behavior. The results showed that the mixed sinter and coke started to generate H 2 S at 100 °C under the mixed H 2 -CO atmosphere and reached the peak between 350 and 400 °C. With the increase of H 2 concentration, the peak temperature of H 2 S generation initially decreased and then increased, with the lowest peak temperature observed under a 50% H 2 -50% CO atmosphere. Furthermore, COS generation started around 300 °C and reached its peak at approximately 800 °C. The peak content of COS generation increased as the CO concentration. Low temperatures favored the generation of H 2 S from the mixed sinter and coke, while high temperatures were conducive to the generation of COS. [ABSTRACT FROM AUTHOR]

• Isothermal kinetics of reduction and nitridation of ilmenite concentrate by ammonia gas is studied. • Both model–free and model–fitting methods are used to compare the isothermal kinetics. • The mechanism function and apparent activation energy of the reduction and nitridation stages are obtained. • The mechanism on reduction and nitridation is discussed. Low-temperature chlorination is considered a suitable process for ilmenite containing high contents of MgO and CaO. However, reduction carbonization or nitridation is essential to convert titanium oxide to carbide or nitride, which can be enriched by magnetic separation. In this paper, the isothermal reduction–nitridation kinetics of Panzhihua ilmenite concentrate in an ammonia atmosphere was investigated. Both model–free and model–fitting methods were used to compare the isothermal kinetics. The reaction process can be divided into two successive stages: the reduction reaction and the nitridation reaction. The average apparent activation energy for the reduction reaction was 139.63 kJ/mol, obtained by the model–free method. The reduction process can also be subdivided into two stages by the model–fitting method. The chemical reaction (G(α) = 1–(1– α)1/3 = kt) and three–dimensional diffusion (G (α) = [1–(1– α)1/3]2 = kt) were identified as the mechanism function for the reduction process. The activation energies of these two stages were 121.73 kJ/mol and 141.40 kJ/mol, respectively. The function G(α) = 1–(1– α)1/3 = kt , which also corresponds to the chemical reaction mechanism (R 3), exhibited the best fit for the nitridation stage. The corresponding activation energy was 32.10 kJ/mol. Metallic iron and Ti 3 O 5 were formed in the reduction stage, while Ti 3 O 5 was then transformed to Ti(N,O) in the nitridation stage. [ABSTRACT FROM AUTHOR]

Abstract The thermal behavior of poplar-fat coal (biomass-coal) blends and organic functional structure of formed coal-char in the co-pyrolysis temperature were investigated using Thermogravimetric analyzer, Differential scanning calorimetry, Mass spectrometry and Attenuated total reflection Fourier transform infrared spectroscopy analysis. Furthermore, the interactions between poplar and coal during co-pyrolysis were deduced. The results indicate that poplar decomposed prior to the decomposition of fat coal is not surprising, but results also indicate that the presence of poplar enhanced the thermal decomposition of fat coal at low temperature. The occurring interactions showed positive and negative effects with increasing temperature, which could be explained by chemical reaction and physical interaction, respectively. In the blends, these interactions lowered the apparent activation energy and frequency factor. The added poplar had a positive effect on decomposition of the organic functional groups. Interactions would indirectly cause higher hydrocarbon-generating potential and thermal maturity, and reduced aliphatic chains length and aromaticity. The synergistic effects between fat coal and poplar during co-pyrolysis occurred mainly at lower temperature. For the better application of poplar-fat coal blends, the suitable blending ratio of poplar to coal is below 16%. In addition, the pyrolysis temperature should be kept in 345–390 °C to obtain biomass-coal tar. Graphical abstract Image 102942 Highlights • Interactions of biomass-coal blends during co-pyrolysis were studied using TGA. • Kinetics and char structure in the co-pyrolysis temperature were evaluated. • Interactions presented positive and negative effects with increasing temperature. • Interactions lowered the apparent activation energy and frequency factor. • Interactions caused higher A -factor, C -factor and reduced CH 2 /CH 3 and A ar / A al values. [ABSTRACT FROM AUTHOR]

Abstract The reduction of metal oxides by hydrogen is a very significant reaction in metallurgical industries. Particularly, hydrogen reduction is one of the effective methods to reduce CO 2 emission in iron and steel industry. The mathematical modeling of H 2 reduction process would help to define the operating parameters and to get a better control of the reduction process. In this study, a new kinetic model regarding hydrogen reduction of metal oxides controlled by external gas diffusion has been proposed. The model has incorporated numbers of parameters such as temperature, size of the metal oxides, diffusion coefficient constant, hydrogen partial pressure, density of metal oxides and time. Furthermore, the shape of metal oxides (spherical, cylindrical, lamellar particles) was considered as well, and the models for the reduction of metal oxides with different shapes were combined to a formula. Also, the developed model can be applied to describe the reduction kinetics under both isothermal and non-isothermal conditions. Because the model is in the analytic function, therefore, it is convenient for usage and theoretical analysis. Application of the developed model to practical systems validated that its predicted values agreed very well with the experimental data. Highlights • Kinetic model for the external gas diffusion controlling reduction was proposed. • The model is in the analytic function and is convenient for theoretical analysis. • The shape of metal oxides was considered. • The models for different shapes were combined to a formula. [ABSTRACT FROM AUTHOR]

Strontium niobates with different crystalline structure and morphology have been prepared via a hydrothermal method and applied as a support for ruthenium catalyst in ammonia synthesis. The sample synthesized with a nominal Sr/Nb = 2.0, having a pure Sr 2 Nb 2 O 7 crystalline phase and specific surface area of 87 m 2  g −1 , exhibits the best performance as support for Ru catalyst. The flake-structured Sr 2 Nb 2 O 7 substrate induced epitaxial growth of truncated pyramid shaped ruthenium nanoparticles with a dispersion as high as 93%, which have abundant steps and B 5 sites playing a key role in ammonia synthesis catalysis. Adding Cs- or Ba-promoter enhanced the activity of Ru/Sr 2 Nb 2 O 7 catalyst drastically. The highest ammonia synthesis rate over 8Cs- or 4Ba-2 wt%Ru/Sr 2 Nb 2 O 7 was 4986 and 2317 (μmol g −1 cat h −1 ) at 0.1 MPa and 673 K, respectively. In addition, both catalysts were stable over reaction for 72 h at 673 K and 0.1 MPa. Thus, the synthesized Sr 2 Nb 2 O 7 is expected to be a practically promising oxide support for ruthenium ammonia synthesis catalsyts. [ABSTRACT FROM AUTHOR]

Structured catalysts and reactors have wide applications in environmental remediation and production of important energy-related chemicals. In thermal catalytic processes, external heater are often required to raise the temperature and ignite the reactions, which might lead to huge setups. Herein, we introduce a novel Joule-heat-ignition catalytic reactor. Using Fe-Cr-Al alloy as catalyst substrate, electric currents can pass directly through the substrate, generating Joule heat and bringing the catalysts to the target temperatures. Therefore, the setup can be simplified by omitting the additional heater; the heat produced inside the substrates can be transferred directly to the catalyst coat to achieve rapid ignition; and the reaction temperature can be flexibly controlled by adjusting the input power. In this work, we loaded manganese oxide catalyst onto an alloy wire and used it to build a Joule-heat-ignition reactor for the catalytic oxidation of carbon monoxide and toluene. The anodization pretreatment generated channels on the alloy surface, which effectively enhanced the catalyst loading. The use of alumina as a secondary support also favored catalyst loading and promoted catalyst dispersion. By adding proper amounts of zirconium, the mechanical stability of the catalyst layer increased. The Joule-heat-ignition catalytic system might provide some inspiration in related environmental catalysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Silica-supported nano-Fe 2 O 3 for FTS was prepared by colloidal deposition method. • Nano-Fe/silica showed higher selectivity to light olefins than impregnated catalyst. • Nano-Fe/silica exhibited significantly superior durability over impregnated catalyst. • Nano-Fe particles were geometrically favorable for coking resistance. Nano-iron catalysts exhibit good performances in the Fischer–Tropsch synthesis to lower olefins (FTO), however, there is still a lack of simple methods for their preparation. In this work, we introduced a facile colloidal deposition (CD) method to fabricate silica-supported Fe 2 O 3 nanoparticles using a colloidal solution readily prepared from ferric hydroxide. With increasing the Fe loading from 16.3 % to 31.6 %, the Fe 2 O 3 particle size increased from 1.3 to 6.1 nm. The catalytic performances in FTO were tested at a H 2 /CO molar ratio of 1. At a Fe loading of 30.4 %, the catalyst having a particle size of 4.7 nm showed the highest lower olefin selectivity and the lowest CO 2 selectivity, outperforming analogs prepared by impregnation method. Furthermore, this catalyst showed good stability in a 200-hour durability test, while the impregnated analogue quickly deactivated due to serious coking. Presumably, the effective contact areas between the nanoparticles and the generated carbon sheets are geometrically small, which results in weak van der Waals forces between them, preventing the former from being heavily covered by the latter. Besides, from the point of view of the carbide decomposition mechanism of coking, due to the relatively low volume to surface area ratios of the intermediate carbide nanoparticles, the surface concentrations of carbon atoms released from them are low, which delays the coke formation. This study may provide a simple method to fabricate supported nano-iron catalysts, and cast some light on understanding catalyst durability in FTO. [ABSTRACT FROM AUTHOR]

Wet scrubbing is a low-cost process for disposing of air pollutants. Nevertheless, this method is rarely used for the treatment of volatile organic compounds (VOCs) because of their poor water solubility. In this study, we used a unique wet scrubbing system containing H 2 O 2 and activated carbon (AC)-supported iron oxychloride (FeOCl) nanoparticles to remove airborne dichloroethane (DCE). The operating conditions of the wet scrubber were optimized, and the mechanism was explored. The results showed that the adsorption of dissolved DCE onto AC promoted its transfer from air to water, while the accumulation of DCE on AC facilitated its oxidation by •OH generated on FeOCl catalyst. The wet scrubber performed well at pH 3 and low H 2 O 2 concentrations. By pulsed or continuous dosing H 2 O 2 , the cooperative adsorption-catalytic oxidation allowed long-term DCE removal from air. Benefiting from satisfactory cost-effectiveness, avoidance of toxic byproduct formation, and less corrosion and catalyst poisoning, wet scrubbers coupled with cooperative adsorption and heterogeneous advanced oxidation processes could have broad application potentials in VOC control. [Display omitted] • FeOCl/AC was prepared by a facile calcination method. • Wet scrubber containing H 2 O 2 and FeOCl/AC was effective in dichloroethane removal. • Intermittent or continuous dosing H 2 O 2 allowed long-term VOC removal from air. • Adsorption and catalytic oxidation cooperated in the wet scrubbing process. [ABSTRACT FROM AUTHOR]

Fe-based cermets are of considerable research interest owing to their excellent physical and mechanical properties. In this study, a new process for the reduction and nitridation of Panzhihua ilmenite using NH 3 was proposed to prepare Fe-TiN composites, and the process was deemed feasible by thermodynamic calculations. The final products, Fe and TiN, could be formed based on the reaction conditions. The experimental results validated that metallic Fe could be easily formed, while MgTiO 3 was more difficult to reduce than FeTiO 3. The final products of Fe/TiN/MgO obtained at 1373–1473 K were consistent with those from the thermodynamic analysis. By increasing the reduction temperature or duration, the Fe particles increased in size and mixed with the TiN particles. The elemental content of Mg, Al, and Ca in the magnetic product was 5.85 wt% after magnetic separation. A Fe-TiN cermet was prepared from the magnetic product by hot-pressing (HP) sintering. Fe and TiN were uniformly distributed in the cermet, and the hardness of the obtained cermet reached 18.2 GPa. This work could offer a new approach to the preparation of Fe-based cermets from low-grade ilmenite. [Display omitted] • A novel method for synthesizing Fe–TiN composites from low–grade ilmenite is proposed. • Clean ammonia gas is used as reduction and nitridation agent. • The phase transformation and microstructure evolution of ilmenite during the reduction roasting process are studied. • The Fe–TiN cermet with a hardness of 18.2GPa is prepared by hot pressing (HP) sintering. [ABSTRACT FROM AUTHOR]

In the present study, CO 2 methanation with Ru nanoparticles loaded onto three TiO 2 nanocrystal supports (TiO 2 anatase with both exposed (001) facets and oxygen vacancies, TiO 2 anatase with exposed (001) facets and general TiO 2 anatase) was demonstrated. The three samples were denoted as Ar700-R, 700-R and Ana-R, respectively. XRD results confirmed that Ar700-R and 700-R sample exposed (001) facets, XPS and EPR results demonstrated the presence of oxygen vacancies on the surface of Ar700-R. In tests of CO 2 methanation activity, Ar700-R showed the highest CO 2 conversion efficiency of 75% and CH 4 formation rate of 18.84 μmol•g−1•s−1 (GHSV = was 21600 ml•h−1•g−1) at 400 °C. The enhanced CO 2 methanation activity of Ar700-R was attributed to the co-activity achieved by exposing (001) facets and oxygen vacancies on the surfaces of TiO 2 nanocrystal supports. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reduction and nitridation of V 2 O 3 with clean ammonia gas is investigated. • The phase and microstructure evolution are revealed. • A DFT study systematically reveals the adsorption of NH x and H on the V 2 O 3 (0001) surface. • The reaction route is as follows: V 2 O 3 → VN x O 1– x → VN. Vanadium nitride (VN) has a wide range of application because of its excellent properties, which include high hardness, outstanding wear resistance, and good electrical conductivity. This study investigated the mechanism for the reduction and nitridation of V 2 O 3 with clean ammonia gas, using both experimental and density functional theory (DFT) studies. The experimental results indicated that V 2 O 3 could easily be converted to VN in an ammonia atmosphere at 500–800 °C. The reaction pathway to form VN was V 2 O 3 → VN x O 1– x → VN. Increasing the reaction temperature was conducive to an increase in the N content of VN x O 1– x. A DFT study systematically revealed the adsorption of NH x and H on the V 2 O 3 (0001) surface. The results showed that with the dissociation of NH 3 , its adsorption energy on the surface of vanadium oxide became higher. The whole reaction process could be divided into NH 3 decomposition on the surface and the formation of H 2 O(g). Both of these were endothermic reactions, and the reaction step of generating H 2 O(g) needed a higher temperature. The bonding of V 3c –N facilitated the desorption of O 3c atoms to form H 2 O(g), which explained why VN can be prepared by the reaction of NH 3 and V 2 O 3. [ABSTRACT FROM AUTHOR]

• Ni-Fe hydroxides derived from the coprecipitation of Ni2+ and Fe2+ at neutral pH lead to the generation of H•. • H• effectively dechlorinate TCE producing nontoxic ethylene and ethane. • Ni-Fe hydroxides with the 3.0 Ni/Fe ratio shows the highest electron selectivity for TCE hydrodechlorination. • Density functional theory analysis revealed the hydrodechlorination mechanism. Atomic hydrogen (H•) is highly reactive for the hydrodechlorination of trichloroethylene (TCE). In this work, we found that the coprecipitation of Ni2+ and Fe2+ at neutral pH led to an unprecedented catalytic generation of H•. The generated H• effectively dechlorinate TCE to nontoxic ethylene and ethane, and Fe2+ is the only electron donor. The abundant adsorbed H• produced with a Ni/Fe ratio of 0.4 enhances hydrogen evolution reaction causing a low efficiency for hydrodechlorination. In contrast, the active absorbed H• is generated in the crystal lattice of Ni-Fe hydroxides with a Ni/Fe ratio of 3.0 causing highly efficient hydrodechlorination of TCE. This work not only reveals the mechanism of catalytic hydrodechlorination by Ni-Fe hydroxides at neutral pH, but also provides a novel approach to detoxify TCE in contaminated water using facile precipitated Ni-Fe hydroxides. [Display omitted] [ABSTRACT FROM AUTHOR]

Molten potassium hydroxide disperses catalyst particles and isolates nascent graphene sheets during catalytic graphitization process. [Display omitted] • KOH-catalyst joint treatment allows fabricating highly porous well-graphitized carbons. • Molten KOH promotes catalytic graphitization by dispersing metal catalysts. • Molten KOH prevents intensive graphene stacking by isolating neighboring sheets. • Thin graphitized flakes construct mesoporous structures. Porous graphitized carbons (PGCs), with the texture mimicking activated carbons while the framework resembling few-layer graphene, promise intriguing opportunities in versatile applications. Nonetheless, shortage of facile strategies to achieve high graphitization levels without compromising porosity remains a bottleneck. We demonstrate that various carbon precursors, including activated carbon, biomass, biochar, anthracite and synthetic polymer, can be converted to large-surface-area PGCs by joint treatment using both potassium hydroxide and a catalyst. In particular, using activated carbon as the precursor, BET surface areas exceeding 2000 m2/g can be readily achieved. Besides, joint treatment introduces mesoporosities to the products. We propose that molten potassium hydroxide can promote metal-catalyzed graphitization of carbon precursors, while preventing intensive graphene sheet stacking, forming thin graphitized flakes that construct highly porous structures. The PGCs can be used as moisture-resistant VOC adsorbents owing to their excellent hydrophobicity. The joint-treatment process can realize a scale-up fabrication of high-quality PGCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ba 5 Ta 4 O 15 was originally applied as a support of Ru catalysts for ammonia synthesis. • 3Cs-Ru/Ba 5 Ta 4 O 15 demonstrated superior activity and stability for ammonia synthesis. • Ru accepts election from reduced Ba 5 Ta 4 O 15 and Cs-promoter for N 2 activation. • The formation of NH 3 can be realized on Ba 5 Ta 4 O 15 with OVs even without Ru catalysts. Efficient ammonia synthesis is a significant but challenging target. Herein, the perovskite Ba 5 Ta 4 O 15 nanosheets were prepared as a support to rationally construct Cs modified Ru/Ba 5 Ta 4 O 15 (Cs-Ru/Ba 5 Ta 4 O 15) for this end. The Cs-Ru/Ba 5 Ta 4 O 15 catalyst exhibits high catalytic activity and stability in 72 h ammonia synthesis reaction process at 400 ℃ and 0.1 MPa. Characterizations by various physicochemical techniques reveal that Ba 5 Ta 4 O 15 can be reduced, resulting in formation of oxygen vacancies (OVs) under reaction conditions. The presence of OVs in Ba 5 Ta 4 O 15 significantly enhances the ammonia synthesis of the Ru based catalyst. The activation of N 2 and formation of NH 3 can be realized on Ba 5 Ta 4 O 15 with OVs even without Ru metals. Moreover, the kinetic experiments indicate that hydrogen poisoning is greatly inhibited through promotion of hydrogen spillover from Ru to support of Ba 5 Ta 4 O 15. Therefore, Ba 5 Ta 4 O 15 is expected to be a promising support of Ru based ammonia synthesis catalysts. [ABSTRACT FROM AUTHOR]

• OH− or e− encaged in mayenites promotes the activation of CO 2 on the supports. • The catalytic activity of Ru/C12A7:OH− is drastically higher than that of Ru/C12A7:e− and Ru/ γ -Al 2 O 3. • *CO adsorbed on Ru is the vital intermediate for methane formation and carbon deposition. • Electrons in mayenite electrides are transferred to Ru metal, thus accelerating the dissociation of *CO into *C (carbon deposition). Mayenites (C12A7) encaged with OH− or e− have been synthesized and applied as supports for ruthenium catalyst in CO 2 methanation. The catalytic activity of Ru/C12A7:OH− (TOF at 225 °C = 6.04 × 10-2 s-1, E a =70.9 kJ mol-1) is drastically higher than that of Ru/C12A7:e− (TOF at 225 °C = 2.41 × 10-2 s-1, E a =94.4 kJ mol-1) and Ru/ γ -Al 2 O 3 (TOF at 225 °C = 0.23 × 10-2 s-1, E a =105.8 kJ mol-1). It has been proposed that the OH− or e− encaged in mayenite promotes the formation of carbonates and bicarbonates from CO 2 on the supports. It is supposed that at the interface between Ru and mayenite support the surface carbonates and bicarbonates are hydrogenated into formates, which are further dissociated into *CO adsorbed on Ru. The formed *CO is the intermediate for methane formation and carbon deposition. The different anions (OH− or e−) encaged in the framework of mayenites have been found to influence drastically the ionization potential of Ru. Electrons in mayenite electrides are transferred to Ru metal, thereby enhancing the back donation from Ru to the antibonding orbitals of *CO intermediate. As a consequence, the dissociation of *CO into *C and subsequent into deposition of carbons are accelerated, which is responsible for the inferior catalytic performance of Ru/C12A7:e−. Based on the experimental results, we propose an effective technique for tailoring the catalytic performance of metallic sites supported on mayenites via changing encaged anions. [ABSTRACT FROM AUTHOR]