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Anthropogenic carbon dioxide (CO2) levels are rising to alarming concentrations in earth's atmosphere, causing adverse effects and global climate changes. In the last century, innovative research on CO2 reduction using chemical, photochemical, electrochemical and enzymatic approaches has been addressed. In particular, natural CO2 conversion serves as a model for many processes and extensive studies on microbes and enzymes regarding redox reactions involving CO2 have already been conducted. In this review we focus on the enzymatic conversion of CO2 to carbon monoxide (CO) as the chemical conversion downstream of CO production render CO particularly attractive as a key intermediate. We briefly discuss the different currently known natural autotrophic CO2 fixation pathways, focusing on the reversible reaction of CO2, two electrons and protons to CO and water, catalyzed by carbon monoxide dehydrogenases (CODHs). We then move on to classify the different type of CODHs, involved catalyzed chemical reactions and coupled metabolisms. Finally, we discuss applications of CODH enzymes in photochemical and electrochemical cells to harness CO2 from the environment transforming it into commodity chemicals. [ABSTRACT FROM AUTHOR]

Chemical reduction in oxides plays a crucial role in engineering the material properties through structural transformation and electron filling. Controlling the reduction at nanoscale forms a promising pathway to harvest functionalities, which however is of great challenge for conventional methods (e.g., thermal treatment and chemical reaction). Here, we demonstrate a convenient pathway to achieve nanoscale chemical reduction for vanadium dioxide through the electron-beam illumination. The electron beam induces both surface oxygen desorption through radiolytic process and positively charged background through secondary electrons, which contribute cooperatively to facilitate the vacancy migration from the surface toward the sample bulk. Consequently, the VO2 transforms into a reduced V2O3 phase, which is associated with a distinct insulator to metal transition at room temperature. Furthermore, this process shows an interesting facet-dependence with the pronounced transformation observed for the c-facet VO2 as compared with the a-facet, which is attributed to the intrinsically different oxygen vacancy formation energy between these facets. Remarkably, we readily achieve a lateral resolution of tens nanometer for the controlled structural transformation with a commercial scanning electron microscope. This work provides a feasible strategy to manipulate the nanoscale chemical reduction in complex oxides for exploiting functionalities. The authors demonstrate a nanoscale chemical reduction for VO2 into V2O3 through electron-beam illumination, showcasing potential for nanoscale manipulation of oxygen ionic evolution for advanced harvesting functionalities. [ABSTRACT FROM AUTHOR]

In this work, we fabricated gold nanoparticles (AuNPs) capped with both polyvinyl pyrrolidone (PVP) and iodine (I2) to act as efficient chemiluminescent coreactants for luminol. AuNPs synthesis was based on the direct chemical reduction of Au3+ with NaBH4 in the presence of PVP-I2 complex. The successful synthesis of PVP-I2@AuNPs was confirmed with scanning electron microscopy (SEM) and UV-vis spectrophotometry. Chemiluminescence (CL) intensity of luminol was greatly enhanced, upon its chemical reaction with chemisorbed I2 on AuNPs surfaces owing to the excellent catalytic activity of AuNPs. The PVP-I2@AuNPs/luminol CL sensing system was successfully applied for determination of Hg2+ ions and the results displayed linearity in a wide range from 0.5 to 2000 nM and an ultrasensitive response to 1.0 nM Hg2+. The detection limit of Hg2+ ions was 0.1 nM, which was 100 times lower than the limit value (10 nM) defined by the U.S. Environmental Protection Agency in drinkable water. This ultrasensitive luminogenic system for Hg2+ detection also exhibited excellent selectivity among 13 types of metals, suggesting that the luminol/PVP-I2@AuNPs system is a promising sensor for real-time detection of Hg2+. [ABSTRACT FROM AUTHOR]

While temporal considerations are of prime importance for chemical reactions, as well as for molecular stability, most chemical concepts (outside of the field of chemical kinetics) are not explicitly formulated on a diachronic basis (Earley in Found Chem 14:235, 2012). It will be argued here that a formulation explicitly incorporating temporal and epistemological considerations enables us to treat chemical reactions and chemical substances on ontologically equivalent terms, instead of assigning a more fundamental status to the latter. After all, in collision theory, a chemical substance is just a collision complex (a "resonance") that takes too long. How long qualifies as "too long", and "too long" in relation to what, are crucial questions that distinguish chemical substances from chemical reactions, and reversible reactions from irreversible ones, thereby introducing anthropocentric considerations into these distinctions. Too long for a lab chemist is very different from too long for an astrochemist studying chemical reactions between chemical substances in inter-stellar space on cosmological timescales. Examining several physical and chemical properties on the basis of which chemical substances are distinguished from one another, the role of temporal and anthropocentric considerations in defining molecular properties is emphasized. I conclude with some observations on the much-debated reduction of chemistry to other disciplines, arguing that such reduction depends on our aesthetic choices as to what kinds of observations demand explanation, and what kinds of explanation are acceptable. [ABSTRACT FROM AUTHOR]

In this paper, silver nanoparticles (Ag NPs) were successfully prepared in situ by chemical pulp fiber (CPF) without any additional reductants. In the green synthesis of Ag NPs, CPF acted as both a weak reductant and a stable carrier. The effect of different synthesis conditions was investigated, and the Ag NP load rate was up to 28.12 wt%. The size of the Ag NPs followed a standard Gaussian distribution, ranging from 10 to 50 nm, and a face-centered cubic structure was identified by XRD and TEM. In addition, the AgNPs/CPF composites exhibited good thermostability below 280 °C according to TG analysis. Owing to the high load rate and large specific surface area of Ag NPs, AgNPs/CPF composites exhibited excellent catalytic performance in the reduction of 4-nitrophenol to 4-aminophenol by NaBH4. The conversion rate was up to 95.91% after recycling 50 times, and the catalyst was easily separated from the reaction system. Based on the advantages of high conversion rate, excellent catalytic activity and reusability, AgNPs/CPF composites hold tremendous potential in eliminating nitrophenol and its derivatives from industrial pollution. [ABSTRACT FROM AUTHOR]

The formation of N2O has been studied by means of isothermal lean-rich experiments at 150, 180 and 250 °C over Pt-Ba/Al2O3 and Pt/Al2O3 catalysts with H2 and/or C3H6 as reductants. This allows to provide further insights on the mechanistic aspects of N2O formation and on the influence of the storage component. Both gas phase analysis and surface species studies by operando FT-IR spectroscopy were performed. N2O evolution is observed at both lean-to-rich (primary N2O) and rich-to-lean (secondary N2O) transitions. The production of both primary and secondary N2O decreases by increasing the temperature. The presence of Ba markedly decreases secondary N2O formation. FT-IR analysis shows the presence of adsorbed ammonia at the end of the rich phase only for Pt/Al2O3 catalyst. These results suggest that: (i) primary N2O is formed when undissociated NO in the gas phase and partially reduced metal sites are present; (ii) secondary N2O originates from reaction between adsorbed NH3 and residual NOx at the beginning of the lean phase. Moreover, N2O reduction was studied performing temperature programming temperature experiments with H2, NH3 and C3H6 as reducing agents. The reduction is completely selective to nitrogen and occurs at temperature higher than 250 °C in the case of Pt-Ba/Al2O3 catalyst, while lower temperatures are detected for Pt/Al2O3 catalyst. The reactivity order of the reductants is the same for the two catalysts, being hydrogen the more efficient and propylene the less one. Having H2 a high reactivity in the reduction of N2O, it could react with N2O when the regeneration front is developing. Moreover, also ammonia present downstream to the H2 front could react with N2O, even if the reaction with stored NOx seems more efficient. [ABSTRACT FROM AUTHOR]

Using the effects of chemical polarization of nuclei, mechanism and elementary stages of photochemical reduction of 2,6-diphenyl-1,4-benzoquinone with thiols have been elucidated. The studied quinone is reduced with ethanethiol in two stages (transfer of electron followed by proton transfer). The final photolysis product is a derivative of dibenzofuran. [ABSTRACT FROM AUTHOR]

At present, air cooling and water quenching are traditional treatment methods for molten copper slag. However, the waste heat and valuable metals cannot be recovered efficiently by these methods. Exergy efficiency (EE) of this method is only 21.0%. This paper describes a feasibility of waste heat recovery and direct reduction of copper slag. To investigate the feasibility of this new thermal energy recovery and direct reduction system (TER-DR), thermodynamic compass method was applied. Based on physical and chemical recovery methods, TER-DR1 and TER-DR2 systems are put forward. TER-DR1 system decreases the exergy loss (EXL) and improves the EE to 57.3%, and 0.489 t DRI is acquired for every ton of copper slag. Exergy of six kinds of typical endothermic chemical reactions was analyzed. The exergy of reforming reaction of CH4 by CO2 is the highest and suitable for TER-DR system. Combined with chemical method, TER-DR2 system decreases EXL further and improves the EE to 61.3%. Steam, synthesis gas and DRI are produced by this method. By TER-DR2, for every ton of copper slag, 0.489 t DRI, 67.3 m3 CO and 67.3 m3 H2 are acquired. [ABSTRACT FROM AUTHOR]

Silver nanoparticle-decorated graphene oxide was prepared using a simple green chemical reduction method, and its performance being used for surface-enhanced Raman scattering detection and optical limiting was studied. TEM images, photoluminescence quenching effect and the characteristic absorption peaks of GO and silver nanoparticles confirm the successful preparation of GO-Ag nanocomposite. The Raman spectra results show that the vibration fingerprints of RhB and R6G moleculars are detected only on the GO-Ag substrate, revealing good potential of being used as surface-enhanced Raman scattering substrate for detecting organic molecules. Additionally, nonlinear optical absorption of GO-Ag was measured using z-scan technique with a nanosecond laser operating at the wavelength of 532 nm. The z-scan results show that the transmittance of GO-Ag aqueous suspension has a large decline of 90%, and the nonlinear optical absorption onset input fluence of GO-Ag dispersed PVA film is as low as 1.3 J/cm, indicating that GO-Ag is a good potential optical limiting material for the commonly used high-power 532 nm nanosecond pulsed laser. [ABSTRACT FROM AUTHOR]

Nanoparticles attached just above a flat metallic surface can trap optical fields in the nanoscale gap. This enables local spectroscopy of a few molecules within each coupled plasmonic hotspot, with near thousand-fold enhancement of the incident fields. As a result of non-radiative relaxation pathways, the plasmons in such sub-nanometre cavities generate hot charge carriers, which can catalyse chemical reactions or induce redox processes in molecules located within the plasmonic hotspots. Here, surface-enhanced Raman spectroscopy allows us to track these hot-electron-induced chemical reduction processes in a series of different aromatic molecules. We demonstrate that by increasing the tunnelling barrier height and the dephasing strength, a transition from coherent to hopping electron transport occurs, enabling observation of redox processes in real time at the single-molecule level. [ABSTRACT FROM AUTHOR]

We have investigated the preparation of molybdenum powders by reducing the oxide compounds MoO, MgMoO, and CaMoO with magnesium vapor at residual argon pressures in the range 5-20 kPa and temperatures in the range 700-800°C. Using the MgMoO and CaMoO compounds as precursors, we have obtained molybdenum powders with specific surface areas of up to 20 m/g. The powders have a mesoporous structure. The reduction of the molybdenum compounds under such conditions was accompanied by separation of the reaction products due to the removal of magnesium oxide from the reaction zone. [ABSTRACT FROM AUTHOR]

In this work, the reduction and oxidation of hydrogen peroxide on Au single crystals is studied in weakly adsorbing electrolytes. Results are discussed in terms of the potential of zero charge and the adsorption strength of different anions, which in turn depend on the crystallographic orientation of the electrode. Close to the reaction onset, both reactions follow the same activity trend with Au(100) and Au(111) being the most and the least active surface planes, respectively. At high potentials, gold oxides inhibit the oxidation of HO, which seems to be controlled by a surface process. [ABSTRACT FROM AUTHOR]

Proceeding from TeCl and 1-octene a regioselective method was developed of the synthesis of trichloro(2-chlorooctyl)tellane. At adding methanol to this compound chlorine was easily replaced at room temperature by a methoxy group affording trichloro(2-methoxyoctyl)tellane. The reaction of TeBr with 1-octene in methanol resulted in tribromo(2-methoxyoctyl)tellane. A reduction of trichloro- and tribromo(2-methoxyoctyl)tellanes occurs the most selectively in the system NaBH4-water-THF giving 1,2-bis(2-methoxyoctyl)ditellane. The reactions are characterized by a high selectivity and quantitative yields of the products. [ABSTRACT FROM AUTHOR]

The authors describe a method for the fabrication of graphene micro-aerogels (GMA) using a multiple emulsion as a soft template. A mixed surfactant consisting of polymannitol oleate ester and polyoxyethylene castor oil was dissolved in toluene. An aqueous dispersion of graphene oxide was dropped into the above solution to produce a water-in-oil-in-water multiple emulsion. Hydrazine was used to reduce the graphene oxide. The partly reduced sheets of graphene oxide diffuse into the oil phase due to their low polarity. This induces the self-assembly of graphene sheets at the oil-water interface to finally form GMA. Following freeze drying and thermal annealing at 900 °C under Ar/H, GMA is obtained which possesses a microcapsule-like structure, high electrical conductivity (3250 S m), a large specific surface (1253 m g) and a well-defined porous structure. A glassy carbon electrode modified with the GMA shows ultrahigh sensitivity for the electrochemical detection of p-acetamidophenol. The differential pulse voltammetric peak current increases linearly over the 1 × 10 to 8.0 × 10 M p-acetamidophenol concentration range, and the detection limit is 5.7 × 10 M (at an S/N ratio of 3). The sensitivity is much better than that of sensors based on the use of graphene, graphene aerogel, or high density graphene aerogel. The method was successfully applied to the determination of p-acetamidophenol in tablets. The study also provides promising prospects in terms of graphene aerogel materials with improved electrochemical performance in electrocatalysis, supercapacitors and lithium ion batteries. [ABSTRACT FROM AUTHOR]

Gold nanoparticles are one of the most used nanomaterials. They are usually synthesized by the reduction of gold(III) chloride. However, the presence of halide ions in the reaction mixture is not always welcome. In some cases, these ions have detrimental influence on the morphology and structure of resulting nanoparticles. Here, we present a simple and halogen-free procedure to prepare gold nanoparticles by reduction of gold(III) oxide in neat oleylamine. The method provides the particles with an average size below 10 nm and dispersity of tens of percent. The process of nanoparticle formation was monitored using UV-Vis spectroscopy. The structure and chemical composition of the nanoparticles was determined by SEM, XPS and EDX. We also proposed the mechanism of reduction of gold(III) oxide based on MS, IR and NMR data. Importantly, the synthetic protocol is general and applicable for the preparation of other coinage metal nanoparticles from the corresponding metal oxides. For instance, we demonstrated that the absence of halogen enables efficient alloying of metals when preparing gold-silver bimetallic nanoparticles. [ABSTRACT FROM AUTHOR]

Although the chemical reduction and advanced oxidation processes have been widely used individually, very few studies have assessed the combined reduction/oxidation approach for soil remediation. In the present study, experiments were performed in spiked sand and historically contaminated soil by using four synthetic nanoparticles (Fe, Fe/Ni, FeO, FeNiO). These nanoparticles were tested firstly for reductive transformation of polychlorinated biphenyls (PCBs) and then employed as catalysts to promote chemical oxidation reactions (HO or persulfate). Obtained results indicated that bimetallic nanoparticles Fe/Ni showed the highest efficiency in reduction of PCB28 and PCB118 in spiked sand (97 and 79 %, respectively), whereas magnetite (FeO) exhibited a high catalytic stability during the combined reduction/oxidation approach. In chemical oxidation, persulfate showed higher PCB degradation extent than hydrogen peroxide. As expected, the degradation efficiency was found to be limited in historically contaminated soil, where only Fe and Fe/Ni particles exhibited reductive capability towards PCBs (13 and 18 %). In oxidation step, the highest degradation extents were obtained in presence of Fe and Fe/Ni (18-19 %). The increase in particle and oxidant doses improved the efficiency of treatment, but overall degradation extents did not exceed 30 %, suggesting that only a small part of PCBs in soil was available for reaction with catalyst and/or oxidant. The use of organic solvent or cyclodextrin to improve the PCB availability in soil did not enhance degradation efficiency, underscoring the strong impact of soil matrix. Moreover, a better PCB degradation was observed in sand spiked with extractable organic matter separated from contaminated soil. In contrast to fractions with higher particle size (250-500 and <500 μm), no PCB degradation was observed in the finest fraction (≤250 μm) having higher organic matter content. These findings may have important practical implications to promote successively reduction and oxidation reactions in soils and understand the impact of soil properties on remediation performance. [ABSTRACT FROM AUTHOR]

The W-AlO system at T = 2400 K and standard pressure (controlled Ar + H atmosphere) has been calculated by stochastic simulation. It is shown that the presence of hydrogen leads to the formation of aluminum hydrides, hydrogen oxides, and aluminum hydroxides; the compounds from the two latter groups (except for water) can interact directly with tungsten. The main chemical reactions occurring in the system are determined, based on which a conclusion about the cyclic character of the processes is drawn. Some recommendations on the composition and pressure of controlled atmosphere for growing sapphire crystals are given. [ABSTRACT FROM AUTHOR]

The selective leaching of zinc from high iron-bearing zinc calcine after reduction roasting was optimized by Taguchi experimental design method. The experimental parameters and their ranges were 303 to 343 K (30 to 70 °C) for leaching temperature ( T), 7 to 15 mL/g for liquid/solid ratio ( L/ S), 70 to 150 g/L for HSO concentration ( C), 5 to 25 minutes for time ( t), and 100 to 500 rpm for stirring speed ( R). The results show that the optimum conditions were 303 K (30 °C), 9 mL/g, 110 g/L, 20 minutes, and 400 rpm, respectively. Under these conditions, about 92.81 pct Zn was extracted and more than 86 pct Fe was reported into the leach residue. L/ S and C had significant effects on the extractions of zinc and iron, while t and R had no significant effects, and T had significant effect on iron extraction but negligible effect on zinc extraction. This indicates that diffusion was not a major control step of the leaching process, and the dissolution of iron was controlled by chemical reaction. The interactive effects of parameters were negligible. The leach residue was mainly composed of FeO and ZnS, and its particle size was very fine. [ABSTRACT FROM AUTHOR]

A New Zealand ironsand sample was characterized by scanning electron microscopy (SEM), X-ray fluorescence spectroscopy, qualitative and quantitative X-ray diffraction, and electron probe microanalysis. The titanomagnetite-rich ironsand was added into an industrial sinter blend in the proportion of 5 wt pct, and the mixture was uniaxially pressed into cylindrical tablets and sintered in a tube furnace under flowing gas with various oxygen potentials and temperatures to develop knowledge and understanding of the behavior of titanium during sintering. An industrial sinter with the addition of 3 wt pct ironsand was also examined. Both the laboratory and industrial sinters were characterized by optical and SEM. Various morphologies of relict ironsand particles were present in the industrial sinter due to the heterogeneity of sintering conditions, which could be well simulated by the bench-scale sintering experiments. The assimilation of ironsand during sintering in a reducing atmosphere started with the diffusion of calcium into the lattice of the ironsand matrix, and a reaction zone was formed near the boundary within individual ironsand particles where a perovskite phase was generated. With increasing sintering temperature, in a reducing atmosphere, ironsand particles underwent further assimilation and most of the titanium moved from the ironsand particles into a glass phase. In comparison, more titanium remained in the original ironsand particles when sintered in air. Ironsand particles are more resistant to assimilation in an oxidizing atmosphere. [ABSTRACT FROM AUTHOR]

In methanol, FeCl reacted readily with L1H ( L1H = bis(1-isoquinolylcarbonyl)amide) and afforded a complex having the formula [Fe( L2)Cl] ( 1) { L2 = N-((1-isoquinolyl)(methoxy)methyl)isoquinoline-1-carboxamide ion}. This reaction involves reduction of one of the two carbonyl groups present in L1H to (methoxy)methyl group. A plausible mechanism for the conversion of L1H to L2 has been proposed. Determination of molecular structure of 1 confirmed this conversion. Fe(III) ion is surrounded by three nitrogen atoms of the ligand and two chloride ions, imparting a rare distorted trigonal bipyramidal NCl coordination environment. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Sugarcane molasses, which is a kind of microbial carbon source, is a viscous by-product of the refining of sugarcane into sugar. However, experiments were designed to ascertain the mechanism and kinetics of Cr(VI) reduction with sugarcane molasses without adding microbes in aqueous solution. Results indicated that sugarcane molasses can reduce Cr(VI) to Cr(III) at pH values that range from 2.0 to 6.1 when no bioreduction occurs in the reaction. Furthermore, the reaction mechanism was proven to be that Cr(VI) acts as an electrophile that readily accepts electrons from the phenolic hydroxyl group of plant polyphenol, and it is then reduced to Cr(III) and in the process oxidizes the phenolic hydroxyl group to a quinone. Meanwhile, the reaction could be described by the pseudo-first-order kinetic model with respect to Cr(VI) concentration. The reaction rate constants were 324.2, 65.9, 21.9, and 14.4 h when pH values were 2.0, 3.5, 5.0, and 6.1, respectively, at 20 °C. The k increased 3.36, 7.02, and 13.48 times with the temperature adjusted from 5 to 10, 20, and 30 °C. [ABSTRACT FROM AUTHOR]

Tellurium tetrabromide readily reacted with 2-allylphenol at room temperature in acetonitrile to give previously unknown tribromo(2,3-dihydro-1-benzofuran-2-ylmethyl)-λ4-tellane in quantitative yield. The reduction of the product afforded bis(2,3-dihydro-1-benzofuran-2-ylmethyl)ditellane and benzyl(2,3-dihydro-1-benzofuran-2-ylmethyl)tellane. [ABSTRACT FROM AUTHOR]

The mechanism of magnesia carbothermic reduction was investigated experimentally in a reduction reaction process in vacuum. The thermodynamic calculation results showed that the initial reduction temperature between MgO and C was 1500 K (1227 °C) at 50 Pa. Other reduction reactions did not occur between the temperature 300 K and 1900 K (27 °C and 1627 °C) and 30 to 100 Pa. Based on the analysis of experimental results, the initial reduction reaction temperature was 1553 K (1280 °C), and it matched well with the thermodynamic calculations. The gas-solid reaction between MgO and CO did not occur at 1723 K (1450 °C), 30 to 100 Pa. Therefore, the main reduction reaction was MgO + C = Mg+ CO in vacuum. This reaction belonged to the solid-solid reaction type, the condensing product was obtained in the condensation zone, and the main component of the product was metal magnesium. A little magnesia was also obtained in the condensing product due to the reverse reaction. [ABSTRACT FROM AUTHOR]

In this paper, the results of the study of the reduction of basic lead sulphate with a gas (CO + CO) mixture are presented. This is a secondary reaction during the reduction of lead sulphate. The change in the both lead and PbS content in the reaction products, depending on the process temperature and the composition of the gaseous phase, was established. The comparison of the rate of the reduction reaction of lead sulphate and basic lead sulphate shows that the process proceeding with a higher output is the reduction of basic lead sulphate. [ABSTRACT FROM AUTHOR]

In order to better understand phosphorus (P) cycling and origins in the sediment of the Lake Illawarra, two sediment cores were extracted in November, 2010 and a modified sequential extraction scheme (SEDEX) was used to profile the exchangeable P (P), reactive Fe/Al-bound P (P), reductive Fe/Al-bound P (P), authigenic apatite P (P), detrital P (P), organic P (P) and residual P (P). The total sedimentary P (TP) ranged from 93 to 437 μg g, and was dominated by inorganic P. The average percentage of each fraction of P in the sediment followed the sequence: P (28.6 %) > P (23.5 %) > P (19.1 %) > P (17.0 %) > P (4.9 %) > P (4.7 %) > P (2.2 %). The profiles of TP and P showed two peak values with depth, which were matched to land use history in the Lake Illawarra catchment. The sediment depth profiles indicated that Fe oxyhydroxides play a predominant role in the P cycle in the sediments of the lagoon. This is supported by significant positive correlation between P and reactive Fe and a negative correlation between P and Fe. P and P concentrations were also well negatively correlated, possibly a result of competitive equilibrium between Fe and Ca for P. The estimated P burial efficiency was up to 82 % for this lagoon, which is likely related to the high sediment accumulation rate and the high value of R. In addition, the bioavailable P, which consists of P, P, and P, represented a significant proportion of the sedimentary P pool, accounting, on average, for 38 % of the TP. This result indicates that the sediment is a potential internal source of P for this lake ecosystem. [ABSTRACT FROM AUTHOR]

The mechanism of reducing silver(I) oxide particles to silver metals was studied using myristyl alcohol as a reducing agent. The reduction temperature of silver oxide with myristyl alcohol decreased to 150 °C from the temperature of silver oxide in air, 400 °C. The reduction temperature was decreased by myristyl alcohol reacting with silver oxide, which was confirmed by our reaction equation model obtained by gas chromatography determination, pyrolysis gas chromatography-mass spectrometry, and Karl Fischer titration. An endothermic of 153.7 kJ mol in the reduction of silver oxide with myristyl alcohol calculated from the reaction model using Hess's law was coincident with that obtained experimentally by differential scanning calorimetry measurements. [ABSTRACT FROM AUTHOR]

Anhydrous ytterbium chloride was obtained via solid-phase reaction from YbO with AlCl as a chlorination agent. The electrochemical behavior of the chloridized YbO was investigated on W electrodes in LiCl-KCl and LiCl-KCl-AlCl melts by cyclic voltammetry and square wave voltammetry. The results showed that the reduction/reoxidation of Yb(III)/Yb(II) was reversible and controlled by diffusion. The signals related to the formation of two Al-Yb intermetallic compounds were detected in LiCl-KCl-AlCl melt. Potentiostatic electrolysis was carried out in LiCl-KCl-AlCl-YbCl melt on W electrodes at 943 K at different potentials and AlYb, AlYb, AlLi and AlLi phases were detected in deposits. Then, the extraction of ytterbium was performed. The currents evolution was recorded by square wave voltammetry and the extraction efficiency was evaluated via inductive coupled plasma atomic emission spectrometer analysis during electrolysis. The initial extraction rate is much higher than that at longer times. The extraction efficiency was about 98.0 % for Yb(III) after potentiostatic electrolysis for 60 h at −1.84 V in LiCl-KCl-AlCl-YbCl melt. [ABSTRACT FROM AUTHOR]

Carbon composite pellets composed of hematite, synthetic graphite, and oxide system were reduced at 1773 K (1500 °C) in a laboratory-scale horizontal tube furnace. The morphological properties of produced pellets after reduction were examined using light optical microscopy and a scanning electron microscope. Microscopic observation confirmed the correlation between morphological change of pellets and compositional difference of CaO-SiO 2-Al 2O 3 ternary oxide systems. Samples were also analyzed by X-ray diffraction to investigate phase change during the reduction process. The impact of oxide chemistry was established as each pellet illustrated different states of iron oxide as a function of time. In addition, the surface area was measured by the BET-N 2 absorption method to clarify the reaction mechanism which is significantly affected by physical contact. [ABSTRACT FROM AUTHOR]

A systematic investigation was conducted on the reduction of mullite by graphite at high temperatures ranging from 1773 K to 1873 K (1500 °C to 1600 °C) in an Ar atmosphere. The reaction products were identified as Al 2O 3, SiC, SiO, CO, and CO 2. The overall reaction rate was accelerated by increasing the temperature, whereas the atmosphere gas flow rate had no significant influence on the reaction process. The reaction mechanism deducted from the experimental results indicated that the Boudouard reaction was a significant rate-controlling step. [ABSTRACT FROM AUTHOR]

The reduction behavior of composite pellets comprising of hematite, synthetic graphite, and several oxide binder systems was investigated in a laboratory-scale horizontal tube furnace. Three oxide binder systems using silica-rich, alumina-rich, and conventional blast furnace slag compositions were selected to examine the effect of oxide chemistry on the reduction behavior of pellets. Compositional differences in the CaO-SiO 2-Al 2O 3 ternary system were confirmed to influence the reactions occurring in composite pellets during the reduction of iron oxide. An in situ visualization approach was used to observe the oxide/iron/carbon interactions at high temperatures from 1623 K to 1773 K (1350 °C to 1500 °C). The off-gas composition was measured by means of an infrared analyzer to determine the pellet reaction rates. Changes in physical appearance during the in situ reaction experiments demonstrated a strong correlation between the oxide composition and internal reactions. Moreover, the mechanical properties of pellets were investigated by measuring compressive strength to understand the relationship between physical properties of pellets and the associated oxide binder systems selected for this study. [ABSTRACT FROM AUTHOR]

ZrB-AlO nanocomposite powder was produced by aluminothermic reduction in Al/ZrO/BO system. In this research, high energy ball milling was used to produce the necessary conditions to induce a mechanically induced self-sustaining reaction. The ignition time of the composite formation was found to be about 13 min. The synthesis mechanism in this system was investigated by examining the corresponding sub-reactions as well as changing the stoichiometry of reactants. Thermal behavior of the system was also studied. [ABSTRACT FROM AUTHOR]

A method for synthesis of radiolabelled silver nanoparticles is reported. The method is based on proton activation of silver metal powder, enriched in 107Ag, with a 30.7 MeV proton beam. At this proton energy 105gAg is efficiently created, mainly via the 107Ag(p,3n) 105Cd →  105gAg reaction. 105gAg has a half-life of 41.29 days and emits easily detectable gamma radiation on decay to 105Pd. This makes it very useful as a tracing radionuclide for experiments over several weeks or months. Following activation and a period to allow short-lived radionuclides to decay, the powder was dissolved in concentrated nitric acid in order to form silver nitrate (AgNO 3), which was used to synthesise radiolabelled silver nanoparticles via the process of sodium borohydride reduction. For comparison, non-radioactive silver nanoparticles were synthesised using commercially supplied AgNO 3 in order to check if the use of irradiated Ag powder as a starting material would alter in any way the final nanoparticle characteristics. Both nanoparticle types were characterised using dynamic light scattering, zeta-potential and X-ray diffraction measurements, while additionally the non-radioactive samples were analysed by transmission electron microscopy and UV–Vis spectrometry. A hydrodynamic diameter of about 16 nm was determined for both radiolabelled and non-radioactive nanoparticles, while the electron microscopy on the non-radioactive samples indicated that the physical size of the metal NPs was (7.3 ± 1.4) nm. [ABSTRACT FROM AUTHOR]

The reaction mechanisms for the carbothermic reduction of complex mineral sulfide concentrates in the presence of lime were studied between 1073 K and 1323 K. The reaction mechanisms were studied by stopping the reduction experiments at different times and analyzing the reaction products by x-ray diffraction and scanning electron microscopy techniques. Magnetite (FeO) and digenite (CuS) were the initial phases formed during reduction of CuFeS and CuFeS mineral particles, such that metallization of iron occurred before copper above 1173 K and at an equal stoichiometric ratio of CaO and C. The metallization of iron was found to take place via reduction of intermediate oxide phase (FeO/FeO), whereas metallization of copper occurred via diffusion of S ions away from the mineral particles or via formation of Cu-O-S liquid phase. Metallic iron and cobalt were embedded in the copper matrix due to a preferential reduction of iron and cobalt from the Cu-Fe-S and Cu-Co-S type of mineral particles. The effects of CaO/C ratio were analyzed and the rate of reactions was increasing with an increase in the CaO/C ratio. The formation of liquid phase has been discussed. The experimental results were found to be in good agreement with the thermodynamic predictions. [ABSTRACT FROM AUTHOR]

In the present article, various nanometric FeNi alloys were synthesized by chemical reduction of the corresponding metal ions, with hydrazine in an aqueous solution. Process variables of reaction temperature, pH of the hydrazine solution and concentration of metal ions were varied in order to determine the optimum synthesis conditions regarding quality, productivity and cost. It is found that pH of hydrazine solution, at low concentration of metal ions, is the most crucial variable affecting the reaction rate, average crystallite and particle sizes of the synthesized nanometric FeNi alloy, followed by the total concentration of metal ions. Thus, increase of pH of hydrazine solution acts as an efficient stabilizer in reducing the particle size. On the contrary, at high concentration of metal ions, the structural characteristics of the nanometric FeNi alloy are almost insensitive to reaction temperature and pH of hydrazine solution, but the reduction rate is remarkably sensitive to reaction temperature. Based on these results, it is decided that a reaction temperature of 80 °C, pH of the hydrazine solution of 12·5 and concentration of metal ions of 0·6 M represent the optimum synthesis conditions. The role of pH of hydrazine solution in reducing the alloy's average particle size as well as efficient stabilizer confirms tremendous effect of synthesis conditions on the alloy structure and therefore, the importance of this study for industrial production of nanometric FeNi alloy. [ABSTRACT FROM AUTHOR]

COREX is the primary process in the current smelting reduction method. The process has strict coal quality standards. Combustion processes of coal used in the COREX operating system were analyzed using a synchronous thermogravimetric analyzer combined with a mass spectrometer. The microcosmic structure and macerals were observed by an electronic scanning microscope. The qualitative and quantitative determinations of oxygen functional groups, such as phenolic hydroxyl, carboxyl, carbonyl, and methoxy groups were detected by the Fourier Transform Infrared spectrometer (FT-IR) and through chemical analysis methods. In addition, the evolution of the chemical structure and transformation mechanism of organic oxygen functional groups during COREX coal combustion have been thoroughly investigated. This study proposes a new coal-requirement index system and coal blending method, which will increase the expansion of coal selection and decrease the overall usage of coal during COREX. [ABSTRACT FROM AUTHOR]

The mechanism on biomass reduction of low-grade manganese dioxide ore was studied by investigating influence factors on manganese recovery degree, such as the reaction temperature, time, biomass/ore ratio, compositions of biomass, nitrogen flow rate, and particle size of raw materials, and it was further identified through analysis of gas composition in the outlet gas, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) for the reduced sample. The results show that the reduction process involved mainly two steps: (1) The biomass was first pyrolyzed to release reductive volatiles and (2) manganese oxide ore was reacted with the reductive volatiles. By an analysis of gas composition in the outlet gas, it was also found that the ratio of biomass/ore had an important effect on the reduction mechanism. With a low biomass/ore ratio of 0.5:10, the reducing reaction of the reductive volatiles with manganese dioxide ore proceeded mainly in two stages: (1) The condensable volatiles (tar) released from biomass pyrolysis reacted with manganese oxide ore to produce reductive noncondensable gases such as hydrogen, carbon monoxide, and some light hydrocarbons; and (2) the small molecule gases further participated in the reduction. XRD pattern analysis on the reduced manganese dioxide ore revealed that the process of biomass reduction of manganese ore underwent in phases (MnO → MnO → MnO). The kinetics study showed the reduction process was controlled by a gas-solid reaction between biomass volatiles and manganese oxide ore with activation energy E of 53.64 kJ mol and frequency factor A of 5.45 × 10 minutes. [ABSTRACT FROM AUTHOR]

The thermodynamics of several aspects of the carbothermic reduction of the alumina process were experimentally verified. The current thermodynamics are based on solution models for the AlO-AlC system and the free energies of formation of a number of phases. In Part I of this paper, the results of reacting carbon and alumina mixtures at high temperatures 2173 K to 2323 K (1900 °C to 2050 °C) are presented. The amount of CO evolved was measured and slag samples analyzed. The initial slag or carbide formation at alumina saturation was measured to be 2220 K (1947 °C) and 1.76 pct C. The slag-making temperature and composition in the liquid region were determined and at carbide saturation were measured to be 2273 K (2000 °C) and 6.29 pct C, respectively. Considering the experimental challenges at the high temperature, with the exception of the initial slag composition, the agreement with the predicted thermodynamics is good. [ABSTRACT FROM AUTHOR]

The response to thermal exposure of ball-milled Cu-Mg/BO powder blends was investigated in the current study to explore the potential of powder metallurgy route to produce Cu-B alloys. Cu-20Mg alloy powder was mixed with BO and subsequently ball milled for 1 hour. Ball milling alone failed to establish a reaction between Cu-Mg compounds and BO. When the ball-milled powder blend was heated, however, BO was reduced by CuMg <773 K (500 °C). The CuMg intermetallic phase, which has survived until 773 K (500 °C), was involved in the reduction of the remaining BO at still higher temperatures, while excess Mg reacted with B to produce MgB and MgB compounds. Cu-Mg alloy with predominantly the CuMg phase must be utilized to take advantage of the capacity of the CuMg (Cu-43 wt pct Mg) compound to reduce BO at temperatures as low as 773 K (500 °C). Once the Cu-43Mg alloy powder is mixed with BO and the powder blend thus obtained is ball milled and subsequently heated at 500 °C, BO is readily reduced by CuMg to yield Cu, B, and MgO. The latter can be easily removed from the powder blend by acid leaching. [ABSTRACT FROM AUTHOR]

Tungsten carbide (WC) is an important material mostly used for cutting-tool applications. The reduction of WO to WC is realized by using several techniques. The existing chemical processes involved in its reduction are long and energy consuming. In our work, we make efforts to reduce WO to WC by the reflux reaction technique. The composite obtained after the reflux reaction is analyzed to check the feasibility of conversion of WO to WC. The preliminary study demonstrates the feasibility of this conversion. The proposed technique seems to be promising and cost-effective for the low-temperature synthesis of ultrafine WC particles. The synthesized powders are studied with the help of X-ray diffraction, scanning electron microscope, energy dispersive X-rays, and transmission electron microscopy for the phase identification and microstructural analyses. [ABSTRACT FROM AUTHOR]

Role of carotenoid end groups on their chain-breaking potency against lipid peroxidation was explored using density functional theory. Hydrogen abstraction and addition of the peroxide and O of the resultant radicals were investigated. The protective potency of CARs is exhibited by their faster reactions with the peroxide radical than fatty acid, and by the much reduced reactivity of the initiated radical toward O. 3,3′-Dihydroxyisorenieratene (DHIR), which consists of hydroxyaryl (3-hydroxy-ϕ) end groups, is by far the most efficient chain-breaking antioxidant. The quinone form of DHIR is also an effective antioxidant. 4-Oxo functional group in β-ring enhances the antioxidative potency of carotenoids, while 3-hydroxyl functional group in β-ring does not have a noticeable effect. [ABSTRACT FROM AUTHOR]

The detailed reaction mechanism of Di-Air, which showed the unprecedented high deNO performance at high temperature conditions, was studied in this work. Since the Di-Air phenomenon occurs with continuous short pulse injections of hydrocarbons over NSR (NO storage and reduction) catalyst, this study focused on the specific function of HC as an effective reductant for NO reduction reaction. As a first step, the deNO performance was compared with three different reductant gases including CO, H and CH in a modified synthetic gas bench equipped with a gas injector which enables continuous small amount of injections. At inlet gas temperature of 450 °C CH showed the best deNO performance whereas H was the best at 150 °C. Moreover the result of temperature programmed desorption showed that intermediate species represented by -NCO (isocyanates) produced from CH was thermally more stable than that produced from CO. These results confirmed that the injected HC reacts with adsorbed NO on NSR catalyst generating thermally stable intermediates, which could contribute the high deNO performance at high temperature conditions. [ABSTRACT FROM AUTHOR]

This study is devoted to an operando study of Pt-Rh/AlO-BaO lean-NO trap catalyst during the regeneration with H/CO reaction mixture. Particular attention was paid to the influence of CO coexisting with H during the regeneration that can simulate the regeneration step by using reformate composed of CO and H. In rich H mixture ammonia predominantly forms. As expected, strongly chemisorbed CO molecules over noble metals lower the efficiency of the trap at 150 °C. Successive hydrogenation of N atoms to ammonia predominates in our conditions. However, the comparison of the outlet gas composition with infrared spectral features also suggests a minor participation of isocyanate species (NCO) as possible intermediates in the production of ammonia especially for long regeneration duration in the absence of water. Interestingly, ammonia formation as reducing agent for the selective reduction of NO can stimulate practical applications for further coupling lean-NO trap with SCR catalysts. [ABSTRACT FROM AUTHOR]

This paper characterizes the integrated activity of fresh and used catalysts on the selective catalytic reduction of NO x using CH. The synthesised K-Ag/AlO catalysts exhibited a promotional effect on deNO x activity in the presence of SO. In addition, 130 h of time-on-stream reactions demonstrated the thermal and mechanical stability of the synthesised materials. A TEM analysis and diffraction patterns demonstrated the sintering of finely dispersed particles to ~0.5 micron size clusters by sulphation. Furthermore, under reaction conditions, the de-sulphation initiated the re-dispersion of the Ag clusters to different sized particles. The TPD studied demonstrated the strong adsorption sites for methane and formation of R-SO x compounds. This surface modification in the SO feed stream is considered to be the reason for the promotional effect on the deNO x reaction. [ABSTRACT FROM AUTHOR]

Chemoselective synthesis of 2-nitroalkanols catalyzed by electro-generated base (EGBs) in the presence of acetonitrile and lithium perchlorate has been studied by cyclic voltammetry and controlled potential electrolysis techniques. Cathodic reduction of nitromethane at platinum cathode produces organic anion which acts as EGBs and undergoes condensation with carbonyl group of substituted aldehydic substrate to produce 2-nitroalkanols in 75-85 % yields. The controlled nucleophilicity of EGBs in organic solvent during electrochemical reaction makes it chemoselective which is a unique feature of this work. [ABSTRACT FROM AUTHOR]

An efficient synthesis of N-mono-substituted β-amino tertiary thiols by reductive ring-opening of 3-thiazolines, obtained by use of the Asinger reaction, is described. This synthesis be regarded as a complementary approach for aminolytic ring-opening of thiiranes. [ABSTRACT FROM AUTHOR]

In this study, iron-mediated activator generated by electron transfer for atom transfer radical polymerization of methyl methacrylate was carried out using two different types of salts, acidic hydroxylamine hydrochloride and basic sodium bisulfite as the reducing agents, ethyl 2-bromoisobutyrate as an initiator, FeCl·6HO as a catalyst and triphenylphosphine (PPh) as a ligand. The polymerization could be carried out in the presence of a limited amount of oxygen (air) and showed highly efficient catalyst activity. The living features were confirmed by the polymerization kinetics, analysis of chain end, and chain-extension experiment. [ABSTRACT FROM AUTHOR]

Feasibility of multidimensional hydrodynamic modeling depends critically on the availability of accurate reduced kinetic mechanisms of physical and chemical processes taking place in the system. Such mechanisms should describe the processes under consideration within a specified error tolerance in the range of initial conditions of interest while keeping the number of species and reactions as small as possible. We have developed an advanced tool for reduction of detailed kinetic mechanisms with a minimal human effort. The tool includes 10 reduction and 2 analysis methods which are based on the results of zero-dimensional modeling. The methods can be combined and applied in sequence. The reduction tool has been implemented as a part the Chemical Workbench computational package and has been tested for a number of large kinetic mechanisms of gas-phase processes. Using this tool, we reduced the mechanism of tar gasification from 177 species and 879 reversible reactions to only 83 species and 278 reactions, while the mechanism of methane combustion initially involving 127 species and 1,206 reactions was reduced to 42 species and 173 reactions. [ABSTRACT FROM AUTHOR]

Polarographic behavior of 2,4-dinitrobenzene and products of its reduction, 2-chloro-5-nitroaniline and 4-chloro-3-nitroaniline, is studied: it is shown that formation of the corresponding chloronitroanilines in the case of polarographic reduction of 2,4-dinitrochlorobenzene is rather problematic. 0.1 M NaOH is recommended as the supporting solution for analytical control of conversion of 2,4-dinitrochlorobenzene and a mixture of 2-chloro-5-nitroaniline and 4-chloro-3-nitroaniline in reaction solutions obtained by preparative electroreduction of 2,4-dinitrochlorobenzene. [ABSTRACT FROM AUTHOR]

Results are provided for an experimental study of an improvement in periclase-carbon torcrete-mix slag resistance by a reduction in molten slag corrosiveness and modification of refractory composite microstructure. Combination of the refractory microstructure modification obtained and slag with changed chemical composition makes it possible to improve torcrete-mix properties considerably and increase its corrosion slag resistance. [ABSTRACT FROM AUTHOR]