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Carbothermic reduction of chromite in the presence of nickel as the alloying element was investigated in a wide temperature range up to 1500 °C using thermogravimetric analysis coupled with continuous off-gas analysis (TG-DSC-MS). Both isothermal and non-isothermal linear heating tests were performed for the kinetic study with the calculation of activation energies. In order to further elucidate the reduction mechanism, the reduced products were characterized by SEM-EDS and XRD. It was concluded that the reduction sequence followed a multi-stage mechanism, reflected partly by the dependency of the activation energy on the extent of reduction. With the progress of reduction, refractory oxide layers gradually formed on/close to the surface of each chromite particle, causing the shift of the rate-limiting factor from chemical control to diffusion control. The promoting effect from the addition of Ni was evident at temperatures higher than 1300 °C due to the formation of alloys of lower melting point. [ABSTRACT FROM AUTHOR]

The oxide mixtures CuO-WO3 of various compositions were synthesized by citrate-gel combustion process, starting with the aqueous solutions of copper nitrate, ammonium tungstate and citric acid. Cu-W nanocomposite powders were produced by reduction of oxide mixtures in hydrogen atmosphere under thermogravimetric control. Characterization of CuO-WO3 mixtures and their reduction products was performed by SEM and XRD methods. The morphology of both oxide and metal particles displayed notable dependence on composition. Copper displayed promoting action during reduction of CuO-WO3 mixtures. The mean reduction temperature shifted monotonously from that of CuO toward that of WO3. The reduction proceeded in three steps, first of which was mainly reduction of CuO and the other two originated mainly of the two-step reduction of WO3. The composition CuO-WO3 at a molar ratio 1:1 was shown to form the compound CuWO4. The reduction of this compound was subjected to a detailed thermokinetic study. For those purposes, model-free expanded Friedman, multiple heating rate Coats-Redfern and Kissinger methods and some model-fitting methods, incorporated in the software Kinetics2015, were used. Among model-fitting models, the nucleation and growth kinetic model enabled the best fit of experimental results for all three reduction stages. [ABSTRACT FROM AUTHOR]

The paper reports an investigation on the reduction of synthetic gypsum and a Tunisian phosphogypsum sample in pure nitrogen or loaded with H2O vapor, using graphite or natural coke. Thermogravimetry analysis in non-isothermal conditions showed that H2O gas has no effect on the onset temperature of reduction (Tred), whereas the use of coke as a carbon source lowers the Tred of about 50 °C but the reduction rate and the conversion degree into CaS are not significantly affected by the coke proportion. The activation energy and the reaction order were determined using the direct Arrhenius plot and the Coats-Redfern kinetic model. These models led to the same reaction order and to close values of activation energies. The FWO isoconversional method shows that the reduction is more complex than a one step process and leads to lower values of activation energy. Addition of 5% mass of various oxide lowered the activation energy; however, the use of the Co2O3/Co3O4 as additive seems to enhance more the reduction rate. [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]

Polystyrene (PS) composites with different loading level and proportions of CNAPP20 [i.e., ammonium polyphosphate (APP) wrapped graphitic carbon nitride (g-C3N4), where mass ratio of g-C3N4 to the CNAPP was 20%] to aluminim phosphinates were fabricated. The results indicated that the additives had good interfacial interaction with PS matrix. It is noted that only the PS-1 achieved the UL-94 V-0 rating, and value of limited oxygen index was also the highest among all the composites. The peak of heat release rate (pHRR) and total heat release of all the composites were greatly reduced as compared to those of virgin PS (77.5% decrease in pHRR for PS-1). Combining CNAPP20 with DAHPi (i.e., aluminim diethylphosphinate) induced the formation of a cohesive and uniform carbonaceous residue. In addition, the concentration of carbon dioxide, smoke and carbon monoxide was reduced upon incorporation of CNAPP20 and DAHPi. The property improvements were attributed to the explanations that the formed continuous and dense char residues acted as protecting layers to prevent the heat and mass permeation, and that the evolved gas diluted the oxygen, which retarded the further combustion of flammable compounds. Also, the generated free-radical scavengers retarded polymeric chain breakage. [ABSTRACT FROM AUTHOR]

The reducibility of Au catalysts on CeO supports doped with 1 and 2.5 mass% YO by two types of preparation methods (impregnation and co-precipitation) has been studied by temperature-programmed reduction and compared with that of pure Au/CeO. The kinetic parameters of reduction were determined simulating each reduction process. The capacities of these catalysts to retain oxygen have been evaluated by temperature-programmed desorption. The catalytic activities in water gas shift reaction were determined measuring CO conversion between 413 and 623 K. The catalytic performances of all these catalysts were explained in terms of mobility of the oxygen ions of the CeO lattice. [ABSTRACT FROM AUTHOR]

The effect of mechanical activation on the reduction kinetics of magnetite concentrate by hydrogen was studied. The magnetite concentrate was milled for 8 h in a planetary ball mill. After 8 h of milling, the average particle size was reduced from 14 to 4.4 µm, resulting in a lattice microstrain of 0.3. Isothermal reduction experiments were conducted by thermogravimetry to focus on the chemical reaction as the rate-controlling factor by eliminating external mass transfer effects and using a thin layer of particles to remove interstitial diffusion resistance. Thus, about 2 mg of magnetite powder was reduced at different temperatures under a sufficient flow of hydrogen. The magnetite concentrate and reduction products were analyzed by SEM and XRD. It was found that the onset reduction temperature decreased from 587 to 500 K (314-227 °C) due to the mechanical activation. The activation energy for hydrogen reduction of the activated concentrate decreased about 10% compared with the as-received concentrate. In view of the results, a reaction rate expression was established based on the nucleation and growth model with an Avrami parameter n = 2.5. [ABSTRACT FROM AUTHOR]

Zinc ferrite is one of the main components present in the electric arc furnace dust. Furthermore, it is necessary to know the mechanisms involved on the zinc ferrite to determine a process for reusing the electric arc furnace dust. Thus, the aim of this paper is to evaluate the kinetic parameters of the reduction of synthetic zinc ferrite pellets by mixture containing hydrogen. The kinetic investigation was performed via Forced Stepwise Isothermal Analysis method in the temperature range of 500-950 °C. The reducing gas was a mixture of hydrogen (10%) and argon (90%). In addition, Thermo-cal software was used in order to support the reduction reaction behavior. The results indicated that between 550 and 750 °C only iron oxide was reduced. In this step, the nucleation was found to be the controlling mechanism, and an activation energy of 84.9 kJ mol was determined. In temperature >800 °C, it was noted an influence of diffusion on the reduction reaction. Images obtained from scanning electron microscope suggested a change in the pellets microstructure after this temperature presenting a sintered structure. The activation energy of 188 kJ mol was determined at this step. [ABSTRACT FROM AUTHOR]

In the current research, silver (Ag) nanoparticles were synthesized by chemical reduction method and polyethylene-silver nanocomposites containing different Ag contents (0-30 mass%) were fabricated by mechanical milling method. All samples were characterized by X-ray diffraction, UV-Vis spectroscopy, scanning electron microscopy, and transmission electron microscopy. Thermal behavior of these nanocomposites was investigated using differential scanning calorimetry (DSC) and thermogravimetric analysis. The results of the DSC tests showed that although the melting temperature ( T ) of PE and its nanocomposites has the same value, the crystallization temperature ( T ) increases by addition of silver nanoparticles (Ag NPs) in the PE matrix, indicating that the Ag NPs act as nucleation sites. Also, crystallinity index of PE and its nanocomposites was calculated. Results show that the crystallization index changes from 45.74 to 57.36% as Ag NPs content increases from 0 to 30%. The mass loss of nanocomposites was lower than that of the pure PE, which could be attributed to the undecomposed Ag NPs. [ABSTRACT FROM AUTHOR]

Brown coal-based materials are excellent adsorbents for reducing chromium(VI) to chromium(III) and afterward immobilizing these chromium(III) by the binding of oxygenic functional groups in adsorbents. In the study, the approach of pyrolysis is employed for the treatment of Cr-loaded solid waste. The effects of adsorbed chromium on the pyrolysis of Xilingol brown coal were studied, and the solid char residues were collected to characterize with XPS, XRD and SEM/EDX. For the pyrolysis in Ar, the mass loss rates of Cr-loaded samples were much higher than that of unloaded samples above 750 °C, together with the increase in CO and H emission. XPS spectra revealed that the increase in CO could be related to formation of [Cr-O-C]. For the pyrolysis in CO, the presence of chromium was more favorable for the conversion of char, especially demineralized brown coal and kerogen. The maximum decomposition temperatures for the Cr-loaded samples were about 200 °C lower than that of unloaded samples. The char residue yields of Cr-loaded samples were obviously higher than that of corresponding unloaded samples (at 1200 °C). Finally, the chromium in the solid residue was recovered in the form of CrO. The present study exploits an approach method for both brown coal waste treatment and chromium recovery. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to study the kinetic reaction of electric arc furnace dust pellets using a reducing gas simulating the reformed natural gas. The kinetic investigation was accomplished via forced stepwise isothermal analysis method. The tests were programmed in the range of 500-1000 °C. It was used a reducing gas contained 25 % of CO and 75 % of H. X-ray patterns were analyzed in order to understand the reduction process. The results show the reduction of electric arc furnace dust pellet occurs in three steps. At 550-650 °C, the zinc ferrite is reduced to magnetite and zinc oxide, followed by the reduction of magnetite to wustite. Carbon deposition on the pellet surface was detected in this step, which impairs the kinetic analysis. In the range of 700-800 °C, wustite is reduced to iron. It was determined a mixed control between nucleation and diffusion with E of 89.2 kJ mol. At 850-950 °C, the main reaction is zinc oxide reduction to gaseous zinc. However, wustite reduction is also observed. The E of 135.5 kJ mol with a mixed control between diffusion and chemical reaction was detected. [ABSTRACT FROM AUTHOR]

The zinc hydroxystannate/reduction graphene oxide (ZHS/RGO) hybrid was successfully prepared through the hydrothermal route, and its structure, composition and thermal properties were confirmed by XRD, FTIR, XPS, SEM, TEM, Raman spectra, and TG. ZHS/RGO hybrid is multilayer sandwich structure by morphological characterization. ZHS/RGO was applied to reduce fire hazards of epoxy (EP) as a flame retardant and smoke suppressant. The incorporation of 3.0 mass% ZHS/RGO provided fire-retardant properties to epoxy resin, testified by the results of cone calorimetry. The results indicated that ZHS/RGO can suppress the formation of smoke and toxic carbon monoxide as well as enhance the flame retardancy of the EP composites. The heat release rate, total heat release, smoke production rate, and total smoke production of EP-ZHS/RGO were greatly decreased compared with the pure EP. During the combustion process, ZHS/RGO may exhibit gaseous phase effect and condensed phase effect. [ABSTRACT FROM AUTHOR]

The utilization of copper slag is an attractive option of iron resource. However, extra energy consumption is required and contributes to greenhouse gases. In this paper, biomass was introduced as a new kind of reductant for the reduction of copper slag to decrease the energy consumption. The reduction kinetics and reduction characteristics of three kinds of biomasses were studied by thermogravimetric analyzer (TG). The TG curves showed the reduction reaction of copper slag and biomass could be divided into three stages during heating process: drying and pyrolysis of biomass process (<959 K), pre-reduction process (959-1100 K) and reduction reaction process (>1100 K). Pine sawdust showed the best reducing property and the reduction ratios of pine sawdust, corncob and straw reached to 80.6, 76.1, and 60.0 %, respectively, when the mass ratio of biomass/slag was 2:1. As the additive, CaO had promotion effects on the reduction reaction. With the increase in CaO addition, the reduction ratio of copper slag increased firstly and reached a peak at CaO/slag was 0.3:1 and then it declined due to the changes of slag viscosity. By kinetics analysis, the reduction reaction confirmed well with shrinking core model (R1). The activation energy of reactions was affected by the addition of biomass and heating rate in experiments. With the increase in the addition of biomass, the activation energy of reduction reaction increased gradually; with the increase in heating rate, the activation energy of reduction reaction decreased. [ABSTRACT FROM AUTHOR]

The main objective of this work was to use the differential scanning calorimetry in conjunction with optical microscopy to study the compatibility of ibuprofen with lactose and polyvinylpyrrolidone and to provide an explanation(s) for the reduction in the dissolution rate observed from the ternary interactive mixture containing ibuprofen in previous study. Mixtures containing micronized ibuprofen-fine lactose 90:10 and 20:80 w/w showed a decrease in the melting peak of lactose by 14.33 and 10.94 °C, respectively. The addition of 5 % fine lactose to the binary system has the highest effect on the melting point of ibuprofen by reducing the melting peak of ibuprofen from 76.2 to 73.72 °C. Microphotographs obtained from optical microscopy for ibuprofen, binary and ternary interactive mixtures showed that agglomeration of ibuprofen was formed in the binary and ternary interactive mixtures. Lactose and polyvinylpyrrolidone must be avoided in the preparation of ternary interactive mixtures of ibuprofen to prevent drug-excipient interaction. [ABSTRACT FROM AUTHOR]

Lisinopril is an angiotensin-converting enzyme inhibitor, exhibiting reduced absorption and bioavailability following oral administration and instability in the presence of lactose. Zofenopril, one of the newest therapeutic agents of the same class, is a highly lipophilic drug with low water solubility. Inclusion complexes between the drug substances and β-cyclodextrin (β-CD) were obtained to improve their solubility, bioavailability, and stability. The purpose of this study was to investigate the guest-host interaction of lisinopril dihydrate (LIS) and zofenopril calcium (ZOF) with β-CD in solid state and in aqueous solution in order to prove the formation of inclusion complexes between the components. The inclusion complexes were prepared using the kneading method, and they were investigated with different analytical technique, including thermal analysis, powder X-ray diffractometry (PXRD), Fourier transform infrared spectroscopy (FTIR), and UV spectroscopy. All these techniques revealed that LIS and ZOF form inclusion complexes with β-CD both in solution and in solid state. The stoichiometry of the inclusion complexes was found to be 1:1 for both drug substances, and the apparent constant stability was calculated as 615.86 and 375.85 M for LIS and ZOF, respectively. The compatibility between the binary system LIS/β-CD and lactose 1:1 (m/m) has been studied by means of thermogravimetry/derivative thermogravimetry, differential thermal analysis and FTIR spectroscopy. As a result of the encapsulation of LIS in the β-CD cavity, the stabilization of drug substance in the presence of lactose has been realized. [ABSTRACT FROM AUTHOR]

To evaluate the effectiveness of the thermal remediation of soil decontamination, samples containing organochlorine insecticide hexachlorocyclohexane (HCH) were subjected to different temperatures depending on the exposure time. For this study, reference material and technical grade HCH were heated separately at β = 1 and 10 °C min in a thermogravimetric analyzer and contaminated soil samples were heated in an oven at different temperatures and heating time. To determine gaseous emissions generated during the heating of HCH isomers, HCH technical grade samples were heated in a closed system (reactor) and sample gases/vapors were collected for qualitative analysis. The results indicate that the contaminants are removed from soil to temperatures considerably lower than the respective boiling point. The thermogravimetric curves have shown that heating to 400 °C HCH results in fusion processes followed by evaporation, and investigating in the oven, the reduction in HCH concentration present in the contaminated soil depends on the temperature and length of heating. Gaseous emissions detected were from isomers of HCH, chlorine derivatives and benzene compounds. The laboratory tests show that parameters such as temperature, heating time and air flow can influence the thermal decontamination process of the subsoil. [ABSTRACT FROM AUTHOR]

In this paper, the use of lignite char as the reductant is proved to be promising in direct reduction of iron (DRI) technology. A better understanding of the reducing characteristics of lignite char is necessary for the development of efficient DRI technologies. The application of lignite char as reductant in direct reduction of hematite has been investigated in this study, and the results are compared with those of lignite coal and graphite. Thermogravimetric analysis was used to analyze the thermal behavior of the composite pellets. Maximum iron oxide reduction rate occurred at 865, 829.5, and 920 °C when lignite coal, lignite char, and graphite were used as reductants, respectively, indicating that iron oxide can be reduced at lower temperatures in the presence of lignite char. X-ray diffraction analysis showed that complete reduction of hematite to elemental iron was achieved with lignite char after 15-min reduction at 1000 °C. Scanning electron microscopy-energy-dispersive X-ray analysis results showed that the atomic ratio of Fe/O was increased from 0.39 in pellets before reduction to 0.51, 0.55, and 0.71 after reduction by graphite, coal, and lignite char, indicating that lignite char reduced hematite to a higher degree compared to lignite coal and graphite. [ABSTRACT FROM AUTHOR]

The mechanism of copper (II) oxide and molybdenum (VI) oxide co-reduction by Mg + C mixture was investigated at non-isothermal conditions by carrying out simultaneous differential thermal (DTA) and thermogravimetric (TG) analyses combined with X-ray diffraction (XRD) analysis of intermediate and final products. The whole process was found to involve several phenomena: interaction between oxides with CuMoO salt formation, high-exothermic reactions occurring directly between metal oxides and magnesium, as well as low-exothermic carbothermal reactions. In order to better understand the complex nature of calorimetric and TG curves, the behaviour of each single reagent as well as that of binary, ternary and quaternary mixtures was studied at linear heating. It was revealed that the simultaneous reduction of Cu and Mo oxides proceeds more easily by carbon than by magnesium. Only due to the decisive role of carbon on the reaction pathway, the combined and complete reduction of oxides by Mg/C reducing mixture becomes possible at relatively low temperatures. The sequence of chemical reactions possibly occurring during the heating process on the basis of DTA/TG curves and XRD analyses results of quenched reaction products has been proposed. [ABSTRACT FROM AUTHOR]

In this paper, the results of the thermogravimetric tests reduction of lead and zinc sulphates by hydrogen are presented. Tests performed under isothermal conditions allowed to determine the effect of temperature on the formed products of the reaction. The temperatures at which the maximum content of sulphides present in the products of reduction were determined. For the reduction of lead sulphate, value of the activation energy of the process and the participation of partial reactions in the process were determined. [ABSTRACT FROM AUTHOR]

The temperature dependences of the a( T) and c( T) crystal structure parameters for HoB and ErB at temperatures of 5-300 K are experimentally investigated. Anomalies of these dependences for tetraborides studied at magnetic ordering temperatures were found for HoB T = 5.7 K, T = 7.1 K and for ErB T = 15.4 K. The regular lattice a( T) and c( T) contribution to the thermal expansion of the rare-earth tetraborides studied in the present work and in the authors previous works were calculated. The temperature changes in the lattice components of the tetraborides thermal expansion, as well as their heat capacity of previous works of the authors, are considered within the Einstein and Debye approximations. The characteristic temperatures $$\theta _{{\rm Di}}, \theta _{{\rm E}}$$ of the examined rare-earth tetraborides were found. A slight decrease in the characteristic temperatures for RB tetraborides was observed with an increase in the rare-earth metal atomic number in the Periodic Table, which is conditioned by the predominant effect of the R ion mass on the lattice dynamics of the analyzed borides in comparison with the lanthanide reduction. [ABSTRACT FROM AUTHOR]

Basic oxygen furnace (BOF) dust is a by-product of steel plants that is rich in iron oxide. Reduction of this by-product may provide reutilization alternatives in steel industry. In this context, kinetic study was conducted using BOF dust pellets applying the forced stepwise isothermal analysis method. This work examines the reduction of BOF dust pellets using a mixture between hydrogen and carbon monoxide. Mass loss of 26 % was obtained after reduction of the BOF. Carbon oxide present in the reducing gas led to the formation of a carbon layer around the pellet between 550 and 650 °C. At higher temperatures, from 700 to 850 °C, it was observed that reduction was controlled by porous diffusion. In the range 900-1,000 °C, the control mechanism was determined as reactive species diffusion through metallic alloy lattice in individual particles. [ABSTRACT FROM AUTHOR]

Activated carbon-supported copper catalysts (Cu/AC) were prepared by impregnation of AC support with aqueous copper (II) nitrate solutions and subsequent microwave carbothermic reduction under different irradiation conditions. This was done to investigate the effect of the valence of copper on the vapor-phase oxidative carbonylation of methanol to dimethyl carbonate (DMC). Thermogravimetric analysis-mass spectrometry were carried out to explore the mechanism of carbothermic reduction in catalyst preparation. X-ray diffractometry, hydrogen temperature-programmed reduction, X-ray photoelectron spectroscopy, and scanning electron microscopy were employed to examine the bulk and surface properties of the Cu/AC catalysts. Microwave irradiation of the catalyst precursors rapidly induced a series of successive reactions, namely decomposition of Cu(OH)NO into CuO, reduction in CuO to CuO, and carbothermic reduction in CuO to Cu. These reactions resulted in mixed-valence copper species, CuO, CuO, and Cu, in the Cu/AC catalysts. CuO, CuO, and Cu were active in DMC synthesis, but the catalytic performance of Cu/AC was highly dependent on the Cu concentration. High irradiation temperatures resulted in higher Cu concentrations because of enhanced carbothermic reduction, and fast heating rates improved the degree of dispersion of CuO and Cu. The catalyst irradiated at 540 °C at a heating rate of 48 °C min showed the highest catalytic activity in the oxidative carbonylation of methanol. [ABSTRACT FROM AUTHOR]

Tantalum nanoparticles have been synthesized by the single-step chemical reaction route. Simultaneous reduction of Tantalum Pentoxide (TaO) with the in situ produced hydrogen and carbon at 600 °C is a new approach for the production of Ta nanopowder. Δ H values obtained from thermodynamic calculations are used to predict the entire mechanism of reduction of bulk TaO into Ta nanoparticles. The results of X-ray diffraction studies show that the final product consists of predominately nano α-Ta with β-Ta as the minority phase. The lattice strain in the final product was calculated using Williamson-Hall formula. The effect of lattice strain on thermal stability of the samples was analyzed by differential scanning calorimetry and thermal gravimetry in the air atmosphere. The morphology and particle size distribution of Ta nanosized powders have been analyzed by scanning electron microscope and transmission electron microscope. The results show that average crystallite size of the product Ta nanopowder is about 2-7 nm. [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 this paper, novel low-cost oxygen carriers containing FeO are evaluated for use in chemical looping combustion. Sewage sludge ashes and reference samples were prepared and used in cyclic reduction and oxidation experiments in a thermogravimetric analyzer (TG). A gaseous (3 % H) fuel and a solid fuel (hard coal) were tested. Three-cycle CLC tests were carried out in the 600-800 °C temperature range and long-term testing was performed at 950 °C. A reactivity study showed that the natural sewage sludge ash sample was stable during the cycling TG tests when hydrogen was used as a fuel at all of the temperatures investigated. Strong temperature effects on the oxygen transport capacity were observed. An one-cycle test at 900 °C showed also that the sewage sludge ash successfully reacted with coal. The oxygen released was fully used for coal combustion, with appreciable reaction rate at temperature of ~750-800 °C, that is significantly lower than that obtained for pure FeO-based oxygen carrier. The oxidation reaction was much faster than the reduction reaction. Moreover, the sewage sludge ash showed a low tendency toward agglomeration in the cyclic test, which was superior to the behavior of synthetic materials. The sewage sludge ash exhibited also high mechanical strength, an attrition index of 1 % and a high-temperature resistance of 1,170 °C in a reducing atmosphere. We conclude that sewage sludge ash can be effectively used as a low-cost, valuable oxygen carrier in practical application in chemical looping combustion technology for power generation. [ABSTRACT FROM AUTHOR]

Chemical looping air separation (CLAS), based on the chemical looping principle, is a novel and energy-efficient method to separate oxygen from air. The oxygen carriers used capture oxygen from air in an oxidation reactor and release oxygen in a reduction reactor. In this work, the adaptability of Cu/Zr oxygen carrier used for CLAS was investigated through thermodynamic analysis and experimental methods. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to measure the phases and surface morphology of oxygen carriers before and after experiments. The results show that CuO has the capability of releasing oxygen when the temperature is higher than 725 °C in the nitrogen atmosphere, and the minimum oxygen reduction temperatures increase with the increasing of oxygen concentrations. The Cu/Zr oxygen carrier has high oxygen reduction and oxidation rates when temperature is higher than a certain values. For reduction, the value is about 860 °C. For oxidation, the value is about 500 °C. The reactivity of oxygen carrier increases significantly with the temperature increasing. On overall, reactivity of oxygen carrier has little difference under different particle sizes. The oxygen carrier exhibits a stable oxygen reduction and oxidation behavior during reduction-oxidation cycles. XRD patterns show that the main phases in reduced samples are CuO and ZrO. The main phases in fresh and oxidized samples are CuO and ZrO. SEM images show that the fresh and reacted oxygen carriers are porous. The surface of reacted samples is smoother than fresh samples and no agglomeration has been found. [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]

This work describes and characterizes an algorithm for the nonambiguous reduction of multiexponentially decaying luminescence signals to scalar values of corresponding calibration temperatures. Previous evaluation schemes in phosphor thermometry make use of an intermediate step, where data reduction is achieved by fitting a model equation to phosphorescence decays in order to translate one or more fitting parameters into temperature. However, every slight mismatch between model equation and experimental data may lead to substantial errors in connection to noise-related inaccuracies during the retrieval of adequate fitting windows. Additionally, there is a need for fitting windows, capable of automatically adapting to largely varying signal time scales. In this context, the authors propose to set the fitting window length according to the time where the signal falls below a given percentage of the initial intensity. In comparison to fitting windows, defined by multiple decay times, modeling results suggest substantial precision benefits for as long as signal-to-noise ratios stay above 4. Nevertheless, by comparing signal shapes of measured curves directly with a library of temperature-calibrated decay signals, all necessary assumptions on the mathematical description of measured signals become redundant and evaluation errors connected to uncertain fitting windows are largely circumvented. Resulting capabilities of the proposed signal shape recognition method (SSR) in terms of temperature precision and accuracy were compared to a conventional least-squares fitting approach, using a set of temperature-calibrated phosphorescence decay signals from CdWO. Accordingly, the SSR algorithm was found to reduce statistical temperature errors by at least 9 %. [ABSTRACT FROM AUTHOR]

The effect of milling on the aluminothermic reduction of niobium pentaoxide was investigated. Charges of NbO and Al (containing 5 % excess Al) were milled for different time (2, 5 and 10 h). XRD profile of milled samples indicated no phase formations during milling; only peak broadening were seen. Milled and unmilled charges were heated in a thermal analyser up to 1,400 °C. Products of milled charges showed formation of Nb, NbO and AlO; whereas unmilled hand mixed charges showed formations of NbAl along with Nb and AlO. The tendency of milled charges towards Nb formations without the presence of aluminides was explained from the increase in surface area of charges caused by particle reduction. [ABSTRACT FROM AUTHOR]

A possible technology that can contribute reduction of carbon dioxide emission is oxy-fuel combustion of fossil fuels enabling to increase CO concentration in the exhaust gas by carrying out the combustion process with oxygen and replacing air nitrogen with recycling combustion products to obtain a capture-ready CO stream. The laboratory studies and pilot-scale experiments discussed during the last years have indicated that oxy-fuel combustion is a favorable option in retrofitting conventional coal firing. Estonian oil shale (OS) with its specific properties has never been studied as a fuel in oxy-fuel combustion, so, the aim of the present research was to compare thermo-oxidation of OS and some coal samples under air and oxy-fuel combustion conditions by means of thermal analysis methods. Experiments were carried out in Ar/O and CO/O atmospheres with two oil shale and two coal samples under dynamic heating conditions. FTIR analysis was applied to characterize evolved gases and emission dynamics. Kinetic parameters of oxidation were calculated using a model-free kinetic analysis approach based on differential iso-conversional methods. Comparison of the oxidation characteristics of the samples was given in both atmospheres and it was shown that the oxidation process proceeds under oxy-fuel conditions by all studied fuels with lower activation energies, however, it can last longer as the same temperatures are compared. [ABSTRACT FROM AUTHOR]

We studied the temperature-programmed reduction by NH (NH-TPR) as a supplement to the temperature-programmed reduction by H (H-TPR) for the characterization of supported Cu species. The NH-TPR profile of Cu/SiO, which contained only bulk CuO, exhibited two peaks for N formation in equal amounts, suggesting stepwise reduction of the bulk CuO. In contrast, the H-TPR profile exhibited only one H consumption peak. We also studied Cu-NaZSM-5 samples with various Cu and Na loadings. The Cu ions on ZSM-5 were reduced to Cu but no further. Kinetic analysis revealed that the NH-TPR profile exhibited peaks for separate reductions of isolated and binuclear Cu ions. Thus, we found NH-TPR to be useful for detailed analysis of the reducibility of Cu to Cu in zeolite pores. [ABSTRACT FROM AUTHOR]

This article presents the test results of thermal properties and flammability of crosslinked nitrile rubber in the presence of zinc oxide or nano-zinc oxide containing waste keratin, using the test results obtained by means of a derivatograph, DSC, and oxygen index. The influence of modified montmorillonite (NanoBent) on selected properties of investigated elastomer-protein composites has also been studied. The composites' thermal stability and flammability depend on the method of composite preparation and the quantity of added keratin. The addition of waste keratin reduces the flammability of NBR-keratin composites. [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]

Biomass is an effective substitute for fossil fuels and has a substantial impact on CO reduction. Meanwhile, alkali metal-related problem is a major barrier in biomass combustion. Sludge is a waste with low heating value, high water, sulfur, and nitrogen contents, as well as high phosphorus content, which makes the sludge a potential choice to inhibit the alkali metal-related problems during biomass combustion. The nitrogen behavior and the emissions of NO and NO are one of the key problems when sewage sludge is co-fired with biomass. Thus, nitrogen transformation during co-pyrolysis of cotton stalk and sludge at different heating rates were studied. The results show that HCN and HNCO are the major nitrogen-containing species for petrochemical sludge. The addition of petrochemical sludge changes the path of the conversion of fuel nitrogen and the presence of cotton stalk in the mixture promotes NH and HCN formation. [ABSTRACT FROM AUTHOR]

The use of unconventional synthesis methods in the formation of CaO·2AlO (CA) is justified because it reduces the formation temperature of the compound. CA is formed by classical method at temperatures above 1,400 °C. The polymeric precursor method allows a significant temperature decrease in CA synthesis reaching temperatures of 1,000 °C. This paper deals with CA synthesis by 'citrate' method which is often presented as Pechini method, starting from a mixture of citric acid, ethylene glycol and calcium, and aluminum nitrates. A method based on the formation of a polymeric precursor was also used, starting from a mixture of acrylic acid and nitrates of calcium and aluminum. The results showed a net difference in favor of samples obtained from acrylic acid, which by annealing at 800 °C for 1 h, contain pure CA. The samples obtained from citric acid, after annealing at 800 °C are amorphous. After annealing at 900 °C in all samples CA is single phase. [ABSTRACT FROM AUTHOR]

The aim of this work is to evaluate the feasibility of preparation of Nb10Hf1Ti alloy by magnesiothermic reduction of its oxides. DTA studies were conducted to identify the reduction temperature for co reduction of the mixed oxides of NbO, HfO, and TiO by magnesium under reducing atmosphere. Based on DTA analysis, experiments were carried out to prepare Nb10Hf1Ti alloy by magnesiothermic reduction of their oxides at 750 °C. The reduced product was analyzed for its phases by X-ray diffraction. The excess Mg was leached out, the alloy mixture was vacuum dried, pelletized, sintered, and electron beam melted to get a consolidated alloy of the required composition. The alloy was characterized using different techniques such as optical microscopy, scanning electron microscopy, and chemical analysis. Microstructural observations revealed the formation of coarse grain structure in the consolidated alloy. The alloy product was also evaluated for its micro hardness. [ABSTRACT FROM AUTHOR]

The present paper deals with differential thermal analysis studies conducted to find out the onset temperature for silicothermic reduction of MoO to Mo. The reaction kinetics of Si-MoO system has been analyzed by a model-free Kissinger method. X-ray diffraction analysis has confirmed the formation of Mo metal and SiO as the slag phase after silicothermic reduction of MoO. The activation energy for silicothermic reduction of MoO to Mo was evaluated to be 309 kJ mol. [ABSTRACT FROM AUTHOR]

Alkaline earth aluminates with the overall nominal compositions CaSrAlO, CaMgAlO and MgSrAlO doped with 1 mol% of Eu ions were prepared by the modified aqueous sol-gel method. The thermal behaviour of the xerogels was studied by the TG/DSC-MS technique under an argon and a reductive atmosphere (Ar/H-5 %). Appropriate luminescent efficiency of the materials was achieved after annealing at temperatures lower than those in conventional solid state reactions. All three aluminates are mixtures of at least two phases; the monoclinic phase of CaAlO, the hexagonal phase of SrAlO and the cubic phase of MgAlO were identified. Solid solubility was recognised in the CaSrAlO:Eu composition due to the similar ionic radii of Ca and Sr. UV excited luminescence was observed in the blue region (λ = 441 nm) in the aluminates containing the monoclinic phase of CaAlO and in the green region (λ = 520 nm) in the MgSrAlO:Eu composition. [ABSTRACT FROM AUTHOR]

The thermochemical approach to analysis of thermal decomposition of solids, developed earlier by L'vov, is extended here, for the first time, to interpret the kinetics and mechanism of the reduction of an oxide (NiO) by a gas (H). This approach is based on the mechanism of congruent dissociative vaporization of the reactant, Langmuir kinetics and determination of the Arrhenius E parameter by the third-law method. The calculated enthalpy of the reaction is in good agreement with the experimentally measured E value. Many other mechanistic and kinetic features of the reaction are explained within the framework of the given theoretical approach. These include: the formation of metal nuclei; the initial autocatalytic behavior; the formation of nanocrystalline structure of the reduced metal product; the equimolar and isobaric modes of reduction; the dependence of reduction rate on hydrogen pressure; the more than twofold decrease of the E parameter with the extent of reaction α, and the systematic increase of E with temperature. [ABSTRACT FROM AUTHOR]

Copper monoxide (CuO) was successfully obtained by microwave-assisted hydrothermal method, using different conditions-in a solution without base, in a solution alkalinized with NaOH or with NHOH. The powders were analyzed by thermal analysis (TG/DTA), X-ray diffraction (XRD), infrared spectroscopy, UV-Visible spectroscopy, and scanning electronic microscopy. XRD results showed that CuO was obtained with monoclinic structure and without secondary phases. Thermal analysis and infrared spectra indicated the presence of acetate groups on the powder surface. TG curves also showed a mass gain assigned to the Cu(I) oxidation indicating that a reduction possibly occurred during synthesis. The high and broad absorption band in the UV-Vis spectroscopy from 250 to 750 nm indicated the coexistence of Cu(II) and Cu(I), confirming the Cu(II) reduction, inside the CuO lattice. It was also possible to confirm the Cu(II) reduction by a displacement of the Me-O vibration bands observed in the IR spectra at around 500 cm. [ABSTRACT FROM AUTHOR]

In this study, we have attempted to explain the complex reactions that occur during the dehydration of Ca(OH), in the presence of solid carbon and FeO, in order to clarify their role as eventual precursors to the reduction and high temperature strength characteristics in feedstock agglomerates of iron and steelmaking by-products. A series of simultaneous thermo-gravimetric (TG), differential thermal analytic (DTA), and mass spectrometric (MS) tests were performed on agglomerated sample mixes of Ca(OH), C, and FeO to test the influence of heating rate and particle size on the transformations occurring below 1,073 K in inert atmosphere. The overall transformation begins with calcium hydroxide dehydration. Nucleation and growth of CaO grains during dehydration, as well as subsequent gasification of solid carbon, are highly dependent on the governing interstitial particle porosity and mildly dependent on the heating rate in and around agglomerates. The reduction of hematite in current agglomerates is, by association to preceding reactions, partly dependent on porosity and heating rate, but the mechanism of reduction was also found to be highly dependent on the particle size of iron oxides. Furthermore, in areas of intimate contact between CaO and iron oxide, a calcium ferrite phase appears in the form of angular and calcium-rich particles. [ABSTRACT FROM AUTHOR]

From the peculiarities of Temperature-programmed reduction (TPR) method and using the Sestak–Berggren conversion function, we describe first the TPR curve simulation procedure. The influence of the Sestak–Berggren exponents on the TPR peak maximum and shape is demonstrated, by analyzing several synthetic TPR profiles. Finally, the kinetic parameters of Au/CeO2 promoted with yttrium as well as those of Au/CeO2–Al2O3 promoted with V2O5 are discussed. [ABSTRACT FROM AUTHOR]

The thermal decomposition of synthetic serrabrancaite (MnPO4 · H2O) was studied in N2 atmosphere using TG-DTG-DTA. Thermal analysis results indicate that the decomposition occurs in two stages, which are assigned to the dehydration and the reduction processes and the final product is Mn2P2O7. X-ray powder diffraction, FT-IR and FT-Raman techniques were used for identification of the solid decomposition product. The decomposition kinetics analysis of MnPO4 · H2O was performed under non-isothermal condition through isoconversional methods of Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS). The dependences of activation energies on the extent of conversions are observed in the dehydration and the reduction reactions, which could be concluded the “multi-step” processes. [ABSTRACT FROM AUTHOR]

The possibility to determine the kinetic parameters for temperature programmed reduction of Cu/Fe3O4 using only one TPR profile is analyzed. The same data are analyzed both by Friedman’s iso-conversional method and another one previously derived and published by the authors. One shows that taking into account the experimental restrictions of Monti and Baiker, the Friedman’s method, although gives values of the activation energy smaller than the real values, indicates a very similar dependence of these on the reduction degree. On the basis of some synthetic data one shows that the errors are very large when these recommendations are neglected, being possible to determine a false dependence on the degree of reduction. [ABSTRACT FROM AUTHOR]

The thermal decomposition of electrolytic manganese dioxide (EMD), in an inert atmosphere, and the effect of chemical reduction on EMD, using 2-propanol under reflux (82°C), was investigated by differential scanning calorimetry (DSC). This study is an extension of a study investigating the thermal decomposition of EMD and reduced EMD by TG-MS (J. Therm. Anal. Cal., 80 (2005)625)). The DSC characterisation was carried out up to 600°C encompassing the water loss region up to 390°C and the first thermal reduction step. Water removal was observed in two distinct endothermic peaks (which were not deconvolved in the TG-MS) associated with the removal of bound water. For the lower degrees of chemical reduction, thermal reduction resulted in the formation of Mn2O3; for higher degrees of chemical reduction, the thermal reduction resulted in Mn3O4 at 600°C. In the DSC the thermal reduction of the EMD and chemically reduced specimen was observed to be endothermic. The reduced specimens, however, also showed an exothermic structural reorganisation. [ABSTRACT FROM AUTHOR]

Samples of electrolytic manganese dioxide (EMD) were chemically reduced using 2-propanol under reflux (82°C) for 1, 2, 3, 6 and 24 h intervals. XRD analysis showed that the ?-MnO2 structure was preserved although the lattice dimensions were observed to increase with increasing degree of reduction to accommodate the intercalation of protons. The exception was the 24 h reduced sample which contained two phases; ? -MnO2 and ? -MnOOH. Three regions of decomposition in the range of 50 to 1000°C were observed using thermogravimetric analysis coupled with mass spectrometry (TG-MS) and were accounted for as water removal below 390°C, reduction of MnO2 to Mn2O3 between 400 and 600°C, and Mn2O3 to Mn3O4 between 600 and 1000°C. Again the exception proved to be the 24 h reduced sample which was observed to decompose predominantly in one step between 400 and 600°C directly to Mn3O4. [ABSTRACT FROM AUTHOR]

In this work the properties of HY zeolite containing nickel oxide was investigated using thermal analysis (TG/DTA) and temperature programmed reduction (TPR). The results obtained by XRD and FTIR showed that the impregnation method used did not change the structure of HY zeolite. TPR profiles showed two events at 238 and 507°C which were attributed to reduction of nickel oxide on the HY cavities at different temperatures. The thermodesorption ofn-butylamine from Ni*/HY zeolite showed typically two larger mass loss events attributed to the elimination of n-butylamine adsorbed on the weak acid sites and on the medium+strong acid sites. [ABSTRACT FROM AUTHOR]

Excipient compatibility of a new chemical entity was assessed using an isothermal microcalorimeter. Mixtures of an active pharmaceutical ingredient with a primary amine group and excipients were prepared in a 1:1 ratio and compatibility monitored by exposing to 50, 60 and 70°C in presence of 200 mL of water. The new chemical entity, a primary amine, reacted with reducing sugars such as lactose and resulted in a brown discoloration. This reaction is the Maillard type condensation reaction between amines and reducing sugars. The rate of reaction was dependent on the temperature with rapid degradation at higher temperatures. No other incompatibility was apparent between the primary amine and other excipients [ABSTRACT FROM AUTHOR]

The physico-chemical properties and reactivity tested by hydrogen have been studied for two series of NiO-ZnO mixed oxides of various composition. The solid nickel oxide or zinc oxide in interaction with the solution of nitrate of the second component were used as the precursors in each series. The differences in some physico-chemical parameters of the samples in both series were correlated with their reduction behaviour, followed both in iso- and non-isothermal regime. Moreover, the influence of various factors modifying the reactivity of mixed oxides was also investigated and the results were compared with those obtained from earlier studied analogous systems of quite different origin. [ABSTRACT FROM AUTHOR]

Uses the fractal approach to data concerning the reduction with hydrogen of inorganic oxides mainly nickel oxide. Application of the formula used for solid-gas decompositions; Fractality of the nuclei; Similarity of the reduction of ferrous oxide with hydrogen.