Synthesis, thermal and spectroscopic study of light lanthanide nicotinate, in the solid state

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of the iron doping on the thermal decomposition of the polymeric precursor for the titanium dioxide powder synthesis

The Polymeric Precursor Method has proved suitable for synthesizing reactive powders using low temperatures of calcination, especially when compared with conventional methods. However, during the thermal decomposition of the polymeric precursor the combustion event can be releases an additional heat that raises the temperature of the sample in several tens of degrees Celsius above the set temperature of the oven. This event may be detrimental to some material types, such as the titanium dioxide semiconductor. This ceramic material has a phase transition at around 600 ° C, which involves the irreversible structural rearrangement, characterized by the phase transition from anatase to rutile TiO2 phase. The control of the calcination step then becomes very important because the efficiency of the photocatalyst is dependent on the amount of anatase phase in the material. Furthermore, use of dopant in the material aims to improve various properties, such as increasing the absorption of radiation and in the time of the excited state, shifting of the absorption edge to the visible region, and increasing of the thermal stability of anatase. In this work, samples of titanium dioxide were synthesized by the Polymeric Precursor Method in order to investigate the effect of Fe (III) doping on the calcination stages. Thermal analysis has demonstrated that the Fe (III) insertion at 1 mol% anticipates the organic decomposition, reducing the combustion event in the final calcination. Furthermore, FTIR-PAS, XRD and SEM results showed that organic matter amount was reduced in the Fe (III)-doped TiO2 sample, which reduced the rutile phase amount and increased the reactivity and crystallinity of the powder samples.

Thermal study and characterization of nicotinates of some alkaline earth metals using TG-DSC-FTIR and DSC-system photovisual

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis, characterization and thermal behavior of heterobimetallic carbonyl compounds of the type [W(CO)(4)(bipy)(CuX)] (X=Cl, N-3, ClO4 and BF4)

Four new heterobimetallic metal carbonyls were synthesized by the reaction of [W(CO)4(bipy)] (1) with copper(I) compounds leading to species with the general formula [W(CO)4(bipy)(CuX)] (X = Cl, N3, ClO4, BF4) (2-5). The metal carbonyl compounds were characterized by elemental analysis, infrared and UV -visible electronic spectroscopy and thermogravimetric analysis. The IR data for 2-5 show carbonyl stretching band patterns similar to compound 1 ; ie they exhibit the same number of bands. The UV - vis results show a dissociation reaction generating the starting compound 1 and CuX as consequence of a weak interaction between 1 and CuX. Thermal decomposition mechanisms as well as the thermal stability are influenced by the CuX fragments. The thermal stability decreases in the order [W(CO)4(bipy)] > [W(CO)4(bipy)(CuCl)] > [W(CO)4(bipy) (CuBF4)]. The X-ray results show the formation of WO3, CuWO4, Cu2O and CuO as final decomposition products.

Synthesis, characterization and thermal behavior of cyclopalladated compounds of the type [Pd{C6H4CH2N(CH3)(2)}(mu-X)](2) (X= Cl, NCO, SCN, CN)

The dimeric compound [Pd(dmba)(μ-Cl)]2 (1) (dmba = N,N-dimethylbenzylamine) reacts with KX, in methanol/acetone, affording the analogous dimeric pseudohalide-bridged species [Pd(dmba)(X)]2 [X = NCO(2), SCN(3), CN(4)]. The compounds were characterized by elemental analysis, infrared spectroscopy, NMR and thermogravimetric analysis. The IR data for 2-4 showed bands typical of coordinated pseudohalide ligands indicating clearly the occurrence of the exchange reaction. Their thermal behavior was investigated and suggested that their thermal stability is influenced by the bridging ligand. The thermal stability decreased in the order [Pd(dmba)(μ-SCN)]2>[Pd(dmba)(μ-Cl)] 2>[Pd(dmba)(;u-NCO)]2>[Pd(dmba)(μ-CN)]2. The X-ray results showed the formation of PdO as final decomposition product. © 1999 Elsevier Science Ltd. All rights reserved.

An optimization study of PtSn/C catalysts applied to direct ethanol fuel cell: Effect of the preparation method on the electrocatalytic activity of the catalysts

The aim of this work was to perform a systematic study of the parameters that can influence the composition, morphology, and catalytic activity of PtSn/C nanoparticles and compare two different methods of nanocatalyst preparation, namely microwave-assisted heating (MW) and thermal decomposition of polymeric precursors (DPP). An investigation of the effects of the reducing and stabilizing agents on the catalytic activity and morphology of Pt75Sn25/C catalysts prepared by microwave-assisted heating was undertaken for optimization purposes. The effect of short-chain alcohols such as ethanol, ethylene glycol, and propylene glycol as reducing agents was evaluated, and the use of sodium acetate and citric acid as stabilizing agents for the MW procedure was examined. Catalysts obtained from propylene glycol displayed higher catalytic activity compared with catalysts prepared in ethylene glycol. Introduction of sodium acetate enhanced the catalytic activity, but this beneficial effect was observed until a critical acetate concentration was reached. Optimization of the MW synthesis allowed for the preparation of highly dispersed catalysts with average sizes lying between 2.0 and 5.0 nm. Comparison of the best catalyst prepared by MW with a catalyst of similar composition prepared by the polymeric precursors method showed that the catalytic activity of the material can be improved when a proper condition for catalyst preparation is achieved. (C) 2012 Elsevier B.V. All rights reserved.

Thermal decomposition kinetics of Brazilian limestones: effect of CO2 partial pressure

The influence of the partial pressure of carbon dioxide (CO2) on the thermal decomposition process of a calcite (CI) and a dolomite (DP) is investigated in this paper using a thermogravimetric analyser. The tests were non-isothermal at five different heating rates in dynamic atmosphere of air with 0% and 15% carbon dioxide (CO2). In the atmosphere without CO2, the average activation energies (E-alpha) were 197.4 kJ mol(-1) and 188.1 kJ mol(-1) for CI and DP, respectively. For the DP with 15% CO2, two decomposition steps were observed, indicating a change of mechanism. The values of E-alpha for 15% CO2 were 378.7 kJ mol(-1) for the CI, and 299.8 kJ mol(-1) (first decomposition) and 453.4 kJ mol(-1) (second decomposition) for the DP, showing that the determination of E-alpha for DP should in this case be considered separately in those two distinct regions. The results obtained in this study are relevant to understanding the behaviour changes in the thermal decomposition of limestones with CO2 partial pressure when applied to technologies, such as carbon capture and storage (CCS), in which carbon dioxide is present in high concentrations.

Kinetics of thermal decomposition of niobium hydride

High-purity niobium powders can be obtained from the well-known hydride-dehydride (HDH) process. The aim of this work was the investigation of the structural phase transition of the niobium hydride to niobium metal as function of temperature, heating rate and time. The niobium powder used in this work was obtained by high-temperature hydriding of niobium machining chips followed by conventional ball milling and sieving. X-ray diffraction measurements were carried out in vacuum using a high-temperature chamber coupled to an X-ray diffractometer. During the dehydriding process, it is possible to follow the phase transition from niobium hydride to niobium metal starting at about 380 degrees C for a heating rate of 20 degrees C/min. The heating rate was found to be an important parameter, since complete dehydriding was obtained at 490 degrees C for a heating rate of 20 degrees C/min. The higher dehydriding rate was found at 500 degrees C. Results contribute to a better understanding of the kinetics of thermal decomposition of niobium hydride to niobium metal. (C) 2011 Elsevier Ltd. All rights reserved.

Study of the thermal decomposition of petrochemical sludge in a pilot plant reactor

The pyrolysis of a sludge produced in the waste water treatment plant of an oil refinery was studied in a pilot plant reactor provided with a system for condensation of semivolatile matter. The study comprises experiments at 350, 400, 470 and 530 °C in nitrogen atmosphere. Analysis of all the products obtained (gases, liquids and chars) are presented, with a thermogravimetric study of the char produced and analysis of main components of the liquid. In the temperature range studied, the composition of the gas fraction does not appreciably vary. In the liquids, the light hidrocarbon yield increases with increasing temperature, whereas the aromatic compounds diminish. The decomposition of the solid fraction has been analysed, finding a material that reacts rapidly with oxygen regardless of the conditions it is formed.

Thermal Decomposition of Mobile Phones

Paper submitted to the 31st International Symposium on Halogenated Persistent Organic Compounds (Dioxin 2011), Brussels, Belgium, 21-25 August 2011.

The thermal decomposition of uranium monocarbide /

"Contract AT(30-1)-2789."

The thermal decomposition of ethylene oxide. Submitted as a report on the Navy Contract N6onr-241, Task order I [Project NRo56-051] to the University of Rochester.

Bibliography: leaves 86-88.

Kinetic study on thermal decomposition of woods in oxidative environment

The purpose of this work is to gain knowledge on kinetics of biomass decomposition under oxidative atmospheres, mainly examining effect of heating rate on different biomass species. Two sets of experiments are carried out: the first set of experiments is thermal decomposition of four different wood particles, namely aspens, birch, oak and pine under an oxidative atmosphere and analysis with TGA; and the second set is to use large size samples of wood under different heat fluxes in a purpose-built furnace, where the temperature distribution, mass loss and ignition characteristics are recorded and analyzed by a data post-processing system. The experimental data is then used to develop a two-step reactions kinetic scheme with low and high temperature regions while the activation energy for the reactions of the species under different heating rates is calculated. It is found that the activation energy of the second stage reaction for the species with similar constituent fractions tends to converge to a similar value under the high heating rate.

Studies of clay minerals and their decomposition products

Mõssbauer spectroscopy and X-ray diffraction of five coals revealed the presence of pyrite, illite, kaolinite and Quartz, together with other minor phases. Analysis of the coal ashes indicated the formation of hematite and an Fe (3+) paramagnetic phase, the latter resulting from .the dehydroxylation of the clay minerals during ashing at 700 to 750 C. By using a combination of several physicochemical methods, different successive stages of dehydroxylation, structural consolidation, and recrystallisation of illite, montmorillonite and hectorite upon thermal treatment to 1300 C were investigated. Dehydroxylation of the clay minerals occurred between 450 and 750 C, the X-ray crysdallinity of illite and montmorillonite remaining until 800 C. Hectorite gradually recrystallises to enstatite at temperatures above 700°C. At 900 C the crystalline structure of all three clay minerals had totally collapsed. Solid state reactions occurred above 900 C producing such phases as spinel, hematite, enstatite, cristobalite and mullite. Illite and montmorillonite started to melt between 1200 and 1300°C, producing a silicate glass that contained Fe(3+) and Fe(2+) ions. Ortho-pnstatite, clino-enstatite and proto-enstatite were identified in the thermal products of hectorite, their relative proportions varying with temperature. Protoenstatite was stabilised with respect to metastable clinoenstatite upon cooling from 12000 C by the presence of exchanged transition metal cations. Solid state Nuclear Magnetic Resonance spectroscopy of thermally treated transition metal exchanged hectorite indicated the levels at which paramagnetic cations could be loaded on to the clay before spectral resolution is significantly diminished.

Thermal decomposition behavior of 1,2-bis-(2,4,6-tribromophenoxy)ethane

The thermal decomposition behavior of 1,2-bis-(2,4,6-tribromophenoxy)ethane (BTBPE) widely used as flame retardant plastics additive was studied by HRTG and differential scanning calorimetries. It was pyrolysed in inert atmosphere at 240 and 340 °C in isothermal conditions, the decomposition products were collected and investigated by means of IR and GC-MS, most of them are identified. It was found that BTBPE mostly evaporates at 240 °C. The decomposition products at 340°C depend on rate of their removal from the hot reaction zone. Main primary decomposition products found in case of rapid removal are tribromophenol and vinyl tribromophenyl ether. Whereas, prolonged contact with heating zone also produces hydrogen bromide, ethylene bromide, polybrominated vinyl phenyl ethers and diphenyl ethers, and dibenzodioxins. The nature of the identified compounds are in accordance with a molecular and radical pyrolysis reaction pathway. © 2002 Elsevier Science B.V. All rights reserved.