Thermal Destruction Processes Research Articles

ChemInform Abstract: Differentiation of the Molecular Structures of Nitro Compounds as the Basis for Simulation of Their Thermal Destruction Processes

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Pyrolysis of poly(2-propylheptyl acrylate)

The thermal destruction processes of poly(2- propylheptyl acrylate) take place at the range of tempera- ture 250-950 C was investigated using pyrolysis-gas chromatography. Knowledge of the types and amounts of pyrolysis products will provide important information about the thermal degradation of homopolymer poly(2- propylheptyl acrylate) and the mechanisms involved. Unsaturated monomers 2-propylheptyl acrylate and 2-pro- pylheptyl methacrylate, according to by-product alkyl alcohol 2-propylheptylalcohol, alkene 2-propylheptene-1, carbon dioxide, carbon monoxide, methane, and ethane were formed during thermal degradation of poly(2-pro- pylheptyl acrylate).

An ozone/hydrogen peroxide/microwave-enhanced advanced oxidation process for sewage sludge treatment

Solids destruction and nutrients release from sewage sludge were investigated using thermal destruction and/or oxidation processes. Hydrogen peroxide (H2O2), ozone (O3) and a combination of both were used for the oxidation processes performed at ambient temperature. Thermal destruction using microwave (MW) alone without an oxidant was also conducted. Microwave enhanced advanced oxidation processes (MW-AOP), such as MW/O3, MW/H2O2 and MW/H2O2/O3, were conducted at 100°C. In terms of nutrients release and solids reduction, the MW/H2O2/O3-AOP yielded the best result; an addition of ozone improved the MW-AOP process. More than 30% of TP and 20% of TKN were released into the solution. About 37% of total COD was also solubilized from sludge mass. Both the conventional oxidation processes and the MW-AOP processes could be used to release nutrients and to reduce solids from sewage sludge; however, the MW-AOP processes were superior in performance. Microwave heating alone also resulted in a substantial amount of ortho-phosphate into the solution.

Cross linking and thermal destruction processes in thin films formed from dilute solutions of a copolymer of trifluorochloroethylene and vinylidene fluoride

Thermal desorption mass spectrometry has been used to investigate the mechanisms for thermal destruction of films prepared from dilute solutions of a copolymer of trifluorochloroethylene and vinylidene fluoride. It is shown that compared with films obtained from concentrated solutions, the ratio of the intensities of the low-and high-temperature stages of HCl and HF release changes substantially in this case. It is concluded that the low-temperature stage of hydrogen halide release is attributable to cross-linking processes rather than to intramolecular reactions caused by the formation of double bonds in the chain.

Synthesis of ultrafine powders with mullite-zirconia composition by the sol-gel method

Processes of thermal destruction and phase formation occurring in sol-gel compositions of the Al203 - ZrO2 - SiO2, system during heat treatment are investigated. It is shown that the most uniform phase composition is exhibited in the case of a 3-to-1 Al2O3-to-SiO2 ratio with 20 wt.% ZrO2 in the form of an oxynitrate salt.

An Experimental Investigation of Sulphur-Nitrogen Interactions in Turbulent Spray Flames

ABSTRACT The effects of fuel sulphur on thermal and fuel-NO formation and destruction processes in liquid fuel, spray flames were studied using quinoline and tetrahydrothiophene to simulate fuel-N and fuel-S respectively. The exist gas NO emissions were found to be affected by the addition of sulphur to the fuel to an extent which was dependent on the fuel sulphur to nitrogen ratio, burner operating conditions and fuel type. The increase in fuel-NO emission, at a particular operating condition, due to sulphur addition, was in most cases linearly dependent on the sulphur concentration in the fuel. When the burner was operated in low NOx mode by staging the combustion air, the interactions were found to be dependent on the primary-zone fuel/air equivalence ratios, with greater enhancement observed for fuel-rich conditions. A practical consequence of these results is that the possible reductions in the NO emission by staging are dependent among other factors on the sulphur content of the fuel since the sulph...

Investigation of the thermal decomposition of bis(acetylacetonato)copper(II) vapour by a mass spectrometric method

The thermal destruction processes of bis(acetylacetonato)copper(II) (2,4-pentanedionatocopper(II), Cu(aa) 2) vapour and acetylacetone (2,4-pentanedione, Haa) were investigated using the high-temperature source of a molecular beam with mass spectrometric recording of the gas-phase composition. From the temperature dependence of the ion currents, the thermal stability of the ligand and complex was assessed and schemes of their thermal destruction in vacuo, hydrogen, and oxygen are suggested. The kinetic parameters of these processes are calculated.

Molecular Simulation of Thermal Destruction Processes in Aluminophosphates.

Molecular Simulation of Thermal Destruction Processes in Aluminophosphates.

Closed-Loop Recovery of Site Remediation Gas Phase Contaminants

A novel gas phase treatment system (contaminant absorption and recovery [CAR]) for removal and subsequent recycling of gas phase VOCs from soil vapor extraction/gas stripping systems has been developed. Gas phase removal efficiencies using a packed column contactor exceed 99 percent The VOC-laden absorption fluid is subsequently vacuum-stripped of the VOCs, allowing potential condensation into liquid solvent concentrates. Partition coefficients for trichloroethylene (TCE) in triethylene glycol (TEG) ranged to ca. 5.0 mole fraction gas/mole fraction liquid, indicating a significant capacity for removal from the gas phase. Results of pilot-scale operation indicate favorable removal efficiencies and cost-effective performance in comparison to GAC or thermal destruction processes. System mass transfer coefficient predictions were done, using a variety of mathematical models and compared to experimental results. A modified Mangers and Ponten correlation was found to describe system mass transfer coefficients w...

Evolution of the active surface of carbons produced from various raw materials by steam pyrolysis/activation

AbstractA one step pyrolysis/steam activation was used to produce activated carbons from apricot stones, nuts, coconuts, almond shells and grape seeds, and Bulgarian lignite from Maritza Iztok and Chukurovo deposit. The evolution of the active surface of the carbons produced was investigated. The changes in the structure of activated carbons give evidence for the periodicity of the processes of oxidation and thermal destruction. It was established that the adsorption properties of activated carbons are dependent on the treatment temperature, soak time and the nature of the raw materials.The activated carbons produced from various raw materials have a high concentration of surface functional groups, carboxyl and hydroxyl. Activated carbons with predominantly meso‐ and macropore structures showed high capacity for adsorbing Cu2+ ions from solutions.

Mass spectrometric study of thermal stability of copper(II) bis(dipivaloylmethanate) vapour

The processes of thermal destruction of copper(II) bis(dipivaloylmethanate) (Cu(dpm)2) in the temperature range 150°–550°C were studied by using a two-temperature variant of a double chamber Knudsen cell, with mass spectrometric recording of the gas-phase composition. The temperature range of stability of the vapour of the complex in vacuum was determined, as were those of its mixtures with oxygen in different proportions. The temperature dependence of the rate constant of the thermolysis of (Cu(dpm)2) vapour was obtained. The thermal stability of Hdpm vapour and the influence of oxygen on the thermolysis of the ligand were studied.

Study of the thermal behaviour of copolymers of styrene with magnesium, calcium, strontium and barium acrylates

The processes of thermal destruction of copolymers of styrene with magnesium, calcium, strontium and barium acrylates have been investigated by TG and the temperature characteristics have been determined. Though the thermal stability of the metal acrylates exceeds markedly that of polystyrene, the introduction of low concentrations of the salts caused an observable deterioration of the thermal resistance of the copolymers. This was in agreement with the calculated values of the kinetic parameters of decomposition for the samples studied.

Thermal stabilities of copolymers of styrene with lithium, sodium and potassium acrylates and methacrylates

AbstractThe processes of thermal destruction of copolymers of styrene with Li, Na and K acrylates and methacrylates have been studied and the temperature characteristics have been determined. The kinetic parameters for decomposition of the copolymers are calculated and discussed.

Thermal destruction processes in proteins involving cystine residues.

To ascertain the upper limit of protein thermostability and to evaluate the introduction of additional -S-S- bridges for the enhancement of protein thermostability by site-directed mutagenesis, the stability of cystine residues at 100 degrees C has been investigated in a number of unrelated proteins. All proteins studied (more than a dozen) undergo heat-induced beta-elimination of cystine residues in the pH range from 4 to 8. The time courses of this process closely follow first-order kinetics indicating that the stability of a cystine residue is not significantly affected by its position in the polypeptide chain. Furthermore, the first-order rate constants of beta-elimination of disulfide bonds at 100 degrees C are remarkably similar for different proteins--0.8 +/- 0.3 h-1 and 0.06 +/- 0.02 h-1 at pH 8.0 and 6.0, respectively. Thus, this process is relatively independent of both the primary structure and the elements of higher structures remaining in proteins in 100 degrees C. beta-Elimination of disulfides produces free thiols that cause yet another deleterious reaction in proteins--heat-induced disulfide interchange. This reshuffling of -S-S-bonds, which is much faster than beta-elimination, has also been quantitatively characterized.

Treatment of landfill leachates

Landfill leachate, which resembles concentrated mixed industrial waste water, threatens national groundwater supplies. Several processes drawn from industrial water treatment have been considered for renovating landfill leachate: biodegradation, chemical and thermal degradation, adsorption, reverse osmosis, and coagulation/precipitation. Since transporting leachate off-site entails considerable risk and expense, these technologies must be evaluated for their applicability to on-site treatment. Biodegradation has the greatest potential for removing the varied organic compounds found in leachate streams due to its flexibility and relatively wide application in waste-water treatment. Use of combinations of biological processes, such as sequential aerobic and anaerobic treatment, or of biological and physical processes, such as biologically activated carbon, may improve performance. Alternative chemical or thermal destruction processes are more energy intensive and require finer control than biological processes. Coagulation/precipitation, adsorption, and membrane processes have been studied for treating leachates to remove organic compounds, heavy metals, entrained oil, and colloidal material. Because these processes partition the leachate and, thus, concentrate toxic substances, further treatment of their residues is necessary. They are particularly suited for pretreating influent to a biological process or for polishing a biological effluent. Much work remains in applying these treatment processes to actual landfill leachates. Design of leachate treatment processes must be tailored to the site and will depend on the quantity and characteristics of treatment residues allowed under the prevailing regulatory environment. The variability of landfill leachates both from site to site and temporally within a site makes leachate treatment a challenging problem.

Study of the thermal behaviour of some transition metal acrylate-styrene copolymers

The processes of thermal destruction of copolymers of styrene with zinc, cobalt, nickel and copper acrylates have been studied by TG and the temperature characteristics have been determined. While the thermal stability of zinc-containing copolymers increases at higher metal contents, that of other metal-containing copolymers decreases and, depending on the metal, changes in the sequence Co > Ni > Cu.

Investigation into the processes of thermal and photothermal destruction of F-color centers in alkali-halide crystal phosphors

Using the concept of thermal and photothermal destruction of color centers in alkali-halide phosphors as an ion mechanism, certain formulas are examined which represent these processes. The phenomenon of thermal and photothermal destruction of F-color centers is investigated experimentally for the case of NaCl-Ag. A comparison of the experimental results obtained with the theory enabled an estimate to be made of a number of kinetic characteristics of the processes in question.

Chemical transformations of polymers Communication 19. Thermal destruction of polyarylates based on phenolphthalein with terephthalic and isophthalic acids

1. The processes of thermal destruction of polyarylates P-1 and P-2 were investigated. The infusible solid destruction product represents a carbonized three-dimensional skeleton, close to certain varieties of coals; the low-molecular destruction products consist of diphenyl, triphenylmethane, benzoic acid, and traces of phenol and phenol-phthalein; the only gaseous destruction products are carbon dioxide and carbon monoxide. 2. From a kinetic analysis of the gas evolution, the conclusion was drawn that the process takes place in the form of a parallel-sequential reaction. 3. Theoretical calculations of the rate constants of the steps of the parallel-sequential reactions are in good agreement with the experimental data. 4. The effective activation energies of the destruction processes were determined; the scheme of destruction was proposed, and certain considerations were expressed concerning the mechanism of the process.