Showing papers on "Pyrolysis published in 1974"

Role of Binders in Solid Propellant Combustion

Abstract: : The objective of this program was to investigate and define the effects of inert binder properties on composite solid propellant burning rate. Experimental pyrolysis data were obtained for many binders of practical interest over a wide range of heating rates and pressures, in several environmental gases, with and without 10-percent ammonium perchlorate (AP) contained in the sample, and in some cases with catalysts. These data were used to extract kinetics constants from Arrhenius plots, and heat of decomposition. In addition, motion pictures were taken of the pyrolyzing surface and gas samples were extracted for analysis. Pyrolysis kinetics varied between binders, but were found to be independent of pressure, the presence of AP, and the presence of burn rate catalysts; however, a chlorine gas environment had a material effect upon the results. All of the binders exhibited molten, boiling surfaces mingled with char, to varying degrees; the amount of char increased with AP present, and in chlorine. Relevant data were input to the Derr-Beckstead-Price combustion model in order to associate binder properties with known binder effects on burning rate. Although the effects were predictable, they stemmed from properties other than pyrolysis kinetics; however, the binder data as applied to the model revealed possible deficiencies in the model, which are discussed. It appears that the approach of combustion tailoring by binder modification would have to involve the gas phase combustion processes rather than surface pyrolysis. Therefore, future work concerning the role of binder should be directed toward the gas phase.

Recent advances in pyrolysis mass spectrometry of complex biological materials.

Abstract: Nonvolatile biological materials, such as biopolymers or even whole cells, can be made accessible to mass spectrometric analysis by pyrolysis techniques. In principle, this enables differentiation, classification and identification of these materials. Moreover, pyrolysis mass spectrometry can provide a general picture of the chemical composition and structure of the sample analysed. During the past few years we have investigated several pyrolysis techniques in combination with different mass spectrometric methods. These investigations included Curie point pyrolysis, infrared laser pyrolysis, low voltage electron impact ionization, field ionization1 and pyrolysis field desorption.1 Pyrolysis reactions were performed either at the gas inlet or directly at the ion source. The relative merits of these different experimental approaches are discussed. Additionally, examples of various applications, such as computer identification of bacteria and qualitative analyses of biopolymers, are given.

Pyrolysis of poly(vinyl chloride)

Abstract: A pyrolysis–gas chromatography–mass spectrometric technique has been developed to study the thermal degradation of poly(vinyl chlorides) polymerized at different temperatures. Hydrogen chloride and benzene evolution during successive stages of pyrolysis have been quantitatively determined and correlated to the tacticity and molecular weight of the polymer. It was found that lowering the temperature of polymerization and molecular weight depresses benzene evolution and increases char weight but does not affect the HCl yield. It is suggested that the syndiotactic trans microstructure favored at low temperature of polymerization yields polyenes which cannot cyclize to form benzene. As the molecular weight decreases, the increase in number of vinyl chain ends facilitates pyrolytic crosslinking and char formation.

A method for oxygen isotope analyses of organic material

Abstract: A technique has been developed to measure 18O/16O ratios in milligram amounts of organic material. The organic material is pyrolyzed at 1250°C in the presence of diamonds (easily outgassed carbon source) as the reducing agent. The carbon monoxide formed is converted to carbon dioxide by a high voltage discharge, and the CO2 is analyzed on a mass spectrometer. The precision of the method is ±0.35 permil (1 sigma).

Investigations on poly(vinyl chloride). I. Evolution of aromatics on pyrolysis of poly(vinyl chloride) and its mechanism

Abstract: Poly(vinyl chloride) (PVC) alone or mixed with 10 wt-% and 50 wt-% TiO2, SnO2, ZnO, and Al2O3 were pyrolyzed by using a pyrolysis gas chromatograph. Benzene, toluene, ethylbenzene, o-xylene, styrene, naphthalene, and various chlorobenzenes were identified. No hydrocarbons could be detected in pyrolysis products of any samples at 200°C. More aromatic hydrocarbons than aliphatic hydrocarbons are released from the PVC–TiO2 system and in preheated PVC. The contrary result is observed in the PVC–ZnO and PVC–SnO2 systems. Aromatics having methyl endgroups are easily released from the PVC–ZnO and PVC–SnO2 systems and at elevated pyrolysis temperature, because methylene groups are easily isolated along the chain by ZnO, SnO2 and the heating. The release of ethylbenzene o-xylene, and chlorobenzenes suggests a repeated dehydrochlorination and recombination of HCl and Cl2 to double bonds along the chain. Possible decomposition mechanisms of PVC are discussed.

Controlled generation of cool hydrogen from solid mixtures

Abstract: The hydrogen gas evolution rates and the gas temperatures of certain hydrn gas generating compositions are modified by adding compounds such as LiAlH4 which thermally decompose in the reaction zone producing hydrogen while lowering the reaction temperature; and acetonates, metal oxides, and the like which, when added in relatively small amounts accelerate the hydrogen gas evolution rate.

Pyrolysis of municipal solid waste

Abstract: A state-of-the-art review describing the characteristics of municipal solid waste (MSW) and assessing the chemistry and technology of pyrolysis of municipal solid waste is presented. The economics of the pyrolysis process are outlined. Combustibles constitute on average about 60% of the weight of MSW and result in an average heating value (“as received” basis) of about 3,000 to 6,000 Btu/Ib. This makes MSW attractive for thermal treatment. Municipal solid waste can be converted to gas, liquid and solid products by pyrolysis. Due to the complexity in composition of MSW the exact mechanism of pyrolysis is not known. Both homogeneous and heterogeneous reactions occur at the same time and both heat and mass transfer take place during the process. The relative yields of different products depends on the temperature of pyrolysis and the rate of heating. High pyrolysis temperatures and high heating rates favour the production of gases indicating high energies of activation for gasification reactions. At low temperatures, below 800°C, the pyrolysis process is reaction-rate controlled, while at high temperatures, above 1,200°C, the process is diffusion-rate controlled. Conditions of good heat and mass transfer are required for gasification of MSW. The residual char after pyrolysis can be gasified by further treatment with steam, hydrogen or carbon monoxide and water. The heat available from the products of pyrolysis is sufficient to sustain the process and yield some excess energy. Three types of reactor design have been generally used in the investigation of pyrolysis of MSW; fixed bed reactor, fluidized bed reactor and rotary kiln reactor. The advantages and weak points of each of these are briefly discussed. The costs of disposal of MSW by pyrolysis appear to be competitive with incineration.

Process for gasifying carbonaceous matter

Abstract: A process for the gasification of coal and other carbonaceous materials in which solid particulate carbonaceous material is dried without pyrolysis or oxidation by direct contact with a fluent stream of hot synthesis gas product. The dried carbonaceous material is separated from the moist synthesis gas, water is removed from the moist gas and converted to steam, and the steam is mixed with oxygen bearing gas and reacted with the dried carbonaceous material to produce synthesis gas and an ash residue. The oxygen and steam mixture is heated by direct contact with the ash residue, while the hot synthesis gas is utilized to dry the incoming particulate carbonaceous material. Synthesis gas containing hydrogen and carbon oxides is recovered from the process.

Method for producing isotropic pyrolisis carbon coatings

Abstract: A material having a vapor pressure of at least 5 mm Hg at 490°C. and selected from aromatic and cycloaliphatic hydrocarbons and alkyl derivatives thereof, nitrogen-, oxygen- and sulfur-containing compounds having hetero rings and alkyl derivatives thereof, substituted compounds of these compounds, and substances containing these compounds is used as starting material. Such starting material is brought into contact in a vapor state, if necessary, diluted with an inert gas, with a substrate heated at a temperature of 600°-1500°C. thereby depositing the resulting isotropic pyrolytic carbon on the substrate.

Mechanism of Hydrogen Peroxide Pyrolysis

Abstract: The pyrolysis of hydrogen peroxide was followed mass spectrometrically, under conditions such that a steady-state concentration of the HO2 radical equal to or exceeding 1/100th of the concentration of hydrogen peroxide would have been detected. The actual steady-state concentration of HO2 in a reacting mixture was found to be below the detection limit, from which it is concluded that the simplest mechanism that provides an entirely adequate quantitative description of the pyrolysis is

Quantitative determination of the polymeric constituents in compounded cured stocks by Curie-point pyrolysis-gas chromatography

Abstract: Pyrolysis—gas chromatography has been shown to be an excellent technique for quantitative estimation of polymers. Its acceptance is apparent from the large number of publications reported in the past year. The increasing complexity of the constituents used in various applications has necessitated the use of more precise and sophisticated control over the experimental variables. The Curie-point pyrolysis technique has been able to provide a degree of control which has not been possible with any of the other pyrolysis techniques used. In this technique, the sample is heated in a helium stream to a precisely duplicable temperature which is dependent on the composition of the alloy used for the pyrolysis wire, the maximum temperature being the Curie-point when the ferromagnetic wire becomes paramagnetic and is thus incapable of absorbing any energy from the high frequency induction current source. The fast temperature rise results in more specific products on pyrolysis, and any contamination from pre...

PREDICTION OF INITIAL PRODUCT DISTRIBUTION FROM n-PARAFFIN PYROLYSIS AT HIGHER TEMPERATURES BY CONSIDERING ETHYL RADICAL DECOMPOSITION

Abstract: normal paraffinic hydrocarbons was proposed on the basis of the free-radical chain reaction mechanism. It was then assumed that all ethyl radicals produced in each reaction step converted to ethane via intermolecular H-atom abstraction reaction. The assumption holds well in the relatively low temperature range up to about 500°C and near atmospheric pressure. In practice, however, hydrocarbons are sometimes pyrolyzed at higher temperatures and under lower partial pressures. In such cases, the decomposition of ethyl radicals would occur competitively with the H-atomabstraction reaction8>n). As a result, the amounts of reaction products hydrogen, ethylene, and ethane are considerably affected by the reaction conditions. Nevertheless, no calculations have been published based on both H-atom abstraction and ethyl radical decomposition reactions, except for w-butane pyrolysis shown by Pacey and Purnell10). In this paper, the authors investigated the effect of the ethyl radical decomposition reaction on initial product distribution. By introducing the ethyl radical decomposition reaction into the previously proposed model9\\ the initial product distribution under various reaction conditions can be predicted.

Tellurium extrusion: a novel method for carbon–carbon bond formation

Abstract: Pyrolysis of 9-tellurabicyclo[3,3,1]nona-2,6-diene (II) in [2H8]toluene at 175° leads to loss of elemental tellurium and quantitative formation of bicyclo-[5,1,0]octa-2,5-diene (III) which was also formed independently by the action of Te2– anion on the dibromide (I) during the preparation of (II).

Method of forming a solid tantalum capacitor

Abstract: A method is disclosed for forming a solid tantalum capacitor wherein the cathode is manganese dioxide formed by pyrolysis. The first pyrolysis is performed at a temperature of between 225 DEG C and 300 DEG C while all subsequent pyrolysis treatments are at a temperature of between 175 DEG C and 225 DEG C with each such subsequent pyrolysis temperature being at least 25 DEG C less than the first pyrolysis temperature.

Controlled pyrolysis of cellulosic materials for production of chemicals

Abstract: By treating paper, newsprint, and other waste cellulosic materials with an acidic fire retardant chemical the product spectrum formed during ensuing pyrolysis of the treated materials is reduced from approximately 60 compounds, none of which is produced in amounts justifying recovery, to a small number of principal products, including water, acetic acid, furfural, 5methyl-2-furfural and a compound produced in relatively large amounts which has been identified as 1,5-anhydro-3,4-dideoxyDelta 3- Beta -D-pyranosen-2-one. The latter compound has utility as a precursor to synthetic resins and surfactants and can be converted by oxidation to the novel compound, 1,5-anhydro-3,4dihydroxy- Delta 3- Beta -D-pyranosen-2-one.

Simulation of pyrolysis of paraffinic hydrocarbon binary mixtures

Abstract: =radius of spherical (cylindrical) catalyst =radial co-ordinate = Reynolds number (=Dppu/fj) = Reynolds number (=) = Sherwood number (=kn\\m.DPjD) (Eq. (12)) = average contact time based on superficial flow rate [sec] wOut, and «= superficial velocity in catalyst bed [cm/sec] Kin . = superficial velocity of intraparticle flow [cm/sec] X = conversion of reactant [-] z longitudinal co-ordinate [cm] £ = void fraction \\ [-] ju = viscosity [g/cm « sec] p = density [g/cm3] t = residence time [sec]

The Thermal Decomposition of Formaldehyde in the Presence of Nitric Oxide

Abstract: The pyrolysis of formaldehyde was investigated in the presence of nitric oxide at 500 °C. The kinetics of the reaction suggests that the pyrolysis proceeds by means of a mechanism which is initiate...

Integrated production of olefins and coke

Abstract: An integrated process for production of olefins and coke from an effluent from a pyrolysis furnace, in which a common fractionator is used to both fractionate the pyrolysis products and prefractionate hydrocarbon fractions for introduction into a coking apparatus. Coke drum overhead vapors are introduced into the pyrolysis effluent to serve as flux for a circulating quench fluid stream.