Hydrocarbon thermal destruction

Thermal stabilization of polyolefins has been first demonstrated for low-molecular models-normal structure alkanes [29]. It has been shown that metallic sodium and potassium hydroxide with absorbent birch carbon (ABC) as a carrier are efficient retardants of thermal destruction of n-heptane during a contact time of 12-15 s up to the temperature of 800°C [130]. Olefins and nitrous protoxide, previously reported as inhibitors of the hydrocarbon thermal destruction, are ineffective in this conditions. 

Although the process is commonly named deodorization, it is actually a combination of three different effects on the oil (1) stripping Stripping of volatile components (free fatty acids, odorous compounds, tocopherols, sterols, and contaminants such as pesticides and light polycyclic aromatic hydrocarbons, etc.), (2) actual deodorization Removal of different off-flavors, and (3) temperature effect Thermal destruction of pigments and unwanted side reactions such as cis-trans-iso-merization, polymerization, conjugation, and so on. 

At temperatures greater than a 100°C, thermal degradation of carboxylic acids produces methane and carbon dioxide (Surdam et ai, 1984). As the carboxylic acid anions are consumed due to increasing temperature, the carbonate system becomes internally buffered, and thus the pH may decrease due to increased in the system, leading to carbonate dissolution and the enhancement of secondary porosity (Surdam et ai, 1984). Factors influencing the thermal destruction rate of organic acids include coupled sulphate reduction and hydrocarbon oxidation, and the mineralogy of host sediments (Bell, 1991) the presence of hematite causes rapid rates of acetic acid decomposition. 

In these lean flames the hydrocarbon undergoes initial attack by hydroxyl radical with the formation of a radical C H2 +i. Since hydrocarbon radicals higher than ethane are thermally unstable, methyl radical is usually split off forming the next lower molecular weight olefin. Complex radicals may fission into an intermediate-weight radical and an olefin. It seems probable, however, that the thermal destruction of the complex hydrocarbon radicals is sufficiently rapid so that the major oxidizing step is always connected with methyl radical. The principal evidence in favor of this viewpoint is the absence of oxygenated hydrocarbons (alco-... 

It occurs during the chain cracking and radiolysis of hydrocarbons [38], radical polymerization and oligomerization of monomers [39], thermal and thermooxidative destruction of polymers (see Chapter 19) and hydrocarbon oxidation at low dioxygen pressure. 

Using these systems, the thermal decomposition of DDE, DDT, diazinon, endrin, hexachlorobenzene, Kepone, mirex, and penta-chloronitrobenzene was studied, and in several instances stable intermediate products of incomplete destruction were observed. Kepone at 400 to 500°C yielded hexachlorocyclopentadiene, hexachlorobenzene, and an unidentified chlorinated hydrocarbon, all... 

Incineration is an estabhshed process for virtually complete destruction of organic compounds. It can oxidize solid, liquid, or gaseous combustible wastes to carbon dioxide, water, and ash. In the pesticide industry, thermal incinerators are used to destroy wastes containing compounds such as hydrocarbons (e.g., toluene), chlorinated hydrocarbons (e.g., carbon tetrachloride). 

The HRUBOUT process is a mobile in situ or ex situ thermal desorption process designed to remediate soils contaminated with volatile organic compounds (VOCs) and semivolatile organic compounds (SVOCs). For the ex situ process, excavated soil is treated in a soil pile or in a specially designed container. Heated compressed air is injected into the soil, evaporating soil moisture and removing volatile and semivolatUe contaminants. Heavier hydrocarbons are oxidized as the soil temperature is increased to higher levels over an extended period of time. The vapor is collected and transferred to a thermal oxidizer (incinerator) for destruction. 

The Therminator is an ex situ, commercially available medium-temperature portable thermal des-orption/destruction unit for soils and clays contaminated with petroleum hydrocarbons. According to the vendor, the Therminator offers an alternative to landfilling petroleum-contaminated soils. All information is from the vendor and has not been independently verified. 

In contrast to polymerisates, polycondensates can not be depolymerized under inert conditions. Decomposition usually leads to the destruction of the chemical structure and the monomers. The thermal decomposition of PET starts at about 300°C in an inert atmosphere [25]. Between 320 and 380°C the main products are acetaldehyde, terephthalic acid, and carbon oxides under liquefaction conditions. The amounts of benzene, benzoic acid, acetophenone, C1-C4 hydrocarbons, and carbon oxides increase with the temperature. This led to the conclusion that a P-CH hydrogen transfer takes place as shown in Eigure 25.8 [26]. Today the P-CH-hydrogen transfer is replaced as a main reaction in PET degradation by several analytic methods to be described in the following sections. The most important are thermogravimetry (TG) and differential scanning calorimetry (DSC) coupled with mass spectroscopy and infrared spectroscopy. 

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