Polyvinyl chloride Pyrolysis

Pyrolysis of bis(2-ethylhexyl) phthalate in the presence of polyvinyl chloride at 600 °C produced the following compounds methylindene, naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, biphenyl, dimethylnaphthalene, acenaphthene, fluorene, methylacenaphthene, methylfluorene, phenanthrene, anthracene, methylphenanthrene, methylanthracene, methylpyrene or fluoranthene, and 17 unidentified compounds (Bove and Dalven, 1984). 

Although the great majority of petroleum and coal-based pitch materials, as well as model compounds such as polyvinyl chloride, acenaphthylene, decacyclene and polynuclear aromatic hydrocarbons, form anisotropic graphitizable carbons, it is an almost impossible task to predict the type of optical texture of a coke from an elemental analysis of the pitch. The size, shape and reactivity of peri-condensed polynuclear aromatic molecules in the products of pyrolysis of a pitch play a more important role in determining optical texture. 

The following section reviews the literature data summarizing the behaviour during carbonization of five individual polymers, i.e. polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC) and polyethylene terephthalate (PET). Eor each polymer, results will first be presented for flash pyrolysis then for slow pyrolysis by the isothermal and dynamic methods. 

Figure 11.5 Fourier transform infrared spectra of the oils/waxes derived from the pyrolysis of polyvinyl chloride, polystyrene and polyethylene terephthalate...

Figure 11.8 Molecular weight distribution of the oils derived from the fluidized-bed pyrolysis of polystyrene, polyvinyl chloride and polyethylene terephthalate...

Most commodity hydrocarbon plastics are suitable for pyrolysis. Generally the larger the substituent in the side chain, the easier the plastic can be degraded. The order of increasing side chain size is polyethylene<polyvinyl chlorideProblems with many pre-existing plastic cracking technologies include ... 

A few polymers snch as polyvinyl chloride, ABS, and PET are associated with heteroatoms such as Cl, N, and O apart from carbon and hydrogen. Dnring pyrolysis these heteroatoms get converted into componnds such as HCl, N2, H2O etc. 

Even though vinyl chloride was discovered in 1835, polyvinyl chloride was not produced until 1912. It is now one of our most common polymers production in 1984 was over 6 billion pounds. The monomer is made by the pyrolysis of 1,2-dichloroethane, formed by chlorination of ethylene. Free radical polymerization follows Markovnikov s rule to give the head-to-tail polymer with high specificity ... 

Thermal processes are mainly used for the feedstock recycling of addition polymers whereas, as stated in Chapter 2, condensation polymers are preferably depolymerized by reaction with certain chemical agents. The present chapter will deal with the thermal decomposition of polyethylene, polypropylene, polystyrene and polyvinyl chloride, which are the main components of the plastic waste stream (see Chapter 1). Nevertheless, the thermal degradation of some condensation polymers will also be mentioned, because they can appear mixed with polyolefins and other addition polymers in the plastic waste stream. Both the thermal decomposition of individual plastics and of plastic mixtures will be discussed. Likewise, the thermal coprocessing of plastic wastes with other materials (e.g. coal and biomass) will be considered in this chapter. Finally, the thermal degradation of rubber wastes will also be reviewed because in recent years much research effort has been devoted to the recovery of valuable products by the pyrolysis of used tyres. 

The fluidized bed plants developed by Kaminsky et al. have been used for the conversion of a variety of plastic mixtures. In a recent work,99 the results obtained in the conversion of two different plastic wastes at temperatures of 638, 690 and 735 °C were reported. The raw mixture consisted mainly of polyolefins (65-79%), polystyrene (4-30%) and polyvinyl chloride (4-5%). The following fractions were derived from the pyrolysis of these materials gases (35 42.9%), oils (41-51.8%), residue (5.8-14.3%) and soot (2.2-5.4%). The gases were mainly methane, ethylene and propylene, with a certain concentration of CO and C02 due to the presence of oxygen in the feed material. At the lowest pyrolysis temperature the oil produced contains a high proportion of... 

Pyrolysis and reforming of several types of common plastics (polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polyurethane, and polycarbonate) were studied qualitatively, using a micro-reactor interfaced with a MBMS. Each type of plastic pyrolyzed at 550-750°C. This was followed by steam reforming of vapors in a fixed bed of C-11 NK catalyst at 750-800°C. The composition of the product gas (mass spectrum) was observed for different values of the steam-to-carbon mtio and space velocity that changed depending on the size of plastic samples. Preliminary tests showed that at process conditions similar to those used for reforming natural gas, polymers were almost completely converted to hydrogen and carbon oxides. 

Thiolane 1,1-dioxide, known by the trivial name sulfolane, is obtained industrially by catalytic hydrogenation of 3-sulfolene. Sulfolane, colourless crystals, mp 27.5°C, bp 285°C, is water soluble. Sulfolane is a polar aprotic solvent and is used for the extraction of sulfur compounds from industrial gases and for the extraction of aromatic substances from pyrolysis fractions. It also serves as a solvent for cellulose acetate, polyvinyl chloride, polystyrene, and polyacrylonitrile. 

Table 4.1 Hydrocarbon pyrolysis products from polyvinyl chloride (7.80 °C/s) ...

Computational Results Equilibrium thermochemical calculations (using STANJAN [35] and SOLGASMIX [36] codes) of a mixture of nonplastic and plastic surrogate solids were carried out under conditions of pyrolysis and combustion see Table 15.9. A large thermodynamic data file compiled from JANAF tables is used in these codes [37]. The nonplastic material is assumed to be cellulose while the plastic material may contain any or all of the following plastics polyethylene, polyvinyl chloride, polystyrene, polypropylene, polyethylene ter-aphathalic, nylon, latex in the form of rubber, polyurethane, and acetate. Cellulose represents the organic portion of the waste such as paper and cardboard. 

Table 15.20 Heat of Pyrolysis for Polyvinyl Chloride Decomposition in Nitrogen" ...

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