An exploratory study of the processing of plastics, by means of pyrolysis, with the emphasis on PVC/aluminum combinations

doi:10.1016/0165-2370(91)80080-R

Journal of Analytical and Applied Pyrolysis

Volume 20, July 1991, Pages 321-336

https://doi.org/10.1016/0165-2370(91)80080-R Get rights and content

Abstract

The feasibility of an alternative process for the processing of plastic/aluminum combinations by means of pyrolysis has been studied. Below the melting temperature of aluminum, the main fraction of the plastics can be devolatilized. As the plastic fraction often mainly consists of PVC, it is more economical to incinerate the pyrolysis products on-site, in combination with HCl removal and heat recovery. In the case of a high concentration of other plastics, e.g. ABS and PET, it is possible to get a valuable pyrolysis oil.

Degradation of PVC mainly occurs through elimination of side groups, i.e. chlorine. 90% or more of this chlorine can be released as HCl. During pyrolysis of PVC, hardly any formation of polychlorinated dibenzodioxins and polychlorinated dibenzofuranes occurs.

Depolymerization is the main degradation route of the styrene fraction in ABS (70 wt. %). Reactions of functional groups in the main chain take place during degradation of PET.

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Non-biodegradable polymeric waste pyrolysis for energy recovery
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Citation Excerpt :
However, incineration leads to unacceptable emission of harmful compounds, while recycling have high costs for the separation process and water contamination drawbacks [24], which reduce the process sustainability. Henceforth, utilization of non-biodegradable polymeric wastes for energy recovery stands as a better option to solve the staggering environmental problem as well as compensates the prevalent high energy demand [25, 26, 27, 28]. Extensive research and development of technology for this waste conversion to energy holds great potential, since, petroleum is one of the main sources of non-biodegradable polymer manufacturing and their recovery to liquid oil through the process of pyrolysis produces components having high calorific value in comparable to the commercial fuel [29].
Nowadays, increasing population, widespread urbanization, rise in living standards together with versatile use of polymers have caused non-biodegradable polymeric wastes affecting the environment a chronic global problem, simultaneously, the existing high energy demand in our society is a matter of great concern. Hence forth, this review article provides an insight into the technological approach of pyrolysis emphasizing catalytic pyrolysis for conversion of polymeric wastes into energy products and presents an alternative waste management technique which is a leap towards developing sustainable environment. Pyrolysis of waste non-biodegradable polymer materials involves controlled thermal decomposition in the absence of oxygen, cracking their macromolecules into lower molecular weight ones, resulting into the formation of a wide range of products from hydrogen, hydrocarbons to coke. Nanocatalyzed pyrolysis is a recommended solution to the low thermal conductivity of polymers, promoting faster reactions in breaking the C-C bonds at lower temperatures, denoting less energy consumption and enabling enhancement in the process selectivity, whereby higher value added products are generated with increased yield. Nanotechnology plays an indispensable role in academic research as well as in industrial applications. Existing reviews illustrate that one of the oldest application field of nanotechnology is in the arena of nanocatalysis. Nanocatalysis closes the gap between homo and heterogeneous catalyses while combines their advantageous characteristics and positive aspects, reducing the respective drawbacks. During the current nanohype, nanostructured catalysts are esteemed materials and their exploration provide promising solutions for challenges from the perspective of cost and factors influencing catalytic activity, due to their featured high surface area to volume ratio which render enhanced properties with respect to the bulk catalyst.
Analysis of thermal decomposition products arising from polyvinyl chloride analogs by supersonic jet/multiphoton ionization/mass spectrometry
2000, Talanta
Polyvinyl chloride (PVC) and chlorinated polyvinyl chloride (CPVC) were thermally decomposed at 200–500°C, and the reaction products measured by supersonic jet/multiphoton ionization/mass spectrometry. No precursor molecules of dioxins, such as chlorobenzene, were observed from PVC, although benzene was produced as one of the major components. On the other hand, a large peak corresponding to chlorobenzene was observed, when CPVC was used as a sample. These results suggest that the release of hydrogen chloride and aromatic ring formation occur efficiently and produce chlorinated aromatic hydrocarbons only when excess chlorine atoms are present in the chain of PVC. This method, which has very high selectivity is preferred for trace analysis of specific compounds such as dioxin precursors in a complex mixture. Isomer-selective analysis, e.g. detection of o-, m-, and p-dichlorobenzenes, is also demonstrated in this study.
Determination of the pyrolytic degradation kinetics of virgin-PVC and PVC-waste by analytical and computational methods
2000, Computational and Theoretical Polymer Science
Thermogravimetric curves of virgin- and waste-PVC in an atmosphere of nitrogen and nitrogen saturated with water vapour were recorded at several heating rates to determine degradation kinetics. The degradation curves of virgin-PVC showed two stages of considerable mass loss. Application of the Friedman method to the experimental data proved to be too inaccurate to determine the kinetics unambiguously. Numerical determination of the kinetics parameters resulted in a better description of the data. Two models were fitted to a set of degradation curves of virgin-PVC. Both models showed good reproducibility. The effects of addition of water vapour to the atmosphere were limited to very high temperatures. The degradation curves of rigid PVC-waste showed an additional mass loss between 950 and 1150 K, presumably caused by limestone conversion. The model proposed to describe the degradation of rigid PVC-waste fitted the experimental curves well. Samples from PVC-waste pipes proved to be too heterogeneous to fit the degradation curves with one set of parameters.
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Plastic Waste has become an increased problem in many industrialised countries. Concern over the volumes being created has lead to a number of governments introducing new legislation for its recovery as a resource. Traditional recovery methods have generally concentrated on recycling of materials or incineration for energy. The majority of polymers in waste are mainly hydrocarbon in nature and so can be used as a feedstock for the chemical industries or as a fuel. Pyrolysis is a tertiary recycling process and has an ability to provide three end products: a gas, an oil and a char which all have the potential to be further utilised. It is anticipated that if waste recovery targets currently being set are to be met then methods, such as pyrolysis, will have to be closely examined. The pyrolysis of a plastic mixture in a fluidised bed reactor was studied. The mixture was a simulated fraction of that found in municipal solid waste in Europe. The reactor was constructed of stainless steel and was 70 cm high × 10 cm diameter, with a 17 cm high × 20 cm diameter expander section. The sample was introduced batchwise into the bed. The influence of temperature on product yield and composition was studied. Pyrolysis was carried out at temperatures between 500 and 700°C. This gave widely differing product yields of between 9.79 and 88.76% gas and between 18.44 and 57.11% oil. The oils were analysed for their functional groups using Fourier transform infrared spectroscopy. The molecular weight distribution was also determined using size exclusion chromatography. It was found that as temperature was increased the amount of aromatic compounds in the oil increased. The molecular weight range was also affected. Potential applications for the oils was also investigated.
Pyrolysis kinetics of waste PVC at high conversion
1994, The Chemical Engineering Journal and The Biochemical Engineering Journal
The pyrolysis behavior of poly(vinyl chloride) (PVC) at high conversion (X > 0.6) was examined with a thermal gravimetric analysis reaction system at heating rates of 1, 2 and 5 K min⁻¹. The experiments were carried out over the temperature range 400−800 K and in a nitrogen atmosphere. The results indicated that the reaction pattern of PVC pyrolysis at high conversion can be described by the competitive reaction model with the production of volatiles and char. The corresponding activation energy, pre-exponential factor and reaction order were determined. These results may assist in dealing with the pyrolysis of plastic mixtures containing waste PVC from a knowledge of the behavior of the pure PVC component.
Environmental applications of pyrolysis
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¹: Present address: Netherlands Energy Research Foundation ECN, Westerduinweg 3, P.O. Box 1, 1755 ZG Petten, The Netherlands.

²: Present address: Delft University of Technology, Faculty of Chemical Technology, Julianalaan 136, 2628 BL Delft, The Netherlands.

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An exploratory study of the processing of plastics, by means of pyrolysis, with the emphasis on PVC/aluminum combinations

Abstract

Pure Appl. Chem.

Polym. Degrad. Stab.

Anal. Lett.