Environ. Sci. Technol. 2010, 44, 4169–4175
Chlorinated and Nonchlorinated Compounds from the Pyrolysis and Combustion of Polychloroprene IGNACIO ARACIL,* RAFAEL FONT, AND JUAN A. CONESA Department of Chemical Engineering, University of Alicante. P.O. Box 99, E-03080 Alicante (Spain)
Received January 7, 2010. Revised manuscript received March 30, 2010. Accepted March 31, 2010.
Thermal decomposition of polychloroprene was studied under inert and oxidative atmospheres at temperatures of 500 and 850 °C in a horizontal quartz tubular laboratory reactor in order to determine the products generated. More than two hundred compounds, mainly aromatic hydrocarbons, were identified and quantified, with special focus on chlorinated aromatic compounds, including polychlorinated dibenzo-pdioxins and dibenzofurans (PCDD/Fs), chlorobenzenes (CBzs) and chlorophenols (CPhs). The results showed that pyrolysis of polychloroprene at high temperatures leaded to the formation of many aromatic hydrocarbons in high yields. In addition, the yields of total PCDD/Fs in the combustion experiment at 850 °C were more than three hundred times higher than those from pyrolysis at the same temperature. Results were also compared with those obtained in a previous work for polyvinyl chloride under similar operating conditions.
1. Introduction One of the most important polymers in the group of synthetic rubbers is polychloroprene (PCP), or poly(2chloro-1,3-butadiene). Its combination of properties like chemical inertness, physical toughness, low inflamability and resistance to degradation from sun and weather, makes it suited for many daily applications such as wetsuits, hoses, belts, gaskets, adhesives, etc. However, for the same reason, these properties complicate waste treatment of this rubber. Total production of PCP accounts for 250 000 metric tonnes worldwide annually (1). As part of municipal solid wastes, other alternatives to landfilling have to be investigated. Mechanical recycling is limited, although chemical recycling by pyrolysis or energy recovery by combustion also present problems due to the high chlorine content of the polymersas occurs for the two most consumed chlorinated polymers, polyvinyl chloride (PVC) and polyvinylidene chloride (PVDC)sbecause under thermal treatments the presence of chlorine and carbonaceous material is a potential source of toxic chlorinated aromatic hydrocarbons. However, there are very few studies about the products generated during thermal treatments of PCP (2-5) unlike PVC and PVDC. In fact, to our knowledge, only the paper of Kaminsky et al. (4) deals with the chlorinated products evolved during PCP pyrolysis. This work presents a study of the compounds generated from the pyrolysis and combustion of PCP in a laboratory * Corresponding author phone: +(34) 965903867; fax: +(34) 965903826; e-mail:
[email protected]. 10.1021/es100023a
2010 American Chemical Society
Published on Web 05/07/2010
reactor at different temperatures. Volatile and semivolatile products were measured focusing on polycyclic aromatic hydrocarbons (PAHs), CBzs, CPhs, and PCDD/Fs. The important contributions of this work are the identification and quantification of more than two hundred different compounds and specifically, the analysis of the chlorinated compounds generated because no references of these have been reported for the thermal decomposition of PCP at different temperatures. The results obtained for PCP were compared with those obtained for PVC in a previous work under similar operating conditions (6). Moreover, the present work complements a previous paper about proposed kinetic models for the thermal decomposition of PCP studied by thermogravimetry under inert and oxidative atmospheres (7).
2. Materials and Methods 2.1. Material. The material employed was a polychloroprene rubber Baypren 328-1 from Bayer, commercially used for contact adhesives with a chlorine content of 36% determined by ionic chromatography following the U.S. Environmental Protection Agency (EPA) 5050 analytical method. The content of C, H, and S (51.4, 5.5, and 0.4%, respectively) was obtained by elemental analysis; X-ray fluorescence was employed for the rest of the elements such as Mg and Si (
