Pyrolysis study of a PVDC and HIPS-Br containing mixed waste plastic stream: Effect of the poly(ethylene terephthalate) Thallada Bhaskar, Maki Tanabe, Akinori Muto, Yusaku Sakata * Department of Applied Chemistry, Faculty of Engineering, Okayama University, 3-1-1 Tsushima Naka, 700-8530 Okayama, Japan Received 12 July 2005; accepted 21 January 2006 Available online 3 March 2006 Abstract Pyrolysis of poly(vinylidene chloride) (PVDC), brominated flame retardant containing high impact polystyrene (HIPS-Br), poly(ethylene) (PE), poly(propylene) (PP), poly(styrene) (PS) mixed were performed in the presence and absence of poly(ethylene terephthalate) (PET) under atmospheric pressure at 430 8C using a semi-batch operation. We attempted the dehalogenation (Cl, Br) of chlorinated and brominated liquid hydrocarbons using iron oxide and calcium hydroxide based carbon composites for the production of halogen free liquid hydrocarbons. The presence of PET in the plastics mixture of PP/PE/PS/PVDC/HIPS-Br affected significantly the formation of pyrolysis products and the pyrolysis behavior of plastic mixture. We observed the following effects of PET on the pyrolysis of PP/PE/PS/PVCD/HIPS-Br mixed plastic pyrolysis: (i) The yield of liquid product was decreased and the formation of gaseous products increased during the thermal decomposition, (ii) the waxy residue was observed in addition to the solid carbon residue and (iii) use of calcium hydroxide carbon composite (CaH–C) removed the major portion of chlorine and bromine content from the liquid products from PP/PE/PS/PVDC/HIPS-Br pyrolysis, however in the presence of PET, the combination of calcium hydroxide carbon composite (CaH–C) and iron oxide carbon composites could not dehalogenate the liquid products effectively. X-ray diffraction analysis reveals the presence of antimony compounds in carbon and wax residues. # 2006 Elsevier B.V. All rights reserved. Keywords: PVDC; HIPS-Br; Pyrolysis; PET; Feedstock recycling; Dehalogenation 1. Introduction The conversion of waste plastics into petrochemical feedstock represents a sustainable way for the recovery of the organic content from polymeric waste and also preserves valuable petroleum resources, in addition to protecting the environment [1,2]. The worlds limited reserves of coal, crude oil and natural gas places a great pressure on mankind to reduce, and recycle the existing non-renewable materials and reduce our reliance on them. Among the various recycling methods for the waste plastics, the feedstock recycling has been found to be a promising method. Pyrolysis of waste plastics is favored because of the high rates of conversion into oil, which can be used as fuel or feedstock in refinery. Recycling by pyrolysis has high potential for heterogeneous waste plastic materials, as the separation is not economical. There has been plethora of research work on the pyrolysis of plastics and utilization of pyrolysis products for various applications [3–8] including the monographs on the feedstock recycling of plastics [9]. Municipal waste plastic is a mixture of non-halogenated and halogenated thermoplastics such as polyethylene, polypropylene, polystyrene, poly(vinyl chloride), and PET. It is known that the pyrolysis of mixed plastics containing PVC or PVDC produces inorganic and subsequently organic chlorine compounds during the initial stages of pyrolysis process [10,11]. The disposal of halogenated mixed waste plastics is serious environmental problem [12,13]. Hornung et al. [12] reported the dehalogenation of brominated organic compounds from the pyrolysis of brominated flame retardant plastics with the polypropylene as a reductive agent. The separation of brominated additives from inert and valuable materials in electronic scrap can be done by an established pyrolysis procedure called Haloclean 1 [13]. The main characteristics of this process are good mixing of the electronic scrap by a rotating conveyor screw, better heat transfer through stainless steel balls which are added to the feed and low residence time for gaseous products because of a high nitrogen flow which leaves several sinter metal plates of the screw. In any case, the www.elsevier.com/locate/jaap J. Anal. Appl. Pyrolysis 77 (2006) 68–74 * Corresponding author. Tel.: +81 86 251 8081; fax: +81 86 251 8082. E-mail address: yssakata@cc.okayama-u.ac.jp (Y. Sakata). 0165-2370/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jaap.2006.01.005