Halogen Reduction in Pyrolysis Oil from Bromine-containing Plastics Using Hydrotalcite N. Morita 1 , A. T. Saito 1 , T. Wajima 1 and H. Nakagome 1 1 Chiba University Abstract. In this study, polystyrene, polyethylene, and polypropylene were mixed with tetrabromobisphenol A to simulate plastic samples containing brominated flame retardants and denoted as BR-PS, BR-PP, and BR-PE, respectively. Samples were also mixed with hydrotalcite to reduce the halogen concentration in the obtained product oil after pyrolysis. Hydrotalcite was added to BR-PS, BR-PE, and BR- PP, placed in a glass reactor under a nitrogen atmosphere, and thermally decomposed at 400 °C. The resulting bromine compounds in the oil, residues in the sample chamber and generated gas were examined. The main components of the oil present after the pyrolysis of BR-PS, BR-PE, and BR-PP at 400 °C were different, and the bromine compounds were also different. When using hydrotalcite as an additive, the yield of the product oil increased, and bromine compounds in the product oil were not detected. For the bromine containing samples, simulating a plastic containing a brominated flame retardant, without the hydrotalcite additive, bromine was present in the oil and gas after pyrolysis. Performing thermal decomposition on the samples with hydrotalcite, bromine was present in the residue because it was captured by the hydrotalcite, which reduced the halogen content of the product oil and generated gas. Keywords: Pyrolysis, waste plastic, halogen-based flame retardant, hydrotalcite, product oil 1. Introduction Plastics derived from fossil fuels are used in a number of chemical products, leading to a large amount of waste after use. The recycling of waste plastics includes thermal or chemical recycling, but there is also material recycling. Reducing the amount of fuel using waste plastics by chemical recycling is one of the various recycling waste plastics that has been attracting attention. However, chemical products, such as a flame retardant, are added, and producing a product oil containing a halogen compound is a problem for efficient fuel utilization. By thermal decomposition, plastic is converted to a gas for use as a chemical raw material, as well as in fuels, oils, and as the residual carbon [1]. There is much literature regarding the basic research and chemical recycling on the thermal decomposition of waste plastic using a catalyst [2]-[13]. For example, ZSM-5 zeolite, the red mud mesoporous molecular sieve, was used in the thermal decomposition of plastics, and the product oil yield was increased [14], [15]. However, brominated flame retardants are toxic, which is a particular problem when recycling waste plastics [16]-[20]. For example, the treatment of brominated compounds from 300 to 500 C results in the possible formation of brominated dibenzodioxins and furans [21]. This generation of toxic by-products prevents the promotion of social recycling. Using additives as a catalyst during thermal decomposition has shown to prevent the release of halogen gas in the oil and gas phases [22]. For example, polystyrene (PS), polypropylene (PP), polyethylene (PE), and polyvinyl chloride mixed with a poly-brominated compound can be decomposed using the carbon composite of calcium carbonate (calcium–C) [23]. Moreover, the quality of pyrolysis oil can be improved using a commercial hydrogenation catalyst, DHC-8 [24]. Furthermore, the yield of product oil from thermal decomposition using a catalyst was reported to improve to 96% from 93% when using two types of zeolite catalysts, H-USY and H-Beta, in a vapor contact method [25]. We previously reported to reduce the content Corresponding author. Tel.: +81-43-290-3466; fax: +81-43-290-3466. E-mail address: [email protected]. 2015 International Conference on Advances in Environment Research Volume 87 of IPCBEE (2015) DOI: 10.7763/IPCBEE. 2015. V87. 10 54
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Halogen Reduction in Pyrolysis Oil from Bromine-containing Plastics
Using Hydrotalcite
N. Morita 1
, A. T. Saito 1, T. Wajima
1 and H. Nakagome
1
1 Chiba University
Abstract. In this study, polystyrene, polyethylene, and polypropylene were mixed with
tetrabromobisphenol A to simulate plastic samples containing brominated flame retardants and denoted as
BR-PS, BR-PP, and BR-PE, respectively. Samples were also mixed with hydrotalcite to reduce the halogen
concentration in the obtained product oil after pyrolysis. Hydrotalcite was added to BR-PS, BR-PE, and BR-
PP, placed in a glass reactor under a nitrogen atmosphere, and thermally decomposed at 400 °C. The
resulting bromine compounds in the oil, residues in the sample chamber and generated gas were examined.
The main components of the oil present after the pyrolysis of BR-PS, BR-PE, and BR-PP at 400 °C were
different, and the bromine compounds were also different. When using hydrotalcite as an additive, the yield
of the product oil increased, and bromine compounds in the product oil were not detected. For the bromine
containing samples, simulating a plastic containing a brominated flame retardant, without the hydrotalcite
additive, bromine was present in the oil and gas after pyrolysis. Performing thermal decomposition on the
samples with hydrotalcite, bromine was present in the residue because it was captured by the hydrotalcite,
which reduced the halogen content of the product oil and generated gas.