Journal of Polymers and the Environment, Vol. 11, No. 1, January 2003 (© 2003) 1566-2543/03/0100-0001/0 © 2003 Plenum Publishing Corporation 1 Effect of Metal Compounds and Experimental Conditions on Distribution of Products from PVC Pyrolysis Jatuphorn Wootthikanokkhan, 1,3 Adisak Jaturapiree, 1 and Vissanu Meeyoo 2 Effects of heating rate, gas flow rate, and type of metal compounds on the amount of hydrogen chloride, liquid, gas, and solid pyrolyzate obtained from the pyrolysis of poly(vinyl chloride) (PVC) were investigated. The pyrolysis experiments were carried out in both a thermogravimetric analy- sis (TGA) instrument and a fixed-bed reactor. Products from the fixed-bed reactor were collected and analyzed by using Fourier transform infrared spectroscopy (FTIR), gas chromatography-mass spectroscopy (GC-MS), titration technique, and gravimetry. It was found that heating rate in the TGA experiments did not affect the amount of released hydrogen chloride. However, the TGA profiles significantly changed with the rate. The onset of dehydrochlorination increased with the rate. In addition, as the heating rate was increased from 10 to 20°C/min, there was no solid residue left. The amount of liquid pyrolyzate obtained from the fixed-bed reactor can be either increased or decreased with the heating rate, depending on the gas flow rate and the actual residence time in the reactor. FTIR and GC-MS analysis indicated that the liquid pyrolyzates were mainly ben- zene, toluene, and styrene. By comparing the efficiency of various metal compounds in trapping the HCl, it was found that Ca(OH) 2 was more efficient than Mg(OH) 2 , and that CaO was more efficient than MgO. These results are discussed in light of the reaction mechanism between HCl and the metal compounds. KEY WORDS: Poly(vinyl chloride); pyrolysis; TGA; dehydrochlorination. 1 Division of Materials Technology, School of Energy and Materials, King Mongkut’s University of Technology, Thonburi, Bangkok 10140, Thailand. 2 Center for Advanced Materials and Environmental Research, Mahanakorn University of Technology, Bangkok 10530, Thailand. 3 To whom all correspondence should be addressed. E-mail: jatuphorn. woo@kmutt.ac.th INTRODUCTION Pyrolysis has been considered to be an alternative method of plastic recycling. In the pyrolysis process, organic material is decomposed at an elevated temper- ature in either an oxygen-free or low-oxygen atmo- sphere. When plastic such as poly(vinyl chloride) (PVC) is pyrolyzed, more than 50% of the initial weight is released as a form of HCl, which is considered to be corrosive and harmful. The dehydrochlorination is ini- tiated by the scission of the Cl-C bond, resulting in a chlorine radical. Subsequently, the chlorine radical at- tacks the hydrogen atom in the polymer chains, lead- ing to the formation of hydrogen chloride gas. It was believed that the degradation is related to the presence of some weak points along the PVC chains, such as the head-to-head configuration [1], allylic chlorine [2], and branching (tertiary chlorine) [3, 4]. The chlorine atoms on these positions are considered to be sites for the ini- tiation of dehydrochlorination. This was confirmed by replacing labile chlorine with some stable ligands [5]. HCl may be, theoretically, condensed and reused. In practice, however, there exists today a great over-