Catalytic pyrolysis of non-textile button components as a co-feedstock for bioenergy production

Abstract

Recently, the co-pyrolysis of biomass and various types of plastic waste (PW) has shown great potential in improving H/Ceff ratio of biomass, making it a sustainable and competitive source of bioenergy, especially in the presence of catalysts. However, this strategy is limited by high contamination and the difficulty of sorting PW, requiring the development of another clean and uniform source of PW. In this context, this research presents polyester and nylon buttons (major part of non-textile components) as a new type of clean and sortable PW for this purpose. The experiments at this stage was focused on studying the catalytic pyrolysis of plastic buttons only by thermogravimetric analysis (TGA) coupled with Fourier transform infrared (TG-FTIR) and gas chromatography-mass spectrometry (GC/MS) to provide the basic data needed for future co-pyrolysis with biomass. The energy consumed during the reaction (Ea) and other catalytic pyrolysis characteristics over ZSM-5 zeolite catalyst were evaluated using kinetic models along with determination of their thermodynamic parameters. Also, an artificial neural network (ANN) algorithm was proposed to expect TGA properties of buttons at ambiguous heating parameters. The TGA results revealed that polyester sample can be decomposed in two stages up to 360 °C and 460 °C, while nylon sample decomposed in a single stage up to 490 °C. The TGA-FTIR analysis highlighted that carbonyl groups (polyester) and aliphatic hydrocarbons (nylon) are the main functional groups of polyester and nylon vapors. Meanwhile, benzoic acid (72.94 % at 20 min/°C) the main compound of nylon sample and 1,2-Benzenedicarboxylic acid (plasticizers) the main compound of polyester and its toxic styrene compound was completely removed. Finally, the Ea used in decomposition of buttons was estimated at 241.6–262.7 kJ/mol (polyester) and 165.6–173.4 kJ/mol (nylon). The suggested ANN model showed high potential in predicting the catalytic pyrolysis characteristics with R > 0.98. Based on these findings, plastic buttons can be used as a co-feeding hydrogen-rich source to biomass to enhance its H/Ceff ratio and aromatic compounds.