Pyrolysis and catalytic cracking of municipal plastic waste for recovery of gasoline range hydrocarbons

Abstract

Plastic is an indispensable part of our daily life. Its production and consumption has been rising very rapidly due to its wide range of application. Due to its non biodegradable nature it cannot be easily disposed off. So, nowadays new technology is being used to treat the waste plasic. One of such process is pyrolysis. This paper describes non catalytic pyrolysis and catalytic cracking of plastic wastes into useful gasoline range hydrocarbons. Under the pyrolytic and cracking conditions the plastic wastes can be decomposed into three fractions: gas, liquid and solid residue. Here the main consideration is the recovery of liquid products which are composed of higher boiling point hydrocarbons. The waste plastics consisting of high density polyethylene (HDPE) was pyrolyzed in this study. Pyrolysis appears to be a technique that is able to reduce a bulky, high polluting industrial waste while producing energy and/or valuable chemical compounds. The pyrolysis of plastic wastes produces a whole spectrum of hydrocarbons including paraffins, olefins, naphthalenes and aromatics. By catalytic cracking more aromatics and naphthene in the range of C6-C8 which are valuable gasoline range hydrocarbons can be produced. Different catalysts like Silica Alumina, Modernite and Activated Carbon were used for catalytic cracking. The catalysts were used in different ratios with feed to find out the optimum range at which maximum yield occurs. The liquid product yield is about 60% in all the cases. In thermal pyrolysis, the product obtained gets solidified but in catalytic cracking good liquid product can be obtained which can be used as fuel. This application is further combined with technologies of municipal plastic wastes collection, classification and pretreatment at front end and product purification and testing at back end to determine the properties of the various products obtained.