Mechanism of Cracking Processes

The main task of thermal and catalytic cracking is decomposition of large (long) hydrocarbon molecules into smaller ones. High-molecular feedstock, such as paraffin hydrocarbons and plastic chains produces lower molecular paraffins and a-olefins [5]  

Cracking of primary products, olefins, give higher molecnlar hydrocarbons by polymerization or tar and coke  

It is generally accepted that thermal cracking is a free radical chain reaction (a free radical is an atom or group of atoms with an unpaired electron). Free radicals react with hydrocarbons and produce new hydrocarbons and new free radicals  

Free radicals can decompose by giving olefins and new radicals [6]  

The mechanism of thermal cracking and pyrolysis is discussed by Buekens et al. [7], They proposed four types of pyrolysis reaction. In the case of PE, PP and PS cracking only two type of the mechanisms were stated  

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