Thermal and Catalytic Degradation of Waste HDPE

Feedstock Recycling and Pyrolysis of Waste Plastics Converting Waste Plastics into Diesel and Other Fuels Edited by J. Scheirs and W. Kaminsky 2006 John Wiley Sons, Ltd ISBN 0-470-02152-7 

in thermal and catalytic degradation of waste HDPE the influence of experimental variables, such as reaction temperature, catalyst type and other plastic addition, etc. is described in this chapter. Thus, the discussion focuses on waste HDPE as a reactant and the influence of various experimental variables and also a comparison of the thermal and catalytic degradation in detail. 

The decomposition of plastics can be considered as depolymerization of polymer into 

The decomposition of plastics depends on the plastic type, with different reaction mechanisms of plastics proposed with four types [5]. 

A new macroscopic degradation mechanism of polymers studied by Murata et al. [6] was suggested with two distinct mechanism in the thermal degradation of PE, PP and PS. One is a random scission of polymer links that causes a decomposition of macromolecnles into the intermediate reactants in liquid phase, and the other is a chain-end scission that caused a conversion of the intermediate reactants into volatile prodncts at the gas-liqnid interface. There are parallel reactions via two mechanisms. The random scission of polymer links causes a reduction in molecular weight of macromolecules and an increase of the number of oligomer molecules. The chain-end scission causes a dissipation of oligomer molecules and a generation of volatile products. 

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Table 5.2 Yields of gas, liquid and residue obtained from thermal and catalytic degradation of waste HDPE at 430°C...

The paraffins, olefins, naphthenes and aromatics (PONA) distribution of liquid product with time on stream for thermal and catalytic degradation of waste HDPE at 430°C is shown in Figure 5.11. In the case of thermal degradation, paraffin and olefin components are the main products and aromatic componnds hardly appear, without change by increase... 

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