Catalytic Conversion of Plastic Mixtures and Rubber Wastes

4 Catalytic Conversion of Plastic Mixtures and Rubber Wastes 

This section describes the different processes that have been patented for the catalytic conversion of plastic mixtures without any previous thermal treatment. In many cases, the authors claim that the process is also successful in the degradation of rubber wastes or plastic and rubber mixtures. 

While many studies have been carried out aimed at the feedstock recycling of rubber wastes by pyrolysis and hydrogenation processes (see Chapters 5 and 7), little information is found on the catalytic cracking and reforming of rubber alone. Larsen35 has disclosed that waste rubber, such as used tyres, can be degraded in the presence of molten salt catalysts with properties as Lewis acids, such as zinc chloride, tin chloride and antimony iodide. The decomposition proceeds at temperatures between 380 and 500 °C to yield gases, oil and a residue, in proportions similar to those obtained by simple thermal decomposition. 

Processes involving the use of solid acid catalysts have also been patented. According to Chen and Yan,40 plastic and/or rubber wastes are first subjected to a size reduction step, followed by separation of any metals present and washing to remove any non-plastic material such as paper, labels, etc. Subsequently, the polymer wastes are dissolved or dispersed in a petroleum oil, with a high content of polycyclic aromatic compounds at 300 °C, and catalytically transformed in an FCC reactor at temperatures of about 500 °C. Details are given for the conversion of different wastes used whole tyres, PE bags and PS foam. 

5 Conversion of Plastics by a Combination of Thermal and Catalytic Treatments 

---