Effect of Catalyst Acidity and Structure on Polymer Cracking

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ABSTRACT CTS-9509240 This effort examines the use of catalytic cracking to convert plastic wastes into useful hydrocarbon mixtures. Polymer-cracking properties of amorphous silica-alumina and of various crystalline zeolites are compared to ascertain the effects of zeolite channel dimensions on product distributions; cracking properties of aluminosilicates are compared with those of a sulfated zirconia superacid catalyst to ascertain the effects of catalyst acidity; product distribution changes from cracking in oxygen or hydrogen atmospheres with catalysts containing platinum are also studied. Volatile cracking products are identified from gas chromotagraphy with a microfurnace injector and detection by both mass spectrometry and infrared spectroscopy. A fixed-bed catalytic reactor is used to study catalyst coking processes and the effects of cracking atmosphere and temperature on product distributions. Overall activation energies for polymer cracking are obtained from thermogravimetric (TGA) methods; product-specific activation energies are obtained from TGA-MS using linear programmed thermal degradation mass spectrometry. Polymers studied include polyethylene, polypropylene, polystyrene, and polyvinyl chloride. Most plastics in use today are made of nonbiodegradable polymers; this makes them undesirable in solid-waste landfills. Although "recycling" programs exist in some communities, there is, in fact, no economically acceptable technology to recycle most polymers in a meaningful way. This project lays the fundamental groundwork for such a technology. ***