Depolymerization of polypropylene in an induction-coupled plasma (ICP) reactor

An induction-coupled plasma reactor was used to thermally decompose polypropylene into propylene and other useful chemicals. From a series of statistically designed experiments, it was found that plasma power input, sheath gas flow rate, central gas flow rate, powder feed rate, quench gas flow rate, and interaction of sheath gas flow rate with power and feed rate were the key parameters affecting the yield of monomer in the product gas stream. On average, 78 wt % of the polymer was converted into gas at a power level of 20 kVA. The product gas stream, on an argon-free basis, contained 94% propylene, with the balance being methane, ethylene, and some C-4'S. Transmission electron microscopic analysis of the carbon residue indicated the formation of some novel carbon structures, including carbon nanotubes.