Novel Depolymerization Process

ment, eatment, ample, ization Our research group has developed a novel depolymerization process based on supercritical water partial oxidation (SCWPO). Two major U.S. patents have been issued.

• S. Lee and M. A. Gencer, F. O. Azzam, and K. L. Fullerton, “Depolymerization Process”, U. S. Patent No. 5,386,055, January 31, 1995.
• S. Lee and F. O. Azzam, “Oxidative Decoupling of Scrap Rubber”, U.S. Patent No. 5,516,952, May 14, 1996.

This process is unique in the sense that monomer quality products are obtained with a high selectivity and that the process is versatile enough to handle polymers such as polyethylene, polypropylene, polystyrene, poly(vinyl chloride), and spent tire rubber. For example, if polypropylene is supercritically depolymerized by the process treatment, monomeric propylene is a predominant product species. Recent results also show that the products from depolymerization can be obtained alternatively as low molecular weight polymeric wax, whose molecular weight distribution can be controlled by this process.

• D. Lilac and S. Lee*, “Kinetics and Mechanisms of Styrene Monomer Recovery from Waste Polystyrene by Supercritical Water Partial Oxidation”, Advances in Environmental Research, Vol. 6, pp. 9-16, 2001.
• F. O. Azzam and S. Lee*, “Selective Oxidation of Hydrocarbons via Supercritical Wet Oxidation”, ACS Fuel Preprint, Vol. 37, No. 4, pp. 1280-1283, 1992.

A high-pressure reactor system has been designed and setup for this process, a Hastelloy C-276 reactor is being used for experimentation.  The very same experimental system can be used for complete destruction of toxic or hazardous materials, in supercritical water medium. For such applications, whose required retention time is normally short (typically <1 minute), this 1-liter reactor is large enough to provide pilot-scale data. For more information, please contact us.

The first phase of the depolymerization project was funded by BFGoodrich and the resultant process technology was licensed to the sponsoring company by the University of Akron. A second phase project was initiated at the University of Missouri with a state funding from the Missouri Department of Natural Resources (MDNR) in 1999.

Another innovative project dealing with devulcanization of cured rubber based on destructive SCF extraction process is funded by Goodyear Tire and Rubber Co. This process adopts a totally different approach from its competitors, viz., recycling the vulcanized rubber into revulcanizable resin-grade rubber. This process is not an oxidation process, i.e., not a supercritical water oxidation based technology.  It is an advanced supercritical extraction process exploiting a synergistic combination of co-solvents.  For licensing, please contact Goodyear Tire and Rubber Co.  For this revolutionary devulcanization process of scrap tire rubber into revulcanizable (or, recurable) rubber without any disadvantage, a U.S. patent has been awarded.  Dr. Lee’s team has contributed to the successful development of this process technology.

• D. Benko, R. Beer, S. Lee, and K. Clark, “Devulcanization of Cured Rubber”, U. S. Patent No. 6,992,116, January 31, 2006.

For further reading of related subject, please visit the Devulcanization Process Technologies section of this website.