Experimental studies were performed to demonstrate the feasibility of regenerating non-carbon adsorbents by microwave irradiation to effect recovery of volatile organic compounds (VOCs). These vacuum-purge microwave desorption tests were conducted in a 2450 MHz multimode cavity for water, methyl ethyl ketone, toluene, and n-propyl acetate on molecular sieves 5A and 13X, UOP Molsiv High-silica Zeolite, and Dowex Optipore adsorbents. Each material combination exhibited very high desorption rates but was strongly dependent on the relative dielectric loss factor of both the adsorbent and VOC. The results also show that the dielectrically-enhanced mass transfer characteristics result in a system which follows a quasi-equilibrium process consistent with the manufacturer sorption equilibrium data; accordingly, desorption increases with temperature and decreasing system pressure and, unlike conventional convective regeneration, is not rate-limited by mass transfer resistances. Heat-up and desorption rates were found to be proportional to the power density for a given adsorbent/solvent combination.
Figure 2. Experimental glass adsorption column and multimode microwave chamber.
1. Price, D.W., and P.S. Schmidt, "Microwave Regeneration of Adsorbents for VOC Recovery: Experimental Studies", Proceedings of the 30th International Microwave Power Institute Symposium, Denver, July 1995. p. 38. ISSN: 1070-0129.
2. Weissenberger, A.P., and P.S. Schmidt, "Microwave Regeneration of Adsorbents," Proceedings of the Fourth Biennial Symposium on Microwave Processing of Materials, Materials Research Society, San Francisco, April 1994.
3. Price, D.W., and P.S. Schmidt, "Microwave Regeneration of Adsorbents at Low Pressure: Experimental Kinetics Studies", 1997. (in review).