A NOVEL PROCESS AND MATERIAL FOR THE SEPARATION OF CARBON-DIOXIDE ANDHYDROGEN-SULFIDE GAS-MIXTURES

Carbon fiber composite molecular sieve (CFCMS) synthesis and character ization of the macro-, meso- and micropore structure are reported. CFC MS physical properties, including strength, thermal conductivity and e lectrical resistivity, are reported and the thermal conductivity of CF CMS compared with literature data for granular activated carbon (GAC) and packed beds of GAC. Adsorption studies, including isotherms for CO 2 and CH4 at temperatures of 30, 60 and 100 degrees C on CFCMS samples activated to different burn-offs, are reported. High pressure adsorpt ion data for CO2 and CH4 show that the CFCMS material has sufficient s electivity for CO2 over CH4 for a commercial separation. Breakthrough experiments were conducted for CO2/CH4 and H2S/H-2 gas mixtures and th e selective separation of CO2 and H2S was demonstrated. The electrical conductivity of our novel monolith was exploited to effect the rapid desorption of adsorbed gases. Desorption at low applied voltage was ac companied by a heating of the CFCMS to temperatures <100 degrees C. Th e passage of greater electrical current (similar to 14 A at 3.25 V) ca used the CFCMS temperature to exceed 300 degrees C. During desorption, the release of adsorbed gas was noted to occur prior to a rise in CFC MS bulk temperature. It is demonstrated that the heat of adsorption is responsible fbr this phenomenon. The relationship between the carbon fiber structure, electrical behavior, and the desorption characteristi cs of CFCMS are discussed. A preliminary design of an ''electrical swi ng adsorption'' (ESA) system is outlined. Potential uses of the CFCMS/ ESA technology are suggested. (C) 1997 Elsevier Science Ltd.