RECYCLED SPENT RFCC CATAL YSIS AS VOCs ADSORBENTS
| Autor: | Wang, Chun-Chih, 王俊智 |
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| Rok vydání: | 1996 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 84 Handing or disposal of spent catalysts is an important environmental issue. The petroleum refining industries in Taiwan discard over 4,000 tons of spent FCC (fluidized catalytic cracking) catalysts every year. Neigher has there been any reuse or reprocessing outlet for these spent catalysts. Spent FCC/ROC catalysts are essentially silica- alumina materials that have becomecontaminated with heavy metals during use, principally vanadium and nickel. Afeasibility study for reuse of the spent FCC/ROC catalyst as VOCs adsorbents was investigated. Experimental data indicate that the contaminated metals vanadium and/ornickel on these spent catalysts can be selectively removed by an oxalic (or sulfuric)acid solution with the zeolite structure preserved. Diffuse reflectance infrared spectrareveal that the VOCs such as benzene, toluene, ethylbenzene, and xylene moleculesadsorb preferentially on the zeolite surfaces of the FCC catalysts. The C-H stretching bands of adsorbed benzene molecules are observed at 3040,3070 and 3090 cm-1.Evidently, the adsorbed benzene molecule is only slightly perturbed from the D6hselection rule for the free molecule. This is confirmed by the fact that surface-induced infrared absorptions are not seen when the benzene molecules are adsorbed on thesurvace sites. Typically, an adsorbed molecule experiences a decrease in symmetrywith resulting induced infrared absorptions. Furthermore, the infrared differencespectra also shows that benzene molecules have a high selectivity for adsorption on theenergetic acid sites first. Exxentially, the bands at 3740 cm-1 (SiOH) decreases in intensity while bands of adsorbed benaene are observed to increase. This suggests that benzene molecules adsorb preferentially on the zeolite surfaces of the RFCC catalysts. Experimentally, the VOCs adsorption capability for a regenerated FCC (or FOC)catalysts ia about 17% of a normal activatd carbon adsorbent. However, it turns outto be economically attractive when the regenerated FCC catalysts are used as VOCsadsorbents in a commercial-scale VOCs adsorber. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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