| Summary: | 碩士 === 國立中正大學 === 化學工程研究所 === 99 === The performance of NaY, PtO2-NaY, and V2O5-NaY in removing ethanol from air stream was investigated by a fixed bed adsorber. The structure of catalytic adsorbents was characterized by synchrotron PXRD and EXAFS. The adsorption capacity of these three adsorbents depends on the metal oxide deposited and decreases in the order: Pt-NaY > NaY > V2O5-NaY. EXAFS results suggest that isolated vanadia block adsorption sites on zeolite, leading to a decrease in the adsorption capacity. In contrast, PtO2 clusters on NaY provide additional sites for ethanol adsorption. Since PXRD results indicate the destruction of zeolite structure at 550 C, to extend the adsorbents life cycle, regeneration temperature should be kept as low as possible. Upon air regeneration of the ethanol-saturated adsorbents at 300 C, NaY adsorption capacity decreases slightly, due to the residual ethanol. In the presence of PtO2, ethanol can be completely oxidized catalytically. In addition, evidenced by PXRD and EXAFS, more adsorption sites were induced by CO reduction of PtO2 to Pt clusters after air regeneration. The results motivated us to pre-treat the PtO2-NaY with flowing hydrogen before performance tests. The hydrogen reduction enhances ethanol adsorption capacity whereas after several regeneration cycles the enhancement were depleted by the aggregation of Pt clusters during the air-regeneration and hydrogen reduction cycles, suggested by EXAFS.
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