| Sulfated zirconia had super acidity, good thermal stability and high isomerization activity at low reaction temperature, which attracted more and more attention from researchers. In this dissertion, the effects of process conditions such as activation temperature, the activation gas, reaction temperature and ration of hydrogen to n-hexane on the isomerization activity and deactivation behavior were investigated. The experiment results showed that the reaction temperature and ratio of hydrogen to n-hexane had no great influence on the initial isomerization activity. As for the reaction stability, the low reaction temperature led to the fast deactivation of the PSZA even in the presence of H2, while the enhancement of reaction temperature delayed greatly the deactivation velocity. The yield of iso-hexanes and di-methyl butanes was up to 83% and 25%. respectively after 200h of reaction under the reaction conditions of 200℃. the H2/Oil ratio of 3-6 and WHSV of 1h-1. The deactivation behavior of PSZA catalyst in hydro-isomerization reaction in short time could not be attributed to the coke deposit and the reduction of sulfated species. On the contrast, the deactivation was closely related to the isomerization reaction mechanism over PSZA. The isomerization behavior over Pt/zeolite and PSZA showed different reaction paths. The reaction over the former followed the traditional bi-functional mechanism. For reaction over PSZA, Pt played part in the dissociation of H2 and creation of new Bronsted acid sites by hydrogen atom spillover. The isomerization activity of the deactived PSZA catalyst in short time could be completely restored after regeneration in air at high temperature. However, the activation and regeneration in nitrogen led to the complete loss of catalytic activity. It was proposed that the air activation played not only in the removal of adsorbed water, but in the surface structure rearrangement of active species. |
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