| The skeletal isomerization of n-alkanes to iso-alkanes was one of the important technologies for improvement of the octane number in clean gasoline. Sulfated zirconia (SZ) possessed super acidity, good thermal stability, high isomerization activity at low reaction temperature and high octane number of isomerization products. The solid super acid isomerization process attracted wide attention.In this thesis, the effects of precipitant concentration, drying rate of Zr(OH)4, zirconium solution concentration and the kind of Pt species on the isomerization performance of PtSZA were investigated. The physico-chemical properties of Zr(OH)4and catalyst were characterized by several technologies. The key preparation parameters influencing the isomerization performance of PtSZA were revealed. The long life of PtSZA was evaluated. The physico-chemical properties of PtSZA were characterized before and after reaction by XRD, IR and TG The deactivation reasons at low reaction temperature were discussed. The isomerization performance of Pd-promoted SZA was also investigated.The experiment results showed that the slow drying rate of Zr(OH)4and high precipitant concentration led to high content of hydroxyl groups over Zr(OH)4, which resulted in the high sulfur content and tetragonal phase in catalyst. Thus, a catalyst with high activity was obtained. Under the conditions of200℃, the H2/Oil ratio of4and WHSV of1.5h-1, the conversion of n-hexane on PtSZA was up to86%after1000h. Carbon deposition was hardly detected on the catalyst, crystalline phase was not changed significantly and the content of S only declined slightly after reaction. The spent catalyst after1000h was regenerated7times and the activity hardly changed. The PtSZA catalyst possessed good stability and regeneration performance. Pd-promoted SZA exhibited a similar isomerization performance to PtSZA. The isomerization performance of PdSZA was greatly depended on reaction temperature. Moreover, the isomerization activity of PdSZA was changed with reduction temperature. |
