| Popis: |
Boroaluminosilicate zeolites have been used as n-butene isomerization catalysts in this study. Al[sup 3+] free boron zeolites are inactive for n-butene isomerization. Spectroscopic and microscopic studies have been used to monitor the structure, thermal stability, and acidity of these materials. Kinetic studies are the main focus of this paper, with an emphasis on determination of the mechanism of n-butene isomerization over boron zeolites. Results show that the reaction is first order in n-butenes with slow deactivation via coke formation. Isobutylene, propylene, and C[sub 5]-C[sub 8] polymeric species are the main products. Comparisons of the activity and selectivity of boroaluminosilicates, Al[sup 3+]-free B zeolites, and Al[sup 3+] is necessary to enhance yields of isobutylene. A two-step model is proposed to account for product selectivity, deactivation, and observed kinetic data. 43 refs., 12 figs., 2 tabs. |
