Distribution of Effective Ferrierite Active Sites for Skeletal Isomerization of n-Butene to Isobutene

In this study, the effective active sites of aged ferrierite(FER) were confirmed to be located in the 10-membered ring (10-MR) pore mouths by modification with ammonium hexafluorosilicate((NH4)(2)SiF6 )and long-term experiments. Analysis of SiO2/Al2O3 ratios showed that aluminum atoms were selectively removed from the FER surface after the modification with (NH4)(2)SiF6. Comparison of the catalytic properties before and after modification showed that the catalytic activity of aged FER depended only on the amount of acid sites located in the 10-MR pore mouths. Monitoring of the change in acid amount with reaction time and the difference between aged and deactivated FER showed that aged FER retained only weak acid sites, and its deactivation was caused by carbon deposition on the 10-MR pore mouth acid sites. Therefore, the catalytic performance of FER can be improved by increasing the number of 10-MR pore mouths.