INFLUENCE OF AL DISTRIBUTION AND DEFECTS CONCENTRATION OF FERRIERITE CATALYSTS SYNTHESISED FROM Na-FREE GELS IN THE SKELETAL ISOMERISATION OF N-BUTENE

The skeletal isomerisation of n-butenes to isobutene has been carried out over ferrierite catalysts (Si/Al ~ 15) containing different acid sites distribution and different amount of defects. The zeolite crystals were synthesised under hydrothermal conditions in fluoride medium in the absence of alkaline cations by using suitable combinations of structure directing agents. Template-driven low density of acid sites in 10-membered-ring channels enhances the isobutene selectivity and decreases catalyst deactivation. The presence of high amount of silanol groups and Lewis acid sites increases the yields of by-products and catalysts decay.