In the present study, the reason for the high basicity of KF/Al2O3 and the nature of the basic active sites on KF/Al2O3 were explored. KF modification has also been applied to other metal oxides and molecular sieves. Hydration could produce some partially hydrated fluoride species and promote CO2 adsorption on KF and KF/CaF2, but the basicity of these species was too weak to catalyze 1-butene isomerization at 273K. The effect of pretreatment temperature on the basicity of KF/Al2O3 was examined. Based on the results of Temperature Programmed Decomposition (TPDE), FTIR and probe reaction, the [Al-OH...F^-] species were recognized to be the main active species on KF/Al2O3 in 1-butene isomerization at 273K. Dehydroxylation at high temperature could destroy or suppress these species and caused deactivation on KF/Al2O3. KF was firstly reported to be supported on AlPO4-5 molecular sieve. Through the interaction with the support, KF modification can create strong basic sites on AlPO4-5 and catalyse the butene isomerization at 273K.

Key words: CATALYSIS, INFRARED SPECTROPHOTOMETRY, ALUMINIUM OXIDE, CARBON DIOXIDE, ADSORPTION, BUTENE, POTASSIUM FLUORIDE, ISOMERIZATION