Characterization of Solid Superacidity by Pentane Isomerization Reaction

Pentane reactions on solid acids such as SO42-/MxOy HM and HZSM 5 zeolites at low temperature were studied. In most cases the pentane isomerization selectivity is higher than 90%. The rate of pentane isomerization reaction follows the rate law of a first-order reversible reaction. As the acid strength of the catalysts is increased, the rate constant is increased concurrently. The pentane isomerization at low temperature is a good probe reaction for the characterization of the acidity of solid superacids, whose H-d values are between 12 and 16. The results obtained rank the catalysts correctly in order of increasing acidic strength as judged by Hammett indicators and other methods. The probe reaction provides an effective means to measure superacidity for colored and decomposable samples.