Sorption of alkanes on sulfated zirconias—Modeling of TAP response curves

The transient TAP method was applied to investigate sorption phenomena of alkanes on differently prepared sulfated zirconias to provide further explanation of different catalytic performances in the n-butane isomerization. A modified “three-zone” model was developed to describe the experimental results of a single-pulse response experiment. It allowed the extraction of the ratios of adsorption and desorption rate constants. The introduction of a second sorption center in the model is proposed to reproduce the sorption behavior for larger alkanes quantitatively better, especially in the low-temperature region. Moreover, the new model is able to reflect the heterogeneous distribution of active centers, e.g., different acidic sites in combination with surface sulfate species. Temperature dependent measurements have been performed to calculate heats of adsorption for various alkanes. The impact of these values on the catalytic properties is discussed.