Effect of γ-irradiation on cationic and hydrogen zeolites reactivity: clinoptilolite and ferrierite

Abstract

Cationic and H-forms of clinoptilolite and ferrierite were irradiated with -γ-rays. Presorbed triethylamine (TEA) on the unirradiated and irradiated zeolites was subjected to oxidation in a differential scanning calorimetry (DSC) cell in flowing oxygen, making use of the programmed temperature increase of the DSC system. The sum of ΔH for all DSC effects obtained for TEA oxidation in a thermogram was taken as a measure for the zeolite chemisorptive capacity (acidity). The data given by DSC and the acidities determined thermogravimetrically (TG) for presorbed TEA as well as those determined from the IR spectra of presorbed pyridine (Bronsted pyridine “BPY” and Lewis pyridine “LPY”) show certain discrepancy due to evaluation of some high-temperature DSC effects by extrapolation beyond the DSC maximum temperature. Improvement of the DSC data is discussed. However, similar trends of the DSC ΔH values and the TG and IR values with irradiation dose are observed. The temperature at which the maximum of the principal oxidation DSC effect can be taken as a criterion for correlating the zeolite reactivity to oxidise TEA. In general, γ-irradiation was found to enhance the zeolite reactivity to chemisorb TEA (acidity) and to enhance the rate of oxidizing the presorbed base.