Catalytic and physicochemical properties of modified natural clinoptilolite

•A natural clinoptilolite from Kučin was modified chemically in a systematic way.•Physicochemical properties of the materials obtained were studied.•The kinetics of α-pinene consumption was assessed.•The initial (overall and individual) reaction rate constants were calculated.•Apparent activation energies for the representative samples were obtained.

A natural specimen from the deposit at Kučin (Slovakia), rich in clinoptilolite type zeolite, was dealuminated using HCl solutions of increasing concentration (0.05–11.5 M). The samples were characterized by XRD, sorption of nitrogen, TPD of ammonia, FT IR and NMR spectroscopies. The preparations modified under mild conditions (acid concentration, temperature of dealumination) retained largely their crystallinity and acidity, and were active in the liquid phase isomerization of α-pinene. Upon more severe treatments, the samples became partially amorphous and lost their catalytic activity. The kinetics of α-pinene isomerization was studied over the most active catalysts. The reaction rate constants and apparent energies of activation were obtained. Initial reaction rates over the clinoptilolite type catalysts were compared with other acidic catalysts, including ferrierite-type zeolites.

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