By using modern XPS systems it is possible to obtain spectra with well-resolved spin orbit, multiplet and field splitting even with powder samples mounted using adhesive tape. Measurement of Cr 2 O 3 powder with the latest generation of XPS spectrometers, which are able to analyse non-conductive powders with ultimate energy resolution, revealed multiplet splitting features and satellite emission in the Cr 2p spectrum. Therefore, peak-fit analysis of Cr 2p XPS spectra of Cr(III) compounds requires a more appropriate approach and common practice has to be reconsidered. One possible way to analyse this spectrum is proposed, based on the experimental and theoretical work of other authors.

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In this study, isomerization of a-pinene was studied over several acid-treated natural zeolite catalysts rich in clinoptilolite. Zeolite samples were contacted with HCl at different concentrations at 30 C or at 60 C for 3 and 24 hours and tested in isomerization reaction of alpha-pinene. The catalysts prepared were characterized by XRD, nitrogen adsorption, and acidity studies. Acidity strength and the distribution of Lewis and Brö nsted acid sites of the catalysts were determined, and their catalytic activities in a-pinene isomerization and selectivities to main reaction products, camphene and limonene, were investigated. Acid treatment improved the selectivity of catalyst samples to camphene, decreasing the selectivity to limonene, probably forcing limonene to secondary reactions at high conversions.The kinetics of a-pinene consumption was described by first-order kinetics. Two kinetic models were tested for the reaction mechanism and one model was found to give a good correlation between the theoretical and experimental data. In the models, the key intermediate was the pinylcarbonium ion, which was formed irreversibly from a-pinene.Number and distribution of Lewis and Brö nsted acid sites affect the formation of bicyclic and monocyclic products.

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