Transformations of monoterpene hydrocarbons on ferrierite type zeolites

Transformations of alpha-pinene and limonene over hydrogen forms of commercial ferrierite type zeolites of different origin (Tosoh Corp. and Zeolyst Intern.) have been studied in the liquid phase at 313-363 K. The catalysts were characterized by XRD, sorption of nitrogen, scanning electron microscopy, FTIR and Al-27 & H-1 MAS NMR. The concentration of Bronsted acid sites has been determined by H-1 MAS NMR and FTIR quantitative measurements, while their strength was estimated by adsorption of CO. The liquid-phase isomerization of alpha-pinene proceeds smoothly on the two zeolite catalysts, and the initial reaction rates have been compared. Camphene and limonene were the main products, while the selectivity to these hydrocarbons differed. Isomerization of pure limonene was also studied, showing large difference in activity over the two ferrierite catalysts. The selectivity of alpha-pinene transformations has been rationalized in terms of retarded consecutive isomerization of limonene over the zeolite from Zeolyst. (C) 2012 Elsevier BM. All rights reserved.