Transformations of monoterpene hydrocarbons on ferrierite type zeolites

Transformations of α-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 27Al & 1H MAS NMR. The concentration of Brønsted acid sites has been determined by 1H MAS NMR and FTIR quantitative measurements, while their strength was estimated by adsorption of CO. The liquid-phase isomerization of α-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 α-pinene transformations has been rationalized in terms of retarded consecutive isomerization of limonene over the zeolite from Zeolyst.

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► H-ferrierite from Zeolyst and Tosoh as catalysts for α-pinene isomerization.
► High initial rates of α-pinene transformations in liquid phase.
► Pure limonene reacts readily on ferrierite from Tosoh, but not on zeolite from Zeolyst.
► Different strength of Brønsted acid sites results in various selectivity towards limonene.
► Deposition of oligomeric products on Zeolyst blocks effectively consecutive transformation of limonene formed.