The isomerization of limonene over natural the zeolite, clinoptilolite, was studied. The main products of limonene isomerization were terpinolene, α-terpinene, γ-terpinene and p-cymene. These products have numerous applications in the cosmetic, food and pharmaceutical industries. The main parameters affecting limonene isomerization were reaction time, temperature and catalyst content. These parameters varied within the following ranges: reaction time 15–1440 min; temperature 155–175°C; and catalyst content 5–15 wt.%. Terpinolene was obtained after reaction for 60 min at 175°C using 10 wt.% catalyst. p-Cymene was produced using similar conditions as for terpinolene except for a longer reaction time of 1440 min. The use of optimum experimental conditions allowed the greatest amounts of the desired products to be obtained in the shortest time.
