In this thesis study, catalytic activity of cation exchanged (Na+, Li+, Ca2+, K+, Cs+) zeolite Y, especially NaY, and various microporous and mesoporous (Na exchanged, Beta, Mordenite, and NaX, CsNaX, MCM-41, Montmorillonite KSF and amorphous Silica) catalysts was investigated in the dehydrogenation reaction of terpenes to p-cymene.The results suggested that, there are two types of acid sites are present in cation exchanged zeolites from NH4Y, which are Br Bronsted and Lewis sites. a-terpinene, disproportionated by Br Bronsted acid catalysis into 3-p-menthene and p-cymene, and pcymene was also formed by direct dehydrogenation of a-terpinene can possibly occur with the participation of Lewis acid sites in cation exchanged zeolite Y. Best conversion to p-cymene were observed in the NaHY, LiHY and CaHY exchange from NH4Y that have relatively small cations, which more acidic than the larger ones.With the catalysts that have Bronsted acid sites except ion-exchanged zeolite Y, no conversion or only acid catalyzed isomerization reactions occur that shows the Bronsted acidity was not enough to catalyze the dehydrogenation of a-terpinene. Also Lewis acidic character and the structure morphology are the most important factors affecting the conversion. Lewis acidity is influenced from the cation and zeolite type.