EFFECT OF LEWIS SITES IN THE ISOMERIZATION OF a -PINENE TO CAMPHENE

N. A. COMELLI1, E. N. PONZI2 AND M. I. PONZI1

Rio de janeiro Brasil

Congreso; 2do. Mercosur Congress on Chemical Engineering. 4to. Mercosur Congess on Process Systems Engineering; 2005

Abstract. The isomerization reaction of a-pinene produces bicyclic and monocyclic  compounds and other products. Camphene is important within bicyclic compounds since it is an intermediate product in the manufacture of the camphor. The purpose of this study is to investigate the influence of Lewis and Brönsted acid sites on the catalysts activity and selectivity in the isomerization reaction. Catalyzed reactions in homogeneous and heterogeneous phases were performed. In the homogeneous reaction the catalyst is sulfuric acid, and in the reaction medium Brönsted sites are only present coming from the H+ of the acid.  In the heterogeneous reaction, sulfated zirconia was used and contains sites of different nature. The thermal treatment  affects the ratio between Brönsted and Lewis sites. In order to study the influence of the sites, sulfated zirconia was exposed to different thermal treatments (250, 350 and 500 ºC) (ZS250, ZS350 and ZS500), posterior to its calcination and results were contrasted with those obtained without thermal treatment, where the catalyst, after its calcination, was rehydrated for a period of 24 hours before its use in the catalytic reaction. Results obtained for a reaction time of  60 minutes are shown in the following table:   Catalyst H2SO4 ZS ZS250 ZS350 ZS500 Bicyclic/Monocyclic 0.4 2.9 4.2 3.3 3.5   It is possible to observe that there exists an optimal thermal treatment where the ratio is higher.  In herogeneous reactions, a maximum ratio value of 4.2 was obtained between bicyclic and monocyclic compounds and in the case of the homogeneous reaction this ratio value was 0.4.