Pd/AIPO4 CATALYSED SELECTIVE LIQUID-PHASE HYDROGENATION OF β-IONONE INTO CIS-DIHYDROIONONE
The liquid-phase hydrogenation of β-ionone 1 was carried out at 302 K with 0.205 MPa of initial hydrogen pressure in methanol on Pd/AIPO4 catalyst (2-3 %). The cis-dihydroionone 2. was obtained with a 83 % selectivity which is independent of the degree of conversion. The reaction rate depends on the chloride concentration in the catalyst and the reaction selectivity is a function of the support of the Pd. According to the Langmuir-Hinshelwood kinetic models and the Horiuti-Polanyi type mechanism, the reaction order with respect to β-ionone concentration is negative and of one half order with respect to the hydrogen pressure. The comparison with results obtained over Pd/C catalyst and those obtained in the catalytic hydrogenation of α-ionone suggests that the catalytic hydrogenation of β-ionone could take place on two different active sites of the Pd.