Optimization of the selective semi-hydrogenation of phenylacetylene with supported palladium systems

The influence of factors such as the solvent, temperature, initial hydrogen pressure, addition of amines of different basic strength and steric hindrance, type of catalyst used and procedure followed in its synthesis on the selectivity of the liquid-phase, low-pressure semi-hydrogenation of phenylacetylene with molecular hydrogen by using supported palladium catalysts in a Parr reactor was studied. The optimum experimental conditions found were as follows: 0.01 g of catalyst Pd3-PS400−(4)A, a palladium catalyst containing 3% metal deposited over Pansil sepiolite calcined at 400°C, and containing sodium in an Na+-to-Pd ratio of 4:1, 0.46 M phenylacetylene in cyclohexane, 298 K, 0.138 MPa, and 5·10−4M quinoline. On the other hand, by applying the theory of competitive hydrogenations (procedure 1) and the Sporka equation (procedure 2), the relative reactivities, RT,D, and the relative coefficients of adsorption, DT,D, under various reaction conditions were calculated. Under the optimum conditions, the RT,D values found by the two procedures were the largest possible.