AIPO4-SUPPORTED NICKEL-CATALYSTS .9. LIQUID-PHASE SELECTIVE HYDROGENATION OF PROPARGYL ALCOHOLS

The liquid-phase consecutive hydrogenation of propargyl alcohols (2-propyn-l-ol, 3-butyn-2-ol, and 2-methyl-3-butyn-2-ol) has been carried out at 293-323 K and in an initial hydrogen pressure range of 0.3-0.7 MPa on three nickel catalysts at 20 wt% supported on two different types of AIPO4. A bimetallic NiCu catalyst was also employed as a catalyst. Furthermore, individual hydrogenation of related allyl alcohols was carried out under identical experimental conditions. Thus, by introducing a modification in the classical kinetic equation of competitive hydrogenations, the relative reactivities RD,T as well as the relative adsorption constants KD,T were successfully obtained in the consecutive process. The independence of RD,T with respect to the temperature and the Arrheniustype law obtained from In K vs T-1 was ascribed to the existence of a linear free-energy relationship (LFER) which also manifested itself in the existence of a linear correlation between the activation parameters ΔH≠ and ΔS≠ (and between Ea and In A) known as the "compensation effect". On the basis of these results, valuable information was obtained concerning not only the mechanism of the liquid-phase catalytic hydrogenation of propargyl alcohols but also the parameters affecting the selectivity of the process. © 1990.