Fine chemical intermediates produced by selective hydrogenation of alkynes over a WPd catalyst

M. JULIANA MACCARRONE; CECILIA R. LEDERHOS; CAROLINA BETTI; FERNANDO COLOMA-PASCUAL; CARLOS VERA; MÓNICA E. QUIROGA

Congreso; 16th International Congress on Catalysis (ICC 16); 2016

Some selective hydrogenation reactions dealing with the transformation of carbon-carbon triple bonds intodouble bond ones are a crucial step in the synthesis of a wide range of fine chemicals including vitamins,fragrances, medical drugs and many other products with a total worldwide production of more than 1000tons per year. In this paper the effects of reactant concentration, temperature and hydrogen pressure onthe activity and selectivity of a low cost WPd/Al2O3 catalyst for the selective hydrogenation of 3-hexyne intohexene were studied. Orders of reaction and the apparent activation energy were calculated. The optimal reaction temperature for the partial hydrogenation of 3-hexyne was 323 K, total conversionbeing practically achieved at 150 min reaction time, with a selectivity to (Z)-3-hexene of 95%. The highselectivity was attributed to the absence of the β-PdH phase, responsible for deep hydrogenation, and thepresence of electron-rich Pdd- (92% at/at) as main active sites for insertion of a single hydrogen. This is inturn associated to factors of electronic type, though the influence of geometric factors or both on the catalyticactivity, cannot be discarded. The negative reaction orders for 3-hexyne (-0.45) and hydrogen (-1.04) point tothe presence of strongly inhibiting reactant adsorption effects. A moderate value of the apparent activationenergy, 14.6 kJ mol-1, was regressed from the kinetic data.