INFLUENCE OF CHLORINE POISONING OF COPPER ALUMINA CATALYST ON THE SELECTIVE HYDROGENATION OF CROTONALDEHYDE

The effect of the presence of chlorine on the activity and selectivity of a Cu/Al2O3 catalyst has been examined for the selective hydrogenat ion of an alphabeta unsaturated aldehyde, crotonaldehyde. Cu/Al2O3 in the absence of chlorine poisons produced 1-butanol almost exclusively, whereas catalysts pre-dosed with a suitable amount of chlorine compou nd (CCl4, CHCl3 and CH2Cl2) shifted the product distribution towards f ormation of butanal. The poisoning effectiveness increased in the orde r CCl4 < CHCl3 < CH2Cl2 much less than CH3Cl and methyl chloride was f ound to totally deactivate the catalyst. The most significant enhancem ent in butanal selectivity was observed with CCl4 and CH2Cl2. The effe ct of chlorine as a poison is in contrast to the effect of sulphur whi ch enhances formation of crotyl alcohol and the origins of these effec ts are discussed.