Partial Hydrogenation of 1,4-Butynediol

Abstract

Abstract 1. The effect of lead acetate and the poisons on the Pd-CaCO3 catalyst was studied with the hydrogenation of 1,4-butynediol. 2. The hydrogenation of 1,4-butynediol with the Pd-CaCO3 catalyst at room temperatures takes place in two distinct steps; the first step is the hydrogenation to 1,4-butenediol, and the second is its hydrogenation to 1,4-butanediol. 3. When Pd-CaCO3 catalyst is poisoned by increasing amount of lead acetate, the activity for the hydrogenation of 1,4-butynediol increases at first, and then gradually decreases as the poisoning proceeds. On the other hand, that for the hydrogenation of 1,4-butenediol simply decreases with increasing amount of lead acetate. 4. The hydrogenation of 1,4-butynediol with Pd-CaCO3 catalyst is slightly retarded by quinoline, but not by pyridine or piperidine. On the other hand, the hydrogenation of 1,4-butenediol is retarded to some extent by pyridine, more markedly by piperidine, and stopped almost completely by quinoline. The effect of these bases is almost the same when they are applied to the Pd-CaCO3 catalyst poisoned by lead acetate. 5. The partial hydrogenation of 1,4-butynediol can be achieved by using quinoline, but not by using pyridine or piperidine. 6. The selective hydrogenation may result from the strong adsorption of 1,4-butynediol on the catalyst surface. When the catalyst adsorbs the poisons, the properties of the catalyst surface may be changed. As a result, the selectivity of the catalyst may become very characteristic. Consequently, the selective hydrogenation may take place as observed.