chapter  19
20 Pages

The Selective Hydrogenation of Acetylene in the Vinylchloride Manufacturing Process

WithKlaus M. Deller

During the thermal cracking of 1,2-dichlorethane (EDC)—the basic reaction of the vinylchloride manufacturing process—2 mol of HC1 can be cleaned in consecutive steps and acetylene is formed in small amounts.

In order to use the HC1 efficiently for the production of EDC, the acetylene should be removed nearly completely. The easiest way to do this is by hydrogenation of acetylene. From an economic point of view, the selective formation of ethylene would be most attractive.

Now, a new catalyst for this type of application has been developed, which consists of an acid-resistant silica-based carrier on which palladium is deposited in a thin layer. The support material itself is unporous, so that these uncontrollable parallel and consecutive reactions can hardly occur. In pilot plant runs it was demonstrated that the activity of this catalyst is as high as that of the conventional A12O3-based catalysts and that the selectivity with regard to the formation of ethylene is much higher (65-75%).

The results have been proven over several years by running a large-scale hydrogenation reactor in a vinylchloride plant of Hoechst AG (Gendorf, West Germany).