The isomerization of n-butenes over platinum black in the absence of molecular hydrogen

Abstract

The isomerization reaction (double-bond migration) of 1-butene over platinum black at temperatures between 135 and 180 °C in the absence of molecular hydrogen has been studied by means of a flux and a batch reactor. The reaction has also been studied in the presence of oxygen. Experiments have also been conducted by feeding cis-2-butene into the batch reactor at 135 °C. It has been proved that by means of a suitable residence time platinum black isomerizes n-butenes in the absence of added hydrogen; 1,3-butadiene and traces of n-butane have been found. Oxygen strongly inhibits the isomerization reaction. cis-2-butene isomerizes to trans-2-butene after a noticeable induction time and 1-butene is a significant reaction product. Two reaction mechanisms are discussed, addition-abstraction and abstraction-addition.