Processes of Separation and Transformation in C4-Chemistry

Pure butadiene cannot be separated from the C4-cut by distillation. Both 1,3- butadiene and trans-2-butene form azeotropes with n-butane; vinylacetylene likewise forms azeotropes with cis- or trans-2-butenes, differing only slightly in boiling point from butadiene. Finally, the boiling points of i-butene and 1-butene are so near that their distillative separation is uneconomic (Table 3.1).