Patent ID: 7737318

Claim:
A process for preparing 1-butenic fractions having less than 2000 ppm of isobutene based on the 1-butene from technical mixtures of C 4 hydrocarbons I which contain at least 1-butene and from 2000 ppmw to 8% by mass of isobutene based on the content of 1-butene, comprising the process steps of a) reacting at least a portion of the isobutene present in a technical mixture I with ethanol in a series of at least one reaction zone or a series of at least two reaction zones in the presence of an acidic catalyst to give ethyl tert-butyl ether, b) transferring a reactor effluent II of a last reaction zone of said series into a thermal removal in which a fraction III comprising ethyl tert-butyl ether and a fraction IV which comprises 1-butene and ethanol are obtained, and c) removing said ethanol from fraction IV to obtain a 1-butenic fraction V, and optionally d) removing any C 4 hydrocarbons other than 1-butene or isobutene which are present in the fraction IV in at least one further separating step to obtain a 1-butenic fraction VI, wherein a reaction in a first reaction zone in step a) is carried out with an at least threefold molar excess of ethanol based on said isobutene present in mixture I.