Process for fine purification of 1-butenic streams

A mixture containing over 98% by mass of 1-butene and less than 200 ppmw of isobutene, obtainable by a process comprising steps of

• a) reacting at least a portion of isobutene present in a technical mixture I with ethanol in 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 C4 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) being carried out with an at least threefold molar excess of ethanol based on said isobutene present in mixture I.