Process for fine purification of 1-butenic streams

Abstract

The invention relates to a process for preparing 1-butenic fractions having less than 2000 ppm of isobutene in relation to 1-butene from technical mixtures of C 4 hydrocarbons I which contain at least 1-butene and 2000 ppmw to 8% by mass of isobutene based on the 1-butene, with or without n-butane, isobutane and/or 2-butenes.

1 . 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 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) being carried out with an at least threefold molar excess of ethanol based on said isobutene present in mixture I.   
     
     
         2 . The mixture according to  claim 1 , wherein said technical mixture of C 4  hydrocarbons I which has a content of 1-butene of greater than 50% by mass is used. 
     
     
         3 . The mixture according to  claim 1 , wherein said technical mixture of C 4  hydrocarbons I comprises isobutane, n-butane and/or 2-butenes, and the ethanol-depleted 1-butenic fraction V obtained in process step c) is separated in a further process step d) into a fraction VI which comprises 1-butene and into at least one further stream which comprises at least one compound selected from isobutane, n-butane and 2-butenes. 
     
     
         4 . The mixture according to  claim 1 , wherein said 1-butenic fraction V and/or VI contains less than 0.5% by mass of 2-butenes. 
     
     
         5 . The mixture according to  claim 1 , wherein acid-catalyzed etherification in stage a) is carried out in such a way that at least one reaction zone is designed as a reactive distillation. 
     
     
         6 . The mixture according to  claim 1 , wherein acid-catalyzed etherification in stage a) is carried out in such a way that the last reaction zone is designed as a reactive distillation, in which step b) is also carried out. 
     
     
         7 . The mixture according to  claim 1 , wherein acid-catalyzed etherification in stage a) is carried out in such a way that no reaction zone is designed as a reactive distillation. 
     
     
         8 . The mixture according to  claim 1 , wherein an extraction is carried out in stage c) and the extractant used is selected from the group consisting of water or an aqueous solution. 
     
     
         9 . The mixture according to  claim 1 , wherein residual amounts of ethanol present in fractions V or VI are scrubbed out with water in a further extraction step. 
     
     
         10 . The mixture according to  claim 1 , wherein said technical mixture I has a content of polyunsaturated compounds of less than or equal to 20 ppm by mass. 
     
     
         11 . The mixture according to  claim 1 , wherein polyunsaturated hydrocarbons are present in is used technical mixture of C 4  hydrocarbon I which are catalytically hydrogenated in an additional purification stage which is inserted upstream of one or more of process steps a), b), c) or d). 
     
     
         12 . The mixture according to  claim 11 , wherein the polyunsaturated compounds are hydrogenated in at least two reaction stages, at least the last reaction stage being carried out in the presence of 0.05 to 100 ppmw of CO. 
     
     
         13 . The mixture according to  claim 1 , wherein said acidic catalyst used is an ion exchange resin. 
     
     
         14 . The mixture according to  claim 1 , wherein reaction in step a) is carried out at a temperature of 30 to 70° C. 
     
     
         15 . The mixture according to  claim 1 , wherein reaction in step a) is carried out at a temperature in at least one reaction zone of 30 to 50° C. and a catalyst which has an acid capacity of greater than 3 to 5.5 mol/kg is used, or in that the reaction in step a) is carried out at a temperature of 51 to 70° C. and a catalyst which has an acid capacity of 0.5 to 3 mol/kg is used. 
     
     
         16 . The mixture according to  claim 1 , wherein the reaction in step a) is carried out before the distillation step b) with an LHSV of 0.3 to 2.5 m 3 /(m 3   CAT h). 
     
     
         17 . The mixture according to  claim 1 , wherein the reaction in a first reaction zone in step a) is carried out with a 10- to 15-fold excess of ethanol in relation to the isobutene present in the mixture I. 
     
     
         18 . The mixture according to  claim 1 , wherein said mixture contains less than 0.5% by mass of 2-butenes 
     
     
         19 . The mixture according to  claim 1 , wherein said mixture contains less than 5 ppm by mass of organic oxygen compounds. 
     
     
         20 . The mixture according to  claim 1 , wherein said mixture contains less than 50 ppm by mass of water. 
     
     
         21 . A method of copolymerizing ethylene with 1-butene comprising using the mixture of  claim 1  as a 1-butene-containing feedstock.