Technology

Process for the Recovery of Polymerization grade 1-Butene from a C₄ Fraction free from Isobutene comprising the Stages of:

1. Sending the C₄ Fraction to a 1^st Distillation Column to obtain a Top Stream essentially containing Isobutane and a Bottom Stream containing the Residual Components
2. Sending the Stream of Residual Components to a 2^nd Distillation Column, obtaining a Top Stream of 1-Butene at a purity level of from 80 to 95% and a Bottom Stream comprising the high boiling Compounds, n-Butane and 2-Butenes, characterized in that the Top Stream from the 2^nd Distillation Column is fed to a Selective Hydrogenation Unit (SHU).
3. Selectively Hydrogenating the Butadiene and the Acetylenic derivatives comprised in the Top Stream from the 2^nd Distillation Column, such Compounds being reduced to a concentration comprised within the range from 30 to 200 ppm, the Stream originating from the SHU being finally fed to a 3^rd Distillation Column.
4. Obtaining from the 3^rd Distillation Column a Top Stream made of Polymerization grade 1-Butene and a Bottom Stream made of n-Butane and 2-Butenes with reduced amounts of 1-Butene.

Figure 1 - Process Block Flow Diagram.

1. C₄ Hydrocarbon stream, 2. Methanol stream, 3. MTBE produced in unit 16, 4. C₄ Stream essentially free from Isobutene, 16. Etherifying unit,  18. 1^st Distillation column operated at about 14 atm absolute, 5. Top stream essentially comprising Isobutane, 6. Residual stream fed to second distilation column 19, 19. Second distillation column operated at about 6 atm absolute,  7. Top stream from second distillation column fed to hydrogenation unit 17, 8. Bottom stream containing heavy products, 17. Hydrogenation unit, 9. Hydrogen line feeding hydrogen to hydrogenation unit 17, 10. Hydrogenated stream fed to a fractionation column, 11. Hydrogenation unit discharge stream essentially consisting of excees hydrogen and 1-butene, 20. Fractionation column operated at a pressure of about 7 atm absolute, 12. Fractionated top stream  consisting of uncondensable matter and butene-1, 13. Stream obtained from the 10^th plate from the top of polymerisation grade 1-butene, 14. Fractionated bottom stream substantialy consisting of n-butane and 2-butene, 15. Steam, which is the sum of streams 5, 8 and 14.  

Source: Renzo Comiotto, Bruno de Maglie, IT2229483A, Priority: 28^th Jul 1983, Procedimento per il recupero di butene-1 grado polimerizzazione.