PROCESS FOR RECOVERING 3-METHYLBUT-3-EN-1-OL

Abstract

The present invention relates to a process for recovering 3-methylbut-3-en-1-ol from a feed stream F1 comprising 3-methylbut-3-en-1-ol, one or more solvents, water, and isobutene, wherein 3-methylbut-3-en-1-ol, the one or more solvents and water are separated from isobutene by distillation, the process comprising subjecting the feed stream F1 to distillation conditions in a distillation unit, obtaining a bottoms stream B1 which is enriched in -methylbut-3-en-1-ol, in the one or more solvents and in water compared to the feed stream F1 subjec The present invention relates to a process for recovering 3-methylbut-3-en-1-ol from a feed stream F1 comprising 3-methylbut-3-en-1-ol, one or more solvents, water, and isobutene, wherein 3-methylbut-3-en-1-ol, the one or more solvents and water are separated from isobutene by distillation, the process comprising subjecting the feed stream F1 to distillation conditions in a distillation unit, obtaining a bottoms stream B1 which is enriched in -methylbut-3-en-1-ol, in the one or more solvents and in water compared to the feed stream F1 subjected to distillation conditions, and a top stream T1 which is enriched in isobutene, further subjecting the bottoms stream B1 to distillation conditions in a second distillation unit and obtaining a bottoms stream B2 which is enriched in 3-methylbut-3-en-1-ol compared to the bottoms stream B1 and a top stream T2 which is enriched in water compared to the bottoms stream B1, further subjecting the bottoms stream B2 to distillation conditions in a third distillation unit and obtaining a top stream T3 which is enriched in 3-methylbut-3-en-1-ol compared to the bottoms stream B2 and a bottoms stream B3. ted to distillation conditions, and a top stream T1 which is enriched in isobutene, further subjecting the bot-toms stream B1 to distillation conditions in a second distillation unit and obtaining a bottoms stream B2 which is enriched in 3-methylbut-3-en-1-ol compared to the bottoms stream B1 and a top stream T2 which is enriched in water compared to the bottoms stream B1, further subjecting the bottoms stream B2 to distillation conditions in a third distillation unit and obtaining a top stream T3 which is enriched in 3-methylbut-3-en-1-ol compared to the bottoms stream B2 and a bottoms stream B3.

Claims

1.-20. (canceled)

21. A process for recovering 3-methylbut-3-en-1-ol from a feed stream F1 comprising 3-methylbut-3-en-1-ol, one or more solvents, water, and isobutene, the process comprising (i) subjecting a feed stream F1 to distillation in a first distillation unit (K1200), obtaining a bottoms stream B1 (Su K1200) comprising 3-methylbut-3-en-1-ol, one or more solvents and water, and a top stream TI (De KI200) comprising isobutene; (ii) subjecting the bottoms stream B1 (Su K1200) to distillation in a second distillation unit (K1300), obtaining a bottoms stream B2 (Su K1300) comprising 3-methylbut-3-en-1-ol and a top stream T2 (De K1300) comprising water; (iii) subjecting the bottoms stream B2 to distillation in a third distillation unit (K1500), obtaining a top stream T3 (De K1500) comprising 3-methylbut-3-en-1-ol and a bottoms stream B3 (Su K1500); wherein the bottoms stream B1 (Su K1200) is enriched in methylbut-3-en-1-ol, in the one or more solvents and in water relative to the feed stream F1, wherein the bottoms stream B2 (Su 1300) is enriched in methylbut-3-en-1-ol relative to the bottoms stream B1, wherein the top stream T3 (De K1500) is enriched in methylbut-3-en-1-ol relative to the bottoms stream B2(Su K1300).

22. The process of claim 21, wherein the feed stream F1 (feed_K1200) is a reaction mixture obtainable or obtained by a method for preparing of 3-methylbut-3-en-1-ol, said method comprising (t) providing a mixture comprising formaldehyde, isobutene and the one or more solvents; (tt) contacting the mixture provided in (t) with a condensation catalyst comprising a zeolitic material, obtaining the feed stream F1; wherein the framework structure of the zeolitic material in (tt) comprises Si, O, optionally Al, and a tetravalent element Y which is one or more of Sn, Ti and Zr, wherein in the framework structure of the zeolitic material in (tt), the molar Al:Si ratio is in the range of from 0:1 to 0.001:1.

23. The process of claim 21, wherein at least 5 weight-%, preferably from 10 to 20 weight-% of the feed stream F1 (feed_K1200) consist of methylbut-3-en-1-ol, at least 30 weight-%, preferably from 40 to 50 weight-% of the feed stream F1 consist of the one or more solvents, at least 20 weight-%, preferably from 20 to 40 weight-% of the feed stream F consist of isobutene and at least 1 weight-%, preferably from 3 to 7 weight-% of the feed stream F1 consist of water, and wherein at least 96 weight-%, preferably from 97 to 99 weight-% of the feed stream F1 consist of 3-methylbut-3-en-1-ol, the one or more solvents, water and isobutene, in each case based on the total weight of the feed stream F1.

24. The process of claim 21, wherein at least 10 weight-%, preferably from 15 to 30 weight-% of the bottoms stream B1 (Su K1200) consist of methylbut-3-en-1 ol, at least 50 weight-%, preferably from 60 to 80 weight-% of the bottoms stream B1 (Su K1200) consist in the one or more solvents, at least 3 weight-%, preferably from 5 to 9 weight-% of the bottoms stream B1 (Su K1200) consist of water and less than 0.1 weight-%, preferably from 0.01 to 0.09 weight-% of the bottoms stream B1 consist of isobutene, and wherein at least 96 weight-%, preferably from 97 to 99 weight-% of the bottoms stream B1 consist of 3-methylbut-3-en-1-ol, the one or more solvents and water, in each case based on the total weight of the bottoms stream B1.

25. The process of claim 21, wherein the one or more solvents comprised in the feed stream F1 have a boiling point higher than the boiling point of 3-methylbut-3-en-1-ol wherein the boiling point of 3-methylbut-3-en-1-ol is in the range of from 130 to 132 C. at an absolute pressure of 1 bar, wherein preferably the one or more solvents have a boiling point in the range of from 140 C. to 240 C. at an absolute pressure of 1 bar, more preferably in the range of from 160 to 200 C. at an absolute pressure of 1 bar, wherein preferably the one or more solvents is one or more of a monohydroxy alcohol, a poly-hydroxy alcohol and a ketone, wherein preferably the mono-hydroxy alcohol is a secondary or tertiary alcohol, wherein preferably the secondary and the tertiary alcohol is one or more of 1-pentanol, 2-hexanol, 2-methyl-hexanol, 4-methyl-hexanol, 3-methyl-hexanol, 3-ethylhexanol, 4-heptanol, 2-methyl-2-heptanol, 3-heptanol, 2-heptanol, 3-Ethyl-3hexanol, 3-methyl-2-heptanol, 2-methyl-4-heptanol, 4-ethyl-4-heptanol, 2-octanol, ethylhexanol more preferably the mono-hydroxy alcohol is 2-ethylhexanol, wherein preferably the poly-hydroxy alcohol is one or more of propane diol, glycol and 1,4 butane diol, and wherein preferably the ketone is one or more of cyclo-2-penten-1-one, cyclohexanone and cycloheptanone.

26. The process of claim 21, wherein the distillation unit according to (i) is a distillation tower, wherein the distillation according to (i) is carried out at a pressure at the top of the tower in the range of from 4 to 15 bar(abs), preferably in the range of from 7 to 13 bar(abs), at a temperature at the bottoms of the tower in the range of from 140 to 190 C., preferably in the range of from 170 to 180 C. and at a temperature at the top of the tower in the range of from 40 to 80 C., preferably in the range of from 60 to 75 C. and wherein the tower preferably has from 5 to 40, more preferably from 15 to 25 theoretical plates.

27. The process of claim 21, wherein the distillation unit according to (ii) is a distillation tower wherein the distillation according to (ii) is carried out at a pressure at the top of the tower in the range of from 0.1 to 2 bar(abs), preferably in the range of from 0.5 to 1.5 bar(abs), at a temperature at the bottoms of the tower in the range of from 130 to 180 C., preferably in the range of from 150 to 160 C. and at a temperature at the top of the tower in the range of from 60 to 110 C., preferably in the range of from 85 to 95 C., wherein the tower preferably has from 15 to 50, more preferably from 15 to 25 theoretical plates, wherein the bottoms stream B2 (Su K1300) is enriched in methylbut-3-en-1-ol and in the one or more solvents relative to the bottoms stream B1 (Su K1200) and wherein preferably at least 10 weight-%, more preferably from 20 to 35 weight-% of the bottoms stream B2 (Su K1300) consist of methylbut-3-en-1-ol, preferably at least 55 weight-%, more preferably from 70 to 90 weight-% of the bottoms stream B2 (Su K 1300) consist of the one or more solvents, and preferably less than 0.05 weight-%, more preferably from 0.002 to 0.005 weight-% of the bottoms stream B2 (Su K1300) consist of water, and wherein preferably at least 96 weight-%, more preferably from 98 to 99 weight-% of the bottoms stream B2 consist of 3-methylbut-3-en-1-ol and the one or more solvents, in each case based on the total weight of the bottoms stream B2.

28. The process of claim 21, wherein the distillation unit according to (iii) is a distillation tower, wherein the distillation according to (iii) is carried out at a pressure at the top of the tower in the range of from 0.03 to 1.5 bar(abs), preferably in the range of from 0.09 to 0.5 bar(abs), at a temperature at the bottoms of the tower in the range of from 90 to 150 C., preferably in the range of from 120 to 140 C. and at a temperature at the top of the tower in the range of from 45 to 90 C., preferably in the range of from 65 to 75 C., wherein the tower preferably has from 10 to 45, more preferably from 20 to 30 theoretical plates and wherein the top stream T3 (De K1500) is enriched in methylbut-3-en-1-ol relative to the bottoms stream B2 (Su K1300) and wherein the bottoms stream B3 (Su K1500) is enriched in the one or more solvents relative to the bottoms stream B2 (Su K 1300).

29. The process of claim 21, wherein the top stream T2 (De K1300) additionally comprises 3-methylbut-3-en-1-ol, wherein preferably at least 30 weight-%, more preferably from 45 to 60 weight-% of the top stream T2 (De K1300) consist of methylbut-3-en-1-ol, and wherein at least 7 weight-%, preferably from 15 to 30 weight-% of the top stream T2 (De K1300) consist of water, less than 0.05 weight-%, preferably from 0.005 to 0.00001 weight-% of the top stream T2 consist of the one or more solvents, wherein preferably at least 60 weight-%, more preferably from 75 to 80 weight-% of the top stream T2 consist of 3-methylbut-3-en-1-ol and water, in each case based on the total weight of the top stream T2 and wherein the process further comprises (iv) subjecting the top stream T2 (De K1300) to a separation phase (B1310) in a phase separation unit, and obtaining an aqueous liquid stream L2aq (B 1310 WP) comprising water and 3-methylbut-3-en-1-ol and an organic liquid stream L2or (B1310 OP) comprising 3-methylbut-3-en-1-ol and water, wherein the organic liquid stream L2or is richer in 3-methylbut-3-en-1-ol than the aqueous liquid stream L2aq wherein preferably at least 96 weight-%, more preferably from 97 to 98.7 weight-% of the 3-methylbut-3-en-1-ol comprised in the top stream T2 is recovered in the organic liquid stream L2or; and wherein the process further comprises separating a portion PT2 (Reflux_K1300) and a portion L2or (OP_Out) of the organic liquid stream L2or (B 1310 OP) from the organic liquid stream L2or (B 1310 OP) and feeding the portion PT2 back to the top of the distillation tower according to (ii), wherein the portion PT2 is preferably from 94 to 98 weight-%, more preferably from 96 to 97 weight-% of L2or based in the total weight of L2or.

30. The process of claim 21, wherein the process further comprises recovering the one or more solvents comprised in the bottoms stream B3, (Su K1500) wherein the recovering preferably comprises (v) subjecting the bottoms stream B3 (Su K1500) to distillation (K1600) in a fifth distillation unit; (vi) recovering a side stream S5 (Si K1600) from the fifth distillation unit, comprising the one or more solvents.

31. The process of claim 21, wherein the one or more solvents comprised in the feed stream F1 have a boiling point lower than the boiling point of 3-methylbut-3-en-1-ol wherein the boiling point of 3-methylbut-3-en-1-ol is in the range of from 130 to 132 C., wherein preferably the one or more solvents have a boiling point in the range of from 50 to 125 C., more preferably in the range of from 65 to 120 C., wherein the boiling points are at an absolute pressure of 1 bar, wherein the one or more solvents comprised in the feed stream F1 is one or more of a secondary alcohol, a tertiary alcohol, a ketone, an ester and a nitrile, wherein the secondary alcohol and the tertiary alcohol are preferably one or more of methanol, ethanol, tert-butanol, 2-propanol, 1-propanol, 2-methyl-2-butanol, isobutanol, 3-pentanol, 1-butanol and 2-pentanol, more preferably one or more of tert-butanol, 2-propanol, 2-methyl-2-butanol, isobutanol, 3-pentanol, 1-butanol and 2-pentanol, wherein the ketone is preferably one or more of acetone, 2-butanone and 2-pentanone, wherein the ester is preferably ethyl acetate, wherein the nitrile is preferably acetonitrile.

32. The process of claim 21, wherein the distillation unit according to (i) is a distillation tower, wherein the distillation according to (i) is carried out at a pressure at the top of the tower in the range of from 4 to 20 bar(abs), preferably in the range of from 7 to 13 bar(abs), at a temperature at the bottoms of the tower in the range of from 130 to 180 C., preferably in the range of from 150 to 160 C. and at a temperature at the top of the tower in the range of from 40 to 90 C., preferably in the range of from 60 to 70 C. and wherein the tower preferably has from 7 to 30, more preferably 15 to 20 theoretical plates.

33. The process of claim 21, wherein the distillation unit according to (ii) is a distillation tower, wherein the distillation according to (ii) is carried out at a pressure at the top of the tower in the range of from 0.05 to 3 bar(abs), preferably in the range of from 0.5 to 1.5 bar(abs), at a temperature at the bottoms of the tower in the range of from 130 to 155 C., preferably in the range of from 130 to 140 C. and at a temperature at the top of the tower in the range of from 60 to 95 C., preferably in the range of from 75 to 85 C., wherein the tower preferably has from 10 to 50, more preferably 25 to 35 theoretical plates, wherein at least 84 weight-%, preferably from 93 to 95 weight-% of the bottoms stream B2 (Su K1300) consist of methylbut-3-en-1-ol, less than 0.25 weight-%, preferably from 0.01 to 0.1 weight-% of the bottoms stream B2 (Su K1300) consist of the one or more solvents, less than 0.3 weight-%, preferably from 0.01 to 0.1 weight-% of the bottoms stream B2 (Su K1300) consist of water, in each case based on the total weight of the bottoms stream B2.

34. The process of claim 21, wherein the distillation unit according to (iii) is a distillation tower, wherein the distillation according to (iii) is carried out at a pressure at the top of the tower in the range of from 0.03 to 1.4 bar(abs), preferably in the range of from 0.09 to 0.5 bar(abs), at a temperature at the bottoms of the tower in the range of from 120 to 170 C., preferably in the range of from 140 to 150 C. and at a temperature at the top of the tower in the range of from 45 to 95 C., preferably in the range of from 65 to 75 C., wherein the tower preferably has from 4 to 25, more preferably from 7 to 12 theoretical plates and wherein at least 98 weight-%, preferably from 99.5 to 99.95 weight-%, more preferably from 99.8 to 99.9 weight-% of the top stream T3 (De K1500) consist of 3-methylbut-3-en-1-ol and wherein less than 700 ppm (0.07 weight-%), preferably from 50 to 0.5 ppm (0.005 to 0.00005 weight-%), more preferably from 20 to 1 ppm (0.002 to 0.0001 weight-%) of the top stream T3 (De K1500) consist of the one or more solvents, in each case based on the total weight of the top stream T3.

35. The process of claim 21, wherein at least 92 weight-%, preferably from 97 to 99.9 weight-%, more preferably 98 to 99.6 weight-% of the top stream T1 (Br K1200) consist of isobutene, based on the total weight of the top stream T1 (Br K1200).

36. The process of claim 21, wherein prior to (i) the process comprises (t) providing a mixture comprising formaldehyde, isobutene and the one or more solvents; (tt) contacting the mixture provided in (t) with a condensation catalyst comprising, preferably consisting of an heterogeneous catalyst and obtaining the feed stream F1.

37. The process of claim 36, wherein the heterogeneous catalyst comprises, preferably consists of, a Lewis acid catalyst and/or a Brnsted acid catalyst, preferably a Lewis acid catalyst, wherein preferably the Lewis acid catalyst is a zeolitic material, a mesoporous silica, a metal oxide or mixed metal oxides supported rare earth metals and combination of two or more thereof.

38. The process of claim 36, wherein the zeolitic material is a zeolitic material as defined in claim 22, a metal doped zeolite, preferably a rare-earth metal doped zeolite or a alkaline earth modified Al-containing zeolite, preferably the zeolitic material is as defined in claim 22.

39. The process of claim 36, wherein the mesoporous silica is a Sn mesoporous silica.

40. The process of claim 36, wherein the metal oxide is silica, alumina, clays, TiO2, ZnO, ZnO.sub.2.

Description

EXAMPLES

Reference Example 1: Preparation of MBE

Reference Example 1.1: Preparation of a Zeolitic Material Having Framework Type BEA and Comprising Sn (Sn-BEA

A) Preparation of Sn-BEA-Zeolite

Materials Used:

[0385]

TABLE-US-00001 50 g Deboronated BEA-zeolite, spray-dried (prepared according to Example 1 (ii) of WO 2014/060259 A 14.2 g Sn(OAc).sub.2 (tin(II)acetate) from Aldrich

[0386] 50 g of deboronated BEA zeolite and 14.2 g Sn(OAc).sub.2 were combined in the laboratory mixer and were ground for 15 min. The obtained mixture was then calcined in a muffle furnace by raising the temperature at the rate of 2 K/min to 500 C. for 3 h. 55.5 g of the zeolite of a) were obtained.

b) Acid Treatment

Materials Used:

[0387]

TABLE-US-00002 55 g Sn-BEA zeolite according to a) 1650 g HNO.sub.3 30 weight- % aqueous solution

[0388] 761.5 g of a solution of 65% HNO.sub.3 were added to a stirred 2 L vessel charged with 888.5 g of deionized water. Under continuous stirring, 55 g of the zeolite according to a) were added to the mixture. The obtained suspension was heated to 100 C. and refluxed for 20 h. The suspension was then cooled, filtered and washed with distilled water until neutral pH (<100 microSiemens). The filtered zeolite was then calcined in the muffle furnace by raising the temperature at the rate of 3 K/min to 120 C. for 10 h followed by raising the temperature at the rate of 2 K/min to 550 C. for 10 h. 52.8 g of the zeolite of b) were obtained.

c) Preparation of a Molding

Materials Used:

[0389]

TABLE-US-00003 60 g Sn-BEA zeolite of b) 17.37 g ZrOH(OAc).sub.3 (~10% ZrO.sub.2) from Aldrich 3 g Walocel Wolf Walsrode AG PUFAS Werk KG 53 mL DI water

[0390] 60 g of Sn-BEA zeolite of b), 17.37 g of ZrOH(OAc).sub.3 and 3 g of Walocel@ were combined and mixed in a kneader. 53 mL of deionized water were then added to the mixture which was kneaded until combined. The total kneading time was 30 min. The obtained zeolite was then calcined in the muffle furnace by raising the temperature at the rate of 3 K/min to 120 C. for 6 h followed by raising the temperature at the rate of 2 K/min to 550 C. for 5 h under air. 52.8 g of the molding with a bulk density of 440 g/L were obtained.

Reference Example 1.2: Synthesis of MBE in the High Boiling Solvent 2-ethlyhexanol

[0391] 55 g of an aqueous solution of formaldehyde (FA) (49 weight-%) were dissolved in 445 g of 2-ethlyhexanol. A formaldehyde solution (5.39 weight-%) was obtained. This solution was dosed to an isothermal tubular reactor at 32 g/h (0.05 mol FA/h). The isobutene flask was pressurized with helium (to liquefy the gas) and pumped into the reactor at 31.3 g/h (0.55 mol/h). The two streams were pressurized to 20 bar(abs) and tempered to 100 C. before entering the reactor. The tubular reactor had a length of 110 cm and contained 10.85 g of a Sn-BEA catalyst. The reactor was operated at 100 C. and at a constant pressure of 20 bar(abs). The residence time was of about 15.67 min. The reaction was run for 48 h. The reaction mixture which was obtained was fed as stream F1 according to the invention to the inventive work-up process. In the following, this specific feed stream is denoted as Feed_K1200. The composition of the Feed_K1200 is given in Table 1 below.

Reference Example 1.3: Synthesis of MBE in a Low Boiling Solvent

[0392] 55 g of an aqueous solution of formaldehyde (FA) (49 weight-%) were dissolved in 445 g of tert-butanol. A formaldehyde solution (5.39 weight-%) was obtained. This solution was dosed to an isothermal tubular reactor at 32 g/h (0.05 mol FA/h). The isobutene flask was pressurized with helium (to liquefy the gas) and pumped into the reactor at 31.3 g/h (0.55 molh). The two streams were pressurized to 20 bar(abs) and tempered to 100 C. before entering the reactor. The tubular reactor had a length of 110 cm and contained 10.85 g of a Sn-BEA catalyst according to Reference Example 1.1. The reactor was operated at 100 C. and at a constant pressure of 20 bar(abs). The residence time was of about 15.67 min. The reaction was run for 48 h. The reaction mixture which was obtained was fed as stream F1 according to the invention to the inventive work-up process. In the following, this specific feed stream is denoted as Feed_K1200. The composition of the Feed_K1200 is given in Table 2 below.

Example 1: MBE Recovery from the High Boiling Solvent 2-Ethlyhexanol (FIG. 1)

[0393] The following explains a series of steps of the reaction in accordance with the present invention. The streams and the apparatus are identified according to the abbreviation used in FIG. 1.

a) Distillation of the Feed Stream Feed_K1200 (F1) (First Distillation Unit)

[0394] The reaction mixture of Reference Example 1 Feed-K1200 (F1) was fed at a temperature of 100 C. and at a mass flow rate of 7.510.sup.4 kg/h to a 20-plate distillation tower K1200. The feed was fed at plate 18 of the distillation tower K1200. The distillation was carried out at a top pressure of 9 bar(abs) and a top temperature of 68.7 C. and at a bottoms temperature of 174.0 C. A bottoms stream Su_K1200 (B1) and a top stream Br_K1200 (Ti) were withdrawn. The respective compositions are disclosed in Table 1 herein below.

b) Distillation of the Bottoms Stream Su_K1200 (B1) (Second Distillation Unit)

[0395] The bottoms stream Su_K1200 (B1) of a) was subjected to phase separation in a flash drum unit at a mass flow rate of 4.810.sup.4 kg/h, at a temperature of 117 C. and a pressure of 1 bar(abs). A liquid stream B1300_F1 (L7) and a gas stream B1300_G (G7) were obtained. The liquid stream B1300_F1 (L7) and the gas stream B1300G (G7) were fed into a 35 plate distillation tower K1300 operating at a top pressure of 1 bar(abs) and a top temperature of 91 C. and at a bottoms temperature of 144 C. The liquid stream B1300_F1 (L7) was feed at plate 20 at a mass flow rate of 4.110.sup.4 kg/h and the gas stream B1300_G (G7) was fed at plate 20 at a mass flow rate of 6.210.sup.3 kg/h. A top stream De_K1300 (T2) and a bottoms stream Su_K1300 (T3) were withdrawn from the distillation tower K1300. The respective compositions are disclosed in Table 1 herein below.

c) Distillation K1500 of Bottoms Stream (B2) Su_K1300 (Third Distillation Unit)

[0396] The bottoms stream Su_K1300 (B2) from b) was fed into a phase separation unit (flash drum) B1500 at a mass flow rate of 4.410.sup.4 kg/h. The phase separation unit was operated at a temperature of 102 C. and a pressure of 0.1 bar(abs). A liquid stream B1500_F1 (L8) and a gas stream B1500_Br (G8) were withdrawn. The liquid stream and the gas stream were fed into a 25 plate distillation tower K1500 operating at a top pressure of 0.1 bar(abs), at a top temperature of 73 C. and at a bottoms temperature of 118.5 C. The liquid stream B1500_F1 (L8) and the gas stream B1500_Br (G8) were fed at plate 15 and plate 16 respectively at a respective mass flow rate of 3.010.sup.4 kg/h and 1.410.sup.4 kg/h. A top stream De_K1500 (T3) and a bottoms stream Su_K1300 (B3) were withdrawn. The top stream De_K1500 (T3) consisted of about 100 weight-% of MBE. The compositions of the streams are disclosed in details in Table 1 herein below.

d) Recycling of Top Stream De_K1300 (T3) (Fourth Distillation Unit)

[0397] The top stream De_K1300 (T3) of b) was fed into a phase separation unit B1310 at a mass flow rate of 3.810.sup.4 kg/h. The phase separation unit was operated at a pressure of 1 bar(abs) and a temperature of 40 C. Two streams B1310_WP (L2aq) and B1310_OP (L2) were obtained. B1310_WP (L2aq) was fed directly at a mass flow rate of 4.110.sup.3 into a 22 plate distillation column K1400 at plate 12. Stream B1310_OP was split into a reflux stream Reflux_K1300 (PT2) that was fed at a mass flow rate of 3.310.sup.4 kg/h to the top of the distillation tower K1300 of c) and into a stream OP_out that was fed at plate 12 and at a mass flow rate of 3.910.sup.2 kg/h into the 22 plate distillation column K1400. The distillation tower K1400 was operating at a top pressure of 1 bar(abs), at a top temperature of 65 C. and at a bottoms temperature of 99.5 C. Three streams were withdrawn. The top stream De_K1400 comprising low boilers (waste) and the bottoms stream Su_K1400 were discharged. The side stream DSA (S2) was withdrawn at plate 6. The side stream DSA having a temperature of 95.9 C. was fed at a mass flow rate 1.310.sup.3 into a heat exchanger W1420 operating at a pressure of 1 bar(abs). Two streams were recovered: the condensed stream Kond_W1420 (C3) and the gas stream Abg_W1420. The gas stream was discharged. The liquid stream Kond_W1420 (C3) was fed into a phase separation unit B1420 operating at a pressure of 1 bar(abs) and a temperature of 95.7 C. A liquid stream B1420_OP (L3) and a liquid stream B1420_WP were obtained. The liquid stream B1420_OP (L3) was fed back into distillation tower K1300 of c) at plate 17 and at a mass flow rate of 6.410.sup.2 kg/h. The gas stream B1420_WP was fed back into the distillation tower K1400 at plate 12 and at a mass flow rate of 6.910.sup.2 kg/h. The compositions of the streams are reported in Table 1 herein below.

e) Recovery of the High Boiling Solvent 2-Ethylhexanol (2-EH): Distillation of Bottoms Stream Su_K1500 (B3) (Fifth Distillation Unit)

[0398] The bottoms stream Su_K1500 (B3) obtained from above c) was subjected to a two distillation towers distillation. Su_K1500 (B3) was fed into a 20 plate-pre-column K1600_VK at plate 10 and at a mass flow rate of 3.410.sup.4 kg/h. K1600_VK was operating at a top pressure of 1 bar(abs), a top temperature of 118.1 C. and at a bottoms temperature of 118.5 C. A liquid stream APP10_Lu was withdrawn from plate 1 of K1600_VK and fed into the distillation tower K1600 at plate 10 and at a mass flow rate of 4.810.sup.4 kg/h. A gas stream APP10_GO was withdrawn from plate 20 of K1600_VK and fed at plate 10 into the 40-plate distillation tower K160_HK at a mass flow rate of 3.210.sup.2 kg/h. The distillation tower K1600 HK was operating at a top pressure of 0.1 bar(abs), at a top temperature of 97.5 C. and at a bottoms temperature of 146.5 C. From the distillation tower K1600 the following streams were withdrawn:

[0399] Liquid stream APP10_Lu was withdrawn from plate 31 and fed back to the pre-column K1600_VK at plate 20 and at a mass flow rate of 1.510.sup.2 kg/h; Gas stream APP10_Gu was withdrawn from plate 10 and fed back to the pre-column K1600_VK at plate 1 at a mass flow rate of 3.110.sup.2 kg/h; liquid stream Su_K1600 was withdrawn from the bottoms (evaporator) and discharged; stream De_K1600 was withdrawn from the bottoms and discharged and liquid side stream Si_K1600 (S5) was withdrawn from plate 21. The compositions of the streams are disclosed in Table 1 herein below.

f) Recovery of Isobutene from Top Stream Br_K1200 (T1)

[0400] Top stream Br_K1200 (T1) having a temperature of 68.6 C. was withdrawn from the top of the distillation tower K1200 of a) and fed at a mass flow rate of 3.710.sup.4 kg/h into the heat exchanger W1210 operating at a pressure of 9 bar(abs). A liquid stream Kond_W1210 and a gas stream Abg W1210 were obtained. The gas stream Abg W1210 as discharged. The liquid stream Kond_W1210 was fed into W1215 a condenser operating at a temperature of 40 C. at a mass flow rate of 3.710.sup.4 kg/h. Two streams were obtained: a reflux stream reflux_K1200 which was fed back into distillation tower K1200 at plate 20 and at a mass flow rate of 1.010.sup.2 kg/h and a stream Out_W1215 comprising 99.6 weight-% of isobutene which was recovered.

TABLE-US-00004 TABLE 1 Compositions of the streams in weight-%, if not indicated as ppb Feed_ Su_ Br_ K1200 Reflux_ K1200 K1200 Kond_ Abg_ Out_ F1 K1200 B1 T1 W1210 W1200 W1215 Mass flow rate/(kg/h) MBE 13.8 0.0038 21.6 0.0038 0.0038 292 ppb 0.0038 Isobutene 36.0 99.6 0.0500 99.6 99.6 99.4 99.6 2-EH 44.0 218 ppb 68.8 218 ppb 218 ppb 0 ppb 218 ppb H2O 4.8 0.0563 7.5 0.0563 0.0563 0.0016 0.0563 MBE- 0.2 0.0002 0.3 0.0002 0.0002 27 ppb 0.0002 Formate MP-1,3-Diol 0.9 0 ppb 1.5 0 ppb 0 ppb 0 ppb 0 ppb MeOH 0.3 0.3 0.2 0.3 0.3 0.6 0.3 T_BuOH 0.1 0.0365 0.2 0.0365 0.0365 0.0071 0.0365 Total in 7.506*10.sup.4 1.000*10.sup.4 4.797*10.sup.4 3.709*10.sup.4 3.709*10.sup.4 1.000 2.709*10.sup.4 kg/h B1300_ B1300_ Su_ De_ B1310_ B1310_ FI Gas B1420_ Reflux_ K1300 K1300 WP OP Op_ L7 G7 OP K1300 B2 T2 L2aq L2op out Mass flow rate / (kg/h) MBE 19.4 34.7 74.6 56.3 23.5 50.7 6.2 56.3 56.3 Isobutene 0.0051 0.3 184 ppb 0.3 0.3 0.5 0.3 0.3 2-EH 76.5 22.6 74.9 0 ppb H2O 2.1 39.9 24.3 12.3 20.8 88.4 12.3 12.3 MBE- 0.2 0.6 1.0 24.8 0.0050 22.2 1.0 24.8 24.8 Formate MP-1,3- 1.7 0.1 1.6 Diol MeOH 0.0637 1.1 0.0626 1.9 1.9 2.3 1.9 1.9 T_BuOH 0.0734 0.7 0.0041 4.5 4.1 1.5 4.5 4.5 Total in 4.115*10.sup.4 6.818*10.sup.3 6.414*10.sup.3 3.300*10.sup.4 4.404*10.sup.4 3.357*10.sup.4 4.176*10.sup.3 3.339*10.sup.4 3.943*10.sup.2 kg/h B1500_ B1500_ B1500_ Su_ De_ FI Br Br K1500 K1500 L8 G8 G8 B3 T3 App10_LO App10_GU Mass flow rate/(kg/h) MBE 11.4 50.1 50.1 0.0050 100.0 0.0005 0 ppb Isobutene 2-EH 86.5 49.6 49.6 97.9 0.0010 100.0 99.4 H2O MBE- 0.0021 0.0114 0.0114 1 ppb 0.0213 0 ppb Formate MP-1,3- 2.2 0.3 0.3 2.1 0 ppb 0.0006 0.6 Diol MeOH T_BuOH Total in 3.029*10.sup.4 1.375*10.sup.4 1.375*10.sup.4 3.370*10.sup.4 1.034*10.sup.4 1.462*10.sup.4 3.163 *10.sup.4 kg/h App10_ App10_ Su_ De_ SI_ B1420_ Su_ Lu GO K1600 K1600 K1600 WP K1400 Mass flow rate / (kg/h) MBE 0 ppb 0.0055 16.9 0 ppb 17.6 0.0286 Isobutene 273 ppb 0 ppb 2-EH 98.2 100.0 0.1 83.1 100.0 H2O 82.2 100.0 MBE- 0 ppb 1 ppb 0.0004 0.0686 0 ppb Formate MP-1,3- 1.8 0.0010 99.9 0 ppb 0.0010 Diol MeOH 0.0637 70 ppb T_BuOH 0.0016 0 ppb Total in 4.827*10.sup.4 3.169*10.sup.4 7.004*10.sup.2 1.000*10.sup.1 3.299*10.sup.4 6.943*10.sup.2 3.493*10.sup.3 kg/h De_ DSA Kond_ Abg_ K1400- S2 W1420 W1420 Mass flow rate/(kg/h) MBE 0.3 45.0 45.0 43.7 Isobutene 5.5 231 ppb 230 ppb 0.0002 2-EH H2O 21.1 54.4 54.4 53.3 MBE- 31.0 0.5 0.5 2.8 Formate MP-1,3- Diol MeOH 23.8 0.0633 0.0632 0.2 T_BuOH 18.2 0.0028 0.0028 0.0151 Total in 3.339*10.sup.2 1.337*10.sup.3 1.337*10.sup.3 1.000 kg/h

[0401] In Table 1, MBE stands for 3-methylbut-3-en-1-ol, 2-EH stands for 2-ethylhexanol, MP-1,3-Diol stands for 3-methylbutane-1,3-diol, MBE-Formiate stands for the ester of formic acid and 3-methylbut-3-en-1-ol and T_BuOH stands for tert-butanol.

Example 2 MBE Recovery from the Low Boiling Solvent Tert-Buthanol (FIG. 2)

[0402] The following explains a series of steps of the reaction in accordance with the present invention. The streams and the apparatus are identified according to the abbreviations used in FIG. 2 and the Reference Example 1.3.

a) Distillation of the Feed Stream Feed_K1200 (F1) (First Distillation Unit)

[0403] The reaction mixture of Reference Example 1 (Feed-K1200) was fed at a temperature of 100 C. and at a mass flow rate of 7.5104 kg/h to a 16-plate distillation tower K1200. The feed was fed at plate 12 of the distillation tower K1200. The distillation was carried out at a top pressure of 9 bar(abs), at a top temperature of 66.6 C. and at a bottoms temperature of 151.4 C. A bottoms stream Su_K1200 (B1) and a top stream Br_K1200 (T1) were withdrawn. The respective compositions are disclosed in Table 2 herein below.

b) Distillation of Bottoms Stream Su_K1200 (B1) (Second Distillation Unit)

[0404] The bottoms stream Su_K1200 (B1) was subjected to phase separation in a flash separator at a mass flow rate of 4.810.sup.4 kg/h, at a temperature of 85.5 C. and a pressure of 1 bar(abs). A liquid stream B1300_F1 (L7) and a gas stream B1300_G (G7) were obtained. The liquid stream B1300F1 and the gas stream B1300_G were fed into a 30 plate distillation tower operating at a top pressure of 1 bar(abs) and a top temperature of 79 C. and at a bottoms temperature of 130.5 C. The liquid stream B1300_F1 (L7) was feed at plate 17 at a mass flow rate of 3.110.sup.4 kg/h and the gas stream B1300_G (G7) was fed at plate 18 at a mass flow rate of 1.710.sup.4 kg/h. A top stream De_K1300 (T2) and a bottoms stream Su_K1300 (B2) were withdrawn from the distillation tower. The respective compositions are disclosed in Table 2 herein below.

c) Distillation K1500 of Bottoms Stream (B2) Su_K1300 (Third Distillation Unit)

[0405] The bottoms stream Su_K1300 (B2) from b) was fed into a phase separation unit at a mass flowrate of 3.110.sup.4 kg/h. The phase separation unit flash was operating at a temperature of 74 C. and a pressure of 0.1 bar(abs). A liquid stream B1500_F1 (L8) and a gas stream B1500_Br (G8) were obtained. The liquid stream and the gas stream were fed into a 10 plate distillation tower operating at a top pressure of 0.1 bar(abs), at a top temperature of 73 C. and at a bottoms temperature of 146.5 C. The liquid stream B1500_F1 and the gas stream B1500_Br were fed a plate 5 and plate 6 respectively at a respective mass flow rate of 7.710.sup.3 kg/h and 3.310.sup.3 kg/h. A top stream De_K1500 (T3) and a bottoms stream Su_K1500 (B3) were withdrawn. The respective compositions are disclosed in Table 2 herein below.

d) Recovery of Isobutene from Top Stream Br_K1200 (T1)

[0406] The top stream Br_K1200 (T1) was withdrawn from the top of the distillation tower K1200 of a) and fed at a mass flow rate of 4.910.sup.4 kg/h into the heat exchanger W1210 operating at a pressure of 9 bar(abs) and at a temperature of 66 C. A liquid stream Kond_W1210 and a gas stream Abg_W1210 were obtained. The gas stream Abg W1210 as discharged. The liquid stream Kond_W1210 was fed into the condenser W1215 operating at a temperature of 40 C. at a mass flow rate of 4.910.sup.4 kg/h. Two streams were obtained: a reflux stream reflux_K1200 (PT1) which was fed back into distillation tower K1200 at plate 16 and at a mass flow rate of 2.210.sup.4 kg/h and a stream Out_W1215 comprising 99.6 weight-% of isobutene which was recovered The respective compositions are disclosed in Table 2 herein below.

TABLE-US-00005 TABLE 2 Compositions of the streams in weight-% Feed_ Reflux_ Su_ Br_ Kond_ Abg_ K1200 K1200 K1200 K1200 W1210 W1200 Mass flow rate/(kg/h) MBE 13.8 1 ppb 21.6 1 ppb 1 ppb 0 ppb Isobutene 36.0 99.6 0.0500 99.6 99.6 99.7 H2O 4.8 741 ppb 7.5 741 ppb 741 ppb 22 ppb MBE- 0.2 0 ppb 0.3 0 ppb 0 ppb 0 ppb Formiate MP-1,3- 0.9 1.5 Doil MeOH 0.3 0.2 0.3 0.2 0.2 0.3 T_BuOH 44.0 0.3 68.8 0.3 0.3 0.0531 Total in 7.497*10.sup.4 2.158*10.sup.4 4.788*10.sup.4 4.867*10.sup.4 4.8679*10.sup.4 1.000 kg/h Out_ B1300_ B1300_ Su_ De_ B1500_ W1215 FI gas K1300 K1300 FI Mass flow rate/(kg/h) MBE 1 ppb 30.1 6.2 93.6 0.0500 90.9 Isobutene 99.6 0.0066 0.1 0.0650 H2O 741 ppb 6.2 9.9 0 ppb 9.8 MBE- 0 ppb 0.4 0.1 0.0500 0.4 0.0368 Formiate MP-1,3- 2.3 0.0075 6.3 9.0 Doil MeOH 0.2 0.3 0.4 0.4 T_BuOH 0.3 60.8 83.2 0 ppb 89.3 0 ppb Total in 2.709*10.sup.4 3.081*10.sup.4 1.707*10.sup.3 1.103*10.sup.4 3.685*10.sup.4 7.682*10.sup.3 kg/h B1500_ Su_ De_ Br K1500 K1500 Mass flow rate/(kg/h) MBE 99.8 349 ppb 99.9 Isobutene H2O MBE- 0.0803 0 ppb 0.0534 Formiate MP-1,3- 0.2 100.0 0.0001 Doil MeOH T_BuOH 0 ppb 0 ppb Total in 3.345*10.sup.3 7.000*10.sup.2 1.033*10.sup.4 kg/h

[0407] In Table 2, MBE stands for 3-methylbut-3-en-1-ol, 2-EH stands for 2-ethylhexanol, MP-1,3-Diol stands for 3-methylbutane-1,3-diol, MBE-Formiate stands for the ester of formic acid and 3-methylbut-3-en-1-ol and T_BuOH stands for tert-butanol.

BRIEF DESCRIPTION OF THE FIGURE

[0408] FIG. 1: shows the scheme of the process according to example 1: the MBE recovery from the high boiling solvent 2-ethlyhexanol, the recovery of isobutene and the recovery of high boiling solvent 2-ethlyhexanol

[0409] FIG. 2: shows the scheme of the process according to example 2: the M BE recovery from the low boiling solvent tert-butanol, the recovery of isobutene and the recovery of the azeotrope comprising tert-butanol.

CITED PRIOR ART

[0410] WO 2015/067654 A [0411] WO 2014/060259 A [0412] US 2012059177 A [0413] WO 2011/154330 A [0414] Wa 2011/147919 A [0415] US 2011054083 A