METHOXYPROPANOLS SEPARATION COMBINING MEMBRANE SEPARATION AND DISTILLATION

Abstract

A first aspect of the invention relates to a process for separating 1-methoxypropan-2-ol from an aqueous stream comprising 1-methoxypropan-2-ol and 2-methoxypropan-1-ol, wherein the process comprises providing a stream SO comprising 1-methoxypropan-2-ol, 2-methoxypropan-1-ol and water, and having a molar ratio of 1-methoxypropan-2-ol:2-methoxypropan-1-ol in the range of from 1:5 to 5:1; wherein the final stream S5 comprises 95 weight-% 1-methoxypropan-2-ol based on the total weight of S5. In a second aspect, the invention relates to 1-methoxypropan-2-ol or a mixture of 1-methoxypropan-2-ol and 2-methoxypropan-1-ol obtained or obtainable from the process of the first aspect.

Claims

1.-15. (canceled)

16. A process for separating 1-methoxypropan-2-ol from an aqueous stream comprising 1-methoxypropan-2-ol and 2-methoxypropan-1-ol, wherein the process comprises: (a) Providing a stream S0 comprising 1-methoxypropan-2-ol, 2-methoxypropan-1-ol and water, and having a molar ratio of 1-methoxypropan-2-ol: 2-methoxypropan-1-ol in the range of from 1:5 to 5:1; (b) separating 1-methoxypropan-2-ol and 2-methoxypropan-1-ol from the stream S0 provided in (a) by distillation comprising subjecting the stream S0 provided in (a) to distillation conditions in a distillation unit comprising a distillation column B, obtaining a (top) stream S1 comprising 1-methoxypropan-2-ol, 2-methoxypropan-1-ol and water, which is enriched in 1-methoxypropan-2-ol and 2-methoxypropan-1-ol compared to the stream S0 and a bottoms stream S1a comprising water and being depleted of 1-methoxypropan-2-ol and 2-methoxypropan-1-ol compared to S0; wherein the distillation column B is operated at a pressure of >2 bar; (c.1) separation of the stream S1 obtained in (b) with at least one membrane unit M comprising at least one membrane module, obtaining a stream S2 which is depleted of water and further enriched in 1-methoxypropan-2-ol and 2-methoxypropan-1-ol compared to the stream S1, and a stream S2a comprising water; (c.2) subjecting the stream S2 obtained in (c.1) to distillation conditions in a distillation unit comprising a distillation column C, obtaining a stream S3, which is depleted of water and further enriched in 1-methoxypropan-2-ol and 2-methoxypropan-1-ol compared to the stream S2, and a stream S3a comprising water; (d) separating 1-methoxypropan-2-ol from the stream S3 obtained in (c.2) by distillation, comprising subjecting the stream S2 obtained in (c.2) to distillation conditions in a distillation unit comprising a distillation column D, obtaining a stream S5 comprising 95 weight-% 1-methoxypropan-2-ol and 0.5 weight-% of 2-methoxypropan-1-ol, based on the total weight of stream S5, and a stream S4 comprising 95 weight-% 2-methoxypropan-1-ol based on the total weight of stream S4; (e) optionally recirculating at least a part of the stream S3a to (c.1).

17. The process for separating 1-methoxypropan-2-ol from an aqueous stream comprising 1-methoxypropan-2-ol and 2-methoxypropan-1-ol according to claim 16, wherein the thermal energy of stream S1 is partly transferred to a heat transfer medium stream HTMS1 after (b) and before step (c), obtaining a heat transfer medium stream HTMS1a having an increased thermal energy content compared to HTMS1; wherein HTMS1a is used to provide thermal energy to: the membrane unit of (c.1); and/or the distillation unit of step (c.2), and/or the distillation unit of (d).

18. The process for separating 1-methoxypropan-2-ol from an aqueous stream comprising 1-methoxypropan-2-ol and 2-methoxypropan-1-ol according to claim 17, wherein the thermal energy provided by HTMS1a provides at least 90% of the energy demand of the membrane unit of (c.1), and/or of the distillation unit of (c.2), and/or of the distillation unit of (d).

19. The process for separating 1-methoxypropan-2-ol from an aqueous stream comprising 1-methoxypropan-2-ol and 2-methoxypropan-1-ol according to claim 17, wherein in the range of from 40 to 95% of the thermal energy of stream S1 is transferred to the heat transfer medium stream HTMS1 obtaining a heat transfer medium stream HTMS1a having an increased thermal energy content compared to HTMS1.

20. The process for separating 1-methoxypropan-2-ol from an aqueous stream comprising 1-methoxypropan-2-ol and 2-methoxypropan-1-ol according to claim 16, wherein stream S0 provided in a) comprises water in an amount in the range of from 50 to 90 weight-%, and a mixture of 1-methoxypropan-2-ol and 2-methoxypropan-1-ol in an amount in the range of from 8 to 50 weight-%, the remaining amount up to 100 weight-% being other components (impurities and solvent (MeOH)).

21. The process for separating 1-methoxypropan-2-ol from an aqueous stream comprising 1-methoxypropan-2-ol and 2-methoxypropan-1-ol according to claim 16, wherein stream S0 provided in a) comprises 1-methoxypropan-2-ol and 2-methoxypropan-1-ol in a molar ratio in the range of from 1:4 to 4:1.

22. The process for separating 1-methoxypropan-2-ol from an aqueous stream comprising 1-methoxypropan-2-ol and 2-methoxypropan-1-ol according to claim 16, wherein stream S0 provided in a) comprises propylene glycol dimethyl ether in an amount0.001 weight-%, based on the total weight of S0.

23. The process for separating 1-methoxypropan-2-ol from an aqueous stream comprising 1-methoxypropan-2-ol and 2-methoxypropan-1-ol according to claim 16, wherein the distillation column B comprised in the distillation unit according to b) is operated at a pressure in the range of from 2 to 30 bar.

24. The process for separating 1-methoxypropan-2-ol from an aqueous stream comprising 1-methoxypropan-2-ol and 2-methoxypropan-1-ol according to claim 16, wherein stream S1, which leaves distillation column B over the top, contains less than 0.05 weight-% of propylene glycol dimethyl ether, based on the total weight of S1.

25. The process for separating 1-methoxypropan-2-ol from an aqueous stream comprising 1-methoxypropan-2-ol and 2-methoxypropan-1-ol according to claim 16, wherein the membrane unit M according to (c.1) comprises one or more membrane modules, each membrane module comprising at least one membrane, and optionally one or more further component selected from the group consisting of heat exchanger, pump compressor and condenser.

26. The process for separating 1-methoxypropan-2-ol from an aqueous stream comprising 1-methoxypropan-2-ol and 2-methoxypropan-1-ol according to claim 16, wherein in step (e) at least 50 weight-% of S3a are recycled to the membrane unit M of (c.1).

27. The process for separating 1-methoxypropan-2-ol from an aqueous stream comprising 1-methoxypropan-2-ol and 2-methoxypropan-1-ol according to claim 16, wherein the stream S4 is removed as bottoms stream from distillation column D, wherein S4 comprises >95 weight-% 2-methoxypropan-1-ol and 0.5 weight-% 1-methoxypropan-2-ol, each based on the total weight of stream S4.

28. The process for separating 1-methoxypropan-2-ol from an aqueous stream comprising 1-methoxypropan-2-ol and 2-methoxypropan-1-ol according to claim 16, wherein the stream S5 is removed as top stream from distillation column D, which comprises 95 weight-% 1-methoxypropan-2-ol and 0.5 weight-% of 2-methoxypropan-1-ol, each based on the total weight of stream S5.

29. The process for separating 1-methoxypropan-2-ol from an aqueous stream comprising 1-methoxypropan-2-ol and 2-methoxypropan-1-ol according to claim 16, wherein the stream S5 comprises 0.01 weight-% of propylene glycol dimethyl ether based on the total weight of stream S5.

30. 1-Methoxypropan-2-ol or a mixture of 1-methoxypropan-2-ol and 2-methoxypropan-1-ol obtained or obtained from the process of claim 16.

Description

EXAMPLES

Simulations

[0135] All simulations were done with process simulation software Aspen Plus v.11. The components used in the process simulation and their characteristics respectively, were taken from the Dortmund Database.

Example 1: Separation of 1-methoxypropan-2-ol from an Aqueous Stream (S0) Containing 85 Weight-% of Water and 14.2 Weight-% of a Mixture of 2-methoxypropan-1-ol and 1-methoxypropan-2-olDistillation Column B Operated at 2 Bar

[0136] The feed stream S0 to column B was a variable stream and represented a stream from a propylene oxide production process, wherein a reaction mixture comprising propylene, water, methanol, and hydrogen peroxide had been contacted in an epoxidation zone with an epoxidation catalyst comprising a zeolitic material having a framework structure comprising Si, O, and Ti and being of framework type MFI (titanium silicalite-1 (TS-1)), and the reaction mixture had been subjected to epoxidation reaction conditions in the epoxidation zone.

[0137] The obtained mixture comprising propylene oxide, water, and methanol had been removed as an effluent stream from the epoxidation zone. The effluent stream comprising propylene oxide, water, and methanol had been subjected to further separation and purification steps, wherein propylene oxide and water as well as parts of the organic solvent had been removed, resulting in a stream S0 comprising 1-methoxypropan-2-ol, 2-methoxypropan-1-ol and water and having a molar ratio of 1-methoxypropan-2-ol:2-methoxypropan-1-ol in the range of from 1:5 to 5:1. The composition of stream S1 varied as a function of the operating conditions of the propylene oxide production process. An exemplary composition of stream S0, exemplary compositions of the further streams S1 to S5 are indicated in Table 1a in view of water, 1-methoxypropan-2-ol and 2-methoxypropan-1-ol and physical parameters of these streams, Table 1b shows the energy demand of the reboilers and condensers as well as the respective temperature ranges. In Table 2, compositions of streams S0, S1 and S1a are listed. The expression E-xx in Tables 1a and 2 represents 10.sup.xx, wherein xx is here a placeholder for the respective number indicated in the Tables. Stream S3a was completely recirculated back to the membranes. Therefore, the feed stream to the membrane unit M is the combination of stream S1 and stream S3a.

TABLE-US-00001 TABLE 1a Compositions and physical parameters of streams S0 to S5 as well as energy demand of components S2 (S2 after S2a (after heating up) condensa- Feed to S0 S1a S1 tion) S2 column C S3a S3 S5 S4 Temperature [ C.] 181 179.9 175 38.9 115 170 109 148 154 172.1 Pressure [bar] 10 10 10 0.07 10 10 2 2 3 3 Mass flow [kg/h] 11415 7371 4044 2481 1779 1779 215.4 1558 754.9 803.1 Concentrations in weight-% (unless indicated otherwise) Water 85.79 99.11 60.1 97.88 4 4 31.884 100 ppm 206 ppm 0 1-Methoxypropan-2-ol 6.95 9.42E03 19.43 1.12 50.55 50.55 65.56 48.45 99.95 500 ppm 2-Methoxypropan-1-ol 7.26 5.83E04 20.48 1.01 45.45 45.45 2.55 51.54 300 ppm 99.95

TABLE-US-00002 TABLE 1b Energy demand of condensers and reboilers as well as temperature ranges of these components. Condenser Reboiler Condenser Reboiler Condenser Reboiler column B column B column C column C column D column D W100 W200 Wflash W300 Thermal 9180 8900 232.47 197.14 1100 1121 1079.54 181.32 78.2 1728.73 energy demand [kW] Temperature 177-175 179.9-181 119-109 148-156 156-154 172-174 115-120 115-120 115- 115-38 range [ C.] 170

TABLE-US-00003 TABLE 2 compositions of streams S0, S1a and S1. Streams S0 S1a S1 Parameter Temperature [ C.] 181 179.927 175.099 Pressure [bar] 10 10 10 Mass flow [kg/h] 11415 7371 4044 Components, indicated in weight-% 2-Methoxypropan-1-ol 7.26 5.83E04 20.48 Water 85.17 99.11 59.98 Benzene 1-Methoxypropan-2-ol 6.95 9.42E03 19.46 1,1-Dimethoxyethane 1,1-Dimethoxypropane 1.00E03 1.34E03 1,2-Propanediol (MPG) 1.00E02 1.55E02 9.45E08 1-Butanol 1.00E03 2.27E03 2,4-Dimethyl-1,3-dioxolane 1.00E03 1.81E03 2,6-Dimethyl-4-heptanol 1.00E03 1.71E03 2-Butenal 1.00E03 2.22E03 2-Ethyl-4-methyl-1,3-dioxolane 1.00E03 1.55E03 5.20E06 2-Hexanone 1.00E01 1.56E01 2-Methylcyclohexanol 1.00E03 1.55E03 5.20E06 2-Methylpentanal 4.00E03 4.85E03 2-Propen-1-ol 1.00E03 2.51E03 4-Methyl-1,3-dioxolane 1.00E03 3.53E10 2.76E03 Acetaldehyde 1.00E+00 1.46E03 Acetone 1.00E03 2.06E03 Dimethoxymethane 1.00E03 1.99E03 Dipropyleneglycol (DPG) 2.00E02 3.10E02 1.04E04 Ethanol 1.00E03 2.28E03 Hydroxyacetone 1.00E03 1.51E03 7.55E05 2-Propanol 1.00E03 2.03E03 Methanol 1.99E02 4.84E02 Methylacetate 1.00E03 1.68E03 Methylformate 1.00E03 1.54E03 1.81E05 Propyleneoxide 1.00E03 1.59E03 Tripropylene glycol (TPG) 2.00E02 3.10E02 7.75E10 Dipropylene glycol mono 5.10E01 7.90E01 4.63E06 methyl ether (DPGME) Propylene glycol dimethyl ether 6.50E03 9.23E03 1.56E03 (1,2-Dimethoxypropane)

[0138] Column B was a pre-distillation column, used to enrich the mixture of 1-methoxy-2-propanol and 2-methoxy-1-propanol contained in stream S0. In column B, the mixture of 1-methoxy-2-propanol and 2-methoxy-1-propanol was separated from side components. in order to ensure that the final product 1-methoxy-2-propanol has a purity of >95 weight-%, preferably 98 weight-%, more preferred 99 weight-%, more preferred 99.7 weight-%. Column B had 20 theoretical stages and was operated at 10 bar. Feed stream S0 entered the column B at theoretical stage 17 (between stage 17 and 18). The temperature at the top was 177 C. and at the bottom 180 C. Column B was operated with a reflux ratio of 4.93 g/g and 8900 kW were needed in the reboiler and 9180 kW in the condenser. An azeotropic mixture of water, 1-methoxy-2-propanol and 2-methoxy-1-propanol was removed from column B over the top (stream S1: about 60 weight-% water, 40 weight-% mixture of 1-methoxy-2-propanol and 2-methoxy-1-propanol). Negligible amounts of side components were removed from column B as bottoms stream S1a, which was afterwards send to a subsequent water treatment or recycled into one or more stages of the process or recycled into one or more stages of an upstream HPPO process, from which stream S0 derives, preferably S1a is sent to water treatment or recycled into one or more stages of an upstream HPPO process, from which stream S0 derives.

Membrane Unit M

[0139] Stream S1, was, together with stream S3a, transferred to membrane unit M operated at 10 bar, which consisted of two membrane loops in series, each comprising at least one membrane module. In the first loop, the membrane surface area was 120 m.sup.2. In the second loop, the membrane surface area was 120 m.sup.2 as well. In both loops, the crossflow over the membranes was adjusted to such a value that the temperature drop over the membrane module was 5 C. Both loops operated at a permeate pressure of 0.07 bar using a combined vacuum system. In the membrane unit M, water was separated resulting in a stream S2 having a temperature of 115 C. Stream S2 was flashed before entering Column C in a further flash column, where the pressure was reduced from 10 bar to 2 bar. This decreased the temperature of stream S2.

[0140] The water flux (Flux(water)) through the membrane was calculated by the following equation 1:

Flux(water)=217.57(W.sub.H20,RET).sup.3241.41(W.sub.H20,RET).sup.2+155.39(W.sub.H20,RET)2.5977-equation 1-

[0141] wherein W.sub.H2O,RET is the water concentration (indicated in g water/g total solution) in the retentate.

[0142] The flux of both methoxypropanols (MOP) 1-methoxy-2-propanol and 2-methoxy-1-propanol (Flux(MOP)) through the membrane was calculated by the following equation 2:

Flux(MOP)=15.374(W.sub.H20,RET).sup.37.6276(W.sub.H20,RET).sup.2+2.3173(W.sub.H20,RET)+0.06-equation 2-

[0143] wherein W.sub.H2O,RET is the water concentration (indicated in g water/g total solution) in the retentate.

[0144] In principle, 1-methoxy-2-propanol and 2-methoxy-1-propanol each has its own permeability but the respective values differ from each other by less than 5%. Thus, it was assumed for the above-indicated equation 2 that the permeabilities of the two MOPs 1-methoxy-2-propanol and 2-methoxy-1-propanol are identical. Stream S2 was heated to a temperature of 170 C. and then transferred to Column C at theoretical stage 8, wherein column C was a distillation column with 16 theoretical stages operated at a pressure of 2 bar. Column C had a temperature at the top of 109 C. and at the bottom of 148 C. Column C was operated with a reflux ratio of 2.93 g/g and 197.14 kW were needed in the reboiler and 232.47 kW in the condenser. A bottom streams S3 was removed from Column C, wherein 85 weight-% of S2 consisted of 1-methoxy-2-propanol and 2-methoxy-1-propanol. A stream S3a consisting to more than 90 weight-% of water was removed from column C over the top and condensed in a condenser unit. Stream S3a in condensed form was recycled to membrane unit M. Stream S3 was transferred to column D, which was a distillation column with 48 theoretical stages operated at 3 bar. The temperature at the top of column D was 156 C. and at the bottom 172 C. Column D was operated with a reflux ratio of 12.2 g/g and 1121 kW were needed in the reboiler and 1100 kW in the condenser. From column D, a stream S5 was removed over the top comprising, 99.95 weight-% 1-methoxylpropan-2-ol based on the total weight of stream S5 and having an isolation yield of 95.1%. As bottoms streams, a stream S4 was removed, wherein S4 comprised 99.95 weight-% 2-methoxylpropan-1-ol based on the weight of S4 and having an isolation yield of 96.85. It could be seen that propylene glycol dimethyl was effectively separated: Already in S1, the content of propylene glycol dimethyl was only 1.5610.sup.3 weight-% based on the weight of S1. Stream S5 contained only 5.2510.sup.3 weight-% propylene glycol dimethyl ether based on the total weight of S5.

Heat Integration

[0145] A very important part of the separation process in including columns B to D and membrane unit M was the heat integration, because it reduces significantly the investment costs in terms of steam. For the heat integration there were several possibilities, two thereof were simulated: [0146] 1. as shown in FIG. 4, the thermal energy (heat) of the condenser of column B, i.e. of stream S1, was used to heat the reboiler of column C and the membrane unit M in that thermal energy of stream S1 was partly transferred to a heat transfer medium stream HTMS1 before entering the membrane unit M in a heat exchanger H, wherein a heat transfer medium stream HTMS1a was obtained which had an increased thermal energy content compared to HTMS1. The heat transfer medium stream HTMS1a was used to provide thermal energy to a heat exchanger unit, which supplied the reboiler of column C and to the reboiler of membrane unit M. The total heat demand was 9600 kW. [0147] 2. as shown in FIG. 5, a complete heat integration was made. The thermal energy (heat) of the condenser of column B, i.e. of stream S1, was used to heat the reboiler of columns C and D in that thermal energy of stream S1 was partly transferred to a heat transfer medium stream HTMS1 before entering membrane unit M in a heat exchanger H, wherein a heat transfer medium stream HTMS1a was obtained which had an increased thermal energy content compared to HTMS1. The heat transfer medium stream HTMS1a was used to provide thermal energy to a heat exchanger unit, which supplied the reboiler of column C, to the reboiler of membrane unit M and to heat exchanger unit, which supplied the reboiler of column D. The total energy demand was 8900 kW.

[0148] The heat transfer medium of HTMS1/HTMS1a and of HTMS2/HTMS2a was steam (H.sub.2O.sub.gaseous). This example demonstrates that 1-methoxypropano1-2 with a purity of 99.95% can be obtained with an isolation yield of 95.1%. Additionally, 2-methoxypropano1-1 with a purity of 99.95% can be obtained with an isolation yield of 96.85%.

Comparative Example 1: separation of 1-methoxypropan-2-ol from an Aqueous Stream (S0) Containing 85 Weight-% of Water and 14.2 Weight-% of a Mixture of 2-methoxypropan-1-ol and 1-methoxypropan-2-olDistillation Column B Operated at <2 Bar

[0149] Herein, the same set-up with the same columns B, C and D and membrane unit M as in Example 1 was used, the only difference to Example 1 was that in column B a pressure of 1 bar was used and in columns C and D a pressure of also 1 bar was used. As in Example 1, stream S3a was completely recirculated back to the membranes. Therefore, the feed stream to the membrane unit M is the combination of stream S1 and stream S3a.

[0150] Having 1 bar in column B influenced the pressure of the rest of the columns in the process. In Example 1, column B was designed for 10 bar. Here, operating column B at 1 bar made the separation more difficult and no heat integration possible due to the lower temperatures reached in column B. In column B, more water/MOPs azeotrope went over the top (stream S1) that needed to be separated in the membranes of membrane unit M or in column C. The amount of water in S2 was fixed to 4 weight-%, which implies that the membrane area had to be larger to remove more water. Table 3a shows the composition of streams S0 and S1 to S5 and physical parameters of these streams, Table 3b lists the energy demand in condensers and reboilers and operation temperature ranges of these components. In Table 4, the complete compositions of streams S0, S1a and S1 are indicated.

TABLE-US-00004 TABLE 3a composition of streams S0 and S1 to S5 and physical parameters of these streams S2a (after S2 (after heating condensa- up) Feed to S0 S1a S1 tion) S2 column C S3a S3 S5 S4 Temperature [ C.] 181 99.66 95.29 38.93 115 170 79.45 124.75 115.9 131.42 Pressure [bar] 1 1 1 0.07 1 1 1 1 1 1 Mass flow [kg/h] 11415 5394.80 6020.19 4473 1800 1800 252.40 1542 745.60 796.40 Concentrations in weight-% (unless indicated otherwise) Water 85.79 99.8 72.87 98.03 4 4 27.67 100 ppm 207 ppm 0 1-Methoxypropan- 6.95 5.13E 13.22 1.05 51.36 51.3604 69.58 48.36 99.95 500 ppm 2-ol 03 2-Methoxypropan- 7.26 4.87E 13.91 0.92 44.64 44.6396 2.75 51.63 300 ppm 99.95 1-ol 03

TABLE-US-00005 TABLE 3b Energy demand in condensers and reboilers and operation temperature ranges of these components. Condenser Reboiler Condenser Reboiler Condenser Reboiler column B column B column C column C column D column D W100 W200 Wflash W300 Thermal Energy 18005.9 16930 287.74 213.83 1411 1412 2587.4 272.1 79.18 3120.5 demand [kW] Temperature 98.7-95.29 99.66- 83-79.45 124.75- 119-115.9 131.42- 115- 115- 115- 115- range [ C.] 102.35 138 134 120 120 170 38 Membrane area 178.57 PV100 [m.sup.2] Membrane area 178.57 PV200 [m.sup.2]

TABLE-US-00006 TABLE 4 compositions of streams S0, S1a and S1. Streams S0 S1a S1 Parameter Temperature [ C.] 181 99.66 95.29 Pressure [bar] 1 1 1 Mass flow [kg/h] 11415 5394.81 6020.20 Components, indicated in weight-% 2-Methoxypropan-1-ol 7.26 1.00E02 13.87 Water 85.17 98.8 72.87 Benzene 1-Methoxypropan-2-ol 6.95 2.46E06 13.18 1,1-Dimethoxyethane 1,1-Dimethoxypropane 1.00E03 7.58E04 1,2-Propanediol (MPG) 1.00E02 2.10E02 2.09E09 1-Butanol 1.00E03 1.81E03 2,4-Dimethyl-1,3-dioxolane 1.00E03 1.36E03 2,6-Dimethyl-4-heptanol 1.00E03 1.50E03 2-Butenal 1.00E03 1.72E03 2-Ethyl-4-methyl-1,3-dioxolane 1.00E03 2.09E03 1.26E05 2-Hexanone 1.00E01 1.39E03 2-Methylcyclohexanol 1.00E03 2.09E03 1.26E05 2-Methylpentanal 4.00E03 4.10E03 2-Propen-1-ol 1.00E03 1.83E03 4-Methyl-1,3-dioxolane 1.00E03 1.87E03 Acetaldehyde 1.00E+00 1.21E03 Acetone 1.00E03 1.61E03 Dimethoxymethane 1.00E03 1.22E03 Dipropyleneglycol (DPG) 2.00E02 4.17E02 2.52E04 Ethanol 1.00E03 1.82E03 Hydroxyacetone 1.00E03 1.75E03 3.16E04 2-Propanol 1.00E03 1.76E03 Methanol 1.99E02 3.66E02 Methylacetate 1.00E03 1.36E02 Methylformate 1.00E03 1.35E03 Propyleneoxide 1.00E03 1.24E03 Tripropylene glycol (TPG) 2.00E02 4.20E02 Tripropylene glycol mono 5.10E01 1.07E+00 5.13E07 methyl ether (DPGME) Dipropylene glycol mono methyl ether (DPGME) Propylene glycol dimethyl ether 6.50E03 3.56E03 9.18E03 (1,2-Dimethoxypropane)

[0151] The total thermal energy needed in the reboiler of column B was 16930 kW, higher than in example 1 when column B was operated at 10 bar. This is because the separation was more difficult when column B was operated at a pressure below 2 bar. No heat integration was possible, i.e. the total energy demand was 21494.51 kW.

[0152] Stream S5 contained 99.95 weight-% 1-methoxypropan-2-ol based on the total weight of S5 and the isolation yield was 93.93%. Stream S4, contained 99.95 weight-% 2-methoxypropan-1-oland the isolation yield was 96.05% To achieve 4 weight-% water in S2, each membrane had to have an area of 178.57 m.sup.2, the total membrane area was thus 357.14 m.sup.2.

[0153] Also the impurity content in the final stream S5 was higher when column B was operated at 1 bar: Already in S1, the content of propylene glycol dimethyl was 9.1810.sup.3 weight-% based on the weight of S1 compared to Example 1, where the content of propylene glycol dimethyl was only 1.5610.sup.3 weight-% based on the weight of S1. The propylene glycol dimethyl ether content in S5, based on the total weight of S5, was 0.0482 weight-% compared to only 5.5210.sup.3 weight-% as in Example 1. That is, operating column B, and, consequently, also the further column C at 1 bar did not allow to have less than 0.006 weight-% of propylene glycol dimethyl ether in S5 based on the total weight of S5.

[0154] FIG. 1 shows the process for separating 1-methoxy-2-propanol and the involved columns B to D and membrane unit M schematically, without any heat integration. Stream S3a comprising water 1-methoxypropan-2-ol and 2-methoxypropan-1-ol is at least partially recycled to the membrane unit M, wherein the dotted line for stream S3a represents a non-recycled part, which might be absent in case of complete recycle of stream S3a.

[0155] FIG. 2 shows the process for separating 1-methoxy-2-propanol and the involved columns B to D and distillation unit M schematically as in FIG. 1, together with a first option of heat integration, wherein the thermal energy (heat) of the condenser of column B, i.e. of stream S1, is used to heat the reboiler of column D in that thermal energy of stream S1 is partly transferred to a heat transfer medium stream HTMS1 in a heat exchanger H. The resulting heat transfer medium stream HTMS1a, which has an increased thermal energy content compared to HTMS1, is used to provide thermal energy to a heat exchanger unit, which supplies the reboiler of column D.

[0156] FIG. 3 shows the process for separating 1-methoxy-2-propanol and the involved columns B to D and membrane unit M schematically as in FIG. 1, together with a second option of heat integration, wherein the thermal energy (heat) of the condenser of column B, i.e. of stream S1, is used to heat the reboiler of column C in that thermal energy of stream S1 is partly transferred to a heat transfer medium stream HTMS1 in a heat exchanger H. The resulting heat transfer medium stream HTMS1a, which has an increased thermal energy content compared to HTMS1, is used to provide thermal energy to a heat exchanger unit, which supplies the reboiler of column C.

[0157] FIG. 4 shows the process for separating 1-methoxy-2-propanol and the involved columns B to D and membrane unit M schematically as in FIG. 1, together with a third option of heat integration, wherein the thermal energy (heat) of the condenser of column B, i.e. of stream S1, is used to heat the reboiler of membrane unit M and the reboiler of column C in that thermal energy of stream S1 is partly transferred to a heat transfer medium stream HTMS1 in a heat exchanger H. The resulting heat transfer medium stream HTMS1a, which has an increased thermal energy content compared to HTMS1, is used to provide thermal energy to a heat exchanger unit, which supplies the heat exchanger of membrane unit M and the reboiler of column C.

[0158] FIG. 5 shows the process for separating 1-methoxy-2-propanol and the involved columns B to D and membrane unit M schematically as in FIG. 1, together with a fourth, complete, heat integration. The thermal energy (heat) of the condenser of column B, i.e. of stream S1, is used to heat the reboiler of columns C and D and of the membrane unit M in that thermal energy of stream S1 is partly transferred to a heat transfer medium stream HTMS1 in a heat exchanger H, wherein a heat transfer medium stream HTMS1a is obtained which has an increased thermal energy content compared to HTMS1. The heat transfer medium stream HTMS1a is used to provide thermal energy to a heat exchanger unit, which supplies the reboiler of column C, to heat exchanger unit, which supplies the reboiler of column D, and to heat exchanger unit, which supplies the heat exchanger of membrane unit M.

CITED LITERATURE

[0159] U.S. Pat. No. 5,723,024 A [0160] EP 1 375 462 A1 [0161] EP 0 425 893 A [0162] DE 10 233 388 A1 [0163] US 2004/0000473 A1 [0164] CN 103342631 A [0165] CN 103992214 A