System and method for separating methyl epoxypropane-acetone-methanol system

Abstract

This invention discloses a system and method for separating a methyl propylene oxide-acetone-methanol system. The separation method includes the following steps: using a mixture containing N,N-dimethylacetamide and 1,3-butanediol as the extractant, the mixture rich in methyl propylene oxide, acetone and methanol is sequentially fed into a light-light-removal column, a first extractive distillation column, a first desorption column, a second extractive distillation column, an acetone product column, and a second desorption column. Finally, the yields of the three products, methyl propylene oxide, acetone and methanol, can all reach more than 97%, the purity of methyl propylene oxide is ≥99% (mass percentage), the purity of acetone is ≥99.5% (mass percentage), and the purity of methanol is ≥99.6% (mass percentage).

Description

Technical Field

[0001] This invention belongs to the technical field of complex chemical separation, and relates to a system and method for separating the methyl propylene oxide-acetone-methanol system, particularly to a system and method for separating the methyl propylene oxide-acetone-methanol azeotropic system by composite solvent extractive distillation. Background Technology

[0002] The mixture mainly composed of methyl propylene oxide, acetone, and methanol originates from processes such as the co-oxidation of isobutane and propylene to produce propylene oxide, the acetone cyanohydrin process to synthesize methyl methacrylate, or the synthesis of pharmaceutical intermediates. Methyl propylene oxide, acetone, and methanol are all important basic chemical raw materials. Methyl propylene oxide can be used as a raw material for synthesizing pharmaceutical intermediates, surfactants, cosmetics, and polyether polyols; acetone and methanol are basic raw materials in chemical production or used as solvents. Due to the difficulty of separation, the current main method for treating mixtures mainly composed of methyl propylene oxide, acetone, and methanol is incineration. However, effectively recovering methyl propylene oxide, acetone, and methanol can not only reduce production costs and improve the profitability of the plant, but also reduce the environmental impact of wastewater generation.

[0003] Methyl propylene oxide, acetone, and methanol form two azeotropic pairs under normal pressure: methyl propylene oxide-acetone and acetone-methanol. Industrially, azeotropic distillation and extractive distillation are commonly used to separate azeotropic or near-boiling point mixtures. These two special distillation methods operate on the same principle: adding a third component to the azeotropic or near-boiling point mixture increases the difference in relative volatility between the components, thus enabling separation. Compared to azeotropic distillation, extractive distillation offers easier selection of extractants, lower energy consumption, and greater operational flexibility and control. Extractive distillation achieves separation by adding an extractant to the system being separated, thereby altering the activity coefficients of the components and increasing their relative volatility. Therefore, developing efficient, green, and economical extractants is a research hotspot in extractive distillation.

[0004] Numerous experimental studies have shown that extractive distillation has high separation efficiency when separating azeotropic systems. However, when multiple azeotropic pairs exist in the mixture, it significantly increases the difficulty of selecting extractants and designing extraction processes. Summary of the Invention

[0005] To improve the above-mentioned technical problems, the present invention provides a method for separating a methyl propylene oxide-acetone-methanol system, comprising the following steps: (1) The material stream to be separated enters the light component removal tower, the light component removed is obtained at the top of the tower, and the light component removed stream 1-1 is obtained at the bottom of the tower; (2) Stream 1-1 enters the first extractive distillation column and is extracted and distilled under the action of the composite solvent. Stream 2-1, which is rich in methyl propylene oxide, is obtained at the top of the column, and stream 2-2, which is rich in acetone, methanol, water, heavy components and composite solvent, is obtained at the bottom of the column. (3) Stream 2-2 enters the first desorption tower. Stream 3-1 containing acetone and methanol is obtained at the top of the tower, stream 3-2 containing composite solvent and heavy components is obtained at the bottom of the tower, and stream 3-3 containing desorbed composite solvent is obtained in the lower part of the tower. (4) Stream 3-1 enters the second extractive distillation column from the middle and lower part, and the composite solvent enters the second extractive distillation column from the middle and upper part. The acetone stream 4-1 to be processed is obtained at the top of the column, and the stream 4-2 containing methanol and composite solvent is obtained at the bottom of the column. (5) After heat exchange as the reboiler heat source of the acetone product column, the stream 4-1 enters the acetone product column from the middle. The stream 5-1 containing acetone and methanol azeotrope is obtained at the top of the column and returned to the second extractive distillation column. The acetone product stream 5-2 is obtained at the bottom of the column. (6) Stream 4-2 enters the second desorption tower, and methanol product stream 6-1 is obtained at the top of the tower. Desorbed composite solvent stream 6-2 is obtained at the bottom of the tower. Stream 6-2 is returned to the second extractive distillation tower.

[0006] According to an embodiment of the present invention, the method may further include step (7): feeding the stream 3-2 from step (3) into a propylene glycol column, obtaining a stream 7-1 containing water at the top of the column, obtaining a stream 7-2 containing heavy components at the bottom of the column, and obtaining 2-methyl-1,2-propanediol in the lower part of the column.

[0007] According to an embodiment of the present invention, in step (2), the composite solvent comprises N,N-dimethylacetamide and 1,3-butanediol, or is composed of N,N-dimethylacetamide and 1,3-butanediol.

[0008] Preferably, the content of N,N-dimethylacetamide in the composite solvent is 50wt% to 80wt%, for example, 50wt%, 60wt%, 70wt% or 80wt%.

[0009] Preferably, the content of 1,3-butanediol in the composite solvent can be 20wt% to 50wt%, for example, 20wt%, 30wt%, 40wt% or 50wt%.

[0010] The composite solvent may optionally contain, or not contain, other components besides N,N-dimethylacetamide and 1,3-butanediol. It should be understood that these other components may be inert to both N,N-dimethylacetamide and 1,3-butanediol (i.e., non-reactive with both), or components already present in the material to be separated, such as methyl propylene oxide, acetone, methanol, and one, two, three, or more of other components of the material to be separated.

[0011] More preferably, using the above-mentioned composite solvent as the extractant, the yields of methyl propylene oxide, acetone, and methanol can all reach ≥97 wt%. More preferably, the purity of methyl propylene oxide is ≥99 wt%, the purity of acetone is ≥99.5 wt%, and the purity of methanol is ≥99.6 wt%.

[0012] According to an embodiment of the present invention, in step (1), the material to be separated is a mixed waste liquid from processes such as isobutane and propylene co-oxidation to produce propylene oxide, acetone cyanohydrin synthesis to synthesize methyl methacrylate, or pharmaceutical intermediate synthesis. The main components of this mixed waste liquid are methyl propylene oxide, acetone, and methanol.

[0013] According to the embodiment of the present invention, in step (1), the operating conditions of the light-light removal tower can be: 15 to 30 theoretical plates, -10 to 59°C at the top of the tower, 50 to 120°C at the bottom of the tower, reflux ratio of 1.2 to 3.5, and operating pressure of 200 to 500 kPa.

[0014] In some implementations, the light-removal tower is a plate tower, and the tray type includes at least one of floating valve trays and sieve trays.

[0015] According to an embodiment of the present invention, in step (2), the operating conditions of the first extractive distillation column can be: 40 to 85 theoretical plates, 20 to 50°C for the composite solvent feed, 70 to 130°C for the bottom of the column, 40 to 60°C for the top of the column, 1.5 to 3.8 for the reflux ratio, 1.1 to 4.0:1 for the solvent-to-solid ratio, and 105 to 300 kPa for the operating pressure.

[0016] In some embodiments, the first extractive distillation column is a packed column. Preferably, the packing material used in the first extractive distillation column has a specific surface area ≥1000 m². 2 / m 3 At least one of SiC foam filler and Al2O3 foam filler.

[0017] According to the embodiment of the present invention, in step (3), the operating conditions of the first desorption tower can be: 20 to 40 theoretical plates, 45 to 65°C at the top of the tower, 90 to 190°C at the bottom of the tower, 1.0 to 3.0 reflux ratio, and 80 to 150 kPa operating pressure.

[0018] In some implementations, the first desorption tower is a plate tower, and the tray type includes at least one of floating valve trays and sieve trays.

[0019] According to the embodiment of the present invention, in step (4), the operating conditions of the second extractive distillation column can be: 40 to 100 theoretical plates, 20 to 45°C composite solvent feed temperature, 80 to 180°C bottom temperature, 40 to 65°C top temperature, reflux ratio of 1.0 to 3.0, reagent-to-material ratio of 1.0 to 4.0:1, and operating pressure of 105 to 200 kPa.

[0020] In some embodiments, the second extractive distillation column is a packed column. Preferably, the packing material used in the second extractive distillation column has a specific surface area ≥1000 m². 2 / m 3 At least one of SiC foam filler and Al2O3 foam filler.

[0021] According to an embodiment of the present invention, in step (5), the operating conditions of the acetone product tower can be: 35 to 50 theoretical plates, 45 to 55°C at the top of the tower, 50 to 70°C at the bottom of the tower, 1.5 to 5.0 reflux ratio, and 70 to 140 kPa operating pressure.

[0022] In some embodiments, the acetone product tower is a packed tower. Preferably, the packing material used in the acetone product tower has a specific surface area ≥1000 m². 2 / m 3 At least one of SiC foam filler and Al2O3 foam filler.

[0023] According to an embodiment of the present invention, in step (6), the operating conditions of the second desorption tower can be: 30 to 48 theoretical plates, 58 to 75°C at the top of the tower, 100 to 190°C at the bottom of the tower, 1.5 to 3.0 reflux ratio, and 80 to 160 kPa operating pressure.

[0024] In some implementations, the second desorption tower is a plate tower, and the tray type includes at least one of floating valve trays and sieve trays.

[0025] According to an embodiment of the present invention, in step (7), the operating conditions of the propylene glycol column can be: 40 to 60 theoretical plates, 60 to 80°C at the top of the column, 150 to 190°C at the bottom of the column, 2.0 to 5.0 reflux ratio, and 50 to 80 kPa operating pressure.

[0026] In some embodiments, the propylene glycol column is a packed column. Preferably, the propylene glycol column uses packing with a specific surface area ≥1000 m². 2 / m 3 At least one of SiC foam filler and Al2O3 foam filler.

[0027] According to an embodiment of the present invention, the method may include the following steps: (1) The material stream to be separated enters the light component removal tower from the middle, and the light component stream is obtained at the top of the tower and the light component stream 1-1 is obtained at the bottom of the tower; (2) Stream 1-1 enters the first extractive distillation column from the middle and lower part, and the composite solvent enters the first extractive distillation column from the middle and upper part. Stream 2-1 rich in methyl propylene oxide is obtained at the top of the column, and stream 2-2 rich in acetone, methanol, water, heavy components and composite solvent is obtained at the bottom of the column. (3) Stream 2-2 enters the first desorption tower from the middle. Stream 3-1 containing acetone and methanol is obtained at the top of the tower. Stream 3-2 containing composite solvent and heavy components (partly from the raw material and partly from the hydrolysis of methyl propylene oxide) is obtained at the bottom of the tower. Stream 3-3 containing the desorbed composite solvent is obtained in the lower part of the tower. Stream 3-3 is mixed with the composite solvent after temperature adjustment and enters the first extractive distillation tower. (4) Stream 3-1 enters the second extractive distillation column from the middle and lower part, and the composite solvent enters the second extractive distillation column from the middle and upper part. The acetone stream 4-1 to be processed is obtained at the top of the column, and the stream 4-2 containing methanol and composite solvent is obtained at the bottom of the column. (5) After heat exchange as the reboiler heat source of the acetone product tower, the stream 4-1 enters the acetone product tower from the middle. The stream 5-1 containing acetone and methanol azeotrope is obtained at the top of the tower and returned to be mixed with stream 3-1, and then enters the lower part of the second extractive distillation tower. The bottom of the acetone product tower is acetone product stream 5-2. (6) Stream 4-2 enters the second desorption tower from the middle. Methanol product stream 6-1 is obtained at the top of the tower, and desorbed composite solvent stream 6-2 is obtained at the bottom of the tower. After adjusting the temperature, it is mixed with the composite solvent and enters the second extractive distillation tower. (7) Stream 3-2 enters the propylene glycol tower from the middle section. Stream 7-1 containing water is obtained at the top of the tower, and stream 7-2 containing heavy components is obtained at the bottom of the tower. 2-methyl-1,2-propanediol byproduct is obtained in the lower part of the tower.

[0028] In this invention, the term "upper middle part" refers to any tray from the top 2 / 3 of the total height to the top of the tower, based on the total height of the tower body; "middle part" refers to any tray in the range of 1 / 3 to 2 / 3 of the total height; and "lower middle part" refers to any tray from the bottom of the tower to 1 / 3 of the total height.

[0029] The present invention also provides a system for separating a methyl propylene oxide-acetone-methanol system, comprising a light-light-removal column, a first extractive distillation column, a first desorption column, a second extractive distillation column, an acetone product column, and a second desorption column; The bottom outlet of the light-light-removal column is connected to the inlet of the first extractive distillation column; The bottom outlet of the first extractive distillation column is connected to the inlet of the first desorption column; The top outlet of the first desorption column is connected to the inlet of the second extractive distillation column, and the composite solvent outlet of the first desorption column is connected to the composite solvent inlet of the first extractive distillation column. The top outlet of the second extractive distillation column is connected to the inlet of the acetone product column, and the bottom outlet of the second extractive distillation column is connected to the inlet of the second desorption column. The bottom outlet of the second desorption tower is connected to the composite solvent inlet of the second extractive distillation tower.

[0030] According to an embodiment of the present invention, the system further includes a propylene glycol tower, wherein the outlet of the first desorption tower is connected to the inlet of the propylene glycol tower. Preferably, the propylene glycol tower is a packed tower. Preferably, the packing material used in the propylene glycol tower has a specific surface area ≥1000 m². 2 / m 3 At least one of SiC foam filler and Al2O3 foam filler.

[0031] According to an embodiment of the present invention, the system further includes a first temperature regulator, wherein the composite solvent outlet of the first desorption tower is sequentially connected to the first temperature regulator and the composite solvent inlet of the first extractive distillation tower.

[0032] According to an embodiment of the present invention, the system further includes a second temperature regulator, and the bottom outlet of the second desorption column is sequentially connected to the second temperature regulator and the composite solvent inlet of the second extractive distillation column.

[0033] According to an embodiment of the present invention, the system further includes a reboiler, and the top outlet of the second extractive distillation column is connected to the reboiler and the inlet of the acetone product column.

[0034] According to an embodiment of the present invention, the light-removal tower is a plate tower, and the tray type includes at least one of floating valve trays and sieve trays.

[0035] According to an embodiment of the present invention, the first extractive distillation column is a packed column. Preferably, the packing material used in the first extractive distillation column has a specific surface area ≥1000 m². 2 / m 3 At least one of SiC foam filler and Al2O3 foam filler.

[0036] According to an embodiment of the present invention, the first desorption tower is a plate tower, and the tray type includes at least one of floating valve trays and sieve trays.

[0037] According to an embodiment of the present invention, the second extractive distillation column is a packed column. Preferably, the packing material used in the second extractive distillation column has a specific surface area ≥1000 m². 2 / m 3 At least one of SiC foam filler and Al2O3 foam filler.

[0038] According to an embodiment of the present invention, the acetone product tower is a packed tower. Preferably, the packing material used in the acetone product tower has a specific surface area ≥1000 m². 2 / m 3 At least one of SiC foam filler and Al2O3 foam filler.

[0039] According to an embodiment of the present invention, the second desorption tower is a plate tower, and the tray type includes at least one of floating valve trays and sieve trays.

[0040] Beneficial effects of the present invention: (1) The present invention uses a composite solvent containing N,N-dimethylacetamide and 1,3-butanediol as the extractant for separating the azeotropic system of methyl propylene oxide, acetone and methanol. The composite solvent of the present invention is simple and easy to obtain, which greatly reduces the cost of solvent. Moreover, the composite solvent of the present invention has good selectivity for the components to be separated, which effectively increases the relative volatility of the components inside the system of multiple azeotropes. Combined with the design of extractive distillation process, it can not only obtain high-purity products such as methyl propylene oxide, acetone and methanol, but also reduce the amount of solvent circulation, which can significantly reduce the energy consumption and fixed investment of the equipment.

[0041] (2) For complex azeotropic systems mainly composed of methyl propylene oxide, acetone and methanol, the composite solvent used in this invention can effectively break the azeotropic pair, resulting in good extraction effect and selectivity for each component, reducing the agent-to-material ratio, and significantly reducing operating costs and fixed investment. At the same time, this invention effectively reduces operating energy consumption by recovering heat from the process flow, and realizes full-process recycling of the solvent. The yields of methyl propylene oxide, acetone and methanol can all reach more than 97%, and the purity of the final product is ≥99% (mass percentage) for methyl propylene oxide, ≥99.5% (mass percentage) for acetone and ≥99.6% (mass percentage) for methanol.

[0042] (3) The N,N-dimethylacetamide and 1,3-butanediol composite solvent of the present invention has low requirements for the content of minor components in the system to be separated, and therefore can be applied to the separation of the above mixtures with different contents. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the process flow of the method of the present invention; in the figure: 1-Light weight removal column; 2-First extractive distillation column; 3-First desorption column; 4-Second extractive distillation column; 5-Acetone product column; 6-Second desorption column; 7-Propylene glycol column; 8-First temperature controller; 9-Second temperature controller I; 10-Reboiler. Detailed Implementation

[0044] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0045] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0046] Example 1 according to Figure 1 The process flow uses a mixture of N,N-dimethylacetamide and 1,3-butanediol as the composite solvent, with a mass percentage ratio of 50wt%:50wt%; the mass ratio (solvent-to-material ratio) of the composite solvent to the material to be separated is 3.0:1.

[0047] A method for separating an azeotropic system of methyl propylene oxide, acetone, and methanol by extraction and distillation using a composite solvent includes the following steps: (1) The composition of the materials to be separated is shown in Table 1 below. First, the material stream S01 to be separated is fed into the light component removal tower 1 (30 plates in total, from top to bottom, theoretical number of plates: 30, top temperature: 15.1℃, bottom temperature: 99.5℃, reflux ratio: 2.0, operating pressure: 400kPa; the tower is a plate tower, and the trays are strip-shaped floating valve trays) from the top of the tower to obtain the light component removed stream S02, and the light component removed stream S03 is obtained from the bottom of the tower. (2) Stream S03 enters the first extractive distillation column 2 (counting from top to bottom) from the 50th plate (counting from top to bottom, a total of 80 plates; operating conditions: theoretical number of plates is 80, feed temperature of composite solvent stream S19 and stream S07 is 20℃, bottom temperature is 100.8℃, top temperature is 54.4℃, reflux ratio is 2.2, reagent-to-material ratio is 3.0:1, operating pressure is 105kPa; this column is a packed column, and the packing material has a specific surface area of ​​≥1000m². 2 / m 3 The SIC foam packing material), the composite solvent stream S19 enters the first extractive distillation column 2 from the 5th plate (counting from top to bottom). The top of the column yields the stream S04 rich in methyl propylene oxide, and the bottom of the column yields the stream S05 rich in acetone, methanol, water, heavy components and composite solvent. (3) Stream S05 enters the first desorption tower 3 (40 plates in total, from top to bottom) from the 20th plate (counting from top to bottom); operating conditions: theoretical number of plates is 40, tower top temperature is 54.9℃, tower bottom temperature is 184.2℃, reflux ratio is 2.0, operating pressure is 100kPa; this tower is a plate tower, and the tower tray is a floating valve tray.) Stream S06 containing acetone and methanol is obtained at the top of the tower, and stream S08 containing composite solvent and heavy components (part of which is from the raw material itself, and part of which is due to the hydrolysis of methyl propylene oxide) is obtained at the bottom of the tower. Stream S07 containing desorbed composite solvent is obtained in the lower part of the tower (36th plate from top to bottom). The temperature is adjusted by the first temperature regulator 8, and the stream S07 is mixed with composite solvent stream S19 and enters the first extractive distillation tower 2. (4) Stream S06 enters the second extractive distillation column 4 (counting from top to bottom, a total of 100 plates, counting from top to bottom) from the 70th plate; operating conditions: the feed temperature of the mixed composite solvent S20 and S15 is 20℃, the bottom temperature is 167.1℃, the top temperature is 55.2℃, the reflux ratio is 2.0, the reagent-to-solvent ratio is 3.0:1, and the operating pressure is 105kPa; this column is a packed column, and the packing material has a specific surface area ≥1000m². 2 / m 3 The SiC foam packing material is used. The composite solvent stream S20 enters the second extractive distillation column 4 from the 5th plate (counting from top to bottom). The top of the column yields the acetone stream S09 to be processed, and the bottom of the column yields the stream S10 containing methanol and the composite solvent. (5) After heat exchange with the reboiler 10 of the acetone product tower 5, the material S09 enters the acetone product tower 5 (counting from top to bottom, a total of 50 plates; operating conditions: tower top temperature is 51.1℃, tower bottom temperature is 58.8℃, reflux ratio is 3.0, operating pressure is 85kPa; this tower is a packed tower, and the packing has a specific surface area of ​​≥1000m². 2 / m 3The SiC foam packing is used. ), and the top of the column yields a stream S12 containing an azeotrope of acetone and methanol, which is returned to be mixed with stream S06 and then enters the lower middle part of the second extractive distillation column 4 through the 70th plate (from top to bottom); the bottom of the acetone product column 5 yields an acetone product stream S13; (6) Stream S10 enters the second desorption tower 6 (48 plates in total, from top to bottom) from the 20th plate (counting from top to bottom; operating conditions: top temperature of 66.5℃, bottom temperature of 183.8℃, reflux ratio of 2.0, operating pressure of 105kPa; this tower is a plate tower, and the tray type is a circular floating valve tray.) Methanol product stream S14 is obtained at the top of the tower, and desorbed composite solvent stream S15 is obtained at the bottom of the tower. The temperature is adjusted by the second temperature regulator 9, and it is mixed with composite solvent stream S20 and enters the second extractive distillation tower 4. (7) Stream S08 enters propylene glycol tower 7 (60 plates in total, from top to bottom) from the 22nd plate (counting from top to bottom); operating conditions: theoretical plate number is 60, tower top temperature is 93.4℃, tower bottom temperature is 127.6℃, reflux ratio is 3.0, and operating pressure is 80kPa. This tower is a packed tower, and the packing material has a specific surface area ≥1000m². 2 / m 3 The SiC foam packing material yields a water-containing stream S16 at the top of the column, a heavy component-containing stream S17 at the bottom of the column, and a 2-methyl-1,2-propanediol byproduct stream S18 from the side stream of the 40th plate (from top to bottom).

[0048] The yields and purity of methyl propylene oxide, acetone, and methanol after processing by the method of this embodiment are shown in Table 1 below.

[0049] Table 1 Composition of materials to be separated and product quality

[0050] The results showed that after treatment by the method in this embodiment, the yield of methyl propylene oxide was 97.1% and the purity was 99.2% (mass percentage, the same below); the yield of acetone was 97.4% and the purity was 99.52%; and the yield of methanol was 97.3% and the purity was 99.63%.

[0051] Example 2 according to Figure 1 The process flow uses a composite solvent that is a mixture of N,N-dimethylacetamide and 1,3-butanediol, with a mass percentage ratio of 70wt%:30wt%; the mass ratio of composite solvent to material to be separated is 3:1.

[0052] A method for separating an azeotropic system of methyl propylene oxide, acetone, and methanol by extraction and distillation using a composite solvent includes the following steps: (1) The composition of the materials to be separated is shown in Table 2 below. First, the material stream S01 to be separated is fed into the light component removal tower 1 (20 plates in total, from top to bottom, theoretical number of plates: 20, top temperature: 6.4℃, bottom temperature: 89.1℃, reflux ratio: 3.0, operating pressure: 300kPa; the tower is a plate tower with strip-shaped floating valve trays) from the top of the tower. The light component stream S02 is obtained from the top of the tower, and the light component stream S03 is obtained from the bottom of the tower. (2) Stream S03 enters the first extractive distillation column 2 (counting from top to bottom) from the 60th plate (counting from top to bottom, a total of 85 plates; operating conditions: theoretical number of plates is 85, feed temperature of composite solvent stream S19 and stream S07 is 30℃, bottom temperature is 102.5℃, top temperature is 55.8℃, reflux ratio is 3.0, reagent-to-material ratio is 4.0:1, operating pressure is 110kPa; this column is a packed column, and the packing material has a specific surface area of ​​≥1000m². 2 / m 3 Al2O3 foam packing, etc.), the composite solvent stream S19 enters the first extractive distillation column 2 from the third plate (counting from top to bottom), the top of the column gives stream S04 rich in methyl propylene oxide, and the bottom of the column gives stream S05 rich in acetone, methanol, water, heavy components and composite solvent; (3) Stream S05 enters the first desorption tower 3 (30 plates in total, from top to bottom) from the 15th plate (counting from top to bottom); operating conditions: theoretical number of plates is 30, tower top temperature is 57.7℃, tower bottom temperature is 187.6℃, reflux ratio is 3.0, operating pressure is 110kPa; this tower is a plate tower, and the tower tray is a strip floating valve.) Stream S06 containing acetone and methanol is obtained at the top of the tower, and stream S08 containing composite solvent and heavy components (part of which is from the raw material itself, and part of which is due to the hydrolysis of methyl propylene oxide) is obtained at the bottom of the tower. Stream S07 containing the desorbed composite solvent is obtained in the lower part of the tower (25th plate from top to bottom). The temperature is adjusted by the first temperature regulator 8, and the stream S07 is mixed with the composite solvent stream S19 and enters the first extractive distillation tower 2. (4) Stream S06 enters the second extractive distillation column 4 (counting from top to bottom, a total of 80 plates) from the 69th plate (counting from top to bottom); operating conditions: theoretical plate number is 80, feed temperature of S20 and S15 mixed composite solvent is 25℃, bottom temperature is 171.9℃, top temperature is 59.2℃, reflux ratio is 2.4, reagent-to-solvent ratio is 3.6:1, operating pressure is 120kPa; this column is a packed column, and the packing has a specific surface area ≥1000m². 2 / m 3 Al2O3 foam packing. ), the composite solvent stream S20 enters 4 from the 4th plate (counting from top to bottom), the acetone stream to be processed is obtained at the top of the column S09, and the stream containing methanol and composite solvent S10 is obtained at the bottom of the column; (5) After heat exchange as the reboiler heat source for acetone product tower 5, logistics S09 enters acetone product tower 5 (counting from top to bottom) from the 15th plate (counting from top to bottom, a total of 40 plates; operating conditions: theoretical number of plates is 40, tower top temperature is 47.6℃, tower bottom temperature is 55.7℃, reflux ratio is 3.5, operating pressure is 75kPa; this tower is a packed tower, and the packing has a specific surface area ≥1000m²) 2 / m 3 The Al2O3 foam packing material) is used to obtain the acetone and methanol azeotrope at the top of the column. After being mixed with the acetone product S06, the product enters the lower middle part of the second extractive distillation column 4 through the 69th plate (counting from top to bottom). The acetone product column 5 yields the acetone product stream S13 at the bottom. (6) Stream S10 enters the second desorption tower 6 (30 plates in total, from top to bottom) from the 15th plate (theoretically 30 plates, top temperature 61.3℃, bottom temperature 171.5℃, reflux ratio 1.8, operating pressure 90kPa; this tower is a plate tower with strip-shaped floating valve trays). Methanol product stream S14 is obtained at the top of the tower, and desorbed composite solvent stream S15 is obtained at the bottom of the tower. The temperature is adjusted by the second temperature regulator 9, and it is mixed with composite solvent stream S20 and enters the second extractive distillation tower 4. (7) Stream S08 enters propylene glycol tower 7 (from top to bottom, 40 plates in total; operating conditions: theoretical plate count is 40, tower top temperature is 89.9℃, tower bottom temperature is 123.4℃, reflux ratio is 3.5, operating pressure is 70kPa. This tower is a packed tower, and the packing material has a specific surface area ≥1000m². 2 / m 3 Al2O3 foam packing. ), the top of the column yields a water-containing stream S16, the bottom of the column yields a stream containing heavy components S17, and the side stream from the 30th plate (from top to bottom) yields a 2-methyl-1,2-propanediol byproduct stream S18.

[0053] The yields and purity of methyl propylene oxide, acetone, and methanol after processing by the method of this embodiment are shown in Table 2 below.

[0054] Table 2 Composition of materials to be separated and product quality

[0055] The results showed that after treatment by the method in this embodiment, the yield of methyl propylene oxide was 97.3% and the purity was 99.1% (mass percentage, the same below); the yield of acetone was 97.2% and the purity was 99.54%; and the yield of methanol was 97.4% and the purity was 99.62%.

[0056] Comparative Example 1 according to Figure 1 The process flow is the same as that in Example 2, except that 1,3-butanediol is used as the extractant alone, with a solvent / material to be separated ratio of 3:1 (mass ratio). The separation results are shown in Table 3.

[0057] Table 3 Composition of materials to be separated and product quality

[0058] The results showed that after treatment using the comparative method, the purity of methyl propylene oxide was 95.2% (mass percentage, the same below); the purity of acetone was 98.56%; and the purity of methanol was 98.62%.

[0059] Comparative Example 2 according to Figure 1 The process flow is the same as that in Example 2, except that 1,4-butanediol is used as the extractant alone, with a solvent / material to be separated ratio of 3:1 (mass ratio). The separation results are shown in Table 4.

[0060] Table 4 Composition of materials to be separated and product quality

[0061] The results showed that after treatment using the comparative method, the purity of methyl propylene oxide was 96.64% (mass percentage, the same below); the purity of acetone was 98.69%; and the purity of methanol was 97.11%.

[0062] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for separating a methyl propylene oxide-acetone-methanol system, characterized in that, Includes the following steps: (1) The material stream to be separated enters the light component removal tower, the light component removed is obtained at the top of the tower, and the light component removed stream 1-1 is obtained at the bottom of the tower; (2) Stream 1-1 enters the first extractive distillation column and is extracted and distilled under the action of the composite solvent. Stream 2-1, which is rich in methyl propylene oxide, is obtained at the top of the column, and stream 2-2, which is rich in acetone, methanol, water, heavy components and composite solvent, is obtained at the bottom of the column. (3) Stream 2-2 enters the first desorption tower. Stream 3-1 containing acetone and methanol is obtained at the top of the tower, stream 3-2 containing composite solvent and heavy components is obtained at the bottom of the tower, and stream 3-3 containing desorbed composite solvent is obtained in the lower part of the tower. (4) Stream 3-1 enters the second extractive distillation column from the middle and lower part, and the composite solvent enters the second extractive distillation column from the middle and upper part. The acetone stream 4-1 to be processed is obtained at the top of the column, and the stream 4-2 containing methanol and composite solvent is obtained at the bottom of the column. (5) After heat exchange as the reboiler heat source of the acetone product column, the stream 4-1 enters the acetone product column from the middle. The stream 5-1 containing acetone and methanol azeotrope is obtained at the top of the column and returned to the second extractive distillation column. The acetone product stream 5-2 is obtained at the bottom of the column. (6) Stream 4-2 enters the second desorption tower, and methanol product stream 6-1 is obtained at the top of the tower. Desorbed composite solvent stream 6-2 is obtained at the bottom of the tower. Stream 6-2 is returned to the second extractive distillation tower.

2. The method as described in claim 1, characterized in that, The method further includes step (7): feeding the stream 3-2 from step (3) into a propylene glycol column, obtaining stream 7-1 containing water at the top of the column, obtaining stream 7-2 containing heavy components at the bottom of the column, and obtaining 2-methyl-1,2-propanediol in the lower part of the column.

3. The method as described in claim 1 or 2, characterized in that, In step (2), the composite solvent comprises N,N-dimethylacetamide and 1,3-butanediol, or is composed of N,N-dimethylacetamide and 1,3-butanediol; Preferably, the content of N,N-dimethylacetamide in the composite solvent is 50wt%~80wt%; Preferably, the content of 1,3-butanediol in the composite solvent can be 20wt% to 50wt%.

4. The method according to any one of claims 1-3, characterized in that, In step (1), the operating conditions of the light-light removal tower can be: 15 to 30 theoretical plates, -10 to 59°C at the top of the tower, 50 to 120°C at the bottom of the tower, reflux ratio of 1.2 to 3.5, and operating pressure of 200 to 500 kPa. And / or, in step (2), the operating conditions of the first extractive distillation column can be: 40 to 85 theoretical plates, 20 to 50°C composite solvent feed temperature, 70 to 130°C bottom temperature, 40 to 60°C top temperature, reflux ratio of 1.5 to 3.8, reagent-to-solvent ratio of 1.1 to 4.0:1, and operating pressure of 105 to 300 kPa; And / or, in step (3), the operating conditions of the first desorption tower can be: 20 to 40 theoretical plates, 45 to 65°C at the top of the tower, 90 to 190°C at the bottom of the tower, 1.0 to 3.0 reflux ratio, and 80 to 150 kPa operating pressure; And / or, in step (4), the operating conditions of the second extractive distillation column can be: 40 to 100 theoretical plates, 20 to 45°C composite solvent feed temperature, 80 to 180°C bottom temperature, 40 to 65°C top temperature, reflux ratio of 1.0 to 3.0, reagent-to-solvent ratio of 1.0 to 4.0:1, and operating pressure of 105 to 200 kPa; And / or, in step (5), the operating conditions of the acetone product tower can be: 35 to 50 theoretical plates, 45 to 55°C top temperature, 50 to 70°C bottom temperature, 1.5 to 5.0 reflux ratio, and 70 to 140 kPa operating pressure. And / or, in step (6), the operating conditions of the second desorption tower can be: 30 to 48 theoretical plates, 58 to 75°C at the top of the tower, 100 to 190°C at the bottom of the tower, 1.5 to 3.0 reflux ratio, and 80 to 160 kPa operating pressure; And / or, in step (7), the operating conditions of the propylene glycol column can be: 40 to 60 theoretical plates, 60 to 80°C top temperature, 150 to 190°C bottom temperature, 2.0 to 5.0 reflux ratio, and 50 to 80 kPa operating pressure.

5. The method according to any one of claims 1-4, characterized in that, The method may include the following steps: (1) The material stream to be separated enters the light component removal tower from the middle, and the light component stream is obtained at the top of the tower and the light component stream 1-1 is obtained at the bottom of the tower; (2) Stream 1-1 enters the first extractive distillation column from the middle and lower part, and the composite solvent enters the first extractive distillation column from the middle and upper part. Stream 2-1 rich in methyl propylene oxide is obtained at the top of the column, and stream 2-2 rich in acetone, methanol, water, heavy components and composite solvent is obtained at the bottom of the column. (3) Stream 2-2 enters the first desorption tower from the middle. Stream 3-1 containing acetone and methanol is obtained at the top of the tower. Stream 3-2 containing composite solvent and heavy components (partly from the raw material and partly from the hydrolysis of methyl propylene oxide) is obtained at the bottom of the tower. Stream 3-3 containing the desorbed composite solvent is obtained in the lower part of the tower. Stream 3-3 is mixed with the composite solvent after temperature adjustment and enters the first extractive distillation tower. (4) Stream 3-1 enters the second extractive distillation column from the middle and lower part, and the composite solvent enters the second extractive distillation column from the middle and upper part. The acetone stream 4-1 to be processed is obtained at the top of the column, and the stream 4-2 containing methanol and composite solvent is obtained at the bottom of the column. (5) After heat exchange as the reboiler heat source of the acetone product tower, the stream 4-1 enters the acetone product tower from the middle. The stream 5-1 containing acetone and methanol azeotrope is obtained at the top of the tower and returned to be mixed with stream 3-1, and then enters the lower part of the second extractive distillation tower. The bottom of the acetone product tower is acetone product stream 5-2. (6) Stream 4-2 enters the second desorption tower from the middle. Methanol product stream 6-1 is obtained at the top of the tower, and desorbed composite solvent stream 6-2 is obtained at the bottom of the tower. After adjusting the temperature, it is mixed with the composite solvent and enters the second extractive distillation tower. (7) Stream 3-2 enters the propylene glycol tower from the middle section. Stream 7-1 containing water is obtained at the top of the tower, and stream 7-2 containing heavy components is obtained at the bottom of the tower. 2-methyl-1,2-propanediol byproduct is obtained in the lower part of the tower.

6. A system for separating a methyl propylene oxide-acetone-methanol system, characterized in that, It includes a light component removal column, a first extractive distillation column, a first desorption column, a second extractive distillation column, an acetone product column, and a second desorption column; The bottom outlet of the light-light-removal column is connected to the inlet of the first extractive distillation column; The bottom outlet of the first extractive distillation column is connected to the inlet of the first desorption column; The top outlet of the first desorption column is connected to the inlet of the second extractive distillation column, and the composite solvent outlet of the first desorption column is connected to the composite solvent inlet of the first extractive distillation column. The top outlet of the second extractive distillation column is connected to the inlet of the acetone product column, and the bottom outlet of the second extractive distillation column is connected to the inlet of the second desorption column. The bottom outlet of the second desorption tower is connected to the composite solvent inlet of the second extractive distillation tower.

7. The system as described in claim 6, characterized in that, The system further includes a propylene glycol tower, wherein the outlet of the first desorption tower is connected to the inlet of the propylene glycol tower. Preferably, the propylene glycol tower is a packed tower. Preferably, the packing material used in the propylene glycol tower has a specific surface area ≥1000 m². 2 / m 3 At least one of SiC foam filler and Al2O3 foam filler.

8. The system as described in claim 6 or 7, characterized in that, The system also includes a first temperature regulator, and the composite solvent outlet of the first desorption tower is sequentially connected to the first temperature regulator and the composite solvent inlet of the first extractive distillation tower.

9. The system according to any one of claims 6-8, characterized in that, The system also includes a second temperature regulator, and the bottom outlet of the second desorption tower is sequentially connected to the second temperature regulator and the composite solvent inlet of the second extractive distillation tower.

10. The system according to any one of claims 6-9, characterized in that, The system also includes a reboiler, and the top outlet of the second extractive distillation column is connected to the reboiler and the inlet of the acetone product column.

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