A process for separating high purity n-butylaldehyde from mixed butylaldehydes

Abstract

The present application relates to a method for separating high-purity n-butyl aldehyde from mixed butyl aldehyde of carbonyl synthesis product, comprising the following steps: adding reaction inhibitor to the product of carbonyl synthesis reaction after separating catalyst, part of which enters high-pressure rectifying column, and the other part enters low-pressure rectifying column, n-butyl aldehyde product is obtained from the side line of high-pressure rectifying column and the bottom of low-pressure rectifying column, and iso-butyl aldehyde product is obtained from the top of high / low-pressure column. The present application adds reaction inhibitor to improve product purity, solves the problem of easy polymerization of mixed butyl aldehyde by using the characteristics of low-temperature decomposition of butyl aldehyde trimer, separates high-purity n-iso-butyl aldehyde from mixed butyl aldehyde with low energy consumption, and has low equipment investment cost and can create high economic benefits.

Description

Technical Field

[0001] This invention relates to a method for separating high-purity n- and isobutyraldehyde from mixed butyraldehyde, and is particularly suitable for separating n- and isobutyraldehyde from mixed butyraldehyde obtained by medium- and low-pressure carbonyl synthesis. Background Technology

[0002] Butyraldehyde is an important organic chemical raw material with consistently high market demand. Butyraldehyde has two isomers: n-butyraldehyde and isobutyraldehyde. n-Butyraldehyde is mainly used to produce n-butanol and 2-ethylhexanol, and also to produce fine chemical products such as trimethylolpropane and polyvinyl butyral. Isobutyraldehyde is mainly used to produce isobutanol, neopentyl glycol, 2,2,4-trimethylpentyl glycol, isobutyric acid, and isobutyronitrile.

[0003] Carbonyl synthesis reactions involve alkenes reacting with CO and H2 to form aldehydes or ketones. Except for ethylene, other hydrocarbons only produce aldehydes, and the industrial application of this type of reaction is the production of aldehydes; therefore, it is also called an aldosterone reaction. Relative to the hydrocarbon product, it can also be viewed as the replacement of two hydrogen atoms on the methine group by an oxygen atom; therefore, it is also called oxidative synthesis or hydroformylation.

[0004] Patent CN202310403681.5 describes a co-production apparatus and process for isobutyraldehyde and n-butyraldehyde. The co-production apparatus includes a purification unit, a hydroformylation unit, a falling film evaporator unit, and distillation columns A, B, and C connected in sequence. The n- and isobutyraldehyde products obtained by this apparatus have a purity of over 99.8 mol% and a water content of less than 0.1 mol%. However, this apparatus and process have poor separation performance for materials with a high n-to-isobutyraldehyde ratio (molar ratio of n-butyraldehyde to isobutyraldehyde), and the equipment is complex, without considering separation energy consumption.

[0005] Patent CN202110752194.0 describes a separation process for mixed butyraldehyde obtained from low-pressure carbonyl synthesis. The process includes: the reaction product from the carbonyl synthesis reactor is separated by a catalyst, compressed, and then fed into the middle section of a butyraldehyde isomerization tower. The light component in the reaction product is ≤4 wt%, and the ratio of n-butyraldehyde to isobutyraldehyde is 10–13:1. The light component is collected from the top of the light component removal section at the top of the tower, isobutyraldehyde is collected from the upper side stream of the tower, and the n-butyraldehyde mixture is collected from the bottom of the tower. This method requires significant equipment investment, the side stream operation has high requirements for the isobutyraldehyde content in the mixed butyraldehyde, and the quality of the isobutyraldehyde product is prone to fluctuation.

[0006] This invention proposes a novel and efficient separation method for separating high-purity n-isobutyraldehyde from mixed butyraldehyde. Summary of the Invention

[0007] The purpose of this invention is to solve the problems of high content of trimer in n-butyraldehyde and isobutanol in isobutyraldehyde and high energy consumption in separation in existing butyraldehyde production technology. Taking into account the polymerization of butyraldehyde and other side reactions, this invention proposes a highly efficient and energy-saving method for separating high-purity n- and isobutyraldehyde products from mixed butyraldehyde.

[0008] The technical solution for achieving the objective of this invention is as follows:

[0009] A method for separating isobutyraldehyde from mixed butyraldehyde includes: a portion of the carbonyl synthesis product mixed butyraldehyde after separation catalyst is fed into a high-pressure tower and the other portion into a low-pressure tower, wherein isobutyraldehyde is collected from the top of the high / low-pressure tower and n-butyraldehyde is collected from the bottom of the low-pressure tower and the side stream of the high-pressure tower.

[0010] Specifically, it includes the following steps:

[0011] (1) The carbonyl synthesis product is separated from the catalyst to obtain mixed butyraldehyde, which is divided into two streams, and the two streams enter the high-pressure / low-pressure distillation column respectively.

[0012] (2) The mixed butyraldehyde entering the low-pressure distillation column is separated to obtain isobutyraldehyde product from the top of the column and n-butyraldehyde product from the bottom of the column.

[0013] (3) The mixed butyraldehyde entering the high-pressure distillation column is separated to obtain isobutyraldehyde product from the top of the column and n-butyraldehyde product from the side stream;

[0014] (4) The material in the bottom of the high-pressure distillation column is pumped into the bottom of the low-pressure distillation column after passing through the buffer tank.

[0015] In this invention, in step (1), the carbonyl synthesis product is a mixture of the product obtained by carbonyl synthesis reaction of purified propylene and synthesis gas under the action of homogeneous noble metal catalysts such as rhodium and the catalyst.

[0016] After separation of the catalyst, the total content of n-butyraldehyde and isobutyraldehyde in the mixed butyraldehyde is 99.5% to 99.9%, the molar ratio of n-butyraldehyde to isobutyraldehyde is 1 to 20, and it also includes a very small amount of water and heavy components.

[0017] In this invention, in step (1), the temperature, pressure and composition of the two streams are the same.

[0018] In this invention, in step (1), the flow rate ratio of the distillation column to the high-pressure distillation column and the low-pressure distillation column is 0.1 to 10.

[0019] In this invention, in step (2), the theoretical number of trays in the low-pressure distillation column is 30 to 200, preferably 100 to 150; the feed position is the 10th to 70th tray, preferably 30 to 70; the operating pressure is 0.06 to 3 atm, preferably 0.2 to 0.6 atm; the reflux ratio is 0.1 to 20, preferably 1 to 10; and the reboiler temperature is 20 to 115°C, preferably 33 to 65°C.

[0020] In this invention, in step (3), the theoretical number of plates in the high-pressure distillation column is 30 to 200, preferably 100 to 150; the feed position is the 10th to 75th plate; the operating pressure is 0.2 to 5 atm and higher than that of the low-pressure distillation column, preferably 1 to 1.5 atm; the reflux ratio is 0.1 to 20, preferably 2 to 10; and the top temperature is 25 to 120°C, preferably 65 to 77°C.

[0021] In this invention, further, in step (2), the material at the bottom of the low-pressure distillation column and the material at the top of the high-pressure distillation column in step (3) exchange heat through a coupling heat exchanger, with a heat exchange temperature difference of 5 to 30°C, preferably 8 to 15°C.

[0022] In this invention, in step (4), the main components of the material in the bottom of the high-pressure distillation column are butyraldehyde and butyraldehyde trimer, wherein the butyraldehyde trimer generated at high temperature can decompose at low temperature.

[0023] As a preferred embodiment, in step (1), a reaction inhibitor is added to the mixed butyraldehyde before splitting it into two streams. The reaction inhibitor is selected from one or a mixture of several of isobutyraldehyde, butyl butyrate, isooctyl butyrate, isobutyric acid, and water;

[0024] Preferably, in the reaction inhibitor, the mass content of isobutyraldehyde is 60-99%, preferably 65-95%; the mass content of butyl butyrate is 0.01%-10%, preferably 0.5-10%; the mass content of isooctyl butyrate is 0.01%-10%, preferably 0.5-10%; the mass content of isobutyric acid is 0.1%-10%, preferably 2-10%; and the mass content of water is 0.01%-10%, preferably 1-6%.

[0025] The amount of the reaction inhibitor added is 20 to 30,000 ppm of the mass of the mixed butyraldehyde, preferably 500 to 10,000 ppm, and more preferably 1,000 to 4,000 ppm.

[0026] In this invention, the purity of both n-butyraldehyde and isobutyraldehyde products in steps (2) and (3) is greater than 99 wt%. In a preferred embodiment, the butyraldehyde trimer content in the n-butyraldehyde obtained in steps (2) and (3) is as low as 0.02-0.3%, and the isobutanol content in the isobutyraldehyde is as low as 0.01-0.2%. The butyraldehyde trimer content in the n-butyraldehyde product can be reduced by 58%, and the isobutanol content in the isobutyraldehyde product can be reduced by 73%. The purity of both n-butyraldehyde and isobutyraldehyde products is greater than 99.5 wt%.

[0027] The advantages and positive effects of this invention are as follows:

[0028] The method for separating n- and isobutyraldehyde from mixed butyraldehyde in this invention has the advantage of being able to separate high-purity n-butyraldehyde and isobutyraldehyde products from mixed butyraldehyde with low energy consumption. This is beneficial to the development of carbonyl synthesis processes for butyraldehyde production, can create higher economic benefits, and thus improve the market competitiveness of industries and enterprises.

[0029] This invention utilizes the low-temperature decomposition characteristic of butyraldehyde trimer to solve the problem of easy polymerization of mixed butyraldehyde separation products. Furthermore, by adding a reaction inhibitor in the preferred scheme, the purity of n- and isobutyraldehyde products can be further improved. High-purity n- and isobutyraldehyde products can be separated from mixed butyraldehyde with low energy consumption, achieving a n-butyraldehyde and isobutyraldehyde product mass content of over 99.5 wt%. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the separator. Figure 2 This is a schematic diagram of the process flow of the present invention;

[0031] Among them, S0901-Separator, C0901-Low-pressure distillation column, E0901-Low-pressure distillation column top condenser, E0902-Coupled heat exchanger, C0902-High-pressure distillation column, E0903-High-pressure distillation column top compensating condenser, E0904-High-pressure distillation column bottom reboiler, and D0901-Heavy component buffer tank.

[0032] S00 - Mixed butyraldehyde, S01 - Low-pressure distillation column feed, S02 - Low-pressure distillation column bottom product (n-butyraldehyde), S03 - Coupled heat exchanger tube-side feed, S04 - Coupled heat exchanger tube-side discharge, S05 - Low-pressure distillation column overhead vapor, S06 - Low-pressure distillation column overhead reflux, S07 - Low-pressure distillation column top product (isobutyraldehyde), S08 - Coupled heat exchanger shell-side feed, S09 - High-pressure distillation column top product (isobutyraldehyde), S10 - Coupled heat exchanger shell-side discharge, S11 - High-pressure distillation column bottom material, S12 - High-pressure distillation column bottom heavy components, S13 - High-pressure distillation column bottom return material, S14 - High-pressure distillation column feed, S15 - High-pressure distillation column side stream (n-butyraldehyde), S16 - Exhaust gas, S17 - High-pressure column heavy components, S18 - Reaction inhibitor. Detailed Implementation

[0033] The method and apparatus provided by the present invention will be further described below with reference to the accompanying drawings. However, the scope of the present invention is not limited to the scope covered by the embodiments.

[0034] A method for separating normal and isobutyraldehyde from a mixture of butyraldehyde, wherein the piping connections and process flow are as follows:

[0035] After mixing butyraldehyde (S00) and reaction inhibitor (S18), the mixture enters the separator (S0901), where it is separated into stream 1 (S01) and stream 2 (S14). Stream 1 (S01) enters the low-pressure distillation column (C0901). The vapor stream (S05) at the top of the low-pressure distillation column (C0901) enters the top condenser (E0901) of the low-pressure distillation column. After condensation in the top condenser (E0901), part of the material (S06) is returned to the low-pressure distillation column (C0901), and the other part is collected as product (S07).

[0036] The bottom material of the low-pressure distillation column (C0901) is partly collected as product (S02) and partly enters the coupling heat exchanger (E0902). After heat exchange, the stream (S04) returns to the bottom of the low-pressure distillation column (C0901).

[0037] The stream 2 (S14) obtained by the separator enters the high-pressure distillation column (C0902). The top gas stream (S08) of the high-pressure distillation column (C0902) enters the coupling heat exchanger (E0902). After heat exchange, the stream (S10) enters the top compensating condenser (E0903) of the high-pressure distillation column. After heat exchange, part of it is collected as product (S09), and part is returned to the high-pressure distillation column (C0902).

[0038] Part of the bottom material (S11) of the high-pressure distillation column (C0902) enters the high-pressure distillation column bottom heat exchanger (E0904). After heat exchange, the stream (S13) returns to the bottom of the high-pressure distillation column. The other stream (S12) enters the heavy component buffer tank (D0901). The liquid phase (S17) in the buffer tank enters the low-pressure distillation column, and the gas phase (S16) in the buffer tank enters the purge gas system. The side stream of the high-pressure distillation column produces n-butyraldehyde product (S15).

[0039] Mixed butyraldehyde: Wanhua polyol unit.

[0040] Example 1

[0041] The raw material mixture of butyraldehyde contains n-butyraldehyde and isobutyraldehyde, with n-butyraldehyde accounting for 84.9% by mass and isobutyraldehyde accounting for 15% by mass. The remainder consists of water and other impurities, and the raw material flow rate is 50 t / h. The added reaction inhibitor consists of 94% isobutyraldehyde, 0.5% butyl butyrate, 0.9% isooctyl butyrate, 2.45% isobutyric acid, and 2.15% water, and is added at a flow rate of 100 kg / h.

[0042] The flow rate ratio entering the high / low pressure distillation column is 1. The low-pressure distillation column (C0901) has 140 actual trays, with the feed point on the 50th tray, an operating pressure of 0.5 atm, a reboiler temperature of 60°C, and a reflux ratio of 5. The high-pressure distillation column (C0902) has 150 actual trays, with the feed point on the 55th tray, an operating pressure of 1.2 atm, a top temperature of 70°C, and a reflux ratio of 5. The reboiler material from the low-pressure distillation column (C0901) enters the tube side of the coupled heat exchanger (E0902), and the top material from the high-pressure distillation column (C0902) enters the shell side of the coupled heat exchanger (E0902).

[0043] The final product obtained from the high-pressure distillation column had a butyraldehyde content of 99.5% and a butyraldehyde trimer content of 0.22%; the isobutyraldehyde content was 99.8% and the isobutanol content was 0.05%. The product obtained from the low-pressure distillation column had a butyraldehyde content of 99.9% and a butyraldehyde trimer content of 0.02%; the isobutyraldehyde content was 99.6% and the isobutanol content was 0.12%.

[0044] Example 2

[0045] The raw material mixture of butyraldehyde contains n-butyraldehyde and isobutyraldehyde, with n-butyraldehyde accounting for approximately 49.9% by mass and isobutyraldehyde accounting for approximately 49.8% by mass. The flow rate of the raw material is 80 t / h. The added reaction inhibitor consists of 80% isobutyraldehyde, 9.5% butyl butyrate, 4.9% isooctyl butyrate, 4.45% isobutyric acid, and 1.15% water, added at a flow rate of 200 kg / h.

[0046] The flow rate ratio entering the high / low pressure distillation column is 8. The low-pressure distillation column (C0901) has 130 actual trays, with the feed point on the 70th tray, an operating pressure of 0.6 atm, a bottom temperature of 65°C, and a reflux ratio of 7. The high-pressure distillation column (C0902) has 120 actual trays, with the feed point on the 50th tray, an operating pressure of 1.3 atm, a top temperature of 72°C, and a reflux ratio of 2.5. The bottom material of the low-pressure distillation column (C0901) enters the tube side of the coupled heat exchanger (E0902), and the top material of the high-pressure distillation column (C0902) enters the shell side of the coupled heat exchanger (E0902).

[0047] The final product obtained from the high-pressure distillation column had a butyraldehyde content of 99.5% and a butyraldehyde trimer content of 0.3%; the isobutyraldehyde content was 99.6% and the isobutanol content was 0.18%. The product obtained from the low-pressure distillation column had a butyraldehyde content of 99.6% and a butyraldehyde trimer content of 0.24%; the isobutyraldehyde content was 99.7% and the isobutanol content was 0.04%.

[0048] Example 3

[0049] The raw material mixture of butyraldehyde contains n-butyraldehyde and isobutyraldehyde, with n-butyraldehyde accounting for approximately 92.7% by mass and isobutyraldehyde accounting for approximately 7.1% by mass. The flow rate of the raw material is 30 t / h. The added reaction inhibitor consists of 67% isobutyraldehyde, 9.5% butyl butyrate, 9.9% isooctyl butyrate, 8.42% isobutyric acid, and 5.18% water, added at a flow rate of 30 kg / h.

[0050] The flow rate ratio entering the high / low pressure distillation column is 0.5. The low-pressure distillation column (C0901) has 170 actual trays, with the feed point on the 60th tray, an operating pressure of 0.4 atm, a bottom temperature of 53°C, and a reflux ratio of 1. The high-pressure distillation column (C0902) has 110 actual trays, with the feed point on the 40th tray, an operating pressure of 1.1 atm, a top temperature of 67°C, and a reflux ratio of 8. The bottom material of the low-pressure distillation column (C0901) enters the tube side of the coupled heat exchanger (E0902), and the top material of the high-pressure distillation column (C0902) enters the shell side of the coupled heat exchanger (E0902).

[0051] The final product obtained from the high-pressure distillation column had a butyraldehyde content of 99.7% and a butyraldehyde trimer content of 0.15%; and an isobutyraldehyde content of 99.6% and an isobutanol content of 0.18%. The product obtained from the low-pressure distillation column had a butyraldehyde content of 99.9% and a butyraldehyde trimer content of 0.02%; and an isobutyraldehyde content of 99.5% and an isobutanol content of 0.19%.

[0052] Example 4

[0053] The raw material mixture contains n-butyraldehyde and isobutyraldehyde, with n-butyraldehyde accounting for approximately 92.7% by mass and isobutyraldehyde accounting for approximately 7.1% by mass. The flow rate of the raw material is 30 t / h. No reaction inhibitors are added.

[0054] The flow rate ratio entering the high / low pressure distillation column is 2. The low-pressure distillation column (C0901) has 110 actual trays, with the feed inlet on the 30th tray, an operating pressure of 0.6 atm, a bottom temperature of 65°C, and a reflux ratio of 3. The high-pressure distillation column (C0902) has 120 actual trays, with the feed inlet on the 45th tray, an operating pressure of 1.2 atm, a top temperature of 70°C, and a reflux ratio of 8. The bottom material of the low-pressure distillation column (C0901) enters the tube side of the coupled heat exchanger (E0902), and the top material of the high-pressure distillation column (C0902) enters the shell side of the coupled heat exchanger (E0902).

[0055] The final product obtained from the high-pressure distillation column had a butyraldehyde content of 99.2% and a butyraldehyde trimer content of 0.52%; and an isobutyraldehyde content of 99.0% and an isobutanol content of 0.6%. The product obtained from the low-pressure distillation column had a butyraldehyde content of 99.3% and a butyraldehyde trimer content of 0.57%; and an isobutyraldehyde content of 99.1% and an isobutanol content of 0.72%.

Claims

1. A method for separating normal and isobutyraldehyde from a mixture of butyraldehyde, comprising: (1) The mixed butyraldehyde is divided into two streams, which enter the high-pressure and low-pressure distillation columns respectively; (2) The mixed butyraldehyde entering the low-pressure distillation column is separated to obtain isobutyraldehyde product from the top of the column and n-butyraldehyde product from the bottom of the column; wherein, the theoretical number of plates of the low-pressure distillation column is 100~150, the feed position is the 30th to 70th plate, the operating pressure is 0.2~0.6 atm, the reflux ratio is 1~10, and the bottom temperature is 33~65℃; (3) The mixed butyraldehyde entering the high-pressure distillation column is separated to obtain isobutyraldehyde product from the top of the column and n-butyraldehyde product from the side stream; wherein, the theoretical number of the high-pressure distillation column is 100~150, the operating pressure is 1~1.5atm, the reflux ratio is 2~10, and the top temperature is 65~77℃. (4) The material in the bottom of the high-pressure distillation column is pumped into the bottom of the low-pressure distillation column after passing through the buffer tank.

2. The method according to claim 1, wherein, The total content of n-butyraldehyde and isobutyraldehyde in the mixed butyraldehyde is 99.5% to 99.9%, and the molar ratio of n-butyraldehyde to isobutyraldehyde is 1 to 20.

3. The method according to claim 1, wherein, In step (1), the flow rate ratio of the high-pressure distillation column to the low-pressure distillation column is 0.1~10.

4. The method according to any one of claims 1-3, wherein, The material in the bottom of the low-pressure distillation column and the material in the top of the high-pressure distillation column exchange heat through a coupled heat exchanger with a temperature difference of 5~30℃.

5. The method according to claim 1, wherein, In step (1), a reaction inhibitor is added to the mixed butyraldehyde and then the mixture is divided into two streams. The reaction inhibitor is selected from one or a mixture of isobutyraldehyde, butyl butyrate, isooctyl butyrate, isobutyric acid and water.

6. The method according to claim 5, wherein, The reaction inhibitors contain 60-99% isobutyraldehyde, 0.01-10% butyl butyrate, 0.01-10% isooctyl butyrate, 0.1-10% isobutyric acid, and 0.01-10% water.

7. The method according to claim 6, wherein, The reaction inhibitor contains 65-95% isobutyraldehyde, 0.5-10% butyl butyrate, 0.5-10% isooctyl butyrate, 2-10% isobutyric acid, and 1-6% water.

8. The method according to any one of claims 5-7, wherein the amount of the reaction inhibitor added is 20 to 30,000 ppm of the mass of the mixed butyraldehyde.

9. The method according to any one of claims 5-7, wherein the amount of the reaction inhibitor added is 500-10000 ppm of the mass of the mixed butyraldehyde.

10. The method according to any one of claims 5-7, wherein the amount of the reaction inhibitor added is 1000-4000 ppm of the mass of the mixed butyraldehyde.

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