Low-temperature decompression continuous catalytic rectifying tower for synthesizing diacetone alcohol

Abstract

The utility model relates to a low-temperature decompression continuous catalytic rectifying tower for synthesizing diacetone alcohol, which comprises a catalytic rectifying tower, a condenser and a built-in reboiler, the catalytic rectifying tower comprises a reaction section and a stripping section, and a feed port of the catalytic rectifying tower is positioned between the reaction section and the stripping section. The external condenser is arranged at the tower top of the catalytic rectifying tower, the inlet end of the condenser is connected with a tower top outlet of the catalytic rectifying tower, the outlet end of the condenser is connected with a tower top side inlet of the catalytic rectifying tower, the built-in reboiler is arranged at the tower bottom of the catalytic rectifying tower, and a tower kettle extraction port is formed in the bottom of the catalytic rectifying tower. According to the utility model, not only is the reaction conversion rate (gt: 99.9%) obviously improved, but also the reaction selectivity reaches 100%, the generation of byproducts and the decomposition of diacetone alcohol are avoided, the reaction energy consumption is reduced, in addition, the product does not need to be subsequently separated, and the catalyst does not need to be separated and recycled.

Description

Technical Field

[0001] The utility model relates to a low-temperature and reduced-pressure continuous catalytic distillation process for synthesizing diacetone alcohol and a catalytic distillation tower thereof, belonging to the technical field of continuous catalytic distillation. Background Art

[0002] Diacetone alcohol, also known as 4-hydroxy-4-methyl-2-pentanone and diacetone alcohol (DAA), has the properties and functions of both ketone and alcohol due to its special molecular structure. It is an important raw material and organic solvent in chemical production. Diacetone alcohol has the characteristics of high boiling point, low resistivity and good conductivity. It is regarded as an environmentally friendly solvent that can replace acetone. For example, it can be used as a cleaning solvent or a solvent for cellulose acetate, nitrocellulose and epoxy resin. In addition, it can also be used in the preparation of chemical products such as dyes, paint thinners, preservatives, wood colorants, rust removers and antifreeze agents, hydraulic oil solvents and extractants. At the same time, DAA is also an important chemical intermediate and an intermediate for the preparation of organic products such as methyl isobutyl ketone (MIBK), mesityl oxide and isophorone. Diacetone alcohol is unstable at high temperatures and will decompose violently into acetone above 120 °C.

[0003] At present, the traditional process for preparing diacetone alcohol from acetone as raw material in industry is to use intermittent reactor or fixed bed reactor, and use catalysts such as oxides, hydroxides or carbonates of alkali metals or alkaline earth metals, which has the advantages of simple catalysts, low prices and convenient operation. However, its significant disadvantages are poor selectivity, many by-products, difficult post-treatment and serious environmental pollution. Compared with homogeneous catalysts, the use of heterogeneous catalysts (such as alkaline anion resins, etc.) combined with fixed bed processes to produce diacetone alcohol has the advantages of easy product separation, relatively more environmentally friendly and less corrosive, but this process still does not solve the problem of low conversion rate.

[0004] Chinese patent CN 85100473A discloses an intermittent reactor process for synthesizing diacetone alcohol. Although the reaction time is shortened by using a highly active catalyst and the single-pass conversion rate is increased by lowering the reaction temperature, the yield of diacetone alcohol is still relatively low, about 18-20%, due to the limitation of the equilibrium conversion rate.

[0005] Chinese patent CN 110496414A discloses a continuous reactive distillation equipment and process for synthesizing diacetone alcohol. This process couples the reaction and separation through reactive distillation, breaking the limitation of reaction equilibrium, and the yield of diacetone alcohol far exceeds that of intermittent reactor and fixed bed process; however, this process is atmospheric reactive distillation, which needs to be carried out at a higher temperature, and there is a mismatch between the reaction temperature and the separation temperature, acetone cannot be completely converted, there are many by-products, and the energy consumption is high. At the same time, the concentration of diacetone alcohol obtained in the tower is not high, and it needs to be distilled and separated again, which increases equipment costs and energy consumption. In addition, the high temperature of the tower will also cause the decomposition of diacetone alcohol. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the utility model is to provide a low-temperature and reduced-pressure continuous catalytic distillation tower for synthesizing diacetone alcohol, so that acetone is completely converted to obtain high-purity diacetone alcohol without producing by-products.

[0007] In order to solve the above technical problems, the technical solution of the utility model is:

[0008] The utility model discloses a low-temperature and reduced-pressure continuous catalytic distillation tower for synthesizing diacetone alcohol, which is characterized by comprising a catalytic distillation tower, a condenser and a built-in reboiler, wherein the catalytic distillation tower comprises two parts, a reaction section and a stripping section, a feed inlet of the catalytic distillation tower is located between the reaction section and the stripping section, an external condenser is arranged at the top of the catalytic distillation tower, an inlet end of the condenser is connected to a top outlet of the catalytic distillation tower, an outlet end of the condenser is connected to a side inlet of the top of the catalytic distillation tower, the built-in reboiler is arranged at the bottom of the catalytic distillation tower, and a tower kettle extraction outlet is arranged at the bottom of the catalytic distillation tower.

[0009] Preferably, the reaction section of the catalytic distillation tower is divided into three sections, each section is 4 to 6 m high, the number of plates in the stripping section of the catalytic distillation tower (T101) is 3 to 5, the absolute operating pressure of the catalytic distillation tower (T101) is 12 to 15 kPa, the top reflux mode is total reflux, the top temperature of the catalytic distillation tower (T101) is 0 to 10 ° C, the bottom temperature is 100 to 110 ° C, and the space velocity of the catalytic distillation tower is 0.45 to 0.64 h -1 .

[0010] Preferably, the catalyst in the catalytic filler installed in the above reaction section is a hydroxide-type macroporous alkaline resin, and the reaction section is divided into three sections, the first section is filled with 828 resin, and the second and third sections are filled with D296 resin.

[0011] Preferably, the condenser uses -15 to -20°C ethylene glycol aqueous solution as the condensing liquid.

[0012] Preferably, the above-mentioned built-in reboiler is a single-tube and single-shell tube overflowable reboiler. The reboiler is built into the tower body and placed 0.5 m below the distillation section. The tube size is φ38 mm and the tube length is 1~1.5 m. A gas riser overflow pipe is arranged in the middle, and its cross-sectional area is 1%~5% of the tower cross-sectional area. The pipe mouth is 3~8 cm higher than the pipe mouths of other tubes.

[0013] The utility model discloses a low-temperature, reduced-pressure, continuous catalytic distillation process for synthesizing diacetone alcohol by using the distillation tower, and the process is performed according to the following steps: (1) acetone enters the catalytic distillation tower (T101) from a feed port between a reaction section and a stripping section, the acetone is heated and vaporized and enters the reaction section, and a condensation reaction is performed under the action of a catalyst in a catalytic filler, and unreacted light component acetone is evaporated from the top of the tower and condensed in a condenser, and the condensate is fully refluxed to the top of the catalytic distillation tower, and enters the reaction section again for reaction, and an acetone enrichment zone is formed in the reaction section; (2) the diacetone alcohol generated by the reaction in the reaction section enters the stripping section through the separation action of the catalytic filler, and the acetone entrained by the diacetone alcohol is further separated in the stripping section. Acetone returns to the reaction section to continue the reaction, and diacetone alcohol enters the tube side of the built-in reboiler. The shell side of the reboiler is provided with heat source by heating steam; (3) The built-in reboiler of the catalytic distillation tower (T101) adopts a single-tube-pass single-shell-pass tube-filled overflow reboiler. After the diacetone alcohol is partially vaporized in the single-tube-pass single-shell-pass tube-filled overflow reboiler, a part of the vapor phase enters the stripping section of the catalytic distillation tower (T101) to provide heat source for the whole tower. The unvaporized diacetone alcohol enters the catalytic distillation tower kettle from the reboiler tube side due to gravity. The kettle does not provide additional heat source. The diacetone alcohol product is directly extracted from the kettle, which shortens the residence time of the diacetone alcohol in the kettle and the reboiler, and avoids the high-temperature decomposition of the diacetone alcohol.

[0014] The acetone conversion rate of the process of the utility model is greater than 99.9%, the purity of the diacetone alcohol product is greater than 99.9%, and no byproducts such as mesityl oxide are produced during the reaction process.

[0015] Beneficial effects of the utility model

[0016] The utility model realizes the matching of separation temperature and reaction temperature by reducing pressure, thus significantly improving the selectivity of the reaction, and the product does not need subsequent separation, with low energy consumption and less equipment investment.

[0017] The utility model uses a single-tube-pass single-shell-pass tube-coated overflowable reboiler built into a catalytic distillation tower as a tower kettle heating device, thereby shortening the heating time of diacetone alcohol, preventing diacetone alcohol from being decomposed into acetone by heat, and achieving the advantages of high product purity and stable quality. The diacetone alcohol extracted from the tower kettle of the catalytic distillation tower can be used as a qualified product; the gas riser overflow pipe can realize smooth reverse flow of vapor and liquid, and at the same time ensure smooth flow of vapor and liquid two-phases under large flow.

[0018] In addition, compared with the traditional intermittent reactor and fixed bed process, it solves the problems of low conversion rate in the reaction process, acetone cannot be completely converted and the product needs to be separated later; compared with the normal pressure catalytic distillation tower process, it solves the problems of poor multi-selectivity of by-products, acetone cannot be completely converted and the product needs to be separated later, and reduces one diacetone alcohol distillation tower, greatly reducing equipment investment; at the same time, it lowers the reaction temperature, avoids the decomposition of diacetone alcohol into acetone again, and also reduces energy consumption.

[0019] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the process flow and catalytic distillation tower structure of the utility model;

[0021] Figure 2 It is a schematic diagram of the cross-sectional structure of the connection between the reboiler and the distillation tower of the utility model. DETAILED DESCRIPTION

[0022] In order to make the above features and advantages of the present invention more obvious and easy to understand, the present invention is further described below through specific embodiments in conjunction with the accompanying drawings.

[0023] The utility model discloses a low-temperature and reduced-pressure continuous catalytic distillation tower for synthesizing diacetone alcohol, comprising a catalytic distillation tower A1, a condenser A2 and a built-in reboiler A3. The reboiler A3 (also called a reboiler) functions to vaporize the liquid again, and is a single-tube-pass and single-shell-pass tube-in-tube overflowable reboiler. The catalytic distillation tower A1 comprises a reaction section A11 and a stripping section A12. A feed inlet 1 of the catalytic distillation tower is located between the reaction section A11 and the stripping section A12. An external condenser A2 is arranged at the top of the catalytic distillation tower. An inlet end 2 of the condenser is connected to a top outlet of the catalytic distillation tower. An outlet end of the condenser is connected to a side inlet 3 of the top of the catalytic distillation tower. The built-in reboiler A3 is arranged at the bottom of the catalytic distillation tower. A kettle extraction outlet 4 is arranged at the bottom of the catalytic distillation tower.

[0024] The reaction section of the catalytic distillation tower can be divided into three sections, each section is 4 to 6 m high, the number of plates in the stripping section of the catalytic distillation tower (T101) is 3 to 5, the absolute operating pressure of the catalytic distillation tower (T101) can be 12 to 15 kPa, the top reflux mode is total reflux, the top temperature of the catalytic distillation tower (T101) can be 0 to 10 °C, the bottom temperature can be 100 to 110 °C, and the space velocity of the catalytic distillation tower can be 0.45 to 0.64 h -1 .

[0025] Among them, the catalyst in the catalytic filler installed in the reaction section A11 is a hydroxide-type large-pore alkaline resin. The reaction section is divided into three sections. Specifically, the hydroxide-type large-pore alkaline resin, the first section is filled with 828 resin, and the second and third sections are filled with D296 resin.

[0026] The condenser uses -15 to -20°C ethylene glycol aqueous solution as the condensate.

[0027] The built-in reboiler A3 (single-pass single-course tube-in-tube overflowable reboiler) of the present application is arranged on the inner circumferential wall A13 of the distillation tower body. The structure of the built-in reboiler A3 is a closed cylindrical shell (the outer circumferential wall of the cylindrical shell is in contact with the inner circumferential wall of the distillation tower body). A gas riser overflow pipe A31 is arranged in the middle between the upper and lower surfaces of the shell, and a plurality of tubes A32 are arranged on the outer periphery of the gas riser overflow pipe A31. A cavity is formed between the cylindrical shell and the gas riser overflow pipe A31 and the tubes A32. The cavity performs cyclic heat exchange with the heat source outside the distillation tower body. The built-in reboiler A3 of the present application is placed 0.5 m below the stripping section. The size of the tube A32 is φ38 mm, and the length of the tube is 1~1.5 m. A gas riser overflow pipe A31 is arranged in the middle, and its cross-sectional area is 1%~5% of the cross-sectional area of ​​the tower. The pipe mouth is 3~8 cm higher than the pipe mouths of other tubes.

[0028] The utility model discloses a low-temperature, reduced-pressure, continuous catalytic distillation process for synthesizing diacetone alcohol by using the distillation tower, and the process is performed according to the following steps: (1) acetone enters the catalytic distillation tower (T101) from a feed port between a reaction section and a stripping section, the acetone is heated and vaporized and enters the reaction section, and a condensation reaction is performed under the action of a catalyst in a catalytic filler, and unreacted light component acetone is evaporated from the top of the tower and condensed in a condenser, and the condensate is fully refluxed to the top of the catalytic distillation tower, and enters the reaction section again for reaction, and an acetone enrichment zone is formed in the reaction section; (2) the diacetone alcohol generated by the reaction in the reaction section enters the stripping section through the separation action of the catalytic filler, and the acetone entrained by the diacetone alcohol is further separated in the stripping section. Acetone returns to the reaction section to continue the reaction, and diacetone alcohol enters the tube side of the built-in reboiler. The shell side of the reboiler is provided with heat source by heating steam; (3) The built-in reboiler of the catalytic distillation tower (T101) adopts a single-tube-pass single-shell-pass tube-filled overflow reboiler. After the diacetone alcohol is partially vaporized in the single-tube-pass single-shell-pass tube-filled overflow reboiler, a part of the vapor phase enters the stripping section of the catalytic distillation tower (T101) to provide heat source for the whole tower. The unvaporized diacetone alcohol enters the catalytic distillation tower kettle from the reboiler tube side due to gravity. The kettle does not provide additional heat source. The diacetone alcohol product is directly extracted from the kettle, which shortens the residence time of the diacetone alcohol in the kettle and the reboiler, and avoids the high-temperature decomposition of the diacetone alcohol.

[0029] The acetone conversion rate of the process of the utility model is greater than 99.9%, the purity of the diacetone alcohol product is greater than 99.9%, and no byproducts such as mesityl oxide are produced during the reaction process.

[0030] The utility model realizes the matching of separation temperature and reaction temperature by reducing pressure, thus significantly improving the selectivity of the reaction, and the product does not need subsequent separation, with low energy consumption and less equipment investment.

[0031] The utility model uses a single-tube-pass single-shell-pass tube-coated overflowable reboiler built into a catalytic distillation tower as a tower kettle heating device, thereby shortening the heating time of diacetone alcohol, preventing diacetone alcohol from being decomposed into acetone by heat, and achieving the advantages of high product purity and stable quality. The diacetone alcohol extracted from the tower kettle of the catalytic distillation tower can be used as a qualified product; the gas riser overflow pipe can realize smooth reverse flow of vapor and liquid, and at the same time ensure smooth flow of vapor and liquid two-phases under large flow.

[0032] In addition, compared with the traditional intermittent reactor and fixed bed process, it solves the problems of low conversion rate in the reaction process, acetone cannot be completely converted and the product needs to be separated later; compared with the normal pressure catalytic distillation tower process, it solves the problems of poor multi-selectivity of by-products, acetone cannot be completely converted and the product needs to be separated later, and reduces one diacetone alcohol distillation tower, greatly reducing equipment investment; at the same time, it lowers the reaction temperature, avoids the decomposition of diacetone alcohol into acetone again, and also reduces energy consumption.

[0033] An example of a distillation process using a low-temperature, reduced-pressure continuous catalytic distillation tower for synthesizing diacetone alcohol according to the utility model is as follows:

[0034] Example 1

[0035] The process flow shown in the attached figure is adopted, in which the theoretical number of plates in the stripping section is 3, the height of the reaction section is 12 m (divided into three sections, each section is 4 m high); the operating conditions of the catalytic distillation tower are: the operating absolute pressure is 12 kPa, the top of the tower is full reflux, the condenser uses -20 °C ethylene glycol aqueous solution as the condensate, and the space velocity is 0.45 h -1 The raw material acetone is pumped into the catalytic distillation tower from the lower part of the reaction section through the feed pipe, and contacts and reacts with the catalyst in the reaction section. The tower top temperature is 5.0°C and the tower bottom temperature is 105.6°C. The diacetone alcohol generated by the reaction is separated in the stripping section, and then vaporized and separated in a single-tube-pass single-shell-pass tube-by-tube overflowable reboiler (built-in reboiler A3). The vapor phase enters the stripping section of the catalytic distillation tower, and the liquid phase is withdrawn from the tower bottom through the withdrawal pipe to obtain a product with a mass fraction of 99.96% of diacetone alcohol, wherein there is no by-product mesityl oxide.

[0036] Example 2

[0037] The process flow shown in the attached figure is adopted, in which the theoretical number of plates in the stripping section is 5, the height of the reaction section is 18 m (divided into three sections, each section is 6 m high), and the operating conditions of the catalytic distillation tower are: the operating absolute pressure is 12 kPa, the top of the tower is full reflux, the condenser uses -20 °C ethylene glycol aqueous solution as the condenser, and the space velocity is 0.64 h -1 The raw material acetone is pumped into the catalytic distillation tower from the lower part of the reaction section through the feed pipe, and contacts and reacts with the catalyst in the reaction section. The tower top temperature is 5.0°C, and the tower bottom temperature is 105.1°C. The diacetone alcohol generated by the reaction is separated in the stripping section, and then vaporized and separated in a single-tube-pass single-shell-pass tube overflow reboiler. The vapor phase enters the stripping section of the catalytic distillation tower, and the liquid phase is withdrawn from the tower bottom through the withdrawal pipe to obtain a product with a mass fraction of 99.92% of diacetone alcohol, wherein there is no by-product mesityl oxide.

[0038] Example 3

[0039] The process flow shown in the attached figure is adopted, in which the theoretical number of plates in the stripping section is 4, the height of the reaction section is 15 m (divided into three sections, each section is 5 m high), and the operating conditions of the catalytic distillation tower are: the operating absolute pressure is 15 kPa, the top of the tower is full reflux, the condenser uses -15 ℃ ethylene glycol aqueous solution as the condenser, and the space velocity is 0.45 h -1 The raw material acetone is pumped into the catalytic distillation tower from the lower part of the reaction section through the feed pipe, and contacts and reacts with the catalyst in the reaction section. The tower top temperature is 9.4 ℃, and the tower bottom temperature is 108.9 ℃. The diacetone alcohol generated by the reaction is separated in the stripping section, and then vaporized and separated in a single-tube-pass single-shell-pass tube-filled overflow reboiler. The vapor phase enters the stripping section of the catalytic distillation tower, and the liquid phase is extracted from the tower bottom extraction pipe to obtain a product with a mass fraction of 99.90% of diacetone alcohol, of which there is no by-product mesityl oxide.

[0040] The utility model adopts catalytic distillation technology, utilizes vacuum pump to control vacuum, catalytic distillation tower, condenser, built-in single-pass overflowable reboiler and several pipelines for connection, realizes continuous production, and can directly obtain diacetone alcohol with a purity of not less than 99.9%. The utility model realizes the matching of separation temperature and reaction temperature by reducing pressure, which not only significantly improves the reaction conversion rate (>99.9%), but also achieves 100% reaction selectivity, avoids the generation of by-products and the decomposition of diacetone alcohol, reduces reaction energy consumption, and in addition, the product does not need to be subsequently separated, and the catalyst does not need to be separated and recovered.

[0041] Finally, it should be noted that the present invention is not limited to the above-mentioned best embodiment. Anyone can derive other various forms of vacuum continuous catalytic distillation process and catalytic distillation tower for synthesizing diacetone alcohol under the enlightenment of the present invention. Ordinary technicians in the relevant field should understand that modifications to the specific embodiments of the present invention or equivalent replacement of some technical features without departing from the spirit of the technical solution of the present invention should be included in the scope of the technical solution claimed for protection of the present invention.

Claims

1. A low-temperature and reduced-pressure continuous catalytic distillation tower for synthesizing diacetone alcohol, characterized in that: The invention comprises a catalytic distillation tower, a condenser and a built-in reboiler. The catalytic distillation tower comprises two parts, a reaction section and a stripping section. The feed inlet of the catalytic distillation tower is located between the reaction section and the stripping section. The external condenser is arranged at the top of the catalytic distillation tower. The inlet end of the condenser is connected to the top outlet of the catalytic distillation tower. The outlet end of the condenser is connected to the side inlet of the top of the catalytic distillation tower. The built-in reboiler is arranged at the bottom of the catalytic distillation tower. The bottom of the catalytic distillation tower is provided with a kettle outlet.

2. The low-temperature and reduced-pressure continuous catalytic distillation tower for synthesizing diacetone alcohol according to claim 1, characterized in that: The reaction section of the catalytic distillation tower is divided into three sections, each section is 4 to 6 m high, and the number of plates in the stripping section of the catalytic distillation tower is 3 to 5.

3. The low-temperature and reduced-pressure continuous catalytic distillation tower for synthesizing diacetone alcohol according to claim 2, characterized in that: The absolute operating pressure of the catalytic distillation tower is 12-15 kPa, the top temperature of the catalytic distillation tower is 0-10 °C, the bottom temperature is 100-110 °C, and the space velocity of the catalytic distillation tower is 0.45-0.64 h -1 .

4. The low-temperature and reduced-pressure continuous catalytic distillation tower for synthesizing diacetone alcohol according to claim 1, characterized in that: The catalyst in the catalytic filler installed in the reaction section is a hydroxide-type macroporous alkaline resin.

5. The low-temperature and reduced-pressure continuous catalytic distillation tower for synthesizing diacetone alcohol according to claim 4, characterized in that: The reaction section is divided into three sections, the first section is filled with 828 resin, and the second and third sections are filled with D296 resin.

6. The low-temperature and reduced-pressure continuous catalytic distillation tower for synthesizing diacetone alcohol according to claim 1, characterized in that: The condenser uses -15 to -20°C ethylene glycol aqueous solution as condensate.

7. The low-temperature and reduced-pressure continuous catalytic distillation tower for synthesizing diacetone alcohol according to claim 1, characterized in that: The built-in reboiler is arranged on the inner circumferential wall of the distillation tower body. The structure of the built-in reboiler is a closed cylindrical shell. The outer circumferential wall of the cylindrical shell is in contact with the inner circumferential wall of the distillation tower body. An air riser overflow pipe is arranged in the middle between the upper and lower surfaces of the shell. A plurality of tubes are arranged on the outer circumference of the air riser overflow pipe. A cavity is formed between the cylindrical shell and the air riser overflow pipe and the tubes. The cavity and the heat source outside the distillation tower body are subjected to cyclic heat exchange through pipelines.

8. The low-temperature and reduced-pressure continuous catalytic distillation tower for synthesizing diacetone alcohol according to claim 7, characterized in that: The built-in reboiler is placed 0.5 m below the distillation section, the tube size is φ38 mm, the tube length is 1~1.5 m, the cross-sectional area of ​​the gas riser overflow pipe is 1%~5% of the tower cross-sectional area, and the orifice of the gas riser overflow pipe is 3~8 cm higher than the orifices of other tubes.

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