A bubble column reactor, reaction system and method for producing methyl propionate

Abstract

The application discloses a bubble column reactor for preparing methyl propionate, a reaction system and a method. The reactor comprises a bubble column body, a gas distributor and a sieve plate. The application divides the inner cavity of the reactor into multiple spaces through multiple sieve plates, and performs CO segmented feeding on the reaction of synthesizing methyl propionate from a carbonyl group through multiple gas distributors, so that the partial pressure ratio of CO and ethylene in the reactor is reduced, the gas-liquid ratio is obviously reduced, and the reaction conversion rate is obviously improved.

Description

Technical Field

[0001] This invention relates to a reactor, a reaction system, and a method, and more particularly to a bubble column reactor, a reaction system, and a method for preparing methyl propionate. Background Technology

[0002] Methyl methacrylate (MMA) is an important chemical product, mainly used in the production of PMMA, surface coatings, and PVC additives. It is widely used in the automotive, construction, medical, electronics, textile printing and dyeing, coatings, adhesives, leather processing chemicals, and resin processing industries, making it an indispensable chemical raw material for national economic development. Globally, the industrial production processes for MMA primarily utilize the acetone cyanohydrin (ACH) process, the isobutylene process, and the ethylene process. The ethylene process mainly involves the reaction of ethylene, CO, and methanol with a homogeneous noble metal catalyst to produce methyl propionate. Methyl propionate then undergoes an aldol condensation reaction with formaldehyde to produce MMA. This process offers advantages such as mild reaction conditions, near 100% carbon atom utilization, low equipment corrosivity, and low production costs.

[0003] However, homogeneous noble metal catalysts are prone to deactivation in carbonyl synthesis reactions. Through continuous research, the applicant has found that the main reasons for their deactivation are as follows: (1) prolonged contact between the catalyst and high concentrations of methanol; (2) excessively high partial pressure ratio of CO and ethylene. Therefore, based on the reaction mechanism and numerous small-scale experiments, the applicant proposes the following suggestions for the industrialization conditions of the aforementioned carbonyl synthesis reaction: (1) keep the average methanol concentration in the reaction solution below 50% by mass; (2) control the partial pressure ratio of CO and ethylene in the reaction section to be 1:(7-15).

[0004] To ensure the recommended partial pressure ratio of CO to ethylene, an excess of ethylene gas is required during the carbonyl synthesis of methyl propionate. However, the applicant has found that, due to the reaction temperature of 75-120℃, the reaction pressure above 11 barA, and the fact that the reaction occurs only in the liquid phase, excessive gas flow will cause methanol vaporization, thereby reducing the liquid volume in the reactor, shortening the residence time, and resulting in insufficient reaction conversion. Therefore, how to reduce methanol vaporization in the reactor while maintaining a reasonable partial pressure ratio of CO to ethylene to ensure high conversion and catalyst lifetime is a key challenge in designing the methyl propionate reaction process.

[0005] Current technologies often require large reactor volumes and high energy consumption. Furthermore, to ensure a reasonable partial pressure ratio of CO to ethylene, the methanol conversion rate can only reach 70%, and the catalyst conversion number (TON, the cumulative amount of methyl propionate generated during the reaction in mol / the total amount of active metal added in mol) is low. A lower TON indicates faster catalyst deactivation, a shorter lifespan, and a greater need for continuous catalyst replenishment. Summary of the Invention

[0006] To address the above technical problems, one objective of this invention is to provide a bubble column reactor for preparing methyl propionate.

[0007] Another object of the present invention is to provide a reaction system for preparing methyl propionate.

[0008] Another object of the present invention is to provide a method for preparing methyl propionate.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] First, the present invention provides a bubble column reactor for preparing methyl propionate, comprising a bubble column body (1), a gas distributor, and a sieve plate;

[0011] The bubble tower body (1) is provided with multiple sieve plates from bottom to top. The multiple sieve plates are all horizontally installed on the inner wall of the bubble tower body. The sieve plates are provided with sieve holes. The sieve plates are spaced apart from each other. The multiple sieve plates divide the inner cavity of the bubble tower body into multiple cavities. The multiple cavities are connected through the sieve holes.

[0012] The bottom of the bubbling tower body (1) is provided with a liquid phase inlet (14), the top of the tower body is provided with a gas phase outlet (16), and the side of the tower top is provided with a liquid phase outlet (15). Multiple gas phase inlets are provided on the side wall of the bubbling tower body (1) from bottom to top. Multiple gas distributors are fixedly installed inside the bubbling tower body (1) from bottom to top. The multiple gas distributors are connected to multiple gas phase inlets respectively. The gas distributor is a tubular gas distributor with nozzles that open downwards.

[0013] Furthermore, the sieve plate has multiple sieve holes, preferably with the total opening rate of the sieve holes accounting for 1-7% of the sieve plate area; preferably, the diameter of the sieve holes is 3-5 mm;

[0014] Furthermore, the gas distributor has multiple nozzles, preferably 4-50. The number of nozzles on each gas distributor can be the same or different.

[0015] Furthermore, the sieve plate is divided into at least three layers; preferably, the sieve plate is divided into a first-stage sieve plate (6), a second-stage sieve plate (7), and a third-stage sieve plate (8) from bottom to top.

[0016] Furthermore, the gas distributor is divided into three stages, from bottom to top: a primary gas distributor (3), a secondary gas distributor (4), and a tertiary gas distributor (5).

[0017] Furthermore, the gas phase feed inlet is divided into three parts, which are gas phase feed inlet one (17), gas phase feed inlet two (18), and gas phase feed inlet three (19) from bottom to top.

[0018] Furthermore, the secondary gas distributor (4) and the primary sieve plate (6) are arranged adjacent to each other vertically, preferably with a spacing of 3-5 cm, and the nozzles on the secondary gas distributor (4) correspond one-to-one with the sieve holes on the primary sieve plate (6);

[0019] Furthermore, the tertiary gas distributor (5) and the secondary sieve plate (7) are arranged adjacent to each other, preferably with a spacing of 3-5 cm, and the nozzles on the tertiary gas distributor (5) correspond one-to-one with the sieve holes on the secondary sieve plate (7);

[0020] Furthermore, the primary gas distributor (3) is installed at the bottom of the bubbling tower body (1).

[0021] Furthermore, the first-stage sieve plate (6) is located at 1 / 5-1 / 3 of the tower height from the bottom, the second-stage sieve plate (7) is located at 2 / 5-1 / 2 of the tower height from the bottom, and the third-stage sieve plate (8) is located at 3 / 5-4 / 5 of the tower height from the bottom.

[0022] Furthermore, a temperature control system (2) is provided on the upper part of the bubble column body (1).

[0023] Secondly, the present invention also provides a bubble column reaction system for preparing methyl propionate, including a bubble column reactor, an external circulation heat exchanger (11), a gas-liquid separator (9), and a gas phase condenser (10) as described above.

[0024] The bubbling tower reactor is connected in sequence to the external circulation heat exchanger (11) and the external circulation pump (12) via pipelines. The other end of the external circulation pump (12) is connected to the liquid phase inlet (14) of the bubbling tower reactor via a pipeline. The pipeline connecting the external circulation pump (12) to the liquid phase inlet (14) of the bubbling tower reactor is connected to the methanol feed pipeline and the catalyst feed pipeline.

[0025] The liquid phase outlet (15) of the bubble column reactor is connected to the gas-liquid separator (9) through a pipeline. The lower end of the gas-liquid separator (9) is provided with a liquid phase outlet pipe, and the upper end is connected to the bubble column reactor through a pipeline.

[0026] The gas phase outlet (16) of the bubble column reactor is connected to the gas phase condenser (10) through a pipeline. One end of the gas phase condenser (10) is provided with a gas phase outlet pipe, and the other end is connected to the gas-liquid separator (9).

[0027] Furthermore, the inlet of the connecting pipeline between the bubble column reactor and the external circulation heat exchanger (11) is located in the lower middle part of the bubble column reactor;

[0028] Furthermore, a gas phase concentration detector (13) is installed on the gas phase discharge pipe.

[0029] Furthermore, the present invention also provides a continuous method for preparing methyl propionate, the method comprising the following steps:

[0030] After startup, methanol solution and added precious metal catalyst solution are continuously fed into the bubble column reactor from the liquid phase inlet (14). At the same time, gas phase containing CO and ethylene is fed into the bubble column reactor through the primary gas distributor (3) to carry out carbonylation reaction to synthesize methyl propionate. The partial pressure ratio of CO and ethylene in the feed gas phase is controlled to be 1:(4-7). At this time, CO and ethylene are consumed in equal proportion. The reaction section CO:ethylene = 1:(7-15), and the target conversion rate is 50-70%. CO is fed separately into the bubble column reactor through the secondary gas distributor (4). The feed amount satisfies the partial pressure ratio of CO to ethylene at the gas phase inlet 2 (18) as 1:(6-9), the target conversion rate is 75-85%, and the reaction section CO: ethylene = 1:(7-15); CO is fed separately to the bubble column reactor through the three-stage gas distributor (5), and the CO feed amount here satisfies the partial pressure ratio of CO to ethylene at the gas phase inlet 3 (19) as 1:(6-9), the target conversion rate is 95-98%, and the reaction section CO: ethylene = 1:(7-15); by controlling the target conversion rate of each stage of the reaction, the liquid phase residence time of each stage of the reaction is ensured to be 7-13h.

[0031] During the carbonylation reaction, the external circulation heat exchanger (11) and the external circulation pump (12) are turned on simultaneously, so that part of the reaction liquid is refluxed to the bubble column reactor through the liquid phase feed port (14) after heat exchange in the external circulation heat exchanger (11), forming an external circulation loop; the feed pipelines of methanol solution and precious metal catalyst solution are connected to the end pipeline of the external circulation loop before entering the liquid phase feed port (14).

[0032] Furthermore, during the carbonylation reaction, the feed flow ratio is gas phase:liquid phase = (3.5-7):1, where the gas phase is the total flow rate of CO and ethylene; and the liquid phase is the flow rate of methanol solution.

[0033] Furthermore, during the start-up phase, a precious metal catalyst solution is added to the reactor as a base before feeding; and during the carbonylation reaction, the precious metal catalyst solution is continuously added to ensure the reaction conversion rate.

[0034] Preferably, the noble metal catalyst solution is a methyl propionate solution of a noble metal catalyst;

[0035] Preferably, the total amount of the precious metal catalyst in the reaction system is 0.2 to 0.5 ppm of the methanol solution feed, based on the mass content of the precious metal.

[0036] Preferably, the noble metal catalyst is a homogeneous palladium catalyst, preferably one or more of palladium acetate, palladium neopentanoate, palladium trifluoroacetate, palladium diphenylphosphine ferrocene dichloride, palladium tetraphenylphosphine, and palladium dichlorodiphenylphosphine. The above catalyst selections are all conventional choices for the carbonyl synthesis reaction of ethylene, CO, and methanol to produce methyl propionate. Different catalyst selections do not adversely affect the smooth implementation of the present invention. That is, under the action of different catalysts, the expected technical effects can be obtained by combining the above-disclosed technical solutions of the present invention. Therefore, the following specific embodiments only select conventional palladium acetate catalysts to examine the technical effects of the invention, and will not be elaborated further here.

[0037] Furthermore, the pumping flow rate of the external circulation pump (12) is 100-200 times the feed rate of the methanol solution.

[0038] Furthermore, the reaction liquid obtained from the carbonylation reaction is collected from the top of the tower into a gas-liquid separator (9), and after gas-liquid separation, the liquid phase is discharged, while the separated gas phase is returned to the bubble column reactor.

[0039] Furthermore, the remaining gas phase after the carbonylation reaction is collected from the top of the bubble column into the gas phase condenser (10), and after condensation, it is discharged as a gas phase. At the same time, the condensed reaction liquid is returned to the gas-liquid separator (9).

[0040] Furthermore, the carbonylation reaction conditions are: reaction temperature 75-120℃, and reaction pressure 11-22 barA.

[0041] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0042] 1. Using a tower reactor instead of a stirred tank saves on equipment investment and energy consumption for the stirring motor.

[0043] 2. Through the gas-phase segmented feeding design, the CO concentration in the reactor is effectively controlled, and the partial pressure ratio of CO and ethylene in the reaction section is controlled within the recommended range, which can effectively ensure the activity of the catalyst and extend the service life of the precious metal catalyst.

[0044] 3. By employing a segmented gas-phase feed design, while ensuring a reasonable partial pressure ratio of CO and ethylene, the total consumption of CO and ethylene is significantly lower than that of existing technologies. This results in a significantly reduced gas-liquid ratio, less methanol vaporization, a 60% reduction in reactor volume, and an increase in reaction conversion rate from 70% to over 95%. Without increasing the cost of the reaction process, this design saves on investment in subsequent methanol separation processes and reduces the cost of the gas-phase recirculating compressor. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the structure of a bubble column reactor.

[0046] Figure 2 This is a top view of the sieve plate.

[0047] Figure 3 This is a schematic diagram of the overall structure of the reaction system provided by the present invention.

[0048] The components include: 1. Bubble tower body; 2. Temperature control system; 3. Primary gas distributor; 4. Secondary gas distributor; 5. Tertiary gas distributor; 6. Primary sieve plate; 7. Secondary sieve plate; 8. Tertiary sieve plate; 9. Gas-liquid separator; 10. Gas phase condenser; 11. External circulation heat exchanger; 12. External circulation pump; 13. Gas phase concentration detector; 14. Liquid phase inlet; 15. Liquid phase outlet; 16. Gas phase outlet; 17. Gas phase inlet one; 18. Gas phase inlet two; 19. Gas phase inlet three. Detailed Implementation

[0049] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0050]

Example 1

[0051] This embodiment provides a bubble column reactor for preparing methyl propionate, including a bubble column body, a gas distributor, and a sieve plate.

[0052] The diameter of the bubbling tower body is 0.8m, and the height of the cylinder body is 6m.

[0053] The bubble column is equipped with three layers of sieve plates arranged from bottom to top inside the column body. All three layers of sieve plates are horizontally installed on the inner wall of the bubble column body. The sieve plates are provided with sieve holes with a diameter of 3 mm. The total opening rate of the sieve holes accounts for 2% of the sieve plate area. The sieve plates are spaced apart from each other. The three layers of sieve plates divide the inner cavity of the bubble column body into four cavities, which are connected by the sieve holes.

[0054] Specifically, the sieve plates are divided into a primary sieve plate, a secondary sieve plate, and a tertiary sieve plate from bottom to top; the primary sieve plate is set at 1 / 4 of the height of the tower body from the bottom, the secondary sieve plate is set at 1 / 2 of the height of the tower body from the bottom, and the tertiary sieve plate is set at 3 / 4 of the height of the tower body from the bottom.

[0055] The bottom of the bubbling tower body has a liquid phase inlet, the top has a gas phase outlet, and the side of the top has a liquid phase outlet. Three gas phase inlets are arranged from bottom to top on the side wall of the bubbling tower body. A three-stage gas distributor is fixedly installed from bottom to top inside the bubbling tower body, and each gas distributor is connected to one of the three gas phase inlets. The gas distributor is a tubular gas distributor with downward-opening nozzles installed on it.

[0056] Specifically, the gas distributor is divided into a primary gas distributor, a secondary gas distributor, and a tertiary gas distributor from bottom to top; the gas phase inlet is divided into three, from bottom to top: gas phase inlet one, gas phase inlet two, and gas phase inlet three.

[0057] Each gas distributor has multiple nozzles, with the primary gas distributor having 32 nozzles and the secondary and tertiary gas distributors having 6 nozzles each. The secondary gas distributor is arranged adjacent to the primary sieve plate (spaced 4 cm apart), and the nozzles on the secondary gas distributor correspond one-to-one with the sieve holes on the primary sieve plate; the tertiary gas distributor is also arranged adjacent to the secondary sieve plate (spaced 4 cm apart), and the nozzles on the tertiary gas distributor correspond one-to-one with the sieve holes on the secondary sieve plate; the primary gas distributor is installed at the bottom of the bubble column.

[0058] Specifically, the upper part of the bubbling tower is equipped with a temperature control system for regulating the reaction temperature and the vaporization rate of the reactants.

[0059]

Example 2

[0060] This embodiment provides a reaction system for preparing methyl propionate, including the bubble column reactor, external circulation heat exchanger, gas-liquid separator, and gas phase condenser provided in Example 1;

[0061] The bubbling tower reactor is connected in sequence to an external circulation heat exchanger and an external circulation pump via pipelines. The other end of the external circulation pump is connected to the liquid inlet of the bubbling tower reactor via a pipeline. The pipeline connected to the liquid inlet of the bubbling tower reactor via the external circulation pump is connected to the methanol feed pipeline and the catalyst feed pipeline.

[0062] The liquid phase outlet of the bubble column reactor is connected to the gas-liquid separator via a pipeline. The lower end of the gas-liquid separator is equipped with a liquid phase outlet pipe, and the upper end is connected to the bubble column reactor via a pipeline.

[0063] The gas phase outlet of the bubble column reactor is connected to the gas phase condenser via a pipeline. One end of the gas phase condenser is equipped with a gas phase outlet pipe, and the other end is connected to the gas-liquid separator.

[0064] The inlet of the connecting pipeline between the bubble column reactor and the external circulation heat exchanger is located in the lower middle part of the bubble column reactor.

[0065] A gas phase concentration detector is installed on the gas phase discharge pipe.

[0066]

Example 3

[0067] This embodiment provides a continuous method for preparing methyl propionate. The method uses the reaction system provided in Example 2 for the continuous preparation of methyl propionate, and specifically includes the following steps:

[0068] 2700 kg of a palladium acetate methyl propionate solution (Pd metal concentration of 8 × 10⁻⁵ mol / L) was added to the bottom of the bubble column reactor for initial preparation, and then the reactor was started. A methanol solution at a flow rate of 25 kg / hr and a palladium acetate methyl propionate solution at a flow rate of 0.075 kg / hr (Pd metal concentration of 8 × 10⁻⁴ mol / L) were continuously fed into the bubble column reactor from the bottom liquid inlet. The reaction temperature inside the reactor was controlled at 80-85℃, and the reaction pressure at 11 barA. Simultaneously, a gas phase containing CO and ethylene was introduced into the bubble column reactor through a primary gas distributor at a flow rate of 20 kg / hr for CO and 100 kg / hr for ethylene. A carbonylation reaction was carried out in the reactor to synthesize methyl propionate; this stage is referred to as the first-stage reaction. After the first-stage reaction, CO and ethylene were consumed in equal proportions, and the partial pressure ratio of CO to ethylene in the reaction section became 1:12.6.

[0069] CO at a flow rate of 5 kg / hr is fed separately into the bubble column reactor through a secondary gas distributor. The CO feed rate here satisfies the partial pressure ratio of CO to ethylene at the second gas phase inlet as 1:7.3. The reaction that occurs at this point is called the second-stage reaction. After the second-stage reaction, the partial pressure ratio of CO to ethylene in the reaction section becomes 1:11, which is used to achieve the highest single-stage conversion rate.

[0070] CO at a flow rate of 5 kg / hr is fed separately into the bubble column reactor through a three-stage gas distributor. The CO feed rate here satisfies the partial pressure ratio of CO to ethylene at the three gas phase inlets as 1:6.6. The reaction that occurs at this point is called the third-stage reaction. After the third-stage reaction, the partial pressure ratio of CO to ethylene in the reaction section becomes 1:8.6, which is used to achieve the highest single-stage conversion rate.

[0071] During the carbonylation reaction, the external circulation heat exchanger and external circulation pump are turned on simultaneously, so that part of the reaction liquid containing methyl propionate, methanol and catalyst is heated in the external circulation heat exchanger and then returned to the bubble column reactor to form an external circulation loop; wherein, the pumping flow rate of the external circulation pump is 140 times the feed rate of the methanol solution; the feed lines of the aforementioned methanol solution and the added catalyst solution are connected to the end line of the external circulation loop before entering the reactor.

[0072] The reaction liquid obtained from the carbonylation reaction is collected from the top of the tower to a gas-liquid separator. After gas-liquid separation, the liquid phase is discharged, while the separated gas phase is returned to the bubble column reactor.

[0073] The remaining gas phase after the carbonylation reaction is collected from the top of the bubble column into a gas phase condenser. After condensation, the gas phase is discharged, while the condensed reaction liquid is returned to the gas-liquid separator.

[0074] The entire reaction process in this embodiment was calculated, and the ratio of raw materials used was: total methanol:CO:ethylene = 1:1.2:4, of which the ratio of gas phase to liquid phase was 5.2:1.

[0075] According to the scheme provided in this embodiment, methyl propionate is continuously prepared with a designed load of 60 tons / year. After one year, the methanol conversion rate stabilizes at over 95%. The total amount of catalyst added after startup is 0.056 kg. Based on the mass of metallic Pd, the calculated TON is 12 million.

[0076]

Example 4

[0077] This embodiment provides a bubble column reactor for preparing methyl propionate. Compared to the reactor in Example 1, the only difference is that the bubble column contains four layers of sieve plates arranged from bottom to top. These sieve plates are sequentially divided into a primary sieve plate, a secondary sieve plate, a tertiary sieve plate, and a quaternary sieve plate. The primary sieve plate is located at 1 / 3 of the column height from the bottom, the secondary sieve plate at 1 / 2 of the column height from the bottom, the tertiary sieve plate at 3 / 5 of the column height from the bottom, and the quaternary sieve plate at 4 / 5 of the column height from the bottom. Each sieve plate has sieve holes with a diameter of 4 mm, and the total open area of ​​the sieve holes accounts for 3% of the sieve plate area.

[0078]

Example 5

[0079] This embodiment provides a reaction system for preparing methyl propionate. The only difference between this system and the reaction system in Example 2 is that the bubble column reactor is the same as the bubble column reactor provided in Example 4.

[0080]

Example 6

[0081] This embodiment provides a continuous method for preparing methyl propionate. The method uses the reaction system provided in Example 5 for the continuous preparation of methyl propionate, and specifically includes the following steps:

[0082] A methyl propionate solution of palladium acetate (Pd metal concentration of 9 × 10⁻⁵ mol / L) was added to the bottom of the bubble column reactor for initial preparation, and then the reactor was started. A methanol solution with a flow rate of 9 t / hr and a methyl propionate solution of palladium acetate (Pd metal concentration of 9 × 10⁻⁴ mol / L) with a flow rate of 25 kg / hr were continuously fed into the bubble column reactor from the bottom liquid inlet. The reaction temperature in the reactor was controlled at 80-85℃ and the reaction pressure at 11 barA. Simultaneously, a gas phase containing CO and ethylene was introduced into the bubble column reactor through a primary gas distributor at a flow rate of 24 kg / hr for CO and 110 kg / hr for ethylene. The carbonylation reaction to synthesize methyl propionate took place in the reactor, which is referred to as the first stage reaction. After the first stage reaction, CO and ethylene were consumed in equal proportions, and the partial pressure ratio of CO to ethylene in the reaction section became 1:8.9.

[0083] CO at a flow rate of 3 kg / hr is fed separately into the bubble column reactor through a secondary gas distributor. The CO feed rate here satisfies the partial pressure ratio of CO to ethylene at the second gas phase inlet as 1:7.0. The reaction that occurs at this point is called the second-stage reaction. After the second-stage reaction, the partial pressure ratio of CO to ethylene in the reaction section becomes 1:9.7, which is used to achieve the highest single-stage conversion rate.

[0084] CO at a flow rate of 1 t / hr is fed separately into the bubble column reactor through a three-stage gas distributor. The CO feed rate here satisfies the partial pressure ratio of CO to ethylene at the three gas phase inlets as 1:7.4. The reaction that occurs at this point is called the third-stage reaction. After the third-stage reaction, the partial pressure ratio of CO to ethylene in the reaction section becomes 1:9.7, which is used to achieve the highest single-stage conversion rate.

[0085] During the carbonylation reaction, the external circulation heat exchanger and external circulation pump are turned on simultaneously, so that part of the reaction liquid containing methyl propionate, methanol and catalyst is heated in the external circulation heat exchanger and then returned to the bubble column reactor to form an external circulation loop; wherein, the pumping flow rate of the external circulation pump is 150 times the methanol solution feed rate; the feed lines of the aforementioned methanol solution and the added catalyst solution are respectively connected to the end line of the external circulation loop before entering the reactor.

[0086] The reaction liquid obtained from the carbonylation reaction is collected from the top of the tower to a gas-liquid separator. After gas-liquid separation, the liquid phase is discharged, while the separated gas phase is returned to the bubble column reactor.

[0087] The remaining gas phase after the carbonylation reaction is collected from the top of the bubble column into a gas phase condenser. After condensation, the gas phase is discharged, while the condensed reaction liquid is returned to the gas-liquid separator.

[0088] The entire reaction process in this embodiment was calculated, and the ratio of raw material usage was: total methanol:CO:ethylene = 1:1.2:4, of which the ratio of gas phase to liquid phase was 5.6:1.

[0089] According to the scheme provided in this embodiment, methyl propionate is continuously prepared with a designed load of 60 tons / year. After one year, the methanol conversion rate stabilizes at over 95%. The total amount of catalyst added after startup is 0.061 kg. Based on the mass of metal Pd, the calculated TON is 11 million.

[0090]

Example 7

[0091] Methyl propionate was prepared using essentially the same method as in Example 3, except that the methanol solution, the added catalyst solution, and the feed line of the external circulation loop in the reaction system were not combined, but were fed separately into the reactor.

[0092] According to the scheme provided in this embodiment, methyl propionate is continuously prepared with a designed load of 60 tons / year. After one year, the methanol conversion rate is 92%, and the cumulative catalyst replenishment is 0.075 kg. Based on the mass of metal Pd, the catalyst TON is 9 million.

[0093]

Example 8

[0094] Methyl propionate was prepared using essentially the same method as in Example 3, except that: CO was not fed in stages, and all CO and ethylene were fed into the bubble column reactor through a primary gas distributor, with flow rates of 30 kg / hr for CO and 120 kg / hr for ethylene.

[0095] In this embodiment, the partial pressure ratio of CO to ethylene in the reaction section is 1:7.12. Methyl propionate is continuously prepared according to the scheme provided in this embodiment, with a designed load of 60 tons / year. After one year, the methanol conversion rate is 70%, and the cumulative catalyst replenishment is 0.112 kg. Based on the mass of metallic Pd, the catalyst TON is 6 million.

[0096]

Example 9

[0097] Methyl propionate was prepared using essentially the same method as in Example 3, except that: CO was not fed in stages, and all CO and ethylene were fed into the bubble column reactor through a primary gas distributor, with flow rates of 30 kg / hr for CO and 160 kg / hr for ethylene.

[0098] In this embodiment, the partial pressure ratio of CO to ethylene in the reaction section is 1:8.7. Methyl propionate is continuously prepared according to the scheme provided in this embodiment, with a designed load of 60 tons / year. After one year, the methanol conversion rate is 60%, and the cumulative catalyst replenishment is 0.123 kg. Based on the mass of metallic Pd, the catalyst TON is 5.5 million.

[0099] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A reaction system for preparing methyl propionate, characterized in that, Includes a bubble column reactor, an external circulation heat exchanger (11), a gas-liquid separator (9), and a gas phase condenser (10). The bubble column reactor includes a bubble column body (1), a gas distributor, and a sieve plate; The bubble tower body (1) is provided with multiple sieve plates from bottom to top. The multiple sieve plates are all horizontally installed on the inner wall of the bubble tower body. The sieve plates are provided with sieve holes. The sieve plates are spaced apart from each other. The multiple sieve plates divide the inner cavity of the bubble tower body into multiple cavities. The multiple cavities are connected through the sieve holes. The bottom of the bubble column (1) is provided with a liquid phase inlet (14), the top of the column is provided with a gas phase outlet (16), and the side of the top of the column is provided with a liquid phase outlet (15). Multiple gas phase inlets are provided on the side wall of the bubble column (1) from bottom to top. Multiple gas distributors are fixedly installed inside the bubble column (1) from bottom to top. The multiple gas distributors are connected to multiple gas phase inlets respectively. The gas distributor is a tubular gas distributor with nozzles that open downwards. The bubbling tower reactor is connected in sequence to the external circulation heat exchanger (11) and the external circulation pump (12) via pipelines. The other end of the external circulation pump (12) is connected to the liquid phase inlet (14) of the bubbling tower reactor via a pipeline. The pipeline connecting the external circulation pump (12) to the liquid phase inlet (14) of the bubbling tower reactor is connected to the methanol feed pipeline and the catalyst feed pipeline. The liquid phase outlet (15) of the bubble column reactor is connected to the gas-liquid separator (9) through a pipeline. The lower end of the gas-liquid separator (9) is provided with a liquid phase outlet pipe, and the upper end is connected to the bubble column reactor through a pipeline. The gas phase outlet (16) of the bubble column reactor is connected to the gas phase condenser (10) through a pipeline. One end of the gas phase condenser (10) is provided with a gas phase outlet pipe, and the other end is connected to the gas-liquid separator (9).

2. The reaction system for preparing methyl propionate according to claim 1, characterized in that, The inlet of the connecting pipeline between the bubble column reactor and the external circulation heat exchanger (11) is located in the lower middle part of the bubble column reactor.

3. The reaction system for preparing methyl propionate according to claim 1, characterized in that, A gas phase concentration detector (13) is installed on the gas phase discharge pipe.

4. The reaction system for preparing methyl propionate according to claim 1, characterized in that, The sieve plate has multiple sieve holes.

5. The reaction system for preparing methyl propionate according to claim 4, characterized in that, The total opening ratio of the sieve holes on the sieve plate accounts for 1-7% of the sieve plate area.

6. The reaction system for preparing methyl propionate according to claim 4, characterized in that, The aperture of the sieve is 3-5 mm.

7. The reaction system for preparing methyl propionate according to claim 4, characterized in that, The gas distributor has multiple nozzles; the number of nozzles on each gas distributor may be the same or different.

8. The reaction system for preparing methyl propionate according to claim 7, characterized in that, The gas distributor has 4-50 nozzles.

9. The reaction system for preparing methyl propionate according to any one of claims 1-8, characterized in that, The sieve plate is divided into at least three layers, which are divided into a first-stage sieve plate (6), a second-stage sieve plate (7), and a third-stage sieve plate (8) from bottom to top; the gas distributor is divided into three stages, which are divided into a first-stage gas distributor (3), a second-stage gas distributor (4), and a third-stage gas distributor (5) from bottom to top.

10. The reaction system for preparing methyl propionate according to claim 9, characterized in that, The gas phase feed inlet is divided into three parts, which are gas phase feed inlet one (17), gas phase feed inlet two (18), and gas phase feed inlet three (19) from bottom to top.

11. The reaction system for preparing methyl propionate according to claim 9, characterized in that, The secondary gas distributor (4) is arranged adjacent to the primary sieve plate (6) on the upper and lower sides, and the nozzles on the secondary gas distributor (4) correspond one-to-one with the sieve holes on the primary sieve plate (6).

12. The reaction system for preparing methyl propionate according to claim 11, characterized in that, The secondary gas distributor (4) and the primary sieve plate (6) are arranged adjacent to each other vertically and spaced 3-5 cm apart.

13. The reaction system for preparing methyl propionate according to claim 9, characterized in that, The tertiary gas distributor (5) and the secondary sieve plate (7) are arranged adjacent to each other, and the nozzles on the tertiary gas distributor (5) correspond one-to-one with the sieve holes on the secondary sieve plate (7).

14. The reaction system for preparing methyl propionate according to claim 13, characterized in that, The tertiary gas distributor (5) and the secondary sieve plate (7) are arranged adjacent to each other vertically and spaced 3-5 cm apart.

15. The reaction system for preparing methyl propionate according to claim 9, characterized in that, The primary gas distributor (3) is installed at the bottom of the bubbling tower body (1).

16. The reaction system for preparing methyl propionate according to claim 9, characterized in that, The first-stage sieve plate (6) is located at 1 / 5 to 1 / 3 of the tower height from the bottom, the second-stage sieve plate (7) is located at 2 / 5 to 1 / 2 of the tower height from the bottom, and the third-stage sieve plate (8) is located at 3 / 5 to 4 / 5 of the tower height from the bottom.

17. The reaction system for preparing methyl propionate according to any one of claims 1-8, characterized in that, A temperature control system (2) is provided on the upper part of the bubble tower body (1).

18. A continuous method for preparing methyl propionate, characterized in that, The reaction system for preparing methyl propionate according to claim 10 includes the following steps: After startup, methanol solution and added precious metal catalyst solution are continuously fed into the bubble column reactor through the liquid phase inlet (14). At the same time, gas phase containing CO and ethylene is fed into the bubble column reactor through the primary gas distributor (3) to carry out carbonylation reaction to synthesize methyl propionate. The partial pressure ratio of CO to ethylene in the feed gas phase is controlled to be 1:(4-7). CO is fed separately into the bubble column reactor through the secondary gas distributor (4). The CO feed rate here meets the partial pressure ratio of CO to ethylene at the second gas phase inlet (18) of 1:(6-9). CO is fed separately into the bubble column reactor through the tertiary gas distributor (5). The CO feed rate here meets the partial pressure ratio of CO to ethylene at the third gas phase inlet (19) of 1:(6-9). During the carbonylation reaction, the external circulation heat exchanger (11) and the external circulation pump (12) are turned on simultaneously, so that part of the reaction liquid is refluxed to the bubble column reactor through the liquid phase feed port (14) after heat exchange in the external circulation heat exchanger (11), forming an external circulation loop; the feed pipelines of methanol solution and precious metal catalyst solution are connected to the end pipeline of the external circulation loop before entering the liquid phase feed port (14).

19. The continuous method according to claim 18, characterized in that, During the carbonylation reaction, the feed flow ratio is gas phase:liquid phase = (3.5-7):1, where the gas phase is the total flow rate of CO and ethylene; and the liquid phase is the flow rate of methanol solution.

20. The continuous method according to claim 19, characterized in that, During the start-up phase, a precious metal catalyst solution is added to the reactor as a base before feeding; and during the carbonylation reaction, the precious metal catalyst solution is continuously added to ensure the reaction conversion rate.

21. The continuous method according to claim 20, characterized in that, The noble metal catalyst solution is a methyl propionate solution of a noble metal catalyst.

22. The continuous method according to claim 19, characterized in that, The total amount of the precious metal catalyst in the reaction system is 0.2 to 0.5 ppm of the methanol solution feed, based on the mass content of the precious metal.

23. The continuous method according to claim 19, characterized in that, The noble metal catalyst is a homogeneous palladium catalyst.

24. The continuous method according to claim 23, characterized in that, The noble metal catalyst is one or more of palladium acetate, palladium neopentanoate, palladium trifluoroacetate, palladium diphenylphosphine ferrocene dichloride, palladium tetraphenylphosphine, and palladium dichlorodiphenylphosphine.

25. The continuous method according to claim 19, characterized in that, The pumping flow rate of the external circulation pump (12) is 100-200 times the feed rate of the methanol solution.

26. The continuous processing method according to any one of claims 18-25, characterized in that, The reaction liquid obtained from the carbonylation reaction is collected from the top of the tower into the gas-liquid separator (9). After gas-liquid separation, the liquid phase is discharged, while the separated gas phase is returned to the bubble column reactor.

27. The continuous method according to claim 26, characterized in that, The remaining gas phase after the carbonylation reaction is collected from the top of the bubble column into the gas phase condenser (10), and after condensation, it is discharged as gas phase. At the same time, the condensed reaction liquid is returned to the gas-liquid separator (9).

28. The continuous processing method according to claim 26, characterized in that, The carbonylation reaction conditions are: reaction temperature 75-120℃, reaction pressure 11-22 barA.

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