A production system for preparing pyridine base from formaldehyde, acetaldehyde and ammonia

Abstract

The application discloses a production system for preparing pyridine base from formaldehyde, acetaldehyde and ammonia, and belongs to the technical field of pyridine base production. The production system comprises a reactor, a heat exchange system, a gas-liquid separation tank, an absorption tower, a booster fan, a deamination tower, an extraction tower, a solvent recovery tower, a pyridine tower, a methylpyridine tower, a dehydration tower and a purification system. The above system can be used for adjusting the feeding distribution proportion of acetaldehyde, controlling appropriate reaction conditions, reducing the coking rate of a catalyst, improving the yield of a product, and greatly reducing the energy consumption of the system by adjusting the operation conditions of the absorption tower and the ammonia circulation.

Description

Technical Field

[0001] This application relates to a production system for preparing pyridine bases from formaldehyde, acetaldehyde, and ammonia, belonging to the field of pyridine base production technology. Background Technology

[0002] Pyridine bases (pyridine, 3-methylpyridine, etc.) are key intermediates in the production of highly efficient and low-toxicity heterocyclic tricyclic pesticides, pharmaceuticals, and veterinary drugs. In particular, pyridine pesticides (such as paraquat and diquat) are highly efficient, low in toxicity, and have a long-lasting effect, with good compatibility with humans and other organisms, and are known as the fourth generation of new environmentally friendly pesticides worldwide. At the same time, pyridine bases are also key raw materials for daily chemical products, food flavorings, feed additives, radial tires, etc., and have an important impact on the development of many sectors of the national economy.

[0003] The main production methods for pyridine bases include the traditional coal tar separation method and the current catalytic synthesis method. The coal tar separation method has been gradually phased out due to its low yield, limited product variety, and high energy consumption. Catalytic synthesis has become the primary production method for pyridine bases. Currently, over 95% of pyridine bases are produced through catalytic synthesis using formaldehyde, acetaldehyde, and ammonia as raw materials. The products obtained after separation are pyridine and 3-methylpyridine.

[0004] Patent CN202310823532.4 discloses a new process for the combined production of formaldehyde, acetaldehyde, pyridine, and synthetic ammonia. First, methanol is oxidized and dehydrogenated using a formaldehyde unit; ethanol is oxidized and dehydrogenated using an acetaldehyde unit; then, hydrogen separated from the formaldehyde unit and non-condensable gas separated from the acetaldehyde unit are processed in a synthetic ammonia unit to obtain gaseous ammonia; finally, pyridine is produced by combining formaldehyde from the formaldehyde unit, acetaldehyde from the acetaldehyde unit, and gaseous ammonia from the synthetic ammonia unit. Patent CN201520341221.5 discloses a formaldehyde-pyridine co-production device, including a formaldehyde tank, a formaldehyde preheater, a gas-liquid separator, and a crude product tank. The top of the formaldehyde tank is connected to a formaldehyde conveying pipeline, and the lower part of the formaldehyde tank is connected to the bottom of the formaldehyde preheater via a pipeline. One outlet of the formaldehyde preheater is connected to one side of an ammonia vaporizer via a pipeline, and the other side of the ammonia vaporizer is connected to a crude product cooler via a pipeline. The outlet of the crude product cooler is connected to the upper part of the gas-liquid separator via a pipeline, and the bottom of the gas-liquid separator is connected to the crude product tank via a pipeline. Patent CN202111387435.2 discloses a pyridine base synthesis method, including the following steps: catalyst activation, reaction, cooling, and separation, ultimately separating the pyridine base product. Its characteristic is that, based on the use of ionic liquid-supported zeolite molecular sieves, a reactor with a regenerable catalyst is used to synthesize pyridine bases, thereby improving the yield of pyridine bases. However, the reaction temperature in the production of pyridine base is usually above 400℃. The formaldehyde and acetaldehyde disclosed in the above-mentioned prior art are prone to coking and clogging at the reactor inlet, and the yield of the target product is low. The organic content in the wastewater is too high and difficult to treat. At the same time, the energy consumption in the existing production process is high. Utility Model Content

[0005] To address the aforementioned technical problems, this application provides a production system for preparing pyridine bases from formaldehyde, acetaldehyde, and ammonia. Specifically, it relates to a production and separation system for the catalytic preparation of pyridine bases from aldehydes and ammonia, which uses a staged feed method in the reactor to control the coking rate and sets up an ammonia circulation system to achieve high atomic utilization and low energy consumption production of the target product.

[0006] The technical solution adopted in this application is as follows:

[0007] A production system for preparing pyridine base from formaldehyde, acetaldehyde, and ammonia, characterized in that it includes a reactor, a heat exchange system, a gas-liquid separator, an absorption tower, a booster fan, a deammoniation tower, an extraction tower, a solvent recovery tower, a pyridine tower, a methylpyridine tower, a dehydration tower, and a purification system;

[0008] The reactor is provided with an ammonia inlet at the bottom, and acetaldehyde gas inlet and formaldehyde gas inlet are respectively provided at the lower side of the reactor. The reactor is provided with a reactor outlet at the top. The reactor outlet is connected to the side inlet of the gas-liquid separator through a pipeline. A heat exchange system is provided on the pipeline between the reactor and the gas-liquid separator.

[0009] The upper gas phase outlet of the gas-liquid separator is connected to the lower side gas phase inlet of the absorption tower via a pipeline, and the lower liquid phase outlet of the gas-liquid separator is connected to the side liquid phase inlet of the ammonia removal tower via a pipeline.

[0010] The upper side of the absorption tower is provided with a demineralized water inlet, the top outlet of the absorption tower is connected to the inlet of the ammonia discharge pipe, the ammonia discharge pipe is provided with a branch pipe connected to the ammonia inlet of the reactor, the branch pipe is provided with a booster fan, and the bottom liquid phase outlet of the absorption tower is connected to the side liquid phase inlet of the deammoniation tower through a pipe.

[0011] The top outlet of the deammoniation tower is connected to the inlet of the ammonia circulation pipeline, the outlet of the ammonia circulation pipeline is connected to the branch pipeline, and the bottom outlet of the deammoniation tower is connected to the side inlet of the extraction tower.

[0012] The top outlet of the extraction tower is connected to the side inlet of the solvent recovery tower, and the bottom outlet of the extraction tower is connected to the middle side inlet of the dehydration tower.

[0013] The upper side outlet of the solvent recovery tower is connected to the lower side inlet of the extraction tower, and the bottom outlet of the solvent recovery tower is connected to the middle side of the pyridine tower.

[0014] The upper side of the pyridine tower is provided with a pyridine product outlet, and the bottom outlet of the pyridine tower is connected to the middle side of the methylpyridine tower.

[0015] The upper side of the dehydration tower is connected to the side liquid inlet of the deammoniation tower, and the bottom outlet of the dehydration tower is connected to the inlet of the water purification system. The water purification system is provided with a wastewater outlet and an outlet connected to the middle side pipeline of the methylpyridine tower.

[0016] The upper side of the methylpyridine tower is provided with a 3-methylpyridine product outlet, and the bottom of the methylpyridine tower is provided with a high-boiling-point outlet.

[0017] Optionally, the acetaldehyde gas inlet and formaldehyde gas inlet on the reactor are respectively connected to the outlets of the acetaldehyde supply pipeline and the formaldehyde supply pipeline.

[0018] Optionally, the acetaldehyde supply pipeline is provided with a branch pipeline that is unidirectionally connected to the formaldehyde gas phase pipeline.

[0019] Optionally, the demineralized water inlet on the absorption tower is connected to the outlet of the demineralized water pipeline.

[0020] Optionally, the purification system is selected from one of a membrane separation device, a resin adsorption device, and a molecular sieve dehydration device.

[0021] The production system for preparing pyridine base using formaldehyde, acetaldehyde, and ammonia as described in this application involves the following steps: the reaction raw materials, formaldehyde and acetaldehyde, are fed into the reactor along with circulating ammonia. After heat exchange and gas-liquid separation, the gas phase of the reaction product enters an absorption tower for water washing to absorb organic matter and discharge ammonia. The absorbent liquid and the liquid phase after gas-liquid separation are fed into a deammoniation tower to recover ammonia. The reaction product after deammoniation is then separated by staged distillation to finally obtain pyridine and 3-methylpyridine products.

[0022] The beneficial effects that this application can produce include:

[0023] The production system for preparing pyridine bases from formaldehyde, acetaldehyde, and ammonia provided in this application reduces the catalyst coking rate and increases the yield of the current products by adjusting the acetaldehyde feed ratio and controlling appropriate reaction conditions. Simultaneously, by adjusting the absorption tower operating conditions and ammonia circulation, the system energy consumption is significantly reduced, and the discharged wastewater has a low organic content and is easy to treat. Using this aldehyde-ammonia pyridine base production system, an acetaldehyde conversion rate of over 97.5% and pyridine and methylpyridine yields of over 75% can be achieved. Attached Figure Description

[0024] Figure 1 A schematic diagram of the equipment connection for the production system of formaldehyde, acetaldehyde and ammonia to prepare pyridine base for this application.

[0025] Figure 2 A schematic diagram of the equipment connections for a production system that prepares pyridine bases from conventional formaldehyde, acetaldehyde, and ammonia.

[0026] Attached Figure Labels

[0027] R01 - Reactor, V01 - Gas-liquid separator, T01 - Absorption tower, T02 - Deammoniation tower, T03 - Extraction tower, T04 - Solvent recovery tower, T05 - Pyridine tower, T06 - Methylpyridine tower, T07 - Dehydration tower, C01 - Booster fan. Detailed Implementation

[0028] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0029] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0030] Example 1

[0031] A schematic diagram of the equipment connection for a production system that prepares pyridine bases from formaldehyde, acetaldehyde, and ammonia is shown below. Figure 1 As shown, the system includes reactor R01, heat exchange system, gas-liquid separator V01, absorption tower T01, booster fan C01, deammoniation tower T02, extraction tower T03, solvent recovery tower T04, pyridine tower T05, methylpyridine tower T06T05, dehydration tower T07, and purification system.

[0032] Each feed pipe is connected to an inlet of reactor R01. The upper outlet of reactor R01 is connected to the inlet of the heat exchange system, and the outlet of the heat exchange system is connected to the inlet of gas-liquid separator V01. The gas phase outlet of gas-liquid separator V01 is connected to the lower inlet of absorber T01, and the liquid phase outlet is connected to the inlet of deammoniation tower T02. The upper liquid phase inlet of absorber T01 is connected to the demineralized water pipeline. The gas phase outlet of absorber T01 is split into two streams: one is connected to the inlet of booster fan C01, and the other is discharged as tail gas to the treatment system. The liquid phase outlet of absorber T01 is connected to the inlet of deammoniation tower T02. The booster fan outlet is connected to the ammonia pipeline at the bottom inlet of reactor R01. The top outlet of deammoniation tower T02 is connected to the outlet pipeline of booster fan C01. The bottom liquid outlet of deammoniation tower T02 is connected to the top inlet of extraction tower T03. The bottom inlet of extraction tower T03 is connected to the extractant pipeline, the top outlet of extraction tower T03 is connected to the inlet of solvent recovery tower T04, and the bottom outlet of extraction tower T03 is connected to the inlet of dehydration tower T07. The top outlet of solvent recovery tower T04 is connected to the bottom inlet of extraction tower T03, and the bottom liquid outlet of solvent recovery tower T04 is connected to the inlet of pyridine tower T05. Pyridine product is collected from the top of pyridine tower T05, and the bottom liquid outlet of pyridine tower T05 is connected to the inlet of methylpyridine tower T06. 3-methylpyridine product is collected from the top of methylpyridine tower T06, and high-boiling-point substances are collected from the bottom of the tower. The top outlet of dehydration tower T07 is connected to the inlet of deammoniation tower T02, and the bottom liquid outlet of dehydration tower T07 is connected to the purification system. The purification system outlet is divided into two paths: the organic phase outlet is connected to the inlet of methylpyridine tower T06, and the aqueous phase outlet collects low-COD wastewater.

[0033] The production system for preparing pyridine base using formaldehyde, acetaldehyde, and ammonia according to this invention involves vaporizing ammonia gas and circulating ammonia gas, which are then injected into reactor R01 from the bottom. Vaporized formaldehyde and acetaldehyde gas phases enter reactor R01 from the side wall. The acetaldehyde gas phase is divided into two streams: one enters reactor R01 from the bottom along with the formaldehyde gas, and the other enters from the lower middle section. Formaldehyde, acetaldehyde, and ammonia react in reactor R01. The reaction products are then cooled by a heat exchange system and enter a gas-liquid separator V01. After liquid-liquid separation, the gas phase enters the absorption tower T01, while the liquid phase flows into the ammonia removal tower T02. Demineralized water is introduced at the top of the absorption tower T01. By controlling the flow rate and top temperature, most of the organic matter and a small amount of ammonia in the feed vapor phase are absorbed. Ammonia and byproduct hydrogen are discharged from the top of the tower. Most of the top gas is pressurized by a booster fan and returned to the bottom inlet of reactor R01. The absorbent is sent to the ammonia removal tower T02. The ammonia removal tower T02 removes ammonia from the feed through distillation, and the ammonia discharged from the top is returned to the bottom inlet of reactor R01. The ammonia-free bottom liquid enters the top of extraction tower T03; the extractant enters extraction tower T03 from the bottom. Under the action of extraction, the pyridine base in the feed and the extractant are discharged together from the top of the tower and enter solvent recovery tower T04. Water and polar components in the feed are discharged from the bottom of the tower and enter dehydration tower T07; the low-boiling-point extractant in the feed of solvent recovery tower T04 is collected at the top of the tower and sent back to the bottom of extraction tower T03. The bottom liquid containing pyridine, 3-methylpyridine and heavy components flows into pyridine tower T05; after rectification separation in pyridine tower T05, the top of the tower yields... The pyridine product, 3-methylpyridine and high-boiling-point substances collected from the bottom of the column enter the methylpyridine column T06; after rectification separation in the methylpyridine column T06, 3-methylpyridine product is obtained from the top of the column, and the high-boiling-point substances by-product are collected from the bottom of the column; after rectification separation in the dehydration column T07, a small amount of extractant, pyridine and azeotropic entrained water are collected from the top of the column and sent to the deammoniation column T02, and the organic wastewater collected from the bottom of the column is sent to the purification system; in the purification system, the organic wastewater is physically separated, the organic matter is sent to the methylpyridine column T06, and the low COD wastewater is sent to the sewage treatment plant.

[0034] The reactor is a fluidized bed reactor with an operating temperature of 400–600℃, an operating pressure of 0.01–1.0 MPaG, a formaldehyde / acetaldehyde / ammonia molar ratio of 1:0.5–2:1.5–5, and a mass hourly space velocity of 0.2–0.5 h⁻¹.

[0035] The acetaldehyde gas phase in the reactor is divided into two streams and enters the reactor from the bottom and lower middle sections, with the mass ratio of the bottom and lower middle sections being 1 to 20.

[0036] The absorption tower operates at a pressure of 0–0.5 MPaG, with a top operating temperature of 10–40℃. The ratio of the demineralized water mass flow rate to the inlet vapor standard volume flow rate is 0.1–10 kg / Nm³. 3 .

[0037] The ratio of the gas phase discharged from the top of the absorption tower to the circulating ammonia is 0.01 to 0.5.

[0038] The extraction tower uses one of benzene, toluene, chloroform, or cyclohexane as the extractant, and the mass ratio of the extractant to the feed at the top of the tower is 0.3 to 2.

[0039] The above process description only considers the upstream and downstream connection relationship. The pumps and other conventional equipment such as condensers and reboilers in each tower, which are set up between equipment due to different pressures, are not described in detail.

[0040] use Figure 1 The production system for preparing pyridine base from formaldehyde, acetaldehyde, and ammonia using the equipment connection method described above can achieve an acetaldehyde conversion rate of over 97.5% and a pyridine and methylpyridine yield of over 75%.

[0041] Acetaldehyde conversion rate = (moles of acetaldehyde in feed - moles of acetaldehyde in product) / moles of acetaldehyde in feed × 100%

[0042] Pyridine and methylpyridine yield = (Total carbon atoms of pyridine and methylpyridine in the product) / (Total carbon atoms of the aldehyde in the feed) × 100%

[0043] Test Example 1

[0044] The production system for preparing pyridine bases using formaldehyde, acetaldehyde, and ammonia according to this invention is used. The catalyst is a co-crystallized zeolite catalyst developed by the Dalian Institute of Chemical Physics. The reactor is a fluidized bed reactor, operating at 450℃ and 0.1 MPaG, with a feed formaldehyde / acetaldehyde / ammonia molar ratio of 1:1:2 and a mass hourly space velocity (HHSV) of 0.3 h⁻¹. -1 The acetaldehyde feed mass ratio at the bottom and lower middle sections is 3; the absorption tower operates at atmospheric pressure with a top operating temperature of 20℃; the ratio of demineralized water mass flow rate to vapor standard volume flow rate is 0.5 kg / Nm³. 3 The ratio of the gas phase discharged from the top of the absorption tower to the circulating ammonia is 0.2; the extractant used in the extraction tower is benzene, and the mass ratio of the extractant to the feed at the top of the tower is 0.8; the purification system uses a membrane separation device.

[0045] According to calculations, the acetaldehyde conversion rate in this embodiment is 98.2%, and the yields of pyridine and methylpyridine are 75.5%.

[0046] Comparative Test Case 1

[0047] Pyridine bases were prepared using a conventional production system. The catalyst used was a co-crystallized zeolite catalyst developed by the Dalian Institute of Chemical Physics. The reactor was a fixed-bed reactor. Figure 2 The equipment connection method shown is such that the wastewater discharged from the bottom of the extraction tower is directly sent to the incineration system.

[0048] Calculations show that the acetaldehyde conversion rate in this comparative example is 97.8%, and the yields of pyridine and methylpyridine are 72.5%.

[0049] By comparing Test Example 1 and Comparative Test Example 1, it can be seen that the production system of this invention significantly improves the yield of pyridine and methylpyridine.

[0050] Test Example 2

[0051] The production system for preparing pyridine bases using formaldehyde, acetaldehyde, and ammonia according to this invention is used. The catalyst is a co-crystallized zeolite catalyst developed by the Dalian Institute of Chemical Physics. The reactor is a fluidized bed reactor, operating at 450℃ and 0.1 MPaG, with a feed formaldehyde / acetaldehyde / ammonia molar ratio of 1:1.2:2 and a mass hourly space velocity (WHSV) of 0.3 h⁻¹. -1 The mass ratio of acetaldehyde feed at the bottom and lower middle sections is 2; the absorption tower operates at atmospheric pressure, with an operating temperature of 20℃ at the top; the ratio of demineralized water mass flow rate to vapor standard volume flow rate is 0.8 kg / Nm³. 3 The ratio of the exhaust gas at the top of the absorption tower to the circulating ammonia is 0.1; the extractant used in the extraction tower is cyclohexane, and the mass ratio of the extractant to the feed at the top of the tower is 0.8; the purification system uses a resin adsorption device.

[0052] According to calculations, the acetaldehyde conversion rate in this embodiment is 97.5%, and the yields of pyridine and methylpyridine are 77.9%.

[0053] Test Example 3

[0054] The production system for preparing pyridine bases using formaldehyde, acetaldehyde, and ammonia according to this invention is used. The catalyst is a co-crystallized zeolite catalyst developed by the Dalian Institute of Chemical Physics. The reactor is a fluidized bed reactor, operating at 450℃ and 0.05 MPaG, with a feed formaldehyde / acetaldehyde / ammonia molar ratio of 1:1:3 and a mass hourly space velocity (HHSV) of 0.3 h⁻¹. -1 The acetaldehyde feed mass ratio at the bottom and lower middle sections is 4; the absorption tower operates at atmospheric pressure with a top operating temperature of 25℃; the ratio of demineralized water mass flow rate to vapor standard volume flow rate is 0.7 kg / Nm³. 3 The ratio of the gas phase discharged from the top of the absorption tower to the circulating ammonia is 0.3; the extractant used in the extraction tower is benzene, and the mass ratio of the extractant to the feed at the top of the tower is 1; the purification system uses a resin adsorption device.

[0055] According to calculations, the acetaldehyde conversion rate in this embodiment is 98.5%, and the yields of pyridine and methylpyridine are 75.7%.

[0056] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A production system for preparing pyridine bases from formaldehyde, acetaldehyde, and ammonia, characterized in that, Includes reactors, heat exchange systems, gas-liquid separators, absorption towers, booster fans, ammonia removal towers, extraction towers, solvent recovery towers, pyridine towers, methylpyridine towers, dehydration towers, and purification systems; The reactor is provided with an ammonia inlet at the bottom, and acetaldehyde gas inlet and formaldehyde gas inlet are respectively provided at the lower side of the reactor. The reactor is provided with a reactor outlet at the top. The reactor outlet is connected to the side inlet of the gas-liquid separator through a pipeline. A heat exchange system is provided on the pipeline between the reactor and the gas-liquid separator. The upper gas phase outlet of the gas-liquid separator is connected to the lower side gas phase inlet of the absorption tower via a pipeline, and the lower liquid phase outlet of the gas-liquid separator is connected to the side liquid phase inlet of the ammonia removal tower via a pipeline. The upper side of the absorption tower is provided with a demineralized water inlet, the top outlet of the absorption tower is connected to the inlet of the ammonia discharge pipe, the ammonia discharge pipe is provided with a branch pipe connected to the ammonia inlet of the reactor, the branch pipe is provided with a booster fan, and the bottom liquid phase outlet of the absorption tower is connected to the side liquid phase inlet of the deammoniation tower through a pipe. The top outlet of the deammoniation tower is connected to the inlet of the ammonia circulation pipeline, the outlet of the ammonia circulation pipeline is connected to the branch pipeline, and the bottom outlet of the deammoniation tower is connected to the side inlet of the extraction tower. The top outlet of the extraction tower is connected to the side inlet of the solvent recovery tower, and the bottom outlet of the extraction tower is connected to the middle side inlet of the dehydration tower. The upper side outlet of the solvent recovery tower is connected to the lower side inlet of the extraction tower, and the bottom outlet of the solvent recovery tower is connected to the middle side of the pyridine tower. The upper side of the pyridine tower is provided with a pyridine product outlet, and the bottom outlet of the pyridine tower is connected to the middle side of the methylpyridine tower. The upper side of the dehydration tower is connected to the side liquid inlet of the deammoniation tower, and the bottom outlet of the dehydration tower is connected to the inlet of the water purification system. The water purification system is provided with a wastewater outlet and an outlet connected to the middle side pipeline of the methylpyridine tower. The upper side of the methylpyridine tower is provided with a 3-methylpyridine product outlet, and the bottom of the methylpyridine tower is provided with a high-boiling-point outlet.

2. The production system according to claim 1, characterized in that, The acetaldehyde gas phase inlet and formaldehyde gas phase inlet on the reactor are respectively connected to the outlets of the acetaldehyde supply pipeline and the formaldehyde supply pipeline.

3. The production system according to claim 2, characterized in that, The acetaldehyde supply pipeline is equipped with a branch pipeline that is unidirectionally connected to the formaldehyde gas phase pipeline.

4. The production system according to claim 1, characterized in that, The demineralized water inlet on the absorption tower is connected to the outlet of the demineralized water pipeline.

5. The production system according to claim 1, characterized in that, The purification system is selected from one of the following: membrane separation device, resin adsorption device, and molecular sieve dehydration device.

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