Nitrobenzene continuous isothermal nitration reaction system based on dilute nitric acid

Abstract

The utility model discloses a nitrobenzene continuous isothermal nitration reaction system based on dilute nitric acid, which comprises a first circulation nitrator, a second circulation nitrator, a first nitration kettle, a second nitration kettle and a third nitration kettle which are connected in sequence, and is characterized in that an acidic benzene outlet pipeline of an acidic benzene storage tank is connected with an acid benzene mixer through a pump; a waste acid outlet pipeline of the waste acid head tank is connected with a circulating acid cooler, a cooling acid outlet pipeline of the circulating acid cooler is divided into two branch pipes, one branch pipe is connected with an acid-benzene mixer, and an outlet pipeline of the acid-benzene mixer is connected with an acid-benzene inlet pipeline of the first circulation nitrator. Low-temperature nitration is carried out firstly, then the nitration temperature is gradually increased, generation of by-products dinitrobenzene and nitrophenol is reduced, and continuous automatic production can be achieved.

Description

TECHNICAL FIELD

[0001] The utility model relates to a chemical industry technical field, concretely is a nitrobenzene continuous isothermal nitration reaction system based on dilute nitric acid. BACKGROUND

[0002] Nitrobenzene is important organic intermediate, rubber accelerator, polyurethane foam plastic, perfume and important raw material of industry, is mainly used in the production of aniline, also can be used as the raw material of making explosive. In addition, nitrobenzene is often used as solvent.

[0003] Nitrobenzene is prepared through benzene nitration process, and the benzene nitration process is the nitration reaction of benzene and nitric acid in the presence of sulfuric acid as dehydrating agent. Nitration reaction is the reaction of generating water, when nitration is used only nitric acid, nitric acid will be diluted by the generated water, when nitric acid is diluted to a certain limit, the reaction will not proceed, and the generated water of nitration reaction is absorbed by sulfuric acid to ensure the full use of nitric acid.

[0004] The existing nitration reaction, such as the method and device for producing nitrobenzene disclosed by CN 105017024 B, adopts concentrated nitric acid for reaction, and the mass fraction of nitric acid is greater than 98%, which requires high nitric acid.

[0005] There are also some nitration reactions using nitric acid reaction in the nitration reactor, but the temperature is as high as 90-110 DEG C, and there are many side reactions, therefore, the applicant develops a continuous isothermal reaction method to reduce the generation of by-products dinitrobenzene and nitrophenol and ensure the conversion rate of benzene nitration reaction. CONTENT OF UTILITY MODEL

[0006] In view of the deficiency of prior art, the utility model provides a nitrobenzene continuous isothermal nitration reaction system based on dilute nitric acid, which first nitrates at low temperature, then gradually increases the nitration temperature, reduces the generation of by-products dinitrobenzene and nitrophenol, and can realize continuous automatic production.

[0007] In order to realize the above purpose, the utility model realizes through the following technical scheme: a nitrobenzene continuous isothermal nitration reaction system based on dilute nitric acid, which comprises first loop nitration device, second loop nitration device, first nitration kettle, second nitration kettle and third nitration kettle connected in sequence, characterized by: the acid benzene outlet pipeline of acid benzene storage tank is connected with acid benzene mixer through pump, the waste acid outlet pipeline of waste acid high tank is connected with circulating acid cooler, the cooling acid outlet pipeline of circulating acid cooler is divided into two branch pipes, one of which is connected with acid benzene mixer, and the outlet pipeline of acid benzene mixer is connected with the acid benzene inlet pipeline of first loop nitration device;

[0008] The dilute nitric acid outlet pipeline of the dilute nitric acid storage tank is connected to the inlet pipeline of the three-acid mixer through a dilute nitric acid pump, the sulfuric acid outlet pipeline of the sulfuric acid storage tank is connected to the inlet pipeline of the three-acid mixer through a sulfuric acid pump, another branch of the circulating acid cooler is connected to the inlet pipeline of the three-acid mixer, the outlet pipeline of the three-acid mixer is connected to the three-acid cooler, and the outlet pipeline of the three-acid cooler is connected to the three-acid inlet pipeline of the first loop nitration device.

[0009] The nitration liquid outlet of the third nitration kettle is connected to the inlet located in the middle of the nitration separator, the upper-layer acidic nitrobenzene outlet pipeline of the nitration separator is connected to the acidic nitrobenzene buffer tank, the lower-layer waste acid outlet pipeline of the nitration separator is connected to the waste acid cooler, the waste acid outlet of the waste acid cooler is connected to the waste acid buffer tank, and the waste acid buffer tank is connected to the waste acid head tank through a waste acid pump.

[0010] In the above scheme, the acidic benzene outlet pipeline is provided with a flowmeter, a flow-limiting orifice plate, an adjusting valve and a shut-off valve. The automatic metering addition of the acidic benzene can be realized, and the shut-off valve can be installed to be urgently cut off when an accident occurs.

[0011] In the above scheme, the dilute nitric acid outlet pipeline is provided with a flowmeter, a flow-limiting orifice plate, an adjusting valve and a shut-off valve. The concentration of the dilute nitric acid is 65%. The automatic metering addition of the dilute nitric acid can be realized, and the shut-off valve can be installed to be urgently cut off when an accident occurs.

[0012] In the above scheme, the sulfuric acid outlet pipeline of the sulfuric acid storage tank is provided with a flowmeter, a flow-limiting orifice plate, an adjusting valve and a shut-off valve. The automatic metering addition of the sulfuric acid can be realized, and the shut-off valve can be installed to be urgently cut off when an accident occurs. The sulfuric acid is 85% sulfuric acid.

[0013] The cooling acid outlet pipeline of the circulating acid cooler is provided with a flowmeter and an adjusting valve on the branch connected to the first loop nitration device, and is provided with a flowmeter, an adjusting valve and a shut-off valve on the other branch.

[0014] In the above scheme, the first loop nitration device, the second loop nitration device, the first nitration kettle, the second nitration kettle and the third nitration kettle are all provided with a nitrogen pipeline and a tail gas pipeline.

[0015] In the above scheme, the tail gas pipeline is connected with a tail gas treatment device, the tail gas treatment device comprises a water spray tower, an alkali spray tower and two-stage series resin adsorption columns connected in sequence, and the resin adsorption columns are filled with adsorption resin. The generated tail gas comprises organic tail gas (main components are N2, benzene, nitrobenzene, etc.) and acidic tail gas (main components are N2, NO, NO2, benzene, nitrobenzene, etc.). An air extractor is installed on the tail gas pipeline, and the acidic tail gas is sucked into the water spray tower and the alkali spray tower in sequence by the air extractor, and the acidic components are removed. The water spray tower and the alkali spray tower realize automatic water replenishment and water drainage according to the set time and liquid level, and the alkali spray tower realizes automatic alkali replenishment according to the set pH value. The water spray tower and the alkali spray tower are prior art. After the neutral tail gas is pretreated (water spraying + alkali spraying), the neutral tail gas is introduced into the resin adsorption column for further adsorption of organic matters. The waste gas outlet can meet the standard emission requirements. The resin adsorption column can be provided with a standby column, and one column is used and the other column is standby, so that the resin can be regenerated conveniently.

[0016] The acidic benzene from the acidic benzene storage tank is pumped by an acidic benzene pump, flows through a flowmeter, a flow limiting orifice plate, is adjusted in flow by an adjusting valve, and then continuously enters the acid benzene mixer through a shut-off valve. The waste acid flows out from the bottom of the waste acid high tank, is cooled by a circulating acid cooler, and then continuously enters the acid benzene mixer through a flowmeter and an adjusting valve after adjusting the flow, and then enters the first loop nitration reactor after being fully mixed.

[0017] The dilute nitric acid from the dilute nitric acid storage tank is pumped by a dilute nitric acid delivery pump, flows through a flowmeter, a flow limiting orifice plate, is adjusted in flow by an adjusting valve, and then continuously enters the three-acid mixer through a shut-off valve. The 85% sulfuric acid from the sulfuric acid storage tank is pumped by a sulfuric acid pump, flows through a flowmeter, a flow limiting orifice plate, is adjusted in flow by an adjusting valve, and then continuously enters the three-acid mixer through a shut-off valve. Another stream of waste acid cooled by a circulating acid cooler flows through a flowmeter, is adjusted in flow by an adjusting valve, and then continuously enters the three-acid mixer through a shut-off valve. The nitric acid, the sulfuric acid and the waste acid are mixed into nitrosulfur mixed acid in the three-acid mixer. The nitrosulfur mixed acid is cooled by a three-acid cooler and then enters the first loop nitration reactor. The structure of the three-acid cooler is prior art, and condensate water is used as the coolant.

[0018] The acidic benzene and the nitrosulfur mixed acid react in the first loop nitration reactor. The reaction temperature of the first loop nitration reactor is the same as that of the second loop nitration reactor, and a lower temperature is used for reaction. The reaction liquid of the first loop nitration reactor enters the second loop nitration reactor for continuous reaction. After the reaction is completed, the reaction liquid enters the first nitration kettle, the second nitration kettle and the third nitration kettle in sequence for continuous nitration reaction. The temperature of the first nitration kettle, the second nitration kettle and the third nitration kettle gradually increases. The reaction temperature of the third nitration kettle is controlled at about 75°C, and the nitration reaction is completed.

[0019] After the nitration reaction, the reaction mixture enters the middle part of the nitration separator. The acidic nitrobenzene and waste acid are separated in the nitration separator, and the upper layer is the acidic nitrobenzene, and the acidic nitrobenzene buffer tank. The lower layer of the nitration separator is waste acid, which is cooled by the waste acid cooler and then enters the waste acid buffer tank, and is transported by the nitration separation waste acid pump. Part of the waste acid is transported to the waste acid high tank for recycling, and part of the waste acid is transported to the extraction unit after adjusting the flow by the flow meter and the adjusting valve.

[0020] The benzene nitration process is a nitration reaction of benzene and nitric acid in the presence of sulfuric acid as a catalyst. The nitration process adopts a multi-stage series continuous nitration mode, that is, the first and second stage nitration reactors adopt a loop flow nitration reactor, and the third, fourth and fifth stages adopt a kettle type nitration reactor. The process adopts low temperature nitration first, and then gradually increases the nitration temperature, reduces the generation of by-products dinitrobenzene and nitrophenol, and ensures the conversion rate of benzene nitration reaction. At the same time, the utility model can realize automatic continuous production. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The process flow chart of the utility model.

[0022] Figure 2 The structure diagram of the loop flow nitration reactor. DETAILED DESCRIPTION

[0023] The utility model will be further described below in combination with the drawings and examples

[0024] Example 1: A nitrobenzene continuous isothermal nitration reaction system based on dilute nitric acid, comprising first loop flow nitration reactor 1, second loop flow nitration reactor 2, first nitration kettle 3, second nitration kettle 4 and third nitration kettle 5 connected in turn, first loop flow nitration reactor 1, second loop flow nitration reactor 2, first nitration kettle 3, second nitration kettle 4 and third nitration kettle 5 are prior art, and the structure will not be described here. The first nitration kettle 3, the second nitration kettle 4 and the third nitration kettle 5 are provided with stirring, and the outside is provided with a heating sandwich.

[0025] The acid benzene outlet pipeline of the acid benzene storage tank 6 is connected with the acid benzene mixer 8 through the pump 7, the waste acid outlet pipeline of the waste acid high tank 9 is connected with the circulating acid cooler 10, and the waste acid directly enters the circulating cooler 10 through the high position. The circulating cooler 10 is prior art. It comprises a shell layer and a tube layer, the tube layer passes through waste acid, and the shell layer passes through cooling water. The cooling acid outlet pipeline of the circulating acid cooler 10 is divided into two branches, one of which is connected with the acid benzene mixer 8, and the outlet pipeline of the acid benzene mixer 8 is connected with the acid benzene inlet pipeline of the first loop flow nitration reactor 1.

[0026] The dilute nitric acid outlet pipeline of the dilute nitric acid storage tank 11 is connected with the inlet pipeline of the three-acid mixer 13 through a dilute nitric acid pump 12, and the sulfuric acid outlet pipeline of the sulfuric acid storage tank 14 is connected with the inlet pipeline of the three-acid mixer 13 through a sulfuric acid pump 15, all the pumps of the utility model adopt acid corrosion resistant pumps. Another branch pipeline of the circulating acid cooler 10 is connected with the inlet pipeline of the three-acid mixer 13, the outlet pipeline of the three-acid mixer 13 is connected with a three-acid cooler 16, and the outlet pipeline of the three-acid cooler 16 is connected with the three-acid inlet pipeline of the first loop nitration device 1.

[0027] The outlet pipeline of the first loop nitration device 1 is connected with the second loop nitration device 2, the outlet pipeline of the second loop nitration device 2 is connected with the first nitration kettle 3, the outlet pipeline of the first nitration kettle 3 is connected with the second nitration kettle 4, and the outlet pipeline of the second nitration kettle 4 is connected with the third nitration kettle 5. The material transfer can be realized through the pressure of nitrogen or through the high liquid level difference.

[0028] The nitration liquid outlet of the third nitration kettle 5 is connected with the inlet in the middle part of the nitration separator 17, the upper layer acid nitrobenzene outlet pipeline of the nitration separator 17 is connected with the acid nitrobenzene buffer tank 18, the lower layer waste acid outlet pipeline of the nitration separator 18 is connected with the waste acid cooler 19, and the structure of the waste acid cooler 19 is the same as that of the three-acid cooler and the circulating cooler 10. The waste acid outlet of the waste acid cooler 19 is connected with the waste acid buffer tank 20, and the waste acid buffer tank 20 is connected with the waste acid high tank through a waste acid pump 21. Alternatively, the waste acid buffer tank 20 is connected with the subsequent extraction unit through the waste acid pump 21. The extraction unit does not belong to the scope of the utility model and is not described here. The acid benzene mixer and the three-acid mixer adopt the tubular mixer. The structure of the tubular mixer is the prior art and is not described here.

[0029] The acid benzene outlet pipeline is provided with a flowmeter a, a flow limiting orifice plate b, an adjusting valve c and a shut-off valve f. The flowmeter a, the flow limiting orifice plate b, the adjusting valve c and the shut-off valve f are all prior art and their structures are not described here. The dilute nitric acid outlet pipeline is also provided with a flowmeter a, a flow limiting orifice plate b, an adjusting valve c and a shut-off valve d. The sulfuric acid outlet pipeline of the sulfuric acid storage tank is provided with a flowmeter a, a flow limiting orifice plate b, an adjusting valve c and a shut-off valve d. The branch pipeline connected with the first loop nitration device of the cooling acid outlet pipeline of the circulating acid cooler is provided with a flowmeter a and an adjusting valve c. The other branch pipeline is provided with a flowmeter a, an adjusting valve c and a shut-off valve d.

[0030] The first loop flow nitration device, the second loop flow nitration device, the first nitration kettle, the second nitration kettle and the third nitration kettle are all provided with nitrogen pipelines e and tail gas pipelines f. The tail gas pipelines f are connected with tail gas treatment devices, and the tail gas treatment devices comprise water spray towers g, alkali spray towers h and two-stage series resin adsorption columns I connected in sequence, and the resin adsorption columns are filled with adsorption resins. The nitrogen pipelines e and the tail gas pipelines f are respectively provided with valves (not shown in the figure).

[0031] The water spray towers g and the alkali spray towers h are prior art, comprising tower bodies, waste gas inlets are arranged at the bottoms of the tower bodies, atomizing nozzles are arranged at the tops in the tower bodies, and water or alkali liquor is respectively sprayed downward, the alkali liquor can be sodium hydroxide aqueous solution, water or alkali liquor is respectively stored at the bottoms of the tower bodies and is pumped to the atomizing nozzles for spraying. Gases enter from the lower part and are in countercurrent contact with the spray. Purification of tail gas is realized.

[0032] The resin adsorption columns I are also prior art. The resin adsorption columns I are filled with adsorption resins. Waste gas in tail gas is adsorbed by the adsorption resins. When used, the resin adsorption columns I can be provided with standby resin adsorption columns I. After adsorption saturation, resin regeneration is carried out. The regeneration process is prior art, and will not be described here. At this time, standby adsorption columns are used.

[0033] Although the embodiments of the utility model have been shown and described, it can be understood by those skilled in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the utility model, and the scope of the utility model is defined by the appended claims and their equivalents.

Claims

1. A continuous isothermal nitration reaction system of nitrobenzene based on dilute nitric acid, comprising a first loop nitration device, a second loop nitration device, a first nitration kettle, a second nitration kettle and a third nitration kettle connected in sequence, characterized in that: The acid benzene outlet pipeline of the acid benzene storage tank is connected to the acid benzene mixer through a pump, the waste acid outlet pipeline of the waste acid high tank is connected to the circulating acid cooler, one branch of the cooling acid outlet pipeline of the circulating acid cooler is connected to the acid benzene mixer, and the outlet pipeline of the acid benzene mixer is connected to the acid benzene inlet pipeline of the first loop nitration device; The dilute nitric acid outlet pipeline of the dilute nitric acid storage tank is connected to the inlet pipeline of the three-acid mixer through a dilute nitric acid pump, the sulfuric acid outlet pipeline of the sulfuric acid storage tank is connected to the inlet pipeline of the three-acid mixer through a sulfuric acid pump, the other branch of the circulating acid cooler is connected to the inlet pipeline of the three-acid mixer, the outlet pipeline of the three-acid mixer is connected to the three-acid cooler, and the outlet pipeline of the three-acid cooler is connected to the three-acid inlet pipeline of the first loop nitration device; The nitration liquid outlet of the third nitration kettle is connected to the inlet in the middle part of the nitration separator, the upper-layer acid nitrobenzene outlet pipeline of the nitration separator is connected to the acid nitrobenzene buffer tank, the lower-layer waste acid outlet pipeline of the nitration separator is connected to the waste acid cooler, the waste acid outlet of the waste acid cooler is connected to the waste acid buffer tank, and the waste acid buffer tank is connected to the waste acid high tank through a waste acid pump.

2. The continuous isothermal nitration system of nitrobenzene based on dilute nitric acid according to claim 1, characterized in that: Flow meters, flow restriction orifice plates, regulating valves and shut-off valves are arranged on the acid benzene outlet pipeline.

3. The continuous isothermal nitration system based on dilute nitric acid for nitrobenzene according to claim 2, characterized in that: Flow meters, flow restriction orifice plates, regulating valves and shut-off valves are arranged on the dilute nitric acid outlet pipeline.

4. The continuous isothermal nitration system based on dilute nitric acid for nitrobenzene according to claim 3, characterized in that: Flow meters, flow restriction orifice plates, regulating valves and shut-off valves are arranged on the sulfuric acid outlet pipeline of the sulfuric acid storage tank.

5. The continuous isothermal nitration system based on dilute nitric acid of nitrobenzene according to any one of claims 1-4, characterized in that: Nitrogen pipelines and tail gas pipelines are arranged on the first loop nitration device, the second loop nitration device, the first nitration kettle, the second nitration kettle and the third nitration kettle.

6. The continuous isothermal nitration system based on dilute nitric acid for nitrobenzene according to claim 5, characterized in that: The tail gas pipeline is connected to a tail gas treatment device, the tail gas treatment device comprises a water spray tower, an alkali spray tower and two-stage series-connected resin adsorption columns which are sequentially connected, and the resin adsorption columns are filled with adsorption resins.

Images