Method for continuously preparing pore-forming agent H by utilizing dynamic tubular reactor

Abstract

The invention discloses a method for continuously preparing a pore-forming agent H by using a dynamic tubular reactor, and relates to the technical field of preparation of pore-forming agents H. The method comprises the following steps: material preparation, equipment preparation, nitration reaction, parameter control and obtaining of a crude product; compared with a stirring reactor, the dynamic tubular reactor has remarkable advantages, the heat effect treatment capacity is improved, the mixing capacity is enhanced, and the operation window is larger, so that a safer, more efficient, more stable and more sustainable synthesis production process can be developed; the benefits brought in production are not limited to improvement of the process safety, but also implementation of a more efficient and lower-cost process, so that the downstream processing cost and the labor cost are reduced; when the pipe length of the dynamic tubular reactor is far greater than the pipe diameter and the material system is in a turbulent flow state, the equipment is close to ideal plug flow, the material flows forwards like a piston, different paddle forms are matched, interfacial tension is overcome by means of high turbulence, and small-scale macromixing is realized.

Description

Technical Field

[0001] The invention relates to the technical field of pore-forming agent H preparation, and in particular to a method for continuously preparing pore-forming agent H by using a dynamic tubular reactor. Background Art

[0002] N,N-Dinitrosopentamethylenetetramine (DNPT, pore-forming agent H) is widely used in rubber and other industries as a pore-forming agent with excellent performance. It has the advantages of high foaming efficiency, no discoloration and no pollution. It can be used as a pore-forming agent for adhesives or sealants. It is also a commonly used organic microporous pore-forming agent for the manufacture of sponge rubber and foam plastics.

[0003] At present, there are few reports on the synthesis method of pore forming agent H. The Shanxi Chemical Research Institute compiled "Plastic and Rubber Processing Aids". Chemical Industry Press, 1983., 5., P442-446., introduced a method for synthesizing pore forming agent H in a kettle, that is, using a mixed solution of "hexamethylenetetramine" (urotropine) and sodium nitrite, and using an acid (nitric acid, sulfuric acid, hydrochloric acid, acetic acid, etc.) to promote the reaction under cooling conditions to prepare pore forming agent H. The reaction time is 9-10 hours. When the sodium nitrite is excessive during the reaction, trinitrosotrimethylenetriamine will be generated as a by-product, and the final yield is 75-79% based on urotropine.

[0004] Patent (CN1085822A) provides a new method for preparing pore-forming agent H in order to avoid the occurrence of side reactions in the above method and solve the problem of low yield, specifically: firstly, formaldehyde is mixed with ammonia water, and then sodium nitrite, ammonium nitrate and citric acid are added for nitrosation, and the reaction yield is increased to 90%. However, in the specific operation process of this method, in order to avoid the temperature rise of the reactor and the decomposition of nitrite, the dripping speed of the formaldehyde solution must be controlled very slowly, and the operation time of each batch of reaction is 12 hours, which greatly reduces the production efficiency and makes the workshop capacity backward.

[0005] Through the above two methods, we know that in the process of synthesizing pore-forming agent H with urotropine, a molecule of byproduct formaldehyde will be generated, while the mixture of formaldehyde and ammonia water can also obtain pore-forming agent H under the action of nitrosating agent. Therefore, the reason for the low yield of the first method is not only that when the excess sodium nitrite is large, trinitrosotrimethyltriamine is generated as a byproduct by overnitration, but also that the atomic utilization rate is low in the synthesis process using urotropine. The second method can reduce the occurrence of side reactions by reducing the dripping speed of the formaldehyde aqueous solution. The reason is that due to the reduction of the dripping speed, the nitrosation reaction rate will decrease, the instantaneous heat release of the reaction will also decrease significantly (that is, the reaction heat release power is reduced), the temperature control effect of the reactor is better, and it is not easy to overheat, so the activation energy of the side reaction overnitration can be significantly reduced, and the occurrence of the overnitration side reaction can be suppressed. With the limited heat exchange area and large reaction volume of the reactor, it is not easy to quickly remove the heat of the nitration reaction; and the materials in the reactor are mixed under the stirring of the stirring paddle, which is a fully back-mixed state, which means that the reaction product pore-forming agent H and the raw material hexamethylenetetramine and the nitrosation agent sodium nitrite have the same collision opportunities, but the activation energy of the reaction of pore-forming agent H with sodium nitrite is lower than that of the reaction of hexamethylenetetramine with sodium nitrite. However, as time goes on, the product pore-forming agent H will also be partially converted into trinitrosotrimethyltriamine, a by-product of overnitration. Therefore, when the heat exchange efficiency of the reactor is poor, the temperature of the reaction system is increased, and the reaction time is too long, this side reaction will be more likely to occur.

[0006] Both of the above methods use a reactor as a nitration reactor. Since the nitration reaction is accompanied by intense heat release, it is difficult to control the temperature. If the reaction system overheats, the reaction process will be dangerous. If the large amount of heat released by the reaction cannot be conducted out in time, it may cause a reaction safety accident. In particular, the volume of the reactor is generally 3000L, and the material in the reactor is at least about 2000L. If the reaction gets out of control, the energy released by the 2000L nitrification material will be huge, and the resulting safety consequences will be catastrophic. Summary of the invention

[0007] In order to solve the above technical problems, the present invention discloses a method for continuously preparing a pore-forming agent H by using a dynamic tubular reactor, comprising the following steps:

[0008] S1-Material preparation: add urotropine, sodium nitrite, water and ammonia water into the raw material tank in proportion, start the raw material tank to stir, premix the materials into urotropine solution, and pre-cool to -5°C; then add appropriate amount of water into the dilution tank, start the stirring and heat exchange of the dilution tank, slowly drop appropriate amount of acid solution to prepare dilute acid for standby use, and pre-cool to 0°C;

[0009] S2-Equipment preparation: Connect the heat exchanger inlet and outlet of the heat exchanger to the dynamic tubular reactor in advance, set the temperature of the heat exchanger to -10°C, and then connect the metering pump to the slurry feed port of the dynamic tubular reactor, the metering pump to the liquid feed port of the dynamic tubular reactor, and the discharge pipe of the dynamic tubular reactor to the material receiving tank; the material receiving tank is connected to the centrifuge, and the centrifuge is connected to the mother liquor collection tank;

[0010] S3-nitration reaction: The urotropine solution is delivered to the dynamic tubular reactor by a metering pump at a rate of 2000-6000 kg / H, and the dilute acid is delivered to the dynamic tubular reactor by a metering pump at a rate of 1800 kg / H for nitrosation reaction;

[0011] S4-Parameter control: control the reaction temperature in the dynamic tubular reactor to -5-5°C, the residence time to 1-5min, the rotation speed of the dynamic tubular reactor to 100-300r / min, and the pressure in the reaction chamber to normal pressure;

[0012] S5-Obtaining crude product: After the reaction is completed in the dynamic tubular reactor, the reaction liquid flows into the material receiving tank through the discharge pipe. At this time, a large amount of light yellow solid is generated. The solid-liquid mixture in the material receiving tank enters the centrifuge. After centrifugation, the obtained solid is the crude product of the pore-forming agent H, and the centrifuged mother liquor enters the mother liquor collection tank.

[0013] Preferably, in step S1, the mass ratio of hexamethylenetetramine to nitrous acid is 1:1-1:3.

[0014] Preferably, in step S1, the mass ratio of hexamethylenetetramine to water is 1:4-1:12.

[0015] Preferably, in step S1, the mass ratio of hexamethylenetetramine to aqueous ammonia is 1:0.5-1:1.5.

[0016] Preferably, in step S1, the mass ratio of hexamethylenetetramine to acid solution is 1:1-1:5.

[0017] Preferably, the acid solution in step S1 is one of sulfuric acid, hydrochloric acid, acetic acid or citric acid.

[0018] Preferably, the concentration of the diluted acid prepared in step S1 is 10-50%.

[0019] Preferably, the concentration of aqueous ammonia in step S1 is 15-22%.

[0020] Preferably, the liquid holding capacity of the dynamic tubular reactor in step S4 is 100-300L.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) Dynamic tubular reactors have significant advantages over stirred reactors, including improved handling of thermal effects, enhanced mixing capabilities, and a larger operating window, enabling the development of safer, more efficient, robust, and sustainable synthetic production processes.

[0023] (2) The benefits brought in production are not limited to improving process safety, but also include achieving more efficient and lower-cost processes, thereby reducing downstream processing costs and labor costs.

[0024] (3) When the length of the dynamic tubular reactor is much larger than the diameter and the material system is in a turbulent state, the equipment is close to an ideal plug flow, and the material flows forward like a piston. With different blade forms, the high turbulence overcomes the interfacial tension and achieves small-scale macroscopic mixing.

[0025] (4) Under continuous steady-state operation, radial parameters (concentration, temperature, etc.) only change with the direction of material flow and do not change with time.

[0026] (5) The radial direction has a uniform flow velocity, and concentration distribution exists only in the radial direction. The reaction rate only changes in the axial direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 It is the structure and process flow chart of the present invention.

[0029] Reference numerals:

[0030] 1-raw material tank, 2-dilution tank, 3-hot and cold integrated machine, 4-dynamic tubular reactor, 5-metering pump, 6-material receiving tank, 7-centrifuge, 8-mother liquor collection tank. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0032] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0033] In the description of the embodiments, unless otherwise clearly specified and limited, the terms "disposed", "connected" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or it can be connected through an intermediate medium, or it can be a communication between the two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] Embodiment 1:

[0035] like Figure 1 As shown, the method for continuously preparing the pore-forming agent H using a dynamic tubular reactor in this embodiment includes the following steps:

[0036] S1-Material preparation: add urotropine, sodium nitrite, water and ammonia water into raw material tank 1 in proportion, turn on the stirring mechanism in raw material tank 1 to stir the materials, premix the materials into urotropine solution, and pre-cool to -5°C; then add appropriate amount of water into dilution tank 2, turn on the stirring and heat exchange of dilution tank 2, slowly drop appropriate amount of acid solution to prepare dilute acid for standby use, and pre-cool to 0°C.

[0037] Among them, the mass ratio of urotropine and nitrous acid is 1:1, the mass ratio of urotropine and water is 1:4, the mass ratio of urotropine and ammonia water is 1:0.5, the mass ratio of urotropine and acid is 1:1, the acid is one of sulfuric acid, hydrochloric acid, acetic acid or citric acid, the concentration of the diluted acid is 10%, and the concentration of ammonia water is 15%.

[0038] S2-Equipment preparation: connect the heat exchange inlet and outlet of the cold and hot integrated machine 3 to the dynamic tubular reactor 4 in advance, set the temperature of the cold and hot integrated machine 3 to -10°C, and then connect the metering pump 5 to the slurry feed port of the dynamic tubular reactor 4, the metering pump 5 to the liquid feed port of the dynamic tubular reactor 4, and the discharge pipe of the dynamic tubular reactor 4 to the material receiving tank 6; the material receiving tank 6 is connected to the centrifuge 7, and the centrifuge 7 is connected to the mother liquor collection tank 8.

[0039] The raw material tank 1, dilution tank 2, material receiving tank 6 and mother liquid collecting tank 8 are made of carbon steel, and the tank volume is 5000L; the reaction chamber of the dynamic tubular reactor 4 is made of Hastelloy; the centrifuge 7 is made of stainless steel, and the volume is 316L.

[0040] S3-nitration reaction: The urotropine solution is delivered to the dynamic tubular reactor 4 via the metering pump 5 at a metering rate of 2000 kg / H, and the dilute acid is delivered to the dynamic tubular reactor 4 via the metering pump 5 at a metering rate of 1800 kg / H for nitrosation reaction.

[0041] S4- parameter control: control the reaction temperature in the dynamic tubular reactor 4 to -5°C, the residence time to 1min, control the rotation speed of the dynamic tubular reactor 4 to 100r / min, and the pressure in the reaction chamber to normal pressure; wherein, the liquid holding capacity of the dynamic tubular reactor 4 is 100L.

[0042] S5-Obtaining crude product: After the reaction is completed in the dynamic tubular reactor 4, the reaction liquid flows into the material receiving tank 6 through the discharge pipe. At this time, a large amount of light yellow solid is generated. The solid-liquid mixture in the material receiving tank 6 enters the centrifuge 7. After centrifugation in the centrifuge 7, the obtained solid is the crude product of the pore-forming agent H, and the centrifuged mother liquor enters the mother liquor collection tank 8.

[0043] Embodiment 2:

[0044] like Figure 1 As shown, the method for continuously preparing the pore-forming agent H using a dynamic tubular reactor in this embodiment includes the following steps:

[0045] S1-Material preparation: add urotropine, sodium nitrite, water and ammonia water into raw material tank 1 in proportion, turn on the stirring mechanism in raw material tank 1 to stir the materials, premix the materials into urotropine solution, and pre-cool to -5°C; then add appropriate amount of water into dilution tank 2, turn on the stirring and heat exchange of dilution tank 2, slowly drop appropriate amount of acid solution to prepare dilute acid for standby use, and pre-cool to 0°C;

[0046] Among them, the mass ratio of urotropine and nitrous acid is 1:2, the mass ratio of urotropine and water is 1:7, the mass ratio of urotropine and ammonia water is 1:1, the mass ratio of urotropine and acid is 1:3, the acid is one of sulfuric acid, hydrochloric acid, acetic acid or citric acid, the concentration of the diluted acid is 30%, and the concentration of ammonia water is 18%.

[0047] S2-Equipment preparation: connect the heat exchange inlet and outlet of the cold and hot integrated machine 3 to the dynamic tubular reactor 4 in advance, set the temperature of the cold and hot integrated machine 3 to -10°C, and then connect the metering pump 5 to the slurry feed port of the dynamic tubular reactor 4, the metering pump 5 to the liquid feed port of the dynamic tubular reactor 4, and the discharge pipe of the dynamic tubular reactor 4 to the material receiving tank 6; the material receiving tank 6 is connected to the centrifuge 7, and the centrifuge 7 is connected to the mother liquor collection tank 8.

[0048] S3-nitration reaction: The urotropine solution is delivered to the dynamic tubular reactor 4 via the metering pump 5 at a metering rate of 4000 kg / H, and the dilute acid is delivered to the dynamic tubular reactor 4 via the metering pump 5 at a metering rate of 1800 kg / H for nitrosation reaction.

[0049] S4- parameter control: control the reaction temperature in the dynamic tubular reactor 4 to 0°C, the residence time to 3min, the rotation speed of the dynamic tubular reactor 4 to 200r / min, and the pressure in the reaction chamber to normal pressure; wherein, the liquid holding capacity of the dynamic tubular reactor 4 is 200L.

[0050] S5-Obtaining crude product: After the reaction is completed in the dynamic tubular reactor 4, the reaction liquid flows into the material receiving tank 6 through the discharge pipe. At this time, a large amount of light yellow solid is generated. The solid-liquid mixture in the material receiving tank 6 enters the centrifuge 7. After centrifugation in the centrifuge 7, the obtained solid is the crude product of the pore-forming agent H, and the centrifuged mother liquor enters the mother liquor collection tank 8.

[0051] Embodiment three:

[0052] like Figure 1 As shown, the method for continuously preparing the pore-forming agent H using a dynamic tubular reactor in this embodiment includes the following steps:

[0053] S1-Material preparation: add urotropine, sodium nitrite, water and ammonia water into raw material tank 1 in proportion, turn on the stirring mechanism in raw material tank 1 to stir the materials, premix the materials into urotropine solution, and pre-cool to -5°C; then add appropriate amount of water into dilution tank 2, turn on the stirring and heat exchange of dilution tank 2, slowly drop appropriate amount of acid solution to prepare dilute acid for standby use, and pre-cool to 0°C;

[0054] Among them, the mass ratio of urotropine and nitrous acid is 1:3, the mass ratio of urotropine and water is 1:12, the mass ratio of urotropine and ammonia water is 1:1.5, the mass ratio of urotropine and acid is 1:5, the acid is one of sulfuric acid, hydrochloric acid, acetic acid or citric acid, the concentration of the diluted acid is 50%, and the concentration of ammonia water is 22%.

[0055] S2-Equipment preparation: connect the heat exchange inlet and outlet of the cold and hot integrated machine 3 to the dynamic tubular reactor 4 in advance, set the temperature of the cold and hot integrated machine 3 to -10°C, and then connect the metering pump 5 to the slurry feed port of the dynamic tubular reactor 4, the metering pump 5 to the liquid feed port of the dynamic tubular reactor 4, and the discharge pipe of the dynamic tubular reactor 4 to the material receiving tank 6; the material receiving tank 6 is connected to the centrifuge 7, and the centrifuge 7 is connected to the mother liquor collection tank 8.

[0056] S3-nitration reaction: The urotropine solution is delivered to the dynamic tubular reactor 4 via the metering pump 5 at a metering rate of 6000 kg / H, and the dilute acid is delivered to the dynamic tubular reactor 4 via the metering pump 5 at a metering rate of 1800 kg / H for nitrosation reaction.

[0057] S4- parameter control: control the reaction temperature in the dynamic tubular reactor 4 to 5°C, the residence time to 5min, the rotation speed of the dynamic tubular reactor 4 to 300r / min, and the pressure in the reaction chamber to normal pressure; wherein, the liquid holding capacity of the dynamic tubular reactor 4 is 300L.

[0058] S5-Obtaining crude product: After the reaction is completed in the dynamic tubular reactor 4, the reaction liquid flows into the material receiving tank 6 through the discharge pipe. At this time, a large amount of light yellow solid is generated. The solid-liquid mixture in the material receiving tank 6 enters the centrifuge 7. After centrifugation in the centrifuge 7, the obtained solid is the crude product of the pore-forming agent H, and the centrifuged mother liquor enters the mother liquor collection tank 8.

[0059] After the crude pore-forming agent H is prepared, the solid samples in the above three embodiments are taken and sent to the central control room for purity detection. The remaining products are dried and weighed to calculate the yield. After three batches of tests, the test results are shown in the following table. The purity of each batch of pore-forming agent H can reach more than 99%.

[0060] project First batch Second batch The third batch Hexamethylenetetramine input / kg 400 410 420 Theoretical output (pore forming agent H) / kg 531 544 558 Actual output (pore forming agent H) / kg 562 574 586 Purity of pore forming agent H / % 99.4 99.5 99.1 Yield / % 105.8 105.5 105

[0061] In summary, compared with the prior art, the present invention has the following beneficial effects:

[0062] (1) Dynamic tubular reactors have significant advantages over stirred reactors, including improved handling of thermal effects, enhanced mixing capabilities, and a larger operating window, enabling the development of safer, more efficient, robust, and sustainable synthetic production processes.

[0063] (2) The benefits brought in production are not limited to improving process safety, but also include achieving more efficient and lower-cost processes, thereby reducing downstream processing costs and labor costs.

[0064] (3) When the length of the dynamic tubular reactor is much larger than the diameter and the material system is in a turbulent state, the equipment is close to an ideal plug flow, and the material flows forward like a piston. With different blade forms, the high turbulence overcomes the interfacial tension and achieves small-scale macroscopic mixing.

[0065] (4) Under continuous steady-state operation, radial parameters (concentration, temperature, etc.) only change with the direction of material flow and do not change with time.

[0066] (5) The radial direction has a uniform flow velocity, and concentration distribution exists only in the radial direction. The reaction rate only changes in the axial direction.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in the field to implement; when the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

Claims

1. A method for continuously preparing a pore-forming agent H using a dynamic tubular reactor, characterized in that: The following steps are involved: S1-Material preparation: add urotropine, sodium nitrite, water and ammonia water into the raw material tank in proportion, start the raw material tank to stir, premix the materials into urotropine solution, and pre-cool to -5°C; then add appropriate amount of water into the dilution tank, start the stirring and heat exchange of the dilution tank, slowly drop appropriate amount of acid solution to prepare dilute acid for standby use, and pre-cool to 0°C; S2-Equipment preparation: Connect the heat exchanger inlet and outlet of the heat exchanger to the hot and cold integrated machine in advance, set the temperature of the heat exchanger to -10°C, and then connect the metering pump to the slurry feed port of the dynamic tubular reactor, the metering pump to the liquid feed port of the dynamic tubular reactor, and the discharge pipe of the dynamic tubular reactor to the material receiving tank; the material receiving tank is connected to the centrifuge, and the centrifuge is connected to the mother liquid collection tank; S3-nitration reaction: The urotropine solution is delivered to the dynamic tubular reactor by a metering pump at a rate of 2000-6000 kg / H, and the dilute acid is delivered to the dynamic tubular reactor by a metering pump at a rate of 1800 kg / H for nitrosation reaction; S4-Parameter control: control the reaction temperature in the dynamic tubular reactor to -5-5°C, the residence time to 1-5min, the rotation speed of the dynamic tubular reactor to 100-300r / min, and the pressure in the reaction chamber to normal pressure; S5-Obtaining crude product: After the reaction is completed in the dynamic tubular reactor, the reaction liquid flows into the material receiving tank through the discharge pipe. At this time, a large amount of light yellow solid is generated. The solid-liquid mixture in the material receiving tank enters the centrifuge. After centrifugation, the obtained solid is the crude product of the pore-forming agent H, and the centrifuged mother liquor enters the mother liquor collection tank.

2. The method for continuously preparing a pore-forming agent H using a dynamic tubular reactor according to claim 1, characterized in that: In step S1, the mass ratio of hexamethylenetetramine to nitrous acid is 1:1-1:

3.

3. The method for continuously preparing a pore-forming agent H using a dynamic tubular reactor according to claim 1, characterized in that: In step S1, the mass ratio of hexamethylenetetramine to water is 1:4-1:

12.

4. The method for continuously preparing a pore-forming agent H using a dynamic tubular reactor according to claim 1, characterized in that: In step S1, the mass ratio of hexamethylenetetramine to aqueous ammonia is 1:0.5-1:1.

5.

5. The method for continuously preparing a pore-forming agent H using a dynamic tubular reactor according to claim 1, characterized in that: In step S1, the mass ratio of hexamethylenetetramine to acid solution is 1:1-1:

5.

6. The method for continuously preparing a pore-forming agent H using a dynamic tubular reactor according to claim 1, characterized in that: The acid solution in step S1 is one of sulfuric acid, hydrochloric acid, acetic acid or citric acid.

7. The method for continuously preparing a pore-forming agent H using a dynamic tubular reactor according to claim 1, characterized in that: The concentration of the diluted acid prepared in step S1 is 10-50%.

8. The method for continuously preparing a pore-forming agent H using a dynamic tubular reactor according to claim 1, characterized in that: The concentration of the ammonia water in step S1 is 15-22%.

9. The method for continuously preparing a pore-forming agent H using a dynamic tubular reactor according to claim 1, characterized in that: The liquid holding capacity of the dynamic tubular reactor in step S4 is 100-300L.

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