Microchannel continuous reactor and method for continuously preparing 6-chloro-3-nitrotoluene-4-sulfonic acid

Abstract

The invention discloses a micro-channel continuous reactor and a method for continuously preparing 6-chloro-3-nitrotoluene-4-sulfonic acid. The method comprises the following steps: (a) respectively inputting a CLT acid chloride sulfuric acid solution and nitric acid into a micro-channel reaction module for nitration reaction to obtain reaction liquid; the molar ratio of the nitric acid to the CLT acid chloride is (1.5-2.0): 1; the flow of the CLT acid chloride sulfuric acid solution is larger than that of the nitric acid, the flow of the CLT acid chloride sulfuric acid solution is 8-60 ml / min, and the flow of the nitric acid is 6-45 ml / min; and (b) carrying out heat preservation on the reaction liquid through the static tubular reactor to generate the 6-chloro-3-nitrotoluene-4-sulfonic acid. The method effectively overcomes the defect that the CLT acid chloride needs to continuously react for 2-3 hours in a high-temperature environment (60-70 DEG C) in the nitrification process, and can greatly reduce the consumption of high-grade thermal public works.

Description

Technical Field

[0001] The invention belongs to the technical field of continuous production and relates to a production method of 6-chloro-3-nitrotoluene-4-sulfonic acid, and specifically relates to a microchannel continuous reactor and a method for continuously preparing 6-chloro-3-nitrotoluene-4-sulfonic acid. Background Art

[0002] 6-Chloro-3-nitrotoluene-4-sulfonic acid is an important intermediate for the synthesis of CLT acid (i.e. C acid). CLT acid (i.e. 6-chloro-3-aminotoluene-4-sulfonic acid) can be obtained by reduction. As an important red organic pigment intermediate, CLT acid can be used to synthesize lake organic pigments such as plastic scarlet, new treasure red 36b, and golden red c. This pigment is widely used in paints, coatings, color inks, rubber and plastic coloring, etc. CLT acid is one of the organic intermediates with an annual consumption of over 10,000 tons in the world. There are many synthetic routes for CLT acid. According to the different raw materials, there are mainly: toluene sulfonation route, o-chlorotoluene bromination route, o-chlorotoluene nitration route, m-xylene route, m-toluidine route and p-toluenesulfonyl chloride route. However, the domestic industry currently mainly adopts the toluene sulfonation route, that is, the chlorinated material after toluene sulfonation and chlorination is subjected to nitration reaction to generate the intermediate 6-chloro-3-nitrotoluene-4-sulfonic acid.

[0003] The Chinese invention patent application number 201610024978.0 discloses a 6-chloro-3-nitrotoluene-4-sulfonic acid nitration process, i.e., a method for continuously producing CLT acid nitrate in a pipeline, comprising the following steps: step (1): continuously passing CLT acid sulfonate and chlorine gas into a chlorination pipeline reactor for chlorination reaction; step (2): continuously passing the chlorination reaction liquid obtained in step (1) and nitric acid into a nitration pipeline reactor for nitration reaction to obtain CLT acid nitrate. However, the nitration reaction is a highly exothermic reaction. Concentrated nitric acid is unstable during the high-temperature nitration reaction and is prone to produce nitrogen oxides, resulting in low yield and poor selectivity. In addition, the introduction of a nitro group can release about 153 kJ / mol of heat. The higher the temperature and the faster the nitration reaction rate, the more heat is released, which can easily cause temperature runaway and explosion. Therefore, it is urgent to improve the mass transfer and heat transfer capacity during the CLT acid nitration reaction to reduce the accumulation of heat in the reactor, thereby effectively improving the safety and stability of the nitration process. Summary of the invention

[0004] The object of the present invention is to provide a method for continuously preparing 6-chloro-3-nitrotoluene-4-sulfonic acid in order to overcome the deficiencies of the prior art, so as to improve the yield and purity of 6-chloro-3-nitrotoluene-4-sulfonic acid.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a microchannel continuous reactor, which comprises: A microchannel reaction module, wherein the microchannel reaction module comprises at least two feed ports and one discharge port; A first feed pump, the first feed pump is connected to one of the feed ports through a first pipeline; A second feed pump, the second feed pump is connected to another feed inlet through a second pipeline; A static tubular reactor is connected to the discharge port through a third pipeline.

[0006] Optimally, the microchannel reaction module comprises: Carrier board; A microchannel unit is installed on the surface of the carrier plate, comprising a plurality of columns of microchannels arranged parallel to each other and aligned, and a plurality of U-shaped tubes connecting two adjacent columns of the microchannels so as to connect them in series, the end of one column of the microchannels is provided with the discharge port, and the end of the other column of the microchannels is formed with a plurality of the feed ports.

[0007] Furthermore, each column of the microchannels includes a plurality of square reaction chambers connected in series end to end and a square material blocking block arranged in each of the square reaction chambers, and a reaction gap is formed between the square reaction chambers and the square material blocking blocks.

[0008] Furthermore, the width a of the reaction gap is 0.5-1.5 mm, and the cross-sectional width b of the square reaction chamber is 2-5 mm.

[0009] Furthermore, two adjacent square reaction chambers are connected at the corners.

[0010] Another object of the present invention is to provide a method for continuously preparing 6-chloro-3-nitrotoluene-4-sulfonic acid, which adopts the above-mentioned microchannel continuous reactor to carry out the reaction.

[0011] Optimally, the following steps are included: (a) respectively inputting a CLT acid chloride sulfuric acid solution and nitric acid into the microchannel reaction module to perform a nitration reaction to obtain a reaction solution; the molar ratio of the nitric acid to the CLT acid chloride is 1.5-2.0:1; the flow rate of the CLT acid chloride sulfuric acid solution is greater than the flow rate of the nitric acid, the flow rate of the CLT acid chloride sulfuric acid solution is 8-60 ml / min (preferably 8-35 ml / min), and the flow rate of the nitric acid is 6-45 ml / min (preferably 6-25 ml / min); (b) the reaction solution is kept warm in the static tubular reactor to generate 6-chloro-3-nitrotoluene-4-sulfonic acid.

[0012] Furthermore, in step (a), the CLT acid chloride sulfuric acid solution is a mixture containing sulfuric acid obtained by reacting CLT acid sulfonate with chlorine, wherein the concentration of CLT acid chloride in the mixture is 30-60%, the concentration of sulfuric acid is 60-90%; and the concentration of nitric acid is 80-98%.

[0013] Furthermore, in step (a), the residence time of the CLT acid chloride sulfuric acid solution and nitric acid in the microchannel reaction module is 15 to 60 seconds.

[0014] Furthermore, in step (a), the CLT acid chloride sulfuric acid solution and nitric acid are preheated independently of each other before mixing, and the preheating temperature is 30-60°C.

[0015] Due to the application of the above technical scheme, the present invention has the following advantages compared with the prior art: the method for continuously preparing 6-chloro-3-nitrotoluene-4-sulfonic acid of the present invention, by adopting a microchannel continuous reactor with a specific structure to carry out micro-flow mixing for nitration reaction, effectively overcomes the defect that the CLT acid chloride nitration process needs to be continuously reacted for 2~3h under a high temperature environment (60-70℃), and can greatly reduce the consumption of high-level thermal utilities, thereby reducing production costs. By adopting a microchannel reactor with a specific structure for continuous flow process, the reaction time is shortened from the original 2~3 hours to 15~60s, and the reaction time is less than 0.8% of the original, which greatly shortens the reaction time and improves production efficiency; at the same time, the channel content volume of the microchannel reactor is small, the equipment occupies a small area, and the reaction is safer. Since the nitration reaction is a highly exothermic reaction, the release of a large amount of heat in a short time, combined with the efficient heat exchange of the microchannel reactor, can stably control the reaction temperature at 60℃, which can greatly reduce the proportion of other side reactions caused by the reaction materials in a high temperature and strong oxidizing environment for a long time, and improve the reaction yield and product yield and purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of a microchannel continuous reactor of the present invention; Figure 2 It is a schematic structural diagram of a microchannel reaction module in a microchannel continuous reactor of the present invention. DETAILED DESCRIPTION

[0017] The preferred embodiments of the present invention will be described in detail below. Example 1

[0018] This embodiment provides a microchannel continuous reactor, such as Figure 1As shown, the structure mainly includes a first feed pump 1 , a second feed pump 2 , a microchannel reaction module 3 (the microchannel reaction module 3 includes at least two feed ports 301 and one discharge port 34 ), and a static tubular reactor 4 .

[0019] Among them, the first feed pump 1 is connected to a feed port 301 through a first pipeline, and the second feed pump 2 is connected to another feed port 301 through a second pipeline. A third feed port 301 can also be set for standby. The static tubular reactor 4 is connected to the discharge port 34 through a third pipeline, and is used to receive the discharge of the microchannel reaction module 3. It should be noted that the output pressure of the first feed pump 1 (used to input CLT acid chloride sulfuric acid solution, i.e., organic phase) is greater than the output pressure of the second feed pump 2 (used to input nitric acid), so that the organic phase feed pressure is slightly greater than the nitric acid feed pressure. In this way, the CLT acid chloride sulfuric acid solution is highly dispersed in nitric acid, which greatly enhances the mass transfer capacity between the liquid and liquid phases, and can achieve instantaneous uniform mixing of materials and efficient heat transfer. In the microchannel reaction module 3, the CLT acid chloride sulfuric acid solution is dispersed into micro droplets with very small diameters, which greatly increases the contact area between the liquid and liquid phases, and solves the problem of mass transfer control during the traditional liquid-liquid two-phase reaction.

[0020] In this embodiment, the microchannel reaction module 3 mainly includes a carrier plate 31 and a microchannel unit. The microchannel unit is installed on the surface of the carrier plate 31, and includes a plurality of microchannels 32 (four in this embodiment) arranged parallel to each other and aligned, and a plurality of U-shaped tubes 33 (three in this embodiment) connecting two adjacent microchannels 32 in series. Figure 2 The end of the microchannel 32 on the right side of the middle is provided with a discharge port 34. The other microchannel 32 ( Figure 2 A plurality of feed ports 301 are formed at the end of the microchannel 32 on the left side.

[0021] In this embodiment, each column of microchannels 32 includes a plurality of square reaction chambers 321 (fifteen in this embodiment) connected in series end to end and a square material blocking block 322 disposed in each square reaction chamber 321, and a reaction gap 323 is formed between the square reaction chamber 321 and the square material blocking block 322; specifically, the width a of the reaction gap 323 is 0.5-1.5 mm (usually 1 mm), and the cross-sectional width b of the square reaction chamber 321 is 2-5 mm. Two adjacent square reaction chambers 321 are connected at the corners. Example 2

[0022] This embodiment provides a method for continuously preparing 6-chloro-3-nitrotoluene-4-sulfonic acid, which uses the microchannel continuous reactor in Example 1 and specifically includes the following steps: (a) CLT acid chloride sulfuric acid solution (the main product of CLT acid chloride sulfuric acid solution is 3-chloro-4-methylbenzenesulfonic acid, i.e. CLT acid chloride; its preparation process is: CLT acid sulfonate (p-toluenesulfonic acid) solution (sulfuric acid concentration is about 85%) and chlorine gas in a molar ratio of 1:1 are mixed and reacted at 70-80°C, and the temperature is kept until qualified (qualified indicators are: p-toluenesulfonic acid conversion rate ≥99%, main product 3-chloro-4-methylbenzenesulfonic acid content ≥95%, at this time CLT acid chloride in CL The content of CLT acid chloride in sulfuric acid solution is about 58%), the reaction solution is cooled naturally for standby use), and nitric acid (concentration of 98wt%) are respectively mixed at a micro flow rate (i.e., each is input into the microchannel reaction module 3 in Example 1 through a feed port 301, at this time, the flow rate of CLT acid chloride sulfuric acid solution is 8.4ml / min, the flow rate of nitric acid is 6.0ml / min, and the molar ratio of HNO3 and 3-chloro-4-methylbenzenesulfonic acid is 2:1) to carry out nitration reaction to obtain a reaction solution (reaction temperature is about 30°C, residence time is 150s; the feed pressure of CLT acid chloride sulfuric acid solution is slightly greater than the feed pressure of nitric acid, so that the CLT acid chloride sulfuric acid solution is highly dispersed in nitric acid to undergo nitration reaction in the microchannel reaction module 3); (b) The reaction solution is passed through a static tubular reactor 4 and kept warm to generate 6-chloro-3-nitrotoluene-4-sulfonic acid.

[0023] After testing, the conversion rate of CLT acid chloride was 99.7%, the yield of 6-chloro-3-nitrotoluene-4-sulfonic acid was 85.0%, the purity was 90.5%, and the appearance was a yellow oily liquid. Example 3

[0024] This embodiment provides a method for continuously preparing 6-chloro-3-nitrotoluene-4-sulfonic acid, which is basically the same as that in Example 2, except that: In step (a), the flow rate of CLT acid chloride sulfuric acid solution is 17 ml / min, the flow rate of nitric acid is 12.4 ml / min, the reaction temperature is about 50° C., and the residence time is 100 s.

[0025] After testing, the conversion rate of CLT acid chloride was 99.5%, the yield of 6-chloro-3-nitrotoluene-4-sulfonic acid was 84.5%, the purity was 89.5%, and the appearance was a yellow oily liquid. Example 4

[0026] This embodiment provides a method for continuously preparing 6-chloro-3-nitrotoluene-4-sulfonic acid, which is basically the same as that in Example 2, except that in step (a), the flow rate of CLT acid chloride sulfuric acid solution is 35 ml / min, the flow rate of nitric acid is 25 ml / min, the reaction temperature is about 60°C, and the residence time is 80 s.

[0027] After testing, the conversion rate of CLT acid chloride was 99.8%, the yield of 6-chloro-3-nitrotoluene-4-sulfonic acid was 82.4%, the purity was 87.8%, and the appearance was a yellow oily liquid.

[0028] Comparative Example 1 This example provides a method for preparing 6-chloro-3-nitrotoluene-4-sulfonic acid, which is as follows (i.e., intermittent kettle reaction): Take a 250 ml three-necked flask, add 224.5g of CLT acid chloride sulfuric acid solution, control the temperature to 30~40℃, add 41.8g of nitric acid (concentration is 98wt%), and add it in 65 minutes (keep warm for one hour after the addition); after the reaction is completed, control the middle. After testing: the conversion rate of 6-chloro-3-nitrotoluene-4-sulfonic acid is 98.5%, the yield of 6-chloro-3-nitrotoluene-4-sulfonic acid is 60.5%, the purity is 65.5%, and the appearance is a yellow oily liquid.

[0029] It can be seen that the process of Examples 2-4 of the present invention has a high selectivity for 6-chloro-3-nitrotoluene-4-sulfonic acid compared with Comparative Example 1 (traditional nitration process, intermittent reactor reaction). In the microchannel reactor, the liquid-liquid two phases (organic phase and acid phase) are dispersed into micro droplets with very small diameters, which greatly increases the contact area between the liquid-liquid two phases and has high heat transfer efficiency, solving the problem of mass transfer and heat transfer control in the traditional liquid-liquid two-phase nitration reaction. The selectivity of 6-chloro-3-nitrotoluene-4-sulfonic acid in Example 2 is the highest, and it is the best embodiment.

[0030] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They cannot be used to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A microchannel continuous reactor, characterized in that it include: A microchannel reaction module (3), wherein the microchannel reaction module (3) comprises at least two feed ports (301) and one discharge port (34); A first feed pump (1), the first feed pump (1) being connected to one of the feed ports (301) via a first pipeline; a second material delivery pump (2), the second material delivery pump (2) being connected to another of the feed ports (301) via a second pipeline; A static tubular reactor (4), wherein the static tubular reactor (4) is connected to the discharge port (34) via a third pipeline.

2. The microchannel continuous reactor according to claim 1, characterized in that: The microchannel reaction module (3) comprises: Carrier plate (31); A microchannel unit is installed on the surface of the carrier plate (31), comprising a plurality of columns of microchannels (32) arranged parallel to each other and aligned, and a plurality of U-shaped tubes (33) connecting two adjacent columns of the microchannels (32) so as to connect them in series, wherein the end of one column of the microchannels (32) is provided with the discharge port (34), and the end of another column of the microchannels (32) is formed with a plurality of the feed ports (301).

3. The microchannel continuous reactor according to claim 2, characterized in that: Each row of the microchannels (32) comprises a plurality of square reaction chambers (321) connected in series end to end and a square material blocking block (322) arranged in each of the square reaction chambers (321), and a reaction gap (323) is formed between the square reaction chambers (321) and the square material blocking blocks (322).

4. The microchannel continuous reactor according to claim 3, characterized in that: The width a of the reaction gap (323) is 0.5-1.5 mm, and the cross-sectional width b of the square reaction chamber (321) is 2-5 mm.

5. The microchannel continuous reactor according to claim 2, characterized in that: Two adjacent square reaction chambers (321) are connected at the corners.

6. A method for continuously preparing 6-chloro-3-nitrotoluene-4-sulfonic acid, characterized in that: It uses the microchannel continuous reactor described in any one of claims 1 to 5 to carry out the reaction.

7. The method for continuously preparing 6-chloro-3-nitrotoluene-4-sulfonic acid according to claim 6, characterized in that: The following steps are involved: (a) respectively inputting a CLT acid chloride sulfuric acid solution and nitric acid into the microchannel reaction module (3) to perform a nitration reaction to obtain a reaction solution; the molar ratio of the nitric acid to the CLT acid chloride is 1.5-2.0:1; the flow rate of the CLT acid chloride sulfuric acid solution is greater than the flow rate of the nitric acid, the flow rate of the CLT acid chloride sulfuric acid solution is 8-60 ml / min, and the flow rate of the nitric acid is 6-45 ml / min; (b) the reaction solution is passed through the static tubular reactor (4) for heat preservation to generate 6-chloro-3-nitrotoluene-4-sulfonic acid.

8. The method for continuously preparing 6-chloro-3-nitrotoluene-4-sulfonic acid according to claim 7, characterized in that: In step (a), the CLT acid chloride sulfuric acid solution is a mixture containing sulfuric acid obtained by reacting CLT acid sulfonate with chlorine, wherein the concentration of CLT acid chloride in the mixture is 30-60%, the concentration of sulfuric acid is 60-90%; and the concentration of nitric acid is 80-98%.

9. The method for continuously preparing 6-chloro-3-nitrotoluene-4-sulfonic acid according to claim 7, characterized in that: In step (a), the residence time of the CLT acid chloride sulfuric acid solution and nitric acid in the microchannel reaction module (3) is 15 to 60 seconds.

10. The method for continuously preparing 6-chloro-3-nitrotoluene-4-sulfonic acid according to claim 7, characterized in that: In step (a), the CLT acid chloride sulfuric acid solution and nitric acid are preheated independently of each other before mixing, and the preheating temperature is 30-60°C.

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