A method for continuously synthesizing 2,6-di-tert-butylphenol using a microchannel reactor

Abstract

This application relates to the technical field of the synthesis of 2,6 - di - tert - butylphenol, and specifically discloses a method for continuously synthesizing 2,6 - di - tert - butylphenol using a microchannel reactor. This method comprises the following steps: mixing phenol and aluminum, heating until the reaction of aluminum is complete to obtain a preliminary preparation solution; adding 2 - tert - butylphenol to the preliminary preparation solution to obtain a phenol aluminum solution, and introducing the phenol aluminum solution and isobutene into the microchannel reactor for mixing reaction to obtain 2,6 - di - tert - butylphenol. In this method, pre - adding 2 - tert - butylphenol can form a complex with phenol aluminum, reducing the catalytic activity of phenol aluminum, slowing down the introduction of the third tert - butyl group into the phenol ring, thereby inhibiting the formation of 2,4,6 - tri - tert - butylphenol, and significantly improving the selectivity of 2,6 - di - tert - butylphenol. The good mass transfer and heat transfer effects of the microchannel reactor improve the situation of local overheating in the traditional batch reaction, making the material mixing more uniform, shortening the reaction time, and reducing the generation of by - products.

Description

Technical Field

[0001] This application relates to the technical field of the synthesis of 2,6 - di - tert - butylphenol, and particularly relates to a method for continuously synthesizing 2,6 - di - tert - butylphenol by using a microchannel reactor. Background Art

[0002] 2,6 - Di - tert - butylphenol is an important chemical intermediate, widely used as an antioxidant and stabilizer in fields such as medicine and pesticides.

[0003] The traditional method for synthesizing 2,6 - di - tert - butylphenol usually uses a batch - type high - pressure reactor as the reaction vessel, and uses phenol and isobutene as raw materials to synthesize 2,6 - di - tert - butylphenol. Among them, isobutene is introduced into the reaction kettle in one - time required amount at a low temperature state, and then the temperature is raised for reaction. Since the reaction between phenol and isobutene is an exothermic reaction, and in addition, the reaction rate of phenol and isobutene is fast in the initial stage of the reaction, a large amount of heat generated by the reaction cannot be removed in time, resulting in a rapid temperature rise, and the reaction pressure rises to about 2 Mpa at most, resulting in an increase in the by - product 2,4,6 - tri - tert - butylphenol, with its content exceeding 10%, the selectivity of the product 2,6 - di - tert - butylphenol decreases, and the high - pressure reaction will increase the danger.

[0004] The patent application with the Chinese publication number CN1935764A relates to a method for preparing a 2,6 - di - tert - butylphenol alkylation solution. Charge according to the ratio of phenol: aluminum chips of 1:0.001 - 0.01, heat up until the pressure in the reaction kettle rises sharply, keep the temperature for reaction for 0.5 - 1 hour, and then introduce isobutene into the reaction kettle according to the ratio of phenol: isobutene of 1:0.9 - 1.9, control the temperature at 80℃ - 120℃, carry out the alkylation reaction for 2 - 4 hours, and then carry out the analysis operation on the excess isobutene in the reaction kettle, filter to remove the catalyst, and obtain a pure 2,6 - di - tert - butylphenol alkylation solution. This reaction belongs to a batch kettle - type reaction, with low production efficiency, long reaction time, high production cost, and the content of 2,6 - di - tert - butylphenol after reaction is lower than 90%, between 84% - 88%. Summary of the Invention

[0005] In view of the problems of low production efficiency, long reaction time, high production cost, low content of 2,6 - di - tert - butylphenol and many by - products in the synthesis of 2,6 - di - tert - butylphenol by using a batch - type reaction kettle, the following technical solutions are proposed in this application.

[0006] A method for continuously synthesizing 2,6 - di - tert - butylphenol using a microchannel reactor, comprising the following steps: mixing phenol and aluminum, heating until the reaction of aluminum is complete to obtain a preliminary solution; the preliminary solution contains a catalytic amount of aluminum phenoxide, and the solvent is phenol; adding 2 - tert - butylphenol to the preliminary solution to obtain an aluminum phenoxide solution, and introducing the aluminum phenoxide solution and isobutene into the microchannel reactor for mixing reaction to obtain 2,6 - di - tert - butylphenol.

[0007] By adopting the above - mentioned technical solution, the solute of the aluminum phenoxide solution is aluminum phenoxide, and the solvent is a mixed reagent of phenol and 2 - tert - butylphenol. Aluminum phenoxide can catalyze the synthesis of 2,6 - di - tert - butylphenol from phenol, 2 - tert - butylphenol and isobutene respectively. Adding 2 - tert - butylphenol to the preliminary solution can form a complex with aluminum phenoxide without pressurization, reducing the catalytic activity of aluminum phenoxide, slowing down the introduction of the third tert - butyl group into the phenol ring, thereby inhibiting the formation of 2,4,6 - tri - tert - butylphenol, and significantly improving the selectivity of 2,6 - di - tert - butylphenol. The good mass transfer and heat transfer effects of the microchannel reactor improve the situation of local runaway temperature in the traditional batch reaction. At the same time, the microchannel reactor makes the material mixing more uniform, shortens the reaction time, improves the product selectivity, reduces the generation of by - products, and is suitable for industrial production.

[0008] A preferred embodiment of the method for continuously synthesizing 2,6 - di - tert - butylphenol using a microchannel reactor is that the mass ratio of phenol, aluminum and 2 - tert - butylphenol is 1:(0.001 - 0.005):(0.1 - 0.4).

[0009] By adopting the above - mentioned technical solution, a catalytic amount of aluminum phenoxide is generated. Adding a relatively large amount of 2 - tert - butylphenol to the preliminary solution in advance can form a complex with aluminum phenoxide, reducing the catalytic activity of aluminum phenoxide, slowing down the introduction of the third tert - butyl group into the phenol ring, thereby inhibiting the formation of 2,4,6 - tri - tert - butylphenol, and significantly improving the selectivity of 2,6 - di - tert - butylphenol.

[0010] A preferred embodiment of the method for continuously synthesizing 2,6 - di - tert - butylphenol using a microchannel reactor is that among the input raw materials, the molar amount of phenol is x, the molar amount of 2 - tert - butylphenol is y, and the molar amount of isobutene is z, and (2x + y):z = 1:(1 - 2).

[0011] By adopting the above - mentioned technical solution, phenol and 2 - tert - butylphenol can be completely reacted by isobutene.

[0012] A preferred embodiment of the method for continuously synthesizing 2,6-di-tert-butylphenol using a microchannel reactor is that the microchannel reactor includes a plurality of reaction modules connected in series; each of the reaction modules has a plurality of vortex grooves connected in series; each of the vortex grooves includes a strip groove and a circular groove, and the strip groove is tangentially connected to the circular groove. The volume of each vortex groove is 0.1-0.5 mL. In each of the reaction modules, the vortex grooves are connected in series in such a way that the strip groove of an adjacent vortex groove is connected to the circular groove of another vortex groove, and the circular groove is connected to the next strip groove.

[0013] By adopting the above technical solution, the strip grooves are tangentially connected to the circular grooves, so that each vortex groove is in the shape of a "6". First, the vortex grooves can fully mix phenol, 2-tert-butylphenol and isobutylene, so as to efficiently carry out the synthesis reaction, improve production efficiency, reduce reaction time, increase the conversion rate of phenol and 2-tert-butylphenol, and reduce the increase of by-products caused by long reaction time; secondly, the reaction container is divided into multiple miniature vortex grooves, which can make phenol, 2-tert-butylphenol and isobutylene contact in small amounts, and reduce the increase of by-products caused by excessive addition reaction due to large-scale contact of raw materials.

[0014] A preferred embodiment of the method for continuously synthesizing 2,6-di-tert-butylphenol using a microchannel reactor is that the reaction module is in a plate shape, and a plurality of vortex grooves are provided on both the front and back sides of the reaction module. The vortex grooves on the front side are repeatedly connected in a manner that a vortex groove on the back side is connected, so that all the vortex grooves of the reaction module are connected in series, including a strip groove of the vortex groove on the front side connected to a circular groove of the vortex groove on the previous back side, and a circular groove of the vortex groove on the front side connected to a strip groove of the vortex groove on the next back side.

[0015] By adopting the above technical solution, phenol, 2-tert-butylphenol and isobutylene are fully disturbed and mixed, and the reaction efficiency is higher.

[0016] A preferred embodiment of the method for continuously synthesizing 2,6-di-tert-butylphenol using a microchannel reactor is that the microchannel reactor includes four reaction modules connected in series, namely a first reaction module, a second reaction module, a third reaction module and a fourth reaction module. Before the aluminum phenol solution and isobutylene are introduced into the microchannel reactor, the temperature of the first reaction module is set to 50-60°C, the temperature of the second reaction module is set to 70-90°C, the temperature of the third reaction module is set to 100-120°C, and the temperature of the fourth reaction module is set to 130-150°C.

[0017] By adopting the above technical solution, since the synthesis reaction of phenol, 2-tert-butylphenol and isobutene is an exothermic reaction, the stepwise temperature increase can effectively control the heat release amount during the reaction process, so as to avoid too high temperature of the reaction system, thereby reducing the safety risk and energy consumption. At a low temperature of 50-60 °C, almost all of the phenol reacts, and the remaining amount is 5%-8%. Most of it will form 2-tert-butylphenol, and the content is about 55%-65%. As the concentration of the reactants decreases, the temperature is gradually increased subsequently to maintain a high reaction efficiency.

[0018] A preferred embodiment of the method for continuously synthesizing 2,6-di-tert-butylphenol using a microchannel reactor is that the microchannel reactor has a total inlet and a total outlet, and each reaction module has a sub-inlet. The aluminum phenoxide solution enters from the total inlet of the microchannel reactor and passes through each vortex chamber of each reaction module in sequence; the liquefied isobutene enters from the sub-inlet of each reaction module and passes through each vortex chamber of this reaction module and each vortex chamber of the subsequent reaction modules in sequence.

[0019] By adopting the above technical solution, the stepwise introduction of isobutene can better control the concentration gradient of the reactants, reduce the premature gasification of the liquid isobutene and thus reduce the sufficient contact with phenol and 2-tert-butylphenol. The stepwise introduction of isobutene makes the mixing of phenol and liquid isobutene more uniform and the reaction more sufficient, thereby reducing the amount of isobutene used and improving the reaction efficiency. Because in the initial stage of the reaction, the reaction of phenol and isobutene mainly produces 2-tert-butylphenol, and the amount of isobutene required is small. The low flow rate can control the reaction rate, prevent the reaction from being too violent, improve the safety risk and reduce the probability of by-product formation. The unreacted phenol and 2-tert-butylphenol in each module will continue to react with the stepwise introduced isobutene, which also reduces the production amount of the by-product 2,4,6-tri-tert-butylphenol. The total residence time of phenol in the four reaction modules can be 5-50 min.

[0020] A preferred embodiment of the method for continuously synthesizing 2,6-di-tert-butylphenol using a microchannel reactor is that the flow rate of the aluminum phenoxide solution is 2-10 mL / min; the total flow rate of the liquefied isobutene is 3-30 mL / min.

[0021] By adopting the above technical solution, phenol, 2-tert-butylphenol and isobutene can have sufficient contact in the microchannel, with high reaction efficiency, and at the same time, the reaction duration is controlled to be short, the production efficiency is improved, and there are few by-products and high selectivity of 2,6-di-tert-butylphenol. The flow rate of isobutene in each branch can be equal.

[0022] A preferred embodiment of the method for continuously synthesizing 2,6 - di - tert - butylphenol using a microchannel reactor is to mix phenol and aluminum, heat it to 130 - 160 °C until the reaction of aluminum is complete, and obtain the initial prepared solution.

[0023] By adopting the above - mentioned technical solution, aluminum and phenol react to form aluminum phenoxide, which is used to catalyze the synthesis of 2,6 - di - tert - butylphenol from phenol, 2 - tert - butylphenol and isobutene.

[0024] In summary, the method for continuously synthesizing 2,6 - di - tert - butylphenol using a microchannel reactor in this application has the following beneficial effects:

[0025] 1. Using a microchannel reactor as the reactor can make the reactants mix evenly, extend the residence time of phenol, 2 - tert - butylphenol and isobutene in the reactor, and enable the materials to react fully.

[0026] 2. The microchannel reactor has good mass transfer and heat transfer effects. By heating in sections and introducing isobutene in sections, precise control of the reaction temperature, pressure and flow rate can be achieved, and the phenomenon of local runaway temperature is basically not caused. Thus, the problems of too high temperature in the traditional batch reaction and too many by - products of 2,4,6 - tri - tert - butylphenol are solved, and the content and yield of 2,6 - di - tert - butylphenol are improved.

[0027] 3. By adding a certain amount of 2 - tert - butylphenol, the formation of 2,4,6 - tri - tert - butylphenol and 2,4 - di - tert - butylphenol is reduced, the selectivity of 2,6 - di - tert - butylphenol is improved, and the content of 2,6 - di - tert - butylphenol reaches more than 95%. Description of the Drawings

[0028] Figure 1 It is the front - view structure diagram of the reaction module of the microchannel reactor.

[0029] Figure 2 It is the sectional view of the reaction module of the microchannel reactor.

[0030] Figure 3 It is the schematic diagram of the device connection used in Examples 1 - 4.

[0031] Figure 3 Markings in it: 1. Isobutene metering pump; 2. Aluminum phenoxide solution metering pump; 3. First reaction module; 4. Second reaction module; 5. Third reaction module; 6. Fourth reaction module; 7. Back - pressure valve; 8. Receiving bottle. Detailed Embodiments

[0032] The technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. Apparently, the described embodiments are only a part of the embodiments of the present application, rather than all of them. Based on the following embodiments, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present application.

[0033] The microchannel reactor used in the following embodiments is from Shandong Yinglewei Equipment Technology Co., Ltd., and the model of the microchannel reactor is S5-60. The specific structure refers to a microreaction chip with a three-dimensional eddy current channel disclosed in the authorized announcement number CN218131969U.

[0034] The microchannel reactor with the model S5-60 includes four serially connected reaction modules, namely the first reaction module, the second reaction module, the third reaction module, and the fourth reaction module. The volume of each reaction module is 60 mL. Refer to Figure 1 and Figure 2 , and each reaction module has a plurality of serially connected vortex grooves. Each vortex groove includes a strip groove and a circular groove. The strip groove is tangentially connected to the circular groove to form a "6" shape. The volume of each vortex groove is about 0.3 mL.

[0035] The reaction module is in a plate shape, and a plurality of vortex grooves are provided on both the front and back surfaces of the reaction module. In the way that one vortex groove on the front surface is connected to one vortex groove on the back surface, all the vortex grooves of one reaction module are serially connected in this way, including the strip groove of the vortex groove on the front surface being connected to the circular groove of the previous vortex groove on the back surface, and the circular groove of the vortex groove on the front surface being connected to the strip groove of the next vortex groove on the back surface. In this way, all the vortex grooves on the front and back surfaces of one reaction module are serially connected.

[0036] The microchannel reactor has a total inlet and a total outlet, and each reaction module has a sub-inlet. Example 1

[0037] Phenol and aluminum chips were added to a four-necked flask, and the feeding was carried out according to the mass ratio of phenol to aluminum chips of 1:0.0025. 1000 g (933.7 mL, 10.6 mol) of phenol and 2.5 g of aluminum were used. Then, the temperature was raised to 150 °C and kept for 0.5 h. The aluminum was completely reacted, and a small amount of phenol and all the aluminum reacted to form aluminum phenoxide, obtaining a preliminary preparation solution. 300 g (306.7 mL, 2 mol) of 2-tert-butylphenol was added to the preliminary preparation solution to obtain an aluminum phenoxide solution. The volume ratio of phenol to 2-tert-butylphenol was about 3:1, and the molar ratio of phenol to 2-tert-butylphenol was about 5.3:1. As Figure 3, the aluminum phenoxide solution is filled into a container, which is connected to the aluminum phenoxide solution metering pump 2. The aluminum phenoxide solution metering pump 2 is connected to the total inlet of the microchannel reactor through a pipeline. A high-pressure gas cylinder filled with liquefied isobutene (density 0.67 g / mL) is connected to the isobutene metering pump 1. The isobutene metering pump 1 is respectively connected to the sub-inlets of the first reaction module 3, the second reaction module 4, the third reaction module 5, and the fourth reaction module 6 of the microchannel reactor through four branch pipes; a receiving bottle 8 is connected to the total outlet of the microchannel reactor through a rear-end pipeline, and a back pressure valve 7 is installed on this rear-end pipeline.

[0038] Turn on the metering pumps for the aluminum phenoxide solution and isobutene. The volume flow rate of the aluminum phenoxide solution transported by the aluminum phenoxide solution metering pump is 2 mL / min. Among them, the volume flow rate of the transported phenol is 1.5 mL / min, that is, the molar flow rate of the transported phenol is 0.017 mol / min, the volume flow rate of the transported 2-tert-butylphenol is 0.5 mL / min, that is, the molar flow rate of the transported 2-tert-butylphenol is 0.003 mol / min, that is, the molar flow rate of the transported aluminum phenoxide solution is 0.02 mol / min. The required molar flow rate of isobutene is 0.017×2 + 0.003 = 0.037 mol / min. Select the isobutene metering pump to transport the isobutene volume flow rate of 3.3 mL / min, that is, the molar flow rate of the transported isobutene is 0.04 mol / min, which is greater than the required 0.037 mol / min. That is, when the aluminum phenoxide solution and isobutene are fed according to the molar ratio of 0.02:0.04 = 1:2, the phenol and 2-tert-butylphenol can react completely. The aluminum phenoxide solution is fed from the main feed port and sequentially enters the first reaction module, the second reaction module, the third reaction module, and the fourth reaction module. Isobutene is fed into the first reaction module, the second reaction module, the third reaction module, and the fourth reaction module in segments. The temperature of the first reaction module is 50 °C, the temperature of the second reaction module is 80 °C, the temperature of the third reaction module is 100 °C, the temperature of the fourth reaction module is 130 °C, the pressure of the back pressure valve is 0.3 Mpa, and the total residence time of the four reaction modules is 45 min. After the reaction, the reaction solution flows out through the back pressure valve into the receiving bottle to obtain the reaction solution of 2,6-di-tert-butylphenol. By gas chromatography quantitative analysis, the mass percentage content of each component is as follows: 2,6-di-tert-butylphenol 95.1%, 2-tert-butylphenol 0.5%, 2,4-di-tert-butylphenol 0.4%, 2,4,6-tri-tert-butylphenol 3.7%, phenol 0.1%, and other impurities 0.2%. The conversion rate of phenol is 99.9%, and the selectivity of 2,6-di-tert-butylphenol is 95.2%. Example 2

[0039] Add phenol and aluminum chips into a four-necked flask. Charge according to the mass ratio of phenol to aluminum chips of 1:0.001, with 1000 g of phenol and 1 g of aluminum. Then heat up to 130 °C and hold the reaction for 0.5 h. Next, add 100 g of 2-tert-butylphenol to obtain an aluminum phenoxide solution. The volume ratio of phenol to 2-tert-butylphenol is approximately 9:1. This example is installed in the same way as Example 1 and Figure 3 installed in the same way. Start the metering pumps for the aluminum phenoxide solution and isobutene. The volume flow rate of the aluminum phenoxide solution metering pump for transporting the aluminum phenoxide solution is 5 mL / min. Among them, the volume flow rate for transporting phenol is 4.5 mL / min, that is, the molar flow rate for transporting phenol is 0.051 mol / min. The volume flow rate for transporting 2-tert-butylphenol is 0.5 mL / min, that is, the molar flow rate for transporting 2-tert-butylphenol is 0.003 mol / min. That is, the molar flow rate for transporting the aluminum phenoxide solution is 0.051 + 0.003 = 0.054 mol / min. The required molar flow rate of isobutene is 0.051×2 + 0.003 = 0.105 mol / min. Set the volume flow rate of the isobutene metering pump for transporting isobutene to 17.3 mL / min, that is, the molar flow rate for transporting isobutene is 0.210 mol / min, which is greater than the required 0.105 mol / min, and can completely react phenol and 2-tert-butylphenol. The aluminum phenoxide solution is fed from the main feed port and sequentially enters the first reaction module, the second reaction module, the third reaction module, and the fourth reaction module. Isobutene is fed in segments into the first reaction module, the second reaction module, the third reaction module, and the fourth reaction module. The temperature of the first reaction module is 60 °C, the temperature of the second reaction module is 90 °C, the third reaction module is 120 °C, and the fourth reaction module is 140 °C. The pressure of the back pressure valve is 0.3 Mpa. The total residence time of the four reaction modules is 18 min. After the reaction is completed, the reaction solution exits through the back pressure valve and reaches the receiving flask to obtain a reaction solution of 2,6-di-tert-butylphenol. Through gas chromatography quantitative analysis, the mass percentage content of each component is as follows: 2,6-di-tert-butylphenol 97.2%, 2-tert-butylphenol 0.35%, 2,4-di-tert-butylphenol 0.3%, 2,4,6-tri-tert-butylphenol 1.8%, phenol 0.2%, and other impurities 0.15%. The conversion rate of phenol is 99.8%, and the selectivity of 2,6-di-tert-butylphenol is 97.4%. Example 3

[0040] Add phenol and aluminum chips into a four-necked flask. Charge according to the mass ratio of phenol to aluminum chips of 1:0.005, with 1000 g of phenol and 5 g of aluminum. Then heat up to 160 °C and hold the reaction for 0.5 h. Next, add 400 g of 2-tert-butylphenol to obtain an aluminum phenoxide solution. The volume ratio of phenol to 2-tert-butylphenol is approximately 9:4. This example is installed in the same way as Example 1 and Figure 3Install in the following way. Turn on the metering pumps for phenol aluminum solution and isobutene. The volumetric flow rate of the phenol aluminum solution delivered by the phenol aluminum solution metering pump is 13 mL / min. Among them, the volumetric flow rate of phenol delivered is 9 mL / min, that is, the molar flow rate of phenol delivered is 0.102 mol / min. The volumetric flow rate of 2-tert-butylphenol delivered is 4 mL / min, that is, the molar flow rate of 2-tert-butylphenol delivered is 0.024 mol / min. That is, the molar flow rate of the phenol aluminum solution delivered is 0.102 + 0.024 = 0.126 mol / min. The required molar flow rate of isobutene is 0.102×2 + 0.024 = 0.228 mol / min. Set the volumetric flow rate of isobutene delivered by the isobutene metering pump to 28.2 mL / min, that is, the molar flow rate of isobutene delivered is 0.342 mol / min, which is greater than the required 0.228 mol / min, so that phenol and 2-tert-butylphenol can react completely. The phenol aluminum solution is fed from the main feed port and sequentially enters the first reaction module, the second reaction module, the third reaction module, and the fourth reaction module. Isobutene is fed into the first reaction module, the second reaction module, the third reaction module, and the fourth reaction module in segments. The temperature of the first reaction module is 55 °C, the temperature of the second reaction module is 70 °C, the third reaction module is 110 °C, the fourth reaction module is 150 °C, and the pressure of the back pressure valve is 0.3 Mpa. The total residence time of the four reaction modules is 9 min. After the reaction, the reaction solution exits through the back pressure valve and enters the receiving bottle to obtain the reaction solution of 2,6-di-tert-butylphenol. Through gas chromatography quantitative analysis, the mass percentage content of each component is as follows: 2,6-di-tert-butylphenol 94.6%, 2-tert-butylphenol 2.1%, 2,4-di-tert-butylphenol 0.35%, 2,4,6-tri-tert-butylphenol 1.7%, phenol 1.05%, and other impurities 0.2%. The conversion rate of phenol is 98.95%, and the selectivity of 2,6-di-tert-butylphenol is 95.6%. Example 4

[0041] Add phenol and aluminum chips into a four-necked flask, and charge according to the mass ratio of phenol to aluminum chips of 1:0.0025. 1000 g of phenol and 2.5 g of aluminum are used. Then heat up to 150 °C and keep the reaction for 0.5 h. Then add 300 g of 2-tert-butylphenol to obtain the phenol aluminum solution. The volume ratio of phenol to 2-tert-butylphenol is about 3:1. This example is the same as Example 1 in terms of Figure 3Install in the following manner. Turn on the aluminum phenoxide solution and isobutene metering pumps, and feed the aluminum phenoxide solution and isobutene at a molar ratio of 1:2.5. The volumetric flow rate of the aluminum phenoxide solution delivered by the aluminum phenoxide solution metering pump is 5 mL / min. Among them, the volumetric flow rate of the delivered phenol is 3.75 mL / min, that is, the molar flow rate of the delivered phenol is 0.0425 mol / min. The volumetric flow rate of the delivered 2-tert-butylphenol is 1.25 mL / min, that is, the molar flow rate of the delivered 2-tert-butylphenol is 0.0075 mol / min. That is, the molar flow rate of the delivered aluminum phenoxide solution is 0.05 mol / min. The required molar flow rate of isobutene is 0.0425×2 + 0.0075 = 0.0925 mol / min. Select an isobutene metering pump to deliver an isobutene volumetric flow rate of 10.3 mL / min, that is, the molar flow rate of the delivered isobutene is 0.125 mol / min, which is greater than the required 0.0925 mol / min. That is, the aluminum phenoxide solution and isobutene are fed at a molar ratio of 0.05:0.125 = 1:2.5, and phenol and 2-tert-butylphenol can react completely. The aluminum phenoxide solution is fed from the main feed port and successively enters the first reaction module, the second reaction module, the third reaction module, and the fourth reaction module. Isobutene is fed in segments into the first reaction module, the second reaction module, the third reaction module, and the fourth reaction module. The temperature of the first reaction module is 50 °C, the temperature of the second reaction module is 80 °C, the third reaction module is 100 °C, the fourth reaction module is 130 °C, and the pressure of the back pressure valve is 0.3 Mpa. The total residence time of the four reaction modules is 15 min. After the reaction, the reaction solution exits through the back pressure valve and enters the receiving bottle to obtain a 2,6-di-tert-butylphenol reaction solution. Through gas chromatography quantitative analysis, the mass percentage content of each component is as follows: 2,6-di-tert-butylphenol 95.8%, 2-tert-butylphenol 0.28%, 2,4-di-tert-butylphenol 0.18%, 2,4,6-tri-tert-butylphenol 2.7%, phenol 0.13%, and other impurities 0.11%. The conversion rate of phenol is 99.87%, and the selectivity of 2,6-di-tert-butylphenol is 95.9%.

[0042] Comparative Example 1:

[0043] Charge materials according to the mass ratio of phenol to aluminum chips of 1:0.0025. Add 1000 g (10.6 mol) of phenol and 2.5 g of aluminum into a 4 L high-pressure reactor, then heat up to 150 °C and keep the temperature for 0.5 h. After the preparation of aluminum phenoxide catalyst is completed, cool down to 40 °C, and then add 300 g (2 mol) of 2-tert-butylphenol to obtain an aluminum phenoxide solution. Then, pass 1407 g of isobutene (calculated according to the molar ratio of phenol solution to isobutene of 1:2 in Example 1, the required molar amount of isobutene is [10.6×2 + 2]×0.04 / 0.037 = 25.08 mol) into the reactor containing the aluminum phenoxide solution all at once through a metering pump. Heat up to 95 °C and keep the temperature for 10 h. After the reaction ends, a reaction solution containing the crude product of 2,6-di-tert-butylphenol is obtained. By quantitative analysis with gas chromatography, the mass percentage content of each component is as follows: 2,6-di-tert-butylphenol 81.3%, 2-tert-butylphenol 4.6%, 2,4-di-tert-butylphenol 1.1%, 2,4,6-tri-tert-butylphenol 10.8%, phenol 2.1%, and other impurities 0.1%. The conversion rate of phenol is 97.9%, and the selectivity of 2,6-di-tert-butylphenol is 83%.

[0044] Comparative Example 2:

[0045] Add phenol and aluminum chips into a four-necked flask. Charge materials according to the mass ratio of phenol to aluminum chips of 1:0.0025. Add 1000 g (10.6 mol) of phenol and 2.5 g of aluminum, then heat up to 150 °C and keep the temperature for 0.5 h, and then cool down to 40 °C to obtain an aluminum phenoxide solution.

[0046] This comparative example is the same as Example 1 in terms of Figure 3Install in the following manner. Start the metering pumps for phenol aluminum solution and isobutene. Feed the phenol aluminum solution and isobutene according to a molar ratio of 1:2. The volume flow rate of the phenol aluminum solution delivered by the metering pump for phenol aluminum solution is 2 mL / min, that is, the molar flow rate of phenol delivered is 0.0227 mol / min. The required molar flow rate of isobutene is 0.0227×2 = 0.0454 mol / min. Select the metering pump for isobutene to deliver isobutene at a volume flow rate of 4.1 mL / min, that is, the molar flow rate of isobutene delivered is 0.0497 mol / min, which is greater than the required 0.0454 mol / min, and can completely react the phenol. The phenol aluminum solution is fed from the main feed port and sequentially enters the first reaction module, the second reaction module, the third reaction module, and the fourth reaction module. Isobutene is fed in segments into the first reaction module, the second reaction module, the third reaction module, and the fourth reaction module. The temperature of the first reaction module is 50 °C, the temperature of the second reaction module is 80 °C, the third reaction module is 100 °C, and the fourth reaction module is 130 °C. The pressure of the back pressure valve is 0.3 Mpa, and the total residence time of the four reaction modules is 45 min. After the reaction, the reaction solution exits through the back pressure valve and enters the receiving bottle to obtain the reaction solution of 2,6-di-tert-butylphenol. By quantitative analysis with gas chromatography, the mass percentage content of each component is as follows: 2,6-di-tert-butylphenol 90.3%, 2-tert-butylphenol 0.06%, 2,4-di-tert-butylphenol 1.27%, 2,4,6-tri-tert-butylphenol 7.7%, phenol 0.54%, and other impurities 0.13%. The conversion rate of phenol is 99.46%, and the selectivity of 2,6-di-tert-butylphenol is 90.79%.

[0047] Comparative Example 3:

[0048] Charge according to a mass ratio of phenol to aluminum chips of 1:0.0025. Add 1000 g (10.6 mol) of phenol and 2.5 g of aluminum to a 4 L high-pressure reactor, then heat up to 150 °C and keep the temperature for 0.5 h to obtain the phenol aluminum solution. Cool down to 40 °C, and then pass 1190 g of isobutene (add isobutene according to a molar ratio of phenol to isobutene of 1:2) through the metering pump and feed all the isobutene into the reactor containing the phenol aluminum solution at one time. Heat up to 95 °C and keep the temperature for 10 h. After the reaction, obtain the reaction solution containing the crude product of 2,6-di-tert-butylphenol. By quantitative analysis with gas chromatography, the mass percentage content of each component is as follows: 2,6-di-tert-butylphenol 78.9%, 2-tert-butylphenol 1.7%, 2,4-di-tert-butylphenol 4.5%, 2,4,6-tri-tert-butylphenol 13.9%, phenol 0.59%, and other impurities 0.41%. The conversion rate of phenol is 99.41%, and the selectivity of 2,6-di-tert-butylphenol is 79.3%.

[0049] In the above Examples 1 to 4, the solution after the reaction of phenol and a small amount of aluminum and liquid isobutene are used as reaction raw materials, 2-tert-butylphenol is added, and a microchannel reactor is used as the reaction vessel to continuously synthesize 2,6-di-tert-butylphenol. The conversion rate of phenol is 98.95 - 99.9%, and the selectivity of 2,6-di-tert-butylphenol reaches 95.2 - 97.4%.

[0050] In the above Comparative Example 1, the solution after the reaction of phenol and a small amount of aluminum and liquid isobutene are used as reaction raw materials, 2-tert-butylphenol is added, and a high-pressure reaction kettle is used as the reaction vessel to synthesize 2,6-di-tert-butylphenol. The conversion rate of phenol is 97.9%, and the selectivity of 2,6-di-tert-butylphenol is 83%.

[0051] In the above Comparative Example 2, the solution after the reaction of phenol and a small amount of aluminum and liquid isobutene are used as reaction raw materials, and a microchannel reactor is used as the reaction vessel to continuously synthesize 2,6-di-tert-butylphenol. The conversion rate of phenol is 99.46%, and the selectivity of 2,6-di-tert-butylphenol is 90.79%.

[0052] In the above Comparative Example 3, the solution after the reaction of phenol and a small amount of aluminum and liquid isobutene are used as reaction raw materials, and a high-pressure reaction kettle is used as the reaction vessel to synthesize 2,6-di-tert-butylphenol. The conversion rate of phenol is 99.41%, and the selectivity of 2,6-di-tert-butylphenol is only 79.3%.

[0053] Comparing Example 1 and Comparative Example 1, it can be seen that when using a microchannel reactor as the reaction vessel to continuously synthesize 2,6-di-tert-butylphenol, compared with using a high-pressure reaction kettle as the reaction vessel to synthesize 2,6-di-tert-butylphenol, the selectivity of 2,6-di-tert-butylphenol is increased by 12 - 15%. The reason is that based on the microscale effect, efficient mass and heat transfer, and precise process control of the microchannel reactor, the selectivity of the reaction is significantly improved.

[0054] Comparing Example 1 and Comparative Example 2, it can be seen that when the solution after the reaction of phenol and a small amount of aluminum and liquid isobutene are used as reaction raw materials, adding 2-tert-butylphenol can reduce the production amount of the by-product 2,4,6-tri-tert-butylphenol. This is because adding 2-tert-butylphenol can form a complex with aluminum phenoxide, reduce the catalytic activity of aluminum phenoxide, slow down the introduction of the third tert-butyl group into the phenol ring, thereby inhibiting the formation of 2,4,6-tri-tert-butylphenol, and the selectivity of 2,6-di-tert-butylphenol is significantly improved.

[0055] Comparing Example 1 with Comparative Example 3, it can be seen that when the solution obtained by reacting phenol with a small amount of aluminum and liquid isobutene are used as reaction raw materials, if 2-tert-butylphenol is not added and a microchannel reactor is not used as the reaction vessel for continuous synthesis of 2,6-di-tert-butylphenol, but a high-pressure reactor is used as the reaction vessel, the selectivity of 2,6-di-tert-butylphenol is significantly reduced, and the contents of by-products 2,4-di-tert-butylphenol (4.5%) and 2,4,6-tri-tert-butylphenol increase significantly.

[0056] In the microchannel reactor used in this application, the "6"-shaped channel causes strong vortices in the flowing fluid, thereby enhancing the mixing between reactants, improving the contact efficiency between phenol and isobutene, and ensuring sufficient mixing of reactants. The "6"-shaped channel increases the fluid path length, prolongs the residence time of the reactants in the reactor, ensures that the reactants have enough time to react, and improves the conversion rate of the main reaction. The "6"-shaped channel helps to evenly distribute heat, reduces local overheating, maintains the stability of the reaction temperature, and avoids side reactions caused by temperature fluctuations. The continuous double-ring design of the "6"-shaped channel can effectively reduce the backmixing phenomenon of the fluid and improve the selectivity and yield of the reaction.

[0057] Although the present application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A method for continuously synthesizing 2,6-di-tert-butylphenol using a microchannel reactor, characterized in that: The method comprises the following steps: mixing phenol and aluminum, heating to make the aluminum react completely, and obtaining a preliminary solution; the preliminary solution contains a catalytic amount of aluminum phenol, and the solvent is phenol; adding 2-tert-butylphenol to the preliminary solution to obtain an aluminum phenol solution, and passing the aluminum phenol solution and isobutylene into a microchannel reactor for mixed reaction to obtain 2,6-di-tert-butylphenol; The microchannel reactor comprises a plurality of reaction modules connected in series; each of the reaction modules has a plurality of vortex grooves connected in series; each of the vortex grooves comprises a strip groove and a circular groove, and the strip groove is tangentially connected to the circular groove; the volume of each vortex groove is 0.1-0.5 mL; In each of the reaction modules, the vortex grooves are connected in series in such a manner that the strip groove of an adjacent vortex groove is connected to the circular groove of another adjacent vortex groove, and the circular groove is connected to the next strip groove.

2. The method for continuously synthesizing 2,6-di-tert-butylphenol using a microchannel reactor according to claim 1, characterized in that: The mass ratio of phenol, aluminum and 2-tert-butylphenol is 1:(0.001~0.005):(0.1~0.4).

3. The method for continuously synthesizing 2,6-di-tert-butylphenol using a microchannel reactor according to claim 1, characterized in that: Among the raw materials input, the molar amount of phenol is x, the molar amount of 2-tert-butylphenol is y, and the molar amount of isobutylene is z, (2x+y):z=1:(1~2).

4. The method for continuously synthesizing 2,6-di-tert-butylphenol using a microchannel reactor according to claim 1, characterized in that: The reaction module is in a plate shape, and a plurality of vortex grooves are arranged on the front and back sides of the reaction module; The vortex grooves on the front side are repeatedly connected in a manner of connecting one vortex groove on the back side, so as to connect all the vortex grooves of the reaction module in series, including the strip groove of the vortex groove on the front side connected to the circular groove of the previous vortex groove on the back side, and the circular groove of the vortex groove on the front side connected to the strip groove of the next vortex groove on the back side.

5. The method for continuously synthesizing 2,6-di-tert-butylphenol using a microchannel reactor according to claim 1, characterized in that: The microchannel reactor includes four reaction modules connected in series, namely a first reaction module, a second reaction module, a third reaction module and a fourth reaction module. Before the aluminum phenol solution and isobutylene are introduced into the microchannel reactor, the temperature of the first reaction module is set to 50-60°C, the temperature of the second reaction module is set to 70-90°C, the temperature of the third reaction module is set to 100-120°C, and the temperature of the fourth reaction module is set to 130-150°C.

6. The method for continuously synthesizing 2,6-di-tert-butylphenol using a microchannel reactor according to any one of claims 1, 4 and 5, characterized in that: The microchannel reactor has a main inlet and a main outlet, and each reaction module has a sub-inlet; The aluminum phenol solution enters from the main inlet of the microchannel reactor and passes through each vortex groove of each reaction module in sequence; the liquefied isobutylene enters from the branch inlet of each reaction module and passes through each vortex groove of the reaction module and each vortex groove of the subsequent reaction module in sequence.

7. The method for continuously synthesizing 2,6-di-tert-butylphenol using a microchannel reactor according to claim 6, characterized in that: The flow rate of the aluminum phenol solution is 2-10 mL / min; the total flow rate of the liquefied isobutylene is 3-30 mL / min.

8. The method for continuously synthesizing 2,6-di-tert-butylphenol using a microchannel reactor according to claim 1, characterized in that: Phenol and aluminum are mixed and heated to 130-160° C. to allow the aluminum to react completely, thereby obtaining the initial solution.

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