Method for preparing aromatic tetracid through piston continuous flow catalytic oxidation reaction system

Abstract

The invention discloses a method for preparing aromatic tetracid by a piston continuous flow catalytic oxidation reaction system, which adopts a cobalt-manganese-bromine-ternary composite catalytic system, takes acetic acid as a solvent and takes atomic oxygen as an oxidizing agent to carry out piston continuous flow catalytic oxidation reaction gas-liquid catalysis on an aromatic tetramethyl compound so as to prepare aromatic tetracid, and the molar yield is more than 95%. According to the piston continuous flow composite catalytic oxidation reaction system, the liquid holdup of the reaction system is 10 liters or below, radial mechanical stirring is adopted, the efficiency is improved by 100 times or above compared with a traditional reaction kettle, the reaction is safe and environment-friendly, the efficiency is high, and the piston continuous flow composite catalytic oxidation reaction system is suitable for industrial production.

Description

Technical Field

[0001] The invention relates to a method for preparing aromatic tetraacids by a piston continuous flow catalytic oxidation reaction system, belonging to the category of synthetic chemistry. Background Art

[0002] Polyimide is a polymer material with the highest heat resistance level among polyimides, and is lightweight and high-strength. The main method for preparing polyimide is to condense aromatic dianhydrides with diamines. However, in general, most aromatic dianhydrides must be prepared through condensation or coupling of monoanhydrides. For example, the most famous biphenyl-type polyimide, its monomer biphenyl tetracarboxylic dianhydride, is mainly prepared in industry by coupling monosodium chlorophthalate with Pd catalysis. The shortcomings of this method are: 1) the amount of precious metal Pd catalyst used is large, the price is expensive, and the recovery cost is high; 2) the catalytic reaction process easily leads to the dechlorination of chlorophthalic acid, with a yield of ~60%; 3) it can only be used to prepare 3,3',4,4'-biphenyl dianhydride, and it is difficult to prepare other isomers of biphenyl dianhydride. Therefore, the above reasons lead to the high price of biphenyl dianhydride monomer. CN1436780A uses mixed 3- and 4-chlorophthalic acid dimethyl ester or mixed 3- and 4-chlorophthalimide as raw materials to prepare isomeric biphenyl dianhydride. The intermediate mixture generated has similar properties and cannot be separated efficiently. The purification process of biphenyl dianhydride is complicated, the cost is high, and the composition ratio is unstable.

[0003] Compared with kettle reactors, the piston continuous flow reaction system has a small liquid holding capacity and a stirring efficiency equivalent to 100 kettle reactions in series. The reaction can be completed within 10 minutes or even a few seconds, and can achieve unidirectional flow of materials, reduce the occurrence of side reactions, and overcome the blockage problem of solid-liquid mixed materials caused by the narrow channels of the microfluidic reaction system. It is a green chemical process and is suitable for industrial production. Summary of the invention

[0004] In order to overcome the large liquid holding capacity and potential danger of kettle liquid phase oxidation reaction system, the present invention provides a cobalt-manganese-bromine ternary composite catalytic system, which utilizes the small liquid holding capacity of the piston continuous flow reaction system and the high-efficiency radial stirring to disperse the gas in the reaction system into tiny bubbles, thereby increasing the contact probability of reactants, gas-phase oxidant and catalyst at the interface, thereby improving the reaction efficiency, solving the problem that the traditional cobalt-manganese-bromine ternary catalytic system needs 200°C and 2MP for oxidation reaction, improving the safety factor of the reaction, reducing the occurrence of decarboxylation side reaction, and improving the reaction efficiency and yield.

[0005] In order to achieve the above-mentioned invention task, the present invention adopts the following technical scheme: a method for preparing aromatic tetraacids by a piston continuous flow catalytic oxidation reaction system, and the process specifically comprises the following steps:

[0006] 1) mixing the raw material aromatic methyl compound, the catalyst cobalt-manganese-bromine ternary composite catalyst, and the solvent glacial acetic acid in a certain proportion, and then introducing the mixture into a piston flow reactor reaction module, and controlling the liquid flow rate to 50-1000 mL / min;

[0007] 2) At the same time, atomic oxygen gas is introduced into the reaction module of the plug flow reactor, the gas oxidant flow rate is controlled to be 3L-300L / min, and the temperature of the reaction module is controlled at 120-165°C and automatically raised to 0.11-1.2MPa;

[0008] 3) The reaction product flows out from the reactor outlet, and the temperature of the gas-solid separator is controlled at 140-150° C. to achieve gas-solid separation of gaseous acetic acid and aromatic tetraacids, and the solvent acetic acid is recovered by condensation;

[0009] 4) The obtained solid crude product is washed three times with cold water to remove the catalyst and other impurities to obtain the pure aromatic tetraacid;

[0010] The aromatic methyl compounds are a to h in the following structural formulas;

[0011]

[0012] The catalyst is a ternary composite catalyst of cobalt salt, manganese salt, and bromide;

[0013] The solvent is glacial acetic acid, and the oxygen concentration in the atomic oxygen is 20 to 100%.

[0014] Furthermore, the cobalt salt includes one of cobalt acetate, cobalt carbonate, cobalt sulfate, cobalt chloride, and cobalt bromide; the manganese salt includes one of manganese acetate, manganese chloride, manganese carbonate, and manganese bromide; and the bromide includes one of tetrabromoethane, sodium bromide, potassium bromide, and hydrogen bromide.

[0015] Furthermore, the molar ratio of cobalt element: manganese element: bromine element in the catalyst is 1-8: 1-4: 1-5, the mass concentration of the catalyst in the reaction system is 0.05-1.0%, and the mass concentration of the reactants is 10-30%.

[0016] Furthermore, the reaction module of the piston continuous flow reactor can be made of corrosion-resistant and heat-resistant glass, polytetrafluoroethylene, silicon carbide, titanium alloy and Hastelloy; its reaction volume is 100mL-10L, and the reaction modules can be 2 to 10 connected in series or 2 to 10 connected in parallel, adopting a radial mechanical stirring mode, and the residence time of the reactants is 10 seconds to 10 minutes.

[0017] Beneficial technical effects of the present invention:

[0018] The invention discloses a technology for preparing aromatic tetraacids by oxidation using a piston continuous flow ternary composite catalytic system, which avoids the occurrence of a decarboxylation side reaction in the traditional terephthalic acid system for preparing aromatic tetraacids at high temperature and high pressure to the greatest extent, and solves the problem that aromatic methyl compounds cannot be completely converted into carboxyl compounds due to incomplete oxidation reaction at low temperature and normal pressure, and the subsequent dianhydride product purity is affected due to difficulty in separation and purification, and cannot be used for polymerization reaction.

[0019] Compared with traditional kettle reaction systems, piston continuous flow has a small liquid holding volume, has inherent safety characteristics, occupies a small area of ​​equipment, and has high stirring efficiency, which is especially suitable for reaction systems with precipitates. A set of CofloreATR industrial-scale piston continuous flow reaction system can reach an annual flow rate of hundreds to thousands of tons, which meets the requirements of industrial production and conforms to the development trend of chemical production in the new situation to pursue inherent safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Flow chart for the preparation of aromatic tetraacids in a piston continuous flow catalytic oxidation reaction system.

[0021] Figure 2 This is the H NMR spectrum of 3,3',4,4'-biphenyltetracarboxylic acid.

[0022] Figure 3 This is the H NMR spectrum of 2,3,3',4'-biphenyltetracarboxylic acid.

[0023] Figure 4 This is the H NMR spectrum of hexafluoropropylisopropyldiphenyltetracoate.

[0024] Figure 5 It is a technical production equipment for the oxidation preparation of aromatic tetraacids by piston continuous flow ternary composite catalytic system.

[0025] Figure 6 This is a diagram of the radial stirring effect of the reaction module of the piston flow reaction system.

[0026] The present invention is specifically described below in conjunction with embodiments, but the present invention is not limited to the scope of the embodiments.

[0027] Example 1

[0028] In a 20-liter glass flask, 2.1 kg (10 mol) of 3,3',4,4'-tetramethylbiphenyl (aromatic methyl compound e), 10 kg of glacial acetic acid, 48 g of cobalt acetate, 24 g of manganese acetate and 48 g of hydrogen bromide were stirred and mixed, and then pumped into a piston continuous flow reactor containing 4 series reaction modules (each module has a liquid holding capacity of 1 liter) through a metering pump, and the liquid flow rate was controlled at 200 mL / min; at the same time, pure oxygen gas was introduced into the reaction module of the reactor, and the gas flow rate was controlled at 25 L / min. The temperature of the first reaction module was controlled at 120 ° C, and the temperature of the second reaction module was controlled at 120 ° C. The temperature of the second and third modules was controlled at 160°C, and the temperature of the fourth module was controlled at 150°C; the reactants stayed in the reaction module for a total of 3 minutes, and flowed out from the reactor outlet, and the temperature of the gas-solid separator was controlled at 145°C, and the gaseous acetic acid and biphenyltetracid were separated by gas-solid separation, and the acetic acid was recovered and reused after cooling. At this time, the oxygen flow rate was about 24L / min; the reaction was terminated, and the obtained solid crude product was washed three times with cold water, and 3.1kg of 3,3',4,4'-biphenyltetracid was obtained, with a mass yield of 147%. The NMR spectrum of the obtained 3,3',4,4'-biphenyltetracid is as follows Figure 2 shown.

[0029] Example 2

[0030] In a 10-liter flask, 2.1 kg (10 mol) of 2,3,3',4'-tetramethylbiphenyl (aromatic methyl compound f), 6 kg of glacial acetic acid, 24 g of cobalt acetate, 10 g of manganese acetate, and 5 g of tetrabromoethane were stirred and mixed, and then pumped into a reactor containing 5 plug flow reaction modules connected in series (each module had a liquid holding capacity of 1 liter) through a metering pump, and the liquid flow rate was controlled at 300 mL / min; the 100% oxygen gas flow rate was controlled at 50 L / min, the temperature of the first reaction module was controlled at 130 °C, and the temperature of the second to fourth modules was controlled at ~1 65℃, the temperature of the fifth module is controlled at 155℃; the reactants stay in the reaction module for a total of 5 minutes, flow out from the reactor outlet, control the temperature of the gas-solid separator at 150℃, gaseous acetic acid and 2,3,3',4'-biphenyltetracid are separated by gas-solid separation, and the acetic acid is recycled after cooling. At this time, the oxygen flow rate is about 48L / min; the reaction is terminated, and the obtained solid crude product is washed three times with cold water to obtain 3,3',4,4'-biphenyltetracid 3.0kg, with a mass yield of 142%. The NMR spectrum of the obtained 2,3,3',4'-biphenyltetracid is as follows Figure 3 shown.

[0031] Example 3

[0032] In a 20-liter flask, 3.6 kg (10 mol) of 3,3',4,4'-tetramethyldiphenylhexafluoroisopropane (aromatic methyl compound h), 20 kg of glacial acetic acid, 48 g of cobalt acetate, 16 g of manganese acetate, and 10 g of sodium bromide were stirred and mixed, and then pumped into a reactor containing three plug flow reaction modules in series (each module had a liquid holding capacity of 1 liter) through a metering pump, and the liquid flow rate was controlled at 150 mL / min; the air flow rate was controlled at 50 L / min, the temperature of the first reaction module was controlled at 150 °C, and the temperature of the second and The temperature of the third module is controlled at 165°C; the reactants stay in the reaction module for a total of 10 minutes and flow out from the reactor outlet. The temperature of the gas-solid separator is controlled at 150°C, and the gaseous acetic acid and hexafluoropropyl isopropyl diphenyl tetraacid are separated by gas-solid separation. The acetic acid is recovered and reused after cooling. At this time, the air flow rate is 47.5 / min; the reaction is terminated, and the obtained solid crude product is washed three times with cold water. The obtained hexafluoropropyl isopropyl diphenyl tetraacid is 4.64 kg, and the mass yield is 129%. The nuclear magnetic hydrogen spectrum of the obtained hexafluoropropyl isopropyl diphenyl tetraacid is as follows Figure 4 shown.

[0033] The above is a detailed introduction to the method for oxidizing and preparing aromatic tetraacids by a piston continuous flow ternary composite catalytic system provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that one of the characteristics of the piston continuous flow catalytic oxidation reaction system is the smaller amplification effect. Therefore, for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified such as flux amplification without departing from the principle of the present invention. For example, the present method is used to prepare benzoic acid from toluene, to prepare phthalic acid from xylene, to prepare halogenated methylbenzene from halogenated benzoic acid and other similar methods. These improvements and modifications also fall within the scope of full protection of the present invention.

Claims

1. A method for preparing aromatic tetraacids by a piston continuous flow catalytic oxidation reaction system, wherein the process specifically comprises the following steps: 1) mixing the raw material aromatic methyl compound, the catalyst cobalt-manganese-bromine ternary composite catalyst, and the solvent glacial acetic acid in a certain proportion, and then introducing the mixture into a piston flow reactor reaction module, and controlling the liquid flow rate to 50-1000 mL / min; 2) At the same time, atomic oxygen gas is introduced into the reaction module of the plug flow reactor, the gas oxidant flow rate is controlled to be 3L-300L / min, and the temperature of the reaction module is controlled at 120-165°C and automatically raised to 0.11-1.2MPa; 3) The reaction product flows out from the reactor outlet, and the temperature of the gas-solid separator is controlled at 140-150° C. to achieve gas-solid separation of gaseous acetic acid and aromatic tetraacids, and the solvent acetic acid is recovered by condensation; 4) The obtained solid crude product is washed three times with cold water to remove the catalyst and other impurities to obtain the pure aromatic tetraacid; The aromatic methyl compounds are a to h in the following structural formulas; The catalyst is a ternary composite catalyst of cobalt salt, manganese salt, and bromide; The solvent is glacial acetic acid, and the oxygen concentration in the atomic oxygen is 20 to 100%.

2. A method for preparing aromatic tetraacids in a piston continuous flow catalytic oxidation reaction system according to claim 1, characterized in that: The cobalt salt includes one of cobalt acetate, cobalt carbonate, cobalt sulfate, cobalt chloride and cobalt bromide; the manganese salt includes one of manganese acetate, manganese chloride, manganese carbonate and manganese bromide; the bromide includes one of tetrabromoethane, sodium bromide, potassium bromide and hydrogen bromide.

3. A method for preparing aromatic tetraacids in a piston continuous flow catalytic oxidation reaction system according to claim 1, characterized in that: The molar ratio of cobalt element: manganese element: bromine element in the catalyst is 1-8: 1-4: 1-5, the mass concentration of the catalyst in the reaction system is 0.05-1.0%, and the mass concentration of the aromatic methyl reactant is 10-30%.

4. A method for preparing aromatic tetraacids in a piston continuous flow catalytic oxidation reaction system according to claim 1, characterized in that: The reaction module of the piston continuous flow reactor can be made of corrosion-resistant and heat-resistant glass, polytetrafluoroethylene, silicon carbide, titanium alloy and Hastelloy; its reaction volume is 100mL-10L, and the reaction modules can be 2 to 10 connected in series or 2 to 10 connected in parallel, adopting a radial mechanical stirring mode, and the residence time of the reactants is 10 seconds to 10 minutes.

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