Method for preparing aromatic carboxylic acid through piston flow micro-interface reinforced continuous catalytic oxidation reaction

Abstract

The invention discloses a method for preparing aromatic carboxylic acid by a piston flow micro-interface reinforced continuous catalytic oxidation reaction, which adopts a cobalt-manganese-bromine-ternary composite catalytic system, takes acetic acid as a solvent, takes atomic oxygen as an oxidizing agent, and adopts a cobalt-manganese-bromine-ternary composite catalytic system to prepare the aromatic carboxylic acid. A micro-interface formed by the nano material additive enhances the efficiency of preparing the aromatic carboxylic acid by gas-liquid catalysis of the aromatic tetramethyl compound in the piston flow continuous catalytic oxidation reaction, and the molar yield is high. According to the piston flow continuous 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 that of a traditional reaction kettle, the reaction is safe and environmentally friendly, the efficiency is high, and the piston flow continuous catalytic oxidation reaction system is suitable for industrial production.

Description

Technical Field

[0001] The invention relates to a method for preparing aromatic carboxylic acid by plug flow microinterface enhanced continuous catalytic oxidation reaction, 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 monoanhydride derivatives. 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 flow continuous 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 problems of large liquid holding capacity, potential danger, low microchannel reaction flux, and reaction blockage caused by solid participation or generation in kettle-type liquid-phase oxidation reaction systems, the present invention provides a cobalt-manganese-bromine ternary composite catalytic system, which utilizes the small liquid holding capacity and high-efficiency radial stirring of the piston flow continuous reaction system, and further strengthens the dispersion of the gas in the reaction system into smaller bubbles by adding nano additives, thereby increasing the contact probability of the reactants, gas-phase oxidant and catalyst at the interface, thereby improving the reaction efficiency, solving the problem of the traditional cobalt-manganese-bromine ternary catalytic system requiring 200°C and 2MP for oxidation reaction, improving the safety factor of the reaction, reducing the occurrence of decarboxylation side reactions, 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 carboxylic acid by plug flow micro-interface enhanced continuous catalytic oxidation reaction, the process of which specifically includes the following steps:

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

[0007] 2) At the same time, the gas atomic oxygen 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 to be 120-150°C;

[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 recrystallized through a solvent to remove the catalyst, additives and other impurities to obtain a pure aromatic tetraacid;

[0010] The aromatic methyl compounds are a to h in the following structural formula:

[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 atomic oxygen is 20 to 100%;

[0014] The additives are graphene, graphene oxide, silicon dioxide and zirconium oxide with a size of 1 to 500 nm;

[0015] Furthermore, the cobalt salt includes one of cobalt acetate, 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.

[0016] 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%.

[0017] Furthermore, the reaction module of the piston 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.

[0018] Furthermore, the recrystallization solvent is acetone, isopropanol or a mixture of the two; the amount of the nano additive is 0.01-1% of the solvent mass.

[0019] Beneficial technical effects of the present invention:

[0020] The invention discloses a technology for preparing aromatic carboxylic acids by continuous oxidation using a piston flow microinterface enhanced catalytic system, which avoids the occurrence of a decarboxylation side reaction in the traditional terephthalic acid system, such as the high temperature and high pressure preparation of aromatic tetraacids, 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.

[0021] Compared with traditional kettle reaction systems, piston flow has a small liquid holding volume, has inherent safety characteristics, and occupies a small area of ​​equipment. By adding nano-additives to form a tiny interface, combined with its advantage of high radial stirring efficiency, the reaction efficiency is greatly improved, especially suitable for reaction systems with precipitates. A set of CofloreATR industrial-scale piston flow continuous reaction system can reach an annual flow rate of hundreds to thousands of tons, which meets the requirements of industrial production and is in line with the development trend of chemical production in the new situation to pursue inherent safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Flow chart for the preparation of aromatic carboxylic acids by plug flow microinterface enhanced continuous catalytic oxidation reaction.

[0023] Figure 2 This is the C NMR spectrum of 3,3',4,4'-biphenyltetracarboxylic acid.

[0024] Figure 3 This is the NMR carbon spectrum of 2,3,3',4'-biphenyltetracarboxylic acid.

[0025] The present invention is specifically described below in conjunction with embodiments, but the present invention is not limited to the scope of the embodiments.

[0026] Example 1

[0027] 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, 48 g of hydrogen bromide and 2 g of zirconium oxide (10-50 nm) were stirred and mixed, and then pumped into a piston continuous flow reactor containing 3 series reaction modules (each module had 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, 100% 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 reaction module is controlled at 130°C, and the temperature of the second and third modules is controlled at ~150°C; the reactants stay in the reaction module for a total of 2.5 minutes, flow out from the reactor outlet, and the temperature of the gas-solid separator is controlled at 145°C. The gaseous acetic acid and biphenyltetracarboxylic acid are separated by gas-solid separation. The acetic acid is recovered and reused after cooling. At this time, the oxygen flow rate is about 24L / min; the reaction is terminated, and the obtained solid crude product is crystallized by isopropanol to obtain 3.15kg of 3,3',4,4'-biphenylcarboxylic acid with a mass yield of 150%. The NMR spectrum of the obtained 3,3',4,4'-biphenyltetracarboxylic acid is as follows: Figure 1 shown.

[0028] Example 2

[0029] 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, 5 g of tetrabromoethane, and 10 g of ~100 nm silicon dioxide were stirred and mixed, and then pumped into a reactor containing 4 plug flow reaction modules in series (each module had a 2 liter liquid holding capacity) 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 module was controlled at 130°C. The temperature of the third and fourth modules is controlled at 150°C; the reactants stay in the reaction module for a total of 4 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 2,3,3',4'-biphenyltetracid are separated by gas-solid separation. The acetic acid is recovered and reused after cooling. At this time, the flow rate of oxygen is about 48L / min; the reaction is terminated, and the obtained solid crude product is crystallized with acetone to obtain 3.1kg of 2,3,3',4'-biphenyltetracid with a mass yield of 147%. The NMR spectrum of the obtained 2,3,3',4'-biphenyltetracid is as follows: Figure 2 shown.

[0030] Example 3

[0031] 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, 10 g of sodium bromide, and 3.6 g of ~50 nm graphene 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 3 liters) 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 and third modules is controlled at ~150°C; the reactants stay in the reaction module for a total of 6 minutes, flow out from the reactor outlet, and the temperature of the gas-solid separator is controlled at 150°C. Gaseous acetic acid and hexafluoropropylisopropyldiphenyltetracarboxylic acid are separated from each other by gas and solid. The acetic acid is recovered after cooling and reused. At this time, the air flow rate is ~47.5 / min; the reaction is terminated, and the obtained solid crude product is crystallized through acetone to obtain 4.70 kg of hexafluoropropylisopropyldiphenyltetracarboxylic acid with a mass yield of 130%.

[0032] The above is a detailed introduction to the method for preparing aromatic carboxylic acids by continuous oxidation of a piston flow ternary composite catalytic system provided by the present invention. From the given nuclear magnetic carbon spectrum, it can be clearly concluded that the method of the present invention has the characteristic of thorough methyl oxidation. Specific examples are used herein to illustrate the principle and implementation mode 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 flow continuous 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. For example, the present method is used to prepare benzoic acid through toluene, xylene to prepare phthalic acid, halogenated methylbenzene to prepare halogenated benzoic acid and other similar methods. These improvements and modifications also belong to the scope of full protection of the present invention.

Claims

1. A method for preparing aromatic carboxylic acids by plug flow microinterface enhanced continuous catalytic oxidation reaction, characterized in that: The process specifically includes the following steps: 1) mixing the raw material aromatic methyl compound, the catalyst cobalt-manganese-bromine ternary composite catalyst, the additive and glacial acetic acid in a certain proportion, and then introducing the mixture into the reaction module of the plug flow reactor, and controlling the liquid flow rate to 50-1000 mL / min; 2) At the same time, the gas atomic oxygen 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 to be 120-150°C; 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 recrystallized through a solvent to remove the catalyst, additives and other impurities to obtain a pure aromatic tetraacid; The aromatic methyl compounds are a to h in the following structural formula: 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 atomic oxygen is 20 to 100%; The additive is graphene with a size of 1 to 500 nm, graphene oxide, silicon dioxide or zirconium oxide.

2. The method for preparing aromatic carboxylic acid by plug flow microinterface enhanced continuous catalytic oxidation reaction according to claim 1, characterized in that: The cobalt salt includes one of cobalt acetate, cobalt chloride and cobalt bromide; the manganese salt includes one of manganese acetate, manganese chloride and manganese bromide; the bromide includes one of tetrabromoethane, sodium bromide and hydrogen bromide.

3. The method for preparing aromatic carboxylic acid by plug flow microinterface enhanced continuous catalytic oxidation reaction 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. The method for preparing aromatic carboxylic acid by plug flow microinterface enhanced continuous catalytic oxidation reaction 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, 2 to 10 reaction modules can be connected in series or 2 to 10 in parallel, and the residence time of the reactants is 10 seconds to 10 minutes.

5. The method for preparing aromatic carboxylic acid by plug flow microinterface enhanced continuous catalytic oxidation reaction according to claim 1, characterized in that: The recrystallization solvent is acetone, isopropanol or a mixture of the two; the dosage of the nano additive is 0.01-1% of the solvent mass.

Images