Continuous production process and device of benzoic acid

Abstract

The invention relates to a continuous production process of benzoic acid. The continuous production process comprises the following steps: (1) introducing toluene liquid and a catalyst; (2) introducing air, wherein the air reacts with the toluene liquid in the presence of a catalyst; (3) controlling temperature; and (4) discharging benzoic acid, and meanwhile, feeding through a feed opening of a reaction tower to realize continuous reaction. Devices used in the process include a reaction tower, a cooling device, an oil-water separator and an absorption tower, wherein a gas-liquid distribution stirrer is installed on the bottom of the reaction tower, two tubular heat exchangers are arranged at the middle part of the reaction tower, and a benzoic acid discharge opening in the upper part of the reaction tower is connected to a benzoic acid flash column. The continuous production process of benzoic acid and the device thereof provided by the invention can be used for improving the selectivity of the catalyst to the benzoic acid product, the gas-liquid mixing and heat exchange and realizing continuous production, thereby reducing the energy consumption in the process, continuously producing low-pressure vapor, improving the product quality and yield, decreasing by-products and reducing the production cost.

Description

technical field [0001] The invention relates to the field of benzoic acid, in particular to a continuous production process of benzoic acid and a device thereof. Background technique [0002] Industrially, benzoic acid is produced by oxidizing toluene with air in the presence of catalysts such as cobalt and manganese. Since the catalytic reaction is an exothermic process and the catalyst has high requirements and strong dependence on temperature, the higher the temperature, the faster the catalytic reaction, and the faster the catalytic reaction, the higher the temperature, forming a vicious cycle, so the catalyst activity is too high and the selectivity is poor , leading to increased by-products and poor selectivity. As the temperature continues to rise, there may even be overheating, causing the reaction tower to go out of control and cause an explosion. Therefore, in order to control the temperature and improve the selectivity of the process to ensure safe production, t...

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Problems solved by technology

[0004] 1. The reaction must be carried out at a certain temperature, so each batch of raw materials needs to be heated, and the normal oxidation process needs to be cooled, which leads to high energy consumption

[0005] 2. The feeding and discharging needs to be shut down, which wastes time and reduces work efficiency

[0006] 3. When the gas is discharged, some toluene will be brought out. The temperature of the toluene is about 160°C, and it must be cooled.

At present, cooling water is usually used for cooling, and the cooling water after heat exchange becomes hot water. Since the existing reaction is a discontinuous reaction, the hot water obtained after heat exchange cannot be effectively reused, which also causes energy waste.

[0007] 4. The air pressure in the reaction tower is 0.7Mpa, which needs to be maintained by an air compressor. When feeding and discharging, the compressor is basically in an idling state, wasting energy

[0008] 5. The output per unit volume is small

The temperature of the reaction process is not easy to control. If the temperature is too high or too low, a large amount of by-products such as benzaldehyde, benzyl alcohol, and benzyl benzoate will be produced, resulting in unstable product quality and low conversion rate. The current conversion rate is usually 50-55%.

[0010] 7. After cooling, there will be some catalyst and benzyl benzoate precipitated at the bottom of the reactor, which needs to be shut down for cleaning, resulting in prolonged working time

[0011] 8. Too many people and high cost

[0012] In addition, the current gas and toluene raw materials enter from the bottom of the reaction tower. Due to the uneven gas distribution, the catalyst selectivity is poor, which also causes problems such as low conversion rate and high by-products.

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