Bubble column device and its method for producing benzoic acid by liquid-phase oxidation of toluene

Abstract

The invention discloses a bubbling tower device for producing benzoic acid by liquid-phase oxidation of toluene, which comprises a cylindrical tower body, a tower top head, a tower bottom head, a gas phase outlet, a safety pressure relief port, a liquid phase outlet, a cylinder The gas distributor, the spiral plate member and the spoiler member are arranged in sequence from bottom to top in the vertical tower body. External circulation pipes are arranged on both sides of the cylindrical tower body, and a heat exchanger is arranged on the external circulation pipe. The lower end of the external circulation pipe The outlet is located between the gas distributor and the spiral plate member, the upper inlet of the external circulation pipe is located on the upper part of the spoiler; the toluene inlet, the catalyst inlet and the gas inlet are arranged on the cylindrical tower body and located at the lower end of the outer circulation pipe, and the gas inlet is connected to the gas inlet. Distributors are connected. The invention can efficiently realize material circulation in the whole tower without moving components, has sufficient gas-liquid mass transfer, can increase the yield of benzoic acid, reduce the content of impurities such as biphenyl, and ensure production safety. The external heat exchanger of the device can be overhauled without stopping the machine, saving energy and reducing consumption.

Description

technical field [0001] The invention relates to a reaction device for liquid-phase oxidation, in particular to a bubble column device and a method for producing benzoic acid by liquid-phase oxidation of toluene. Background technique [0002] Benzoic acid, also known as benzoic acid, is the simplest aromatic carboxylic acid, which exists in benzoin gum and the stem bark and leaves of some plants, often in the form of free acid, ester or its derivatives. The pure product is needle-like or scale-like crystals, slightly soluble in water, easily soluble in organic solvents such as ether and ethanol. Benzoic acid can be used as an antirust agent for iron and steel equipment, a mordant for dyeing and printing, and a modifier for carboxylic acid resins. It can also be used as an intermediate for pharmaceuticals and dyes. It is an important raw material for the preparation of caprolactam and phenol. Benzoic acid and its sodium salt are important food preservatives with high safety a...

AI Technical Summary

Problems solved by technology

Trichlorotoluene hydrolysis method is owing to contain chlorine, serious corrosion equipment, pollutes environment; The harmful impurity of phthalic anhydride decarboxylation method is less, but the benzoic acid of generation is difficult for refining, and production cost is higher; And toluene liquid-phase air oxidation method reaction condition Mild, less waste, is the most important production method of benzoic acid

Therefore, if crude product benzoic acid content is too high, will cause the yield of industrial grade benzoic acid and the reduction of content thereof in the follow-up rectification process

[0008] In addition, when the content of industrial-grade benzoic acid is lower than a certain value, such as 99.0%, it will be difficult for the content of crystalline benzoic acid in the melt crystallization section to reach 99.99%, which is the required content of pharmaceutical-grade benzoic acid

[0009] In addition, the problem encountered in the use of existing bubble column reactors: the gas is dispersed into smaller bubbles after passing through the gas distributor, but the bubbles will regroup into large bubbles in the process of rising, which is very difficult for gas-liquid phase transmission. quality is unfavorable

This kind of bubble accumulation that is not conducive to mass transfer will cause the decline of the overall reaction rate, and more seriously, it will cause the oxygen content in the tail gas at the outlet of the oxidation reaction device to be too high. If it is higher than 1.5%, it will form an explosive mixture with toluene, and there will be Security risks

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