Bubbling tower and method for producing benzoic acid by liquid phase oxidation of toluene with the same

Abstract

The invention discloses a bubbling tower device for producing benzoic acid by liquid phase oxidation of toluene. The bubbling tower device includes a cylinder tower body, a tower top head, a tower bottom head, a gas phase outlet, a safety pressure relief port and a liquid phase outlet. A gas distributor, a spiral plate member and a flow disturbing member are arranged in the cylinder tower from bottom to top. Outer circulation pipes are arranged on the two sides of the cylinder tower body. Heat exchangers are arranged on the outer circulation pipes. Lower end outlets of the outer circulation pipes are located between the gas distributor and the spiral plate member. Upper end inlets of the outer circulation pipes are located at the upper part of the flow disturbing member. A toluene inlet, acatalyst inlet and a gas inlet are arranged on the cylinder tower body and located at the lower end of the corresponding outer circulation pipe. The gas inlet is connected to the gas distributor. Thebubbling tower device of the invention can effectively realize material circulation of the whole tower without moving members, is sufficient in gas-liquid mass transfer, can improve the yield of thebenzoic acid, can reduce the content of impurities such as biphenyl, and can ensure production safety. The external heat exchangers of the device can be repaired without stopping, which saves energy and reduces 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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