Device used for lowering acid value of TDI product produced through heavy solvent method

Abstract

The invention belongs to the technical field of chemical industry production, and relates to a device used for lowering the acid value of a TDI product produced through a heavy solvent method. A feeding preheater is connected to the middle of a product tower in a butt mode through pipeline communication to preheat photochemical reaction materials, the top of the product tower is connected with a product tower condenser used for condensing and recycling the TDI product, a reboiler arranged at the bottom of the product tower in a communication mode is used for vaporization backflow, the bottom of the product tower is in pipe communication with a purging tower through a residue pump so as to purge acid components conveniently, and the reboiler, the residue pump and the purging tower are in pipe connection and communication. The top of the purging tower is connected with a purging tower condenser used for condensing and recycling acid components. Distribution devices of spray structures arranged in inner cavities at the top and bottom of the purging tower are used for distributing heavy solvent isophthalic acid diethyl ester and inert gas. All the devices are provided with pipelines and ports thereof for conveying materials. The whole device is scientific in design, reasonable in structure, easy to operate, convenient to use and good in application environment.

Description

Technical field: [0001] The invention belongs to the technical field of chemical production, and relates to a device for reducing the acid value of TDI products by the heavy solvent method, which can reduce the generation of by-products when the circulating solvent returns to the previous process to participate in the photochemical reaction, thereby improving the photochemical reaction efficiency and system stability. Background technique: [0002] Toluene diisocyanate (hereinafter referred to as TDI) is an important isocyanate product. Common production and preparation methods in the industry include phosgenation, nitro compound carbonylation and dimethyl carbonate. Among them, phosgenation is generally The following two processes are used: one is to use diethyl isophthalate (hereinafter referred to as DEIP) as a solvent, and carry out photochemical reaction under high pressure conditions, which is called "heavy solvent method"; Chlorobenzene (ODCB) etc. are used as solven...

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Problems solved by technology

[0004] The acidic components produced in the process of producing TDI by the heavy solvent method mainly include hydrogen chloride, benzylic chlorotoluene diisocyanate (hereinafter referred to as Cl-TDI), m-ethyl benzoyl chloride (hereinafter referred to as CBC), etc., wherein Cl- The boiling points of TDI and CBC are between the product TDI and the solvent DEIP. In the product refining process, the product and the solvent are separated in the final product tower. On the one hand, if the acidic component is extracted from the tower with the heavy solvent , because the solvent has to be returned to the system for recycling, the presence of acidic components will cause more photochemical side reactions to generate by-products such as residues, which will affect the reaction yield and the stable operation of the system; if the acidic components enter the product If it is extracted from the top of the tower, it is a heavy component compared to TDI. At this time, if the method of rectification or purging is used, a large amount of products will be brought into the gas phase, which requires high equipment size and energy consumption. and cannot reasonably and effectively separate the acidic components

Therefore, the rectification method and gas purging method, which are more suitable for the light solvent method, are not suitable for the removal of acidic components in TDI products produced by the heavy solvent method.

[0005] In addition, in the prior art, there is also a method of reducing the acid value and acidic component content of TDI products by adding additional substances, such as US Pat. Above 180°C, the heating time is preferably above 240min, which can significantly reduce the content of acidic components in isocyanate; although the above method of adding substances can better remove the acidic components in the product, but at the same time introduces a new impurity group After that, it needs to be separated from the product by nitrogen purging, rectification or extraction, which virtually increases the workload

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