Decolorization method and device for separating obtained crude styrene from pyrolysis gasoline

Abstract

A decolorization method for separating the obtained crude styrene from pyrolysis gasoline, comprising fully mixing and reacting the crude styrene with a dienophilic compound and passing it into the decolorization and refining tower (3) from the middle, and adding a decolorization co-solvent in the decolorization and refining tower , through rectification under vacuum, styrene is distilled from the top of the decolorization refining tower, and part of it flows back into the top of the decolorization refining tower (3), and the refined styrene product is located at the side line at the bottom of the reflux line from the top product pipeline (6) or the tower top (21) Discharging, introducing the liquid on the upper part of the decolorizing and refining tower kettle into the heat exchange tube of the reboiler outside the tower kettle, flowing from top to bottom, and being heated by the heating medium in the reboiler shell, and then by the pipeline (11) Return to the lower part of the decolorization and refining tower tower kettle, a part of the tower bottom component of the decolorization and refining tower returns to the heat exchange tube of the reboiler, and the rest is discharged from the tower bottom pipeline, and the described decolorization co-solvent is an organic compound containing nitrogen or oxygen , and its boiling point is 160-205°C. This method has good decolorization effect, no sewage discharge, and high recovery rate of styrene.

Description

technical field [0001] The invention relates to a method and device for decolorizing crude styrene separated from pyrolysis gasoline, in particular to a method and device for decolorizing crude styrene by using a dienophilic compound. Background technique [0002] Styrene is an important basic organic chemical raw material, and it is also widely used in coatings, pesticides, and medicine. According to statistics, the steam pyrolysis gasoline by-product of ethylene cracking unit contains 3-5% styrene. Due to the difference in raw materials for a set of 1 million tons / year ethylene unit, the styrene content in pyrolysis gasoline is 30,000-35,000 tons / year. year. In the existing process of dealing with pyrolysis gasoline, this part of styrene is hydrogenated into ethylbenzene, which is stored in C 8 In the distillate, this ethylbenzene-rich C 8 The distillate is not ideal for supplying the downstream p-xylene unit as raw material. If ultra-rectification is used to separate ...

AI Technical Summary

Problems solved by technology

The defect of this method is that the decolorization reaction is carried out in the reflux tank at the top of the tower, and the reflux flows into the top of the tower, and it is evaporated from the top of the tower after only one level of equilibrium. Therefore, a lot of maleic anhydride will inevitably be carried in the gas phase, which will affect the decolorization. effect, styrene products also contain maleic anhydride impurities

In addition, because maleic anhydride accumulates at the bottom of the tower and needs to be removed, if it is concentrated, it will easily cause blockage of the reboiler and pipeline at the bottom of the tower, making it difficult to operate the device for a long period of time. If it is not concentrated, more styrene will remain in the bottom of the tower. Resulting in a decrease in the recovery rate of styrene

[0009] CN101429091A discloses a decolorization method for recovering styrene by extraction and rectification. Maleic anhydride is used as a decolorizer. In this method, the decolorizer is added to the solvent for extraction and rectification. To decolorize raw materials containing styrene, the amount of decolorizer is greatly increased, and after adding to the solvent system, since the extraction and rectification process generally contains water, the acid produced by the decomposition of the decolorant when it encounters water will cause strong corrosion to the equipment. How to avoid the equipment during the extraction process Corrosion is not mentioned

However, because maleic anhydride is easily copolymerized with styrene to form a polymer that is insoluble in styrene, plus the self-polymer of styrene, it is easy to cause fouling of the reboiler of the refining tower, and the heating effect is rapid decline, and even cause the plugging of the packed tower, the operation period of the refining tower system is very short, generally less than 1 month

Existing solutions either leave a large amount of styrene (about 10% of the total amount) at the bottom of the refining tower at the cost of diluting the polymer, or add a large amount of polyethylbenzene heavy aromatics diluent to maintain the operation of the device, even if In this way, the operation period is still difficult to exceed 6 months, seriously affecting the economic benefits of the device

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