A method for removing aldehyde impurities in propylene oxide by oxidation

Abstract

The invention provides an efficient method for purifying epoxypropane, which has low product loss and does not generate nitrogenous wastewater. According to the method for purifying the epoxypropane,in an epoxypropane rectifying tower, a hydrogen peroxide solution oxidizes aldehyde impurities in crude products into high-boiling-point acids under the action of a modified molecular sieve filler, and methanol is separated in a stripping section.

Description

technical field [0001] The invention belongs to the field of petrochemical technology, and relates to a method for removing aldehyde impurities in propylene oxide by an oxidation method, and more specifically, relates to a method for removing crude product from hydrogen peroxide solution under the action of molecular sieve filler in a propylene oxide rectification tower. Aldehyde impurities are oxidized to high-boiling acid, and the propylene oxide purification method is used to separate methanol in the stripping section. Background technique [0002] Propylene oxide is the second largest propylene derivative after polypropylene. It is mainly used in the production of polyether polyols, propylene glycol, isopropanolamine, and surfactants. It is widely used in industries such as automobiles, furniture, home appliances, and daily chemicals. . [0003] At present, more than 50% of the production capacity of propylene oxide in China is the highly polluting chlorohydrin method, ...

AI Technical Summary

Problems solved by technology

[0004] Although the HPPO process is environmentally friendly, with high product yield and good selectivity, it inevitably produces aldehyde impurities that are difficult to separate, such as formaldehyde, acetaldehyde, and propionaldehyde. Their boiling points are similar to those of propylene oxide, and ordinary distillation is difficult to separate. Affected the product quality of propylene oxide

Since aldehyde is a polymerization inhibitor for the polymerization of propylene oxide, it affects the chain growth of polyether polyol molecules, increases the pressure during the polymerization reaction, and easily causes production accidents. The chromaticity of ether polyols also has a certain influence, which limits its application in high-end fields. Therefore, the removal of aldehyde impurities in propylene oxide products is one of the key technologies that affect the competitiveness of HPPO process

[0005] Patent CN01804651.7 discloses a method for refining propylene oxide products by extracting and rectifying water and other polar solvents, but still cannot effectively remove aldehyde impurities

Patent CN200380103986.5 discloses a method for extracting and rectifying propylene oxide with a compound containing unsubstituted amine groups (such as hydrazine). This method can effectively remove aldehyde impurities in the product, but the hydrazone products generated by the compound and aldehyde , produces high nitrogen-containing wastewater, which is difficult to treat; patent CN201610115263.6 discloses a method for removing aldehyde impurities with a combination of resin and ethanolamine / hydrazine hydrate, but propylene oxide has a certain swelling effect on polymer resin, causing epoxy High loss of propane, reduction of resin strength and broken problems. In addition, substances such as ethanolamine or hydrazine react with aldehydes to form hydrazones, resulting in nitrogen-containing wastewater, which greatly increases the difficulty of wastewater treatment

Patent CN201610473450.1 discloses a method for adsorbing propylene oxide aldehyde impurities with modified molecular sieves. Although this method overcomes the problems of resin swelling and nitrogen-containing wastewater, the adsorption efficiency decays quickly and regeneration is frequent

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