Method for recovering polyol from wastewater

Abstract

The invention discloses a method for recovering polyol from wastewater. The method comprises the following steps: introducing wastewater containing a low concentration of polyol from the upper portion of a reaction rectifying tower (1), introducing aldehyde from the lower portion of the reaction rectifying tower, and carrying out a reaction of polyol and aldehyde under the catalysis of a strongly acidic cation resin to generate acetal; discharging an azeotropic mixture of acetal and water from the top of the reaction rectifying tower, allowing the azeotropic mixture to enter a hydrolysis tower from the lower portion of the hydrolysis tower, allowing water to enter the hydrolysis from the upper portion of the hydrolysis tower, discharging aldehyde obtained after the hydrolysis from the top of the hydrolysis tower to the reaction rectifying tower, discharging the polyol from the bottom of the hydolysis tower to a refining tower (3), and discharging a stream from the bottom of the refining tower to obtain highly-pure polyol. The disadvantages of large energy consumption and difficult industrialization of traditional separating methods are overcome in the invention. The purity of the above obtained product is high and can be adjusted as needed. Aldehyde can be recycled, so the pollution of wastewater to the environment is reduced. The recovered polyol has high added values, and the operation is simple. The purity of the polyol can reach 99%.

Description

technical field [0001] The invention belongs to the field of polyol wastewater treatment and recovery, and in particular relates to a method for recovering polyol from wastewater. Background technique [0002] Polyol is an important chemical raw material, an important intermediate of alkyd resin, varnish, polyester resin, and explosives, and an important basic raw material for polyurethane, adhesive, plasticizer, and surfactant. Among them, ethylene glycol can be used as a solvent, an antifreeze agent, and a raw material for polyester synthesis, and polyethylene glycol (PEG), a high polymer of ethylene glycol, is an important phase transfer catalyst. 1,3-Propanediol (1,3-PD) is widely used in polyester fibers, polyurethanes, hot melt adhesives, powder coatings, antifreeze agents, packaging materials and organic synthesis intermediates, among which high-performance Polyester fiber PTT is currently the main application. 1,2 Propylene Glycol can be used as a solvent, humectan...

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Problems solved by technology

Although the dividing wall column can integrate the separation process, it still needs to distill a large amount of water, which requires a lot of energy (US20050250965A1); the azeotropic distillation technology using benzene as an entrainer, although the azeotropy of benzene and water can make The energy of rectification is reduced, but the reduced energy is not significant; and the process of combining membrane separation technology and azeotropic technology will inevitably consume a lot of energy, and there is still a big gap from industrial application ( Wang Sheng. Study on separation scheme of water, propylene glycol and propylene glycol monomethyl ether mixture [D]. Dalian University of Technology, 2003.)

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