Preparation method of pentaerythritol and dipentaerythritol

Abstract

The invention discloses a preparation method of pentaerythritol and dipentaerythritol, which comprises the following steps of: S1, heating formaldehyde to a set temperature by taking a formaldehyde aqueous solution as bottom water, adding an alkali solution and an acetaldehyde aqueous solution into the bottom water, and carrying out condensation reaction at a constant temperature; S2, adding a formic acid aqueous solution into the bottom water to stop the reaction to obtain a condensation solution containing pentaerythritol, dipentaerythritol and formate; S3, carrying out multistage evaporation and crystallization, and respectively collecting excessive formaldehyde, pentaerythritol, dipentaerythritol and formate from the condensation solution to obtain the pentaerythritol and the dipentaerythritol, wherein the molar ratio of the formaldehyde to the acetaldehyde is (4-10):1, the molar ratio of the alkali to the acetaldehyde is (1-2):1. According to the invention, the condensation reaction is carried out under the condition of constant temperature, the raw materials are easy to obtain, the control is simple, the product yield is high, and the product purity is high.

Description

technical field [0001] The invention relates to a preparation method of monopentaerythritol and dipentaerythritol. Background technique [0002] Pentaerythritol is mainly used in the coating industry to produce alkyd resins, synthetic greases, non-toxic plasticizers, surfactants, and as raw materials for medicines and explosives. Dipentaerythritol is mainly used as a stabilizer for synthetic lubricants and non-toxic PVC processes. In recent years, it is mainly used as a raw material for the synthesis of UV light-curable monomers, acrylates, inks, fireproof materials, alkyd resins and adhesives. [0003] At present, most domestic enterprises mainly produce pentaerythritol with a content of 92-95%, and the content of dipentaerythritol is generally below 90%. Moreover, due to the long reaction time and large temperature changes, the reaction direction cannot be controlled, and there are a lot of disproportionation reactions in the production process. At the same time, the exis...

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Problems solved by technology

[0004] The current mainstream synthesis technology is to generate monopentaerythritol, dipentaerythritol and tripentaerythritol by one-step reaction in a conventional condensation reactor. For example, the patent application whose application number is CN200710053987.3 discloses a method using calcium hydroxide as a catalyst and formaldehyde and acetaldehyde. The production process for synthesizing dipentaerythritol and / or tripentaerythritol as raw materials, because the method cannot control the existence of condensed aldehydes, it is very difficult to separate and obtain high-purity dipentaerythritol and tripentaerythritol, and the product purity and color number are poor, so it needs to be re- The hydrolysis and decolorization by activated carbon is complicated operation, and the obtaining of high-purity monopentaerythritol and dipentaerythritol requires recrystallization to produce a large amount of mother liquor and washing water, which is not in line with the industrial concept of green and environmentally friendly production; in addition, there are also conventional condensation reactors. A method for step-by-step generation of dipentaerythritol and tripentaerythritol, such as a patent application with application number CN200710037512.5, discloses a rare earth or alkaline earth oxide that uses formaldehyde, acetaldehyde, and pentaerythritol as raw materials and is loaded on porous material SBA-15 Under the action of a catalyst, the method for preparing dipentaerythritol, the method needs to separate the catalyst in the reaction stage, the reaction process is divided into two parts, and the preparation of the catalyst is complicated, which makes the production process complicated and the cost is high. In addition, although the method improves the The yield of dipentaerythritol and tripentaerythritol, but there is also the problem of separation difficulty when higher yield tripentaerythritol is obtained, resulting in poor product color and purity, and by-product impurities such as condensed aldehydes and corresponding acid salts cannot be effectively removed; The patent application with the application number CN200910172347.3 proposes a preparation method for obtaining high-quality monopentaerythritol and dipentaerythritol by precisely controlling the ratio and concentration of raw materials, reaction temperature and feeding procedure to reduce the generation of tripentaerythritol and dipentaerythritol. The process is simple , still can’t control the reaction direction simply, effectively and flexibly. After the recrystallization treatment of pentaerythritol and dipentaerythritol, a large amount of steam is consumed, which makes it economically unreasonable, and the product still needs activated carbon for decolorization treatment, which does not fundamentally solve the by-product pentaerythritol. Problems with acetal impurities

The patent application with the application number CN201310030222.3, a high-yield synthesis of dipentaerythritol and tripentaerythritol, uses a catalyst for the reaction of activated polymer-loaded solid base with formaldehyde and acetaldehyde to synthesize dipentaerythritol and tripentaerythritol with high efficiency. The method for tripentaerythritol, with dipentaerythritol and tripentaerythritol as the target product, the yield of monopentaerythritol is low, and at the same time, due to the existence of tripentaerythritol, the separation of products is extremely difficult, and it is necessary to make qualified products through recrystallization, and energy consumption relatively high

To sum up, the domestic production and technical status cannot meet the growing demand for high quality and quantity of monopentaerythritol and dipentaerythritol

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