Process improvement for producing epichlorohydrin by using glycerin method dichloropropanol as raw material

Abstract

The invention aim at providing a method for producing epichlorohydrin by using glycerin method dichloropropanol as a raw material with step-by-step saponification. Compared with the prior art, the process has the characteristics of mild reaction conditions, simple process, low alkali consumption, low brine TOC, high ECH yield, and the like. Different reaction speeds of each component in DCH are used, the step-by-step saponification method is used, firstly primary normal pressure intermittent or continuous saponification is used, oil and water are layered, an oil layer is rectified in order to obtain an ECH product, and negative pressure secondary saponification is carried out for unreacted DCH in a column reactor. A washing process is used, most monochloropropanediol in a primary saponification rectifying still residue is separated, monochloropropanedio and DCH in a washing water layer return to a glycerin chlorination system for reusage. After washing, negative pressure high alkali ratio is used for the primary saponification rectifying still residue in order to carry out secondary saponification, and continuous industrial production is realized.

Description

technical field [0001] The invention relates to a process improvement method for producing epichlorohydrin by using glycerol method dichloropropanol as raw material. Background technique [0002] Epichlorohydrin (ECH for short) is a colorless and transparent liquid. It is an important chemical product and an intermediate in the synthesis of epoxy resins, elastomers, glycidyl ethers, etc. Chemical products also have important applications. At present, the main methods of producing epichlorohydrin are: propylene high-temperature chlorination method, propylene alcohol method and glycerin method. The first two methods use propylene as raw material. With the shortage of petroleum resources, the source and price of propylene are affected by the market. The glycerol method uses glycerol as a raw material, as a by-product of biodiesel, a renewable resource and green energy, so the production of epichlorohydrin by the glycerol method has very important significance. Disclosed in CN...

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Problems solved by technology

[0003] CN103709124B discloses raw materials DCH and NaOH through pipeline mixer and falling film tubular reactor, and ECH is removed from the reactor in a short time; Excellent mass transfer and heat transfer effects shorten the residence time of ECH in the system and reduce side reactions, but the above two patents have not fundamentally solved the problem of ECH hydrolysis in the alkaline system, resulting in low ECH yield , the total organic carbon content (abbreviation TOC) of brine is higher, which increases the cost of waste water treatment; CN102875494B and CN102603680B all adopt microchannel reactors to synthesize ECH, which has the characteristics of short residence time, mild reaction and high ECH yield, but the alkali consumption (actual use Alkali mol / theoretical mol) is as high as 1.3, and a third medium solvent needs to be introduced for brine extraction, which not only increases the cost of solvent recovery, but also inevitably has a small amount of solvent remaining in the brine, resulting in an increase in brine TOC

At the same time, the throughput of the microchannel reactor is small, which is not suitable for the production of 10,000-ton ECH

[0004] Glycerol method DCH is a mixture of 1,3-DCH and 2,3-DCH, of which 1,3-DCH accounts for about 95% (wt%), 2,3-DCH accounts for about 5% (wt%), the reaction of the former The speed is dozens of times that of the latter, and the reaction speed with alkali is 1,3-DCH>ECH>2,3-DCH, and a large amount of ECH is generated in the alkaline system and is prone to hydrolysis. If the alkaline system cannot be separated in time, the Glycidol, monochloropropanediol (hereinafter referred to as monochlorine), etc. will be generated, which will be further converted into glycerin, resulting in a decrease in ECH yield and an increase in brine TOC. The existing negative pressure saponification process brine TOC is about 10000ppm, resulting in huge environmental protection treatment pressure

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