Oil-water two-phase reaction, yield issue
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Our company produces epichlorohydrin. The current production process involves mixing 20% lime milk with a 4.2% aqueous solution of dichloropropanol to obtain crude epichlorohydrin, which is then distilled to yield pure epichlorohydrin. The company intends to modify the process by mixing 20% lime milk with pure dichloropropanol to produce crude epoxy, which is then refined. As a professional in the field of instrumentation, I somewhat believe that dichloropropanol is an organic compound with poor water solubility; its dispersion in a 20% lime slurry will present problems, resulting in a reduced yield. The COD of wastewater is very high, making it difficult to treat. I would appreciate some guidance from teachers with similar experience.
This post was last edited by Albertlu on 2009-11-22 at 12:49. Production processes are divided into continuous and batch methods. In the continuous process, the reaction mixture obtained from the chlorination of glycerol is subjected to saponification directly without any further treatment to produce epichlorohydrin. In the batch process, after the chlorination of glycerol, an alkaline solution is added to the reaction mixture to neutralize the excess hydrogen chloride; dichloropropanol is then obtained through vacuum distillation, followed by saponification. The continuous process is simple and easy to operate, but since the chlorination products are not treated, an excess of alkali is required during saponification. Moreover, there are many by-products that are difficult to separate, which affects the purification of the saponification products. Although the batch process is more complex to operate than the continuous process, it allows for full utilization of the raw materials; the unreacted glycerol and monochlorinated products can be used again in the production of dichloropropanol. It seems that it was a continuous reaction in the past, but now it should be a batch reaction. The specific yield will depend on the extent to which the reaction takes place and on the selectivity involved; it appears to be a two-phase reaction, and it is likely that a stirred-tank reactor is being used. The stirrer keeps mixing the dichloropropanol, turning it into small oil droplets, while also helping to control the reaction temperature and duration. The total amount of wastewater should decrease; if there are many components in the wastewater that can be reused, they can be recovered as alkaline solutions (assuming this is possible). Since I haven’t observed the actual production process, I can only make predictions.
For the equipment setup, a static mixer may need to be installed to improve its mixing efficiency
Looking back, may I ask what the operating temperature is for the saponification reaction in your company? If production is carried out using the high-temperature propylene method, such problems will arise regardless of whether the reaction is with NaOH or Cu(OH)2. However, according to many studies, at high temperatures it tends to form an azeotrope with ECH and flow out at the top of the tower. Of course, mixing is also a key factor. The above opinions are provided for reference only