Purification and dehydration of epichlorohydrin
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We have around 100 tons of recycled epichlorohydrin in our storage tanks, with a water content of about 1.5%. We would like to refine it and remove the water from it; could you advise if there are any good methods we could use as a reference?
Experience suggests that a heterogeneous azeotrope may form? A self-carrying heterogeneous azeotropic stripping column is used to strip the aqueous azeotrope upward.
Yes, epichlorohydrin at atmospheric pressure forms an azeotrope with water at 88°C, making it difficult to vaporize
A vacuum azeotropic distillation method is employed to keep the temperature at the bottom of the tower below 100°C, with the azeotrope of epichlorohydrin and water being distilled off at the top of the tower. The azeotrope contains about 3/4 epichlorohydrin; after being cooled by the top condenser, the condensed liquid is then separated into an upper aqueous phase and a lower oily phase using a decanter ； The oil phase returns to the top of the tower as reflux. The separated wastewater contains a small amount of epichlorohydrin dissolved in it, but when the water content in the feed before dehydration is around 1.5%, the loss of epichlorohydrin due to dissolution in the wastewater generally does not exceed 0.15% of the amount in the feed.
Currently, the most common methods for dehydrating epichlorohydrin are air-dissolved drying and distillation dehydration. Air-dissolved drying is a method of evaporation and dehydration that uses nitrogen as a medium. It involves using low-temperature air to dissolve water out of epichlorohydrin, and then heating the air to evaporate the water from the nitrogen, thereby achieving dehydration. Distillation dehydration can also effectively remove water from epichlorohydrin. It heats the epichlorohydrin to its boiling point; the hot epichlorohydrin flows into a capillary, where it reaches a supercooled state on the outer wall of the capillary, causing the water in the epichlorohydrin to freeze prematurely, thereby achieving dehydration.
It is also precisely because a heterogeneous minimum azeotrope is formed that the problem becomes easier—to first distill the azeotrope from the top of the tower, condense it, and then separate the phases; the alkane phase is recycled while the water phase is discharged or sent to a stripping tower to recover the trace amounts of alkane dissolved in it.
Thank you; this plan is the most feasible given our current on-site procedures
Dehydration is carried out using molecular sieves; 3A molecular sieves are added to a 1-cubic-meter storage tank, and epichlorohydrin is passed through these molecular sieves. The flow rate is adjusted, and the water content in the distillate is monitored. Once the molecular sieves become ineffective, they are removed and dried in a large oven at 300 degrees for 24 hours before being used again.
Well, alumina and membrane water separation – plans are being developed for both right now
Molecular sieves are better; with them, we can reduce moisture levels to 100–200 ppm