Study On Saponification Process Of Epichlorohydrin Synthesis And Its Wastewater Treatment

When epichlorohydrin is prepared by glycerol method in chemical production,Ca（OH）₂is mostly used as saponification agent to react with dichloropropanol.However,the insoluble Ca CO₃produced in the production process is easy to block the reaction equipment and cause danger.Its wastewater contains high salt and organic matter.The biological treatment of wastewater is deficient.It is difficult to remove the chloride and organic matter in the wastewater,and the treatment cost is high.In order to solve these problems and optimize the production process,the reaction of dichloropropanol with different saponifiers was studied.The advantages and disadvantages of each saponification agent were found.The optimum saponification agent and the optimum reaction conditions were explored.In addition,the wastewater treatment after saponification reaction was studied.The treatment scheme of high salt organic wastewater was put forward to provide scientific data and reference for the production of epichlorohydrin.（1）The optimum process conditions for the reaction of dichloropropanol with three saponifiers（NaOH,Ca（OH）₂,NH₃·H₂O）According to the single factor and orthogonal experimental method,The optimum conditions for the reaction of dichloropropanol with NaOH were as follows:temperature is 70℃,molar ratio of NaOH to dichloropropanol is 1.2:1,and reaction time is 90 s.The optimum conditions for the reaction of dichloropropanol with Ca（OH）₂were as follows:temperature is 80℃,molar ratio of Ca（OH）₂to dichloropropanol is 1.2:1,and reaction time is 240 s.The optimum conditions for the reaction of dichloropropanol with NH₃·H₂O were as follows:temperature is 60℃,molar ratio of NH₃·H₂O to dichloropropanol is 1.2:1,and reaction time is 360 s.If NaOH is used as saponifier,the reaction yield of epichlorohydrin is high（93.9%）,but the cost is high,the reaction rate is fast,and it is difficult to control in the production.If Ca（OH）₂is used as saponifier,the reaction yield is higher（84.5%）,the reaction rate is moderate,the cost is low,and excessive Ca（OH）₂in the reaction is easy to produce Ca CO₃and block the reaction equipment,which causes danger.If NH₃·H₂O is used as saponifier,the cost is low,but the reaction yield is low（46.8%）and the reaction rate is slow.Comparison of reaction processes between dichloropropanol and these three saponifiers:（1）reaction temperature（T）,T_Ca（OH）2>T_NaOH>T_NH3·H2O;（2）reaction rate（ν）,ν_NaOH>ν_Ca（OH）2>ν_NH3·H2O;（3）The yield（Y）,Y_Ca（OH）2>Y_NaOH>Y_NH3·H2O.In addition,NaOH alkalinity is strong,easy to corrode the reaction equipment;Ca（OH）₂as saponification agent,the scale formation in the reaction equipment is serious,and the safety hidden danger is big.When NH₃·H₂O is used as saponifier,the yield is very low,only 46.8%,and the reaction rate is slow.（2）Optimum technological conditions for the reaction of a new saponifier with dichloropropanolBased on the advantages and disadvantages of the three saponification agents,a new saponification agent was designed by mixing NaOH and NH₃·H₂O in a certain molar ratio.The experiment showed that the optimal process conditions for the reaction of dichloropropyl alcohol and mixed alkali were as follows:the molar ratio of mixed alkali to dichloropropanol was 1.2:1,the reaction temperature was70℃,the reaction time was 240 s,and the molar ratio of mixed alkali NaOH to NH₃·H₂O was 3.5:1.（3）Advantages of mixed alkali saponifierCompared with Ca（OH）₂and NaOH,the mixture of NaOH and NH₃·H₂O as the saponification agent,the cyclozation reaction rate of dichloropropanol is moderate,and the yield of epichlorohydrin is higher.Excess alkali will not generate insoluble matter,and the blockage of reaction equipment and pipeline is avoided.Therefore,it can realize low-cost green production of epichlorohydrin.（4）Wastewater treatment of synthetic ECHThe treatment of wastewater from saponification reaction of various saponifiers with dichloropropanol was studied.It was found that the new combination of evaporation concentration and Fenton reagent coagulation precipitation has a good effect on the treatment of wastewater,which can solve the problem of high salt organic wastewater produced in the production of epichlorohydrin.Optimum technological conditions for wastewater treatment are as follows:p H is 3.0,reaction temperature is 60℃,H₂O₂concentration is 2.4 g/L,Fe²⁺concentration is 1.8 g/L,reaction time is 50 min.Under these conditions,the COD removal rate is 93.3%.The mixture of NaOH and NH₃·H₂O is used as saponification agent,and the wastewater from the cyclization of dichloropropanol is easier to be treated,and the removal rate of chlorine salt and COD is high.After the treatment of wastewater,the p H of the wastewater is 7.6,the COD content is165 mg/L,and the chloride ion content is 313 mg/L,which meet the national wastewater discharge standard.