Process Study On The Production Of Urotropine By Ammoniation Offormaldehyde Waste Liquid

Formaldehyde wastewater with high concentration is a typical toxic organic waste solution which is difficult to biodegrade.Among them,formaldehyde can directly react with the microorganisms,thereby inhibiting their biological activity and even causing the death of microorganisms.Therefore,it is difficult to effectively treat formaldehyde wastewater with high concentration by common biochemical treatment processes.Other methods,such as photocatalytic oxidation and Fenton oxidation,have the disadvantages of high operating cost and large-scale application,and the residual concentration of formaldehyde in the treated waste solution cannot be guaranteed to meet the discharge requirements.The formaldehyde content of a formaldehyde waste liquid discharged from the preparation of 1,4-butynediol co-production of propynol at a factory in Chongqing is as high as 50%.And contains other small amounts of highly toxic organic compound impurities such as 1,4-butanediol,1,4-butynediol and so on.In this paper,the solution of producing ulotopine by reacting the waste liquid with ammonia water was put forward and verified in the laboratory.Since the formaldehyde content of the formaldehyde solution purchased by the laboratory was 37%,and in order to prevent the self-polymerization of formaldehyde,8%to 10% methanol was added.Therefore,in this paper,the contents of various substances in factory waste liquid were determined by gas chromatography at first,and the simulated solution of formaldehyde waste liquid in laboratory was prepared by combining with the content of purchased raw materials.Through multiple experiments and optimization processes,the process of producing urotropine by the reaction of formaldehyde waste liquid and ammonia water was determined.The simulated waste liquid and excess ammonia water were prepared in a closed reactor and reacted for 3hours at 80-85℃ to produce ulotropine;The obtained urotropine solution was transferred to a vacuum distillation device,and the temperature was controlled at 70-80°C for about 3.5 hours.Most of the water was removed and the ulotropine crystal was precipitated.The original solution was separated by filtration,and the wetted ulotropine crystal was sent into a vacuum drying oven.The product was dried for 12 hours at a vacuum temperature of 60℃.The product was analyzed by potentiometric titration to determine its purity and yield.In the experiment,it was found that the purity was related to yield,which decreased with the increase of yield.After optimizing the process,the purity of urotropine can reach the qualified purity of national standards,and a part of it can reach the purity of superior grade.The conversion rate of the process can reach up to 95.09%,and no formaldehyde is detected in the treated waste liquid.For the by-produced stock solution,there are two different treatment methods: first,the best decolorizing agent activated carbon to decolorize and purify the stock solution;Second,in the process of decompression,all the water in the original liquid will be steamed out,not the output of the original liquid.By comparison,the purity of the urotropine obtained after decolorizing the original liquid after vacuum distillation and vacuum drying can reach the qualified purity of the national standard.If the purity is to be further improved,recrystallization is required.The purity of ulotropine produced without the original solution can also reach the qualified purity.Therefore,it is concluded that the first method is complicated and not conducive to economy,and the second method is recommended.As a result,the laboratory verified that the conjecture that formaldehyde waste liquid reacted with ammonia to prepare urotropine can be carried out.