The Study Of Stability Of The Urea Ammonium Chloride And The Purification Process

Our research group has proposed a new and simple method for the synthesis of urea ammonium chloride(U-AC)cocrystal on an industrial scale.In this paper,a new process for the separation and purification urea ammonium chloride from solid phase method is proposed,which aims to improve the purity of U-AC.The separation and purification process is composed of a series of operations,mainly divided into two parts: In the first part,L-cysteine assisting U-AC solution recrystallization reduced the decomposition rate of urea ammonium chloride.In the second part,density separation is applied to separate and purify the recrystallization crude products.Finally,the purification process was tested on industrial scale.First of all,urea ammonium chloride was separated from compound fertilizer granules by winnowing method,and then a separation and purification sequence was constructed using dissolution,filtration,L-cysteine assisting recrystallization and density separation method.Among them,the inhibition effect of the inhibitors is decreasing decomposition of urea ammonium chloride,a variety of inhibitors were selected and compared,and the concentration of the inhibitor and the recrystallization temperature were selected.At last,the inhibition mechanism of L-cysteine was analyzed.Through the test,the productivity of L-cysteine assisted recrystallization,compared to the direct recrystallization productivity,the yield increased from 52.41%to 78.26%,which illustrate that L-cysteine have a significant effect.Secondly,due to the decomposition of urea ammonium chloride,the recrystallization product is still a mixture containing other impurities urea,ammonium chloride.In this paper,the separation of urea and ammonium chloride was carried outby density separation method.By adjusting the volume ratio of benzene and carbon tetrachloride to obtain the anticipate purpose,the volume ratio of benzene and carbon tetrachloride was adjusted to 1:2 for the first time.In this propotion,urea was floating on the surface of the medium,urea ammonium chloride and ammonium chloride were sank in the lower.The filtration was carried out to remove urea.Then when the volume proption of benzene and carbon tetrachloride is 1:4.5,in this proportion of medium,urea ammonium chloride float on the surface of the medium,meanwhile,ammonium chloride sink at the bottom of medium.Then,the target material can be obtained by filtration.Finally,the target compounds were identified by XRD,and the content of chlorine and nitrogen.The experiental values were compared with the standard values.The results showed that the purity of U-AC was greatly improved.Finally,the purification method was applied to the large-scale purification process,and the properties of urea ammonium chloride were studied.It is found that the urea ammonium chloride has a fire resistance and can be used as a refractory material.