Study On The Anti-Solvent Crystallization Process Of Hydroxylamine Sulfate

Hydroxylamine sulfate（Hydroxylamine Sulfate,HAS）is one of the most widely used hydroxylamine salts.It is an intermediate in drug synthesis and a reducing agent.It can also be used as a chemical developer and rubber vulcanizing agent.Oxime or hydroxamic acid derivatives are also raw materials for pesticide synthesis.The crystallization process in the industrial production of hydroxylamine sulfate is the key link that affects the quality of its products.Due to the lack of systematic research on the crystallization characteristics of hydroxylamine sulfate in domestic related production enterprises,the quality of crystal products is poor,and the crystallization process has become a bottleneck problem that restricts the improvement of product quality in the production process of hydroxylamine sulfate.Aiming at the crystallization problems existing in the production process of hydroxylamine sulfate,this paper systematically studied the crystallization process of hydroxylamine sulfate.The solid-liquid phase equilibrium and liquid-liquid phase equilibrium of hydroxylamine sulfate were experimentally studied.The crystallization process was investigated,and the optimized crystallization process of hydroxylamine sulfate was determined.:（1）The solid-liquid phase equilibrium data of hydroxylamine sulfate in water-ethanol mixed solvent were determined,and the modified van’t Hoff,Apelblat,van’t Hoff-Jouyban-Acre and Apelblat-Jouyban-Acree models were used to fit the experimental results respectively.The fitting results show that the Apelblat model has the highest prediction accuracy,and the largest prediction error is 6.50%.The Gibbs free energy of dissolution(△_dis^（?）,enthalpy of dissolution(△_dis^（?）,and entropy of dissolution(△_dis^（?）of hydroxylamine sulfate in water-ethanol system were calculated by van’t Hoff model.The results show that the contribution of dissolution enthalpy change to the dissolution Gibbs energy change is greater than the dissolution entropy changed during the dissolution of hydroxylamine sulfate in the experimental solvent.The dissolution of hydroxylamine sulfate in the experimental solvent is an endothermic and entropy-increasing driving process.（2）The oiling-out characteristics of the water-ethanol-hydroxylamine sulfate system were studied,and the ternary phase diagram of oiling-out was constructed.The effect of temperature on the oiling-out phase diagram was investigated,and the nucleation site of the oiling-out crystallization process of hydroxylamine sulfate was determined.The results show that the temperature mainly changes the composition region of each phase by affecting the solid-liquid phase equilibrium of the water-ethanol-hydroxylamine sulfate system,but has no significant effect on the liquid-liquid phase equilibrium point.The nucleation process of hydroxylamine sulfate oiling-out crystallization follows a two-step mechanism:liquid-liquid phase separation occurs firstly in the system,followed by nucleation and crystal growth in the aqueous phase.（3）According to the research results of the solid-liquid phase equilibrium and liquid-liquid phase equilibrium of the water-ethanol-hydroxylamine sulfate system,the characteristics of the evaporative concentration-cooling coupled crystallization and anti-solvent crystallization processes were systematically studied and compared,and the anti-solvent crystallization was finally determined as crystallization method.Using ethanol as the anti-solvent,the effects of different process parameters on the crystal size and distribution of hydroxylamine sulfate were investigated,and the optimal process conditions for the crystallization of hydroxylamine sulfate were finally determined:the crystallization temperature was 313.15 K,the amount of elution agent was 1.05g ethanol/g raw material,and the solvent The droplet acceleration rate of the elution agent was 1.54 mL/min,the stirring rate was 300 rpm,the amount of seed crystal was 1%of the mass of the solute,and the aging time was 1 h.The value of C.V.was 46.74,and the yield was 84.07%.The research on the crystallization thermodynamics and crystallization process of hydroxylamine sulfate provides basic data for the industrial design of the crystallization process of hydroxylamine sulfate,and has important application value.