Study On Process Improvement Of N-(Phosphonomethyl) Iminodiacetic Acid

This study is about the production process of PMIDA by iminodiacetonitrile alkaline hydrolysis to synthesize IDA. The main content is the impact of the reaction conditions of hydrolyzing iminodiacetonitrile such as the dosage of sodium hydroxide, the dose of water, hydrolysis time, hydrolysis temperature, holding time, the temperature of removing the ammonia,feed ratio of reaction materials optimization, phosphorus trichloride dropwise manner and feeding order of raw materials in the synthesis process, the amount of phosphorus trichloride and dropping time, the amount of formaldehyde and dropping time and dropping after the holding time, and the optimal of neutralizing the alkali concentration and final pH value after the reaction.This paper also studied the feasibility of saving caustic soda in the neutralizing process.By the analysis and experimental verification of the reaction principle, sodium hydroxide:iminodiacetic acid of2.2:1,hydrolysis temperature of58-60°C, feeding time of～60min, the temperature of driving out the ammonia of104℃,were determined. Thus, the process optimization of using phosphorus trichloride instead of phosphorous acid and reducing the reaction process and the difficulty of the operation were realized. Through experiments and data analysis, the phosphorus trichloride dropwise conditions were optimized and the probability of blocking material in the reaction process was decreased. Moreover, conditions that affect product yield were adjusted such as adding sequence of materials, the amount and dropping time of phosphorus trichloride and formaldehyde, insulation time after adding phosphorus trichloride and formaldehyde, the concentration of used caustic soda and the final pH value.The final process is to join the IDA to the condensation reaction kettle, and then dropping phosphorus trichloride at68-75℃, dropping formaldehyde at110-116℃and insulate them. Formaldehyde dropping should be kept a uniform dropping velocity and the optimum time was between2.5h～3.Oh. The insulation time after dropping is about1.0h, and the pH was adjusted to～1. The adding time of ammonia is2h. Finally, the cost of150yuan of each batch was saved.