| Ammonium polyphosphate is an inorganic polymer with a high content of N and P,referred to as APP.The low polymerization degree ammonium polyphosphate has good water solubility,and has good chelation for trace metal ions.The dissolved water is applied to the soil and decomposed into orthophosphate which is easily absorbed by vegetation,and becomes a hot research direction of agricultural fertilizer.Very broad development prospects.Foreign countries have a series of application standards for agricultural ammonium polyphosphate to achieve industrial production.In contrast,the quality of domestic products is not satisfactory,and the standards are not uniform,which seriously affects the development of agricultural ammonium polyphosphate agricultural use in China and reduces its society.It reduces its social and economic benefits..The lack of technology and lack of technology are the main reasons for this phenomenon.This topic mainly explores the optimal synthesis conditions for the preparation of low polymerization degree APP by wet-process phosphoric acid,and adds potassium to the product,which has practical significance for the application of agricultural ammonium polyphosphate.In this paper,the optimal synthesis process of low-polymerization ammonium polyphosphate is studied by studying industrial phosphoric acid-urea,and the optimal synthesis process of low-polymerization ammonium polyphosphate by wet-process phosphoric acid-urea is further explored.The method discussed the influence of polymerization time,polymerization temperature and molar ratio of phosphoric acid to urea on the properties of ammonium polyphosphate products,so as to explore the process of preparing low-polymerization ammonium polyphosphate.The gravimetric method is used to determine the phosphorus content and potassium oxide content of the product,the nitrogen content of the product is determined by distillation,the average degree of polymerization of the product is determined by end group titration,the polyaddition rate of the product and the biuret content are determined by the absorbance method,and XRD is determined.Verify the product crystal form.The experimental data show that the optimal process for the synthesis of industrial phosphoric acid-urea polycondensation method: the molar ratio of raw materials(phosphoric acid: urea in industrial phosphoric acid)is 1:0.9,the reaction time is 90 min,and the reaction temperature is 150 °C.The ammonium product has a phosphorus pentoxide content of 62.11%,a nitrogen content of 13.9%,an average degree of polymerization of 14,water solubility reached 100%,a degree of aggregation of 97.07%,and a biuret content of 0.47%,less than 1%.The optimum process conditions of the wet process phosphoric acid-urea condensation method: the molar ratio of raw materials(phosphoric acid: urea in industrial phosphoric acid)is 1:0.9,the reaction time is 90 min,and the reaction temperature is 150 ° C.The low polymerization degree ammonium polyphosphate product is pentoxide.The phosphorus content was 47.61%,the nitrogen content was 26.01%,the average degree of polymerization was 12,water solubility reached100%,the aggregation rate was 96.28%,and the biuret content was 0.57%,less than 1%.On the other hand,potassium dihydrogen phosphate was selected as potassium nutrient to add potassium to the product.The molar ratio of different raw materials,polymerization time and polymerization temperature were investigated to study the effect of potassium potassium polyphosphate on the preparation process.Studies have shown thatpotassium potassium polyphosphate prepared by adding potassium has good water solubility,the aggregation rate is more than 90%,and the biuret content is less than 1%.It is concluded that the total potassium oxide content of potassium polyphosphate potassium phosphate increases with the increase of potassium dihydrogen phosphate dosage,the polymerization time is 1.5h,and the polymerization temperature is 155 °C,which is the best synthesis condition for preparing potassium ammonium polyphosphate. |
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