A Novel Process For Synthesis Of Ammonium Polyphosphate By Ammonium Phosphate

Ammonium polyphosphate?APP? with high phosphorus and nitrogen content,excellent water solubility and slow release property,has already been applied for fertilizer.By developing new processes and solving existing problems,it is of great significance for achieving industrial production.In this paper,four different processes were studied,and the optimal conditions for different processes were obtained.APP-?with polymerization degree of 10 or less were prepared by industrial grade ammonium dihydrogen phosphate and urea in a one-step method.The research result showed that the optimal conditions were as followed:The reaction time was 2 h,molar feed ratio was 1:1.1,reaction temperature was 190?.The product under the optimal process conditions was characterized,and the P₂O₅content?wt%?was55.86%,N content?wt%? was 21.21%,polymerization degree was 3.6,polymerization ratio was 95.35%.A stepwise heating method was developed.By using same materials,the optimum conditions were as followed:The reaction time was 1.5 h,molar feed ratio was 1:1.1,reaction temperature was 190?,the obtained product P₂O₅ content?wt%?was 69.96%,N content?wt%?was 15.31%,polymerization degree was 8.3,polymerization ratio was 99.98%.The product prepared under the optimum conditions was characterized by XRD and IR,and the result showed that it is APP-?.The deep eutectic solvent prepared by urea and organic salt had been used to replace urea in a new method.The optimum conditions were as followed:The reaction time was 2 h,molar feed ratio was 1:1.1,reaction temperature was 190?,the obtained product P₂O₅content?wt%?was 69.81%,N content?wt%?was 15.79%,polymerization degree was 8.2,polymerization ratio was 99.98%.The product prepared under the optimum conditions was characterized by XRD and IR,and the result showed that it is APP-?.A solvent can solved the ammonium dihydrogen phosphate and urea was found,which allows the APP-?synthesized in the liquid phase.The optimum conditions under this process were as followed:The reaction time was 25 min,molar ratio was 1:1.5,reaction temperature was 185?,P₂O₅content?wt%?was 65.92%,N content?wt%?was 18.96%,polymerization degree was 4.6,polymerization ratio was 97.98%.The product prepared under the optimum conditions was characterized by XRD and IR,and the result showed that it is APP-?.