NH_4MnPO_4·H_2O热分解动力学

Kinetics of NH_4MnPO_4·H_2O Thermal Decomposition

以MnSO_4·H_2O、(NH_4)_2SO_4和H_3PO_4为原料,通过共沉淀法制备了NH_4MnPO_4·H_2O,并通过XRD、FTIR、激光粒度分析仪和SEM对产物晶型、化学结构、粒度大小及形貌进行表征。结果表明该产物为NH_4MnPO_4·H_2O,结晶度高,颗粒较细,呈短棒状。通过热分析法研究该产物的热分解过程,表明分解过程分为两个阶段,并对第一阶段分解过程进行了热分解动力学研究,用F1ynn-Wall-Ozawa法和Friedman法求得NH_4MnPO_4·H_2O第一阶段热分解活化能分别为93.201和88.681 kJ×mol^(-1);在以上方法基础上,通过Coats-Redfern法求得第一阶段热解活化能E_1=91.533 kJ×mol^(-1),指前因子A_1=3.846×107 s^(-1),并得到热分解动力学模型和动力学方程,为磷酸铵锰作为缓释氮磷锰肥的使用及其在复肥中的添加应用提供理论依据。

Manganese ammonium phosphate was prepared by co-precipitation of manganese sulfate, ammonium sulfate and phosphoric acid, which was characterized by XRD, FTIR, SEM and laser particle size analysis. The results confirm that NH4 MnPO4·H2 O is produced with high crystallinity, fine particle and rod-like structure. Thermal analysis of NH4 MnPO4·H2 O indicates that the decomposition process can be divided into two stages, and the thermal decomposition kinetics of the first stage was studied. The results show that the activation energies of the first stage is 93.201 kJ×mol^（-1） calculated by F1 ynn-Wall-Ozawa method and 88.681 kJ×mol^（-1） by Friedman method. The kinetic parameters of the first stage calculated by Coats-Redfern method are E1 = 91.533 kJ×mol^（-1） and A1=3.846×107×s^（-1）, and the kinetics model and kinetics equation of thermal decomposition are obtained. These results provide fundamental information for the application of NH4 MnPO4·H2 O as a slow-release nitrogen-manganese-phosphate fertilizer.