(NH_2)_2CO-NH_4H_2PO_4-H_2O三元系10℃相平衡研究
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摘要
采用等温溶解平衡法研究了三元系(NH_2)_2CO-NH_4H_2PO_4-H_2O在10℃时的相平衡,并采用湿渣法与X射线衍射相结合的方法鉴定了平衡固相的组成与结构。结果表明,该体系为简单共饱和型,无复盐或固溶体生成,共饱点的质量组成(以质量分数计):尿素,40.03%;磷酸一铵,13.92%;水,46.05%。相图中有2条单变量曲线,相图被划分为4个区域:不饱和区、(NH_2)_2CO结晶区、NH_4H_2PO_4结晶区和(NH_2)_2CO-NH_4H_2PO_4混合结晶区。用Wilson方程与NRTL方程对实验数据关联计算,实验值与计算值吻合度较高,2个热力学模型计算值与实验值的RAD分别为0.37%和0.71%,RMSD分别为0.20和0.29。
The solid-liquid phase equilibrium of ternary system of(NH_2)_2CO-NH_4H_2PO_4-H_2O was studied by isothermal dissolution equilibrium method at 10 ℃.The composition and structure of the equilibrium solid phase were identified by the combination of wet slag method and X-ray powder diffraction.The result showed that the ternary system was a simple co-saturated type and no double salt or solid solution,the mass composition(in terms of mass fraction) of invariant points was of urea 40.03%,monoammonium phosphate 13.92%,water 46.05%.There were two univariate curves in the phase diagram,which divided the diagram into four regions including the unsaturated region,(NH_2)_2CO crystallization region,N_4H_2PO_4 crystallization region and the mixed crystallization region of(NH_2)_2CO-NH_4H_2PO_4.In addition,two thermodynamic models,Wilson and NRTL,were employed to correlate and calculate the mutual solubility data.The calculated values agreed well with the experimental values,the RAD of the calculated and experimental values of the two thermodynamic models were 0.37% and 0.71% respectively,and the RMSD were 0.20 and 0.29 respectively.
The solid-liquid phase equilibrium of ternary system of(NH_2)_2CO-NH_4H_2PO_4-H_2O was studied by isothermal dissolution equilibrium method at 10 ℃.The composition and structure of the equilibrium solid phase were identified by the combination of wet slag method and X-ray powder diffraction.The result showed that the ternary system was a simple co-saturated type and no double salt or solid solution,the mass composition(in terms of mass fraction) of invariant points was of urea 40.03%,monoammonium phosphate 13.92%,water 46.05%.There were two univariate curves in the phase diagram,which divided the diagram into four regions including the unsaturated region,(NH_2)_2CO crystallization region,N_4H_2PO_4 crystallization region and the mixed crystallization region of(NH_2)_2CO-NH_4H_2PO_4.In addition,two thermodynamic models,Wilson and NRTL,were employed to correlate and calculate the mutual solubility data.The calculated values agreed well with the experimental values,the RAD of the calculated and experimental values of the two thermodynamic models were 0.37% and 0.71% respectively,and the RMSD were 0.20 and 0.29 respectively.
引文
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[2]刘光启,马连湘,刘杰.化学化工物性数据手册无机卷[M].北京:化学工业出版社,2002.
[3]刘光启,马连湘,刘杰.化学化工物性数据手册有机卷[M].北京:化学工业出版社,2002.
[4]陆杏英.相锑抗比色法侧定土壤中的总磷[J].环境科技,1991,4(3):33-34.
[5]刘志刚,赵庆良,孙丽欣,等.PDAB比色法直接测定液相中的常量尿素[J].哈尔滨工业大学学报,2008(8):1214-1217.
[6]Walas S M.Phase equilibria in chemical engineering[M].Amsterdam:Elsevier,1985.
[7]Wilson G M.A new expression for the excess free energy of mixing[J].J.Am.Chem.Soc.,1964,86(2):127-129.
[8]Renon H,Prausnitz J M.Estimation of parameters for the NRTLequation for excess Gibbs energies of strongly nonideal liquid mixtures[J].Industrial&Engineering Chemistry Process Design and Development,1969,8(3):413-419.
[9]Shnidman L,Sunier A A.The solubility of urea in water[J].J.Phys.Chem.,1932,36(4):1232-1240.
[10]Buchanan G H,Winner G B.The solubility of mono-and diammonium phosphate[J].Ind.Eng.Chem.,1919,11(119):448-451.