用液-液复分解法由氯化钠制三聚磷酸钠

提出了由氯化钠取代纯碱或烧碱制取三聚磷酸钠的工艺过程。它由以下几步组成:(1)氯化钠、磷酸与长链烷基伯胺制取磷酸二氢钠的液-液复分解反应;(2)氯化钠、磷酸二氢钠与长链烷基伯胺制磷酸氢二钠的液-液复分解反应;(3)以冷却结晶的方法从反应生成的水溶液中分离出磷酸二氢钠;(4)磷酸二氢钠与磷酸氢二钠聚合制得产物三聚磷酸钠。对液-液复分解反应中两相组成与温度对磷酸或磷酸二氢钠转化率的影响,液-液复分解反应的机理以及磷酸二氢钠与磷酸氢二钠混合物中氯含量对产品三聚磷酸纯度的影响等问题进行了讨论。扩大试验的结果表明,液-液复分解反应过程中磷酸的总转化率大于97%,中间产物十二水磷酸氢二钠含氯化钠0.34%,产品三聚磷酸钠纯度为90.4%。

Liquid-Liquid Double Decomposition for the Production of Sodium Tripolyphosphate from Sodium Chloride

The process for the production of Na_5P_3O_(10) from NaCl consists of the following steps: 1) liquid-liquid double decomposition (LLDD) of NaCl and H_3PO_4 with a long chain primary amine to prepare NaH_2PO_4, 2) LLDD of NaCl and H_3PO_4 with the same amine to prepare Na_2HPO_4, 3) separation of Na_2HPO_4 from the resulting aqueous solution by crystallization, 4) polymerization of NaH_2PO_4 and Na_2HPO_4 to produce Na_5P_3O_(10). The selection of extractant, the effects of composition of both phases and temperature on the conversion of H_3PO_4 to NaH_2PO_4 in LLDD, the mechanism of LLDD and the effect of the chloride content in the mixture of NaH_2PO_4 and Na_2HPO_4 on the purity of Na_5P_3O_(10) product are discussed. The results of bench scale experiment show that the total conversion of H_3PO_4 in LLDD is more than 97%, the content of NaCl in the intermediate product of Na_2HPO_4. 12H_2O is 0.34% and the purity of Na_5P_3O_(10) is 90.4%.