复分解法制备硼氢化钾

Preparation of potassium borohydride by double decomposition

为了减少Schlesinger法生产固体硼氢化钠的母液循环所带来的水解损失和设备负荷,以目前工业硼氢化钠生产中典型结晶母液(25%Na BH4、5%Na OH、70%H2O)和氢氧化钾为原料,采用复分解法直接制备固体硼氢化钾。利用X-射线粉末衍射、光学显微分析和碘量滴定法研究了氢氧化钾用量、反应温度、结晶温度、溶剂蒸发量等因素对产品组成和收率的影响。结果表明,氢氧化钾/硼氢化钠摩尔比为1.10,反应温度低于60℃,结晶温度低于10℃时,硼氢化钾粗产品粒度分布均匀,纯度可以达到86%,收率>80%。

In the production of solid sodium borohydride by Schlesinger method, the crystallization mother liquor must recycle to upstream, resulting in hydrolysis loss of NaBH4 and increase of involved materials. To minimize the problems, a direct double decomposition reaction producing solid potassium borohydride from a typical mother liquor which comprises of 25% NaBH4 ,5% NaOH and 70% H20, and potassium hydroxide is studied. The effects of potassium hydroxide dosage, reaction temperature, crystallization temperature and solvent evaporation on KBH4 purity and yield are also investigated by using X-ray diffraction, optical microscopy and iodometric titration. The results show that when the molar ratio of KOH to NaBH4 is 1. 10,with reaction temperature below 60℃ and crystallization temperature below 10℃, the purity of crude product with uniform size distribution reaches 86% and the yield of the reaction is over 80%.