五硼酸钾高温水解反应动力学的初步研究

Preliminary study on high-temperature hydrolysis kinetics of potassiumpentaborate

五硼酸钾过热的水蒸气气氛发生水解反应。其中温度与蒸汽流量是反应最重要的影响因素。温度在1173 K时,熔体的B2O3/K2O降至3.1;加大蒸汽流量,可将熔体的B2O3/K2O降至2.6。对水解反应的机理进行了初步的研究,认为在高温与蒸汽的作用下KB5O8结构中一部分硼氧键断裂与水分解后产生的H+离子结合形成挥发性的HBO2。分离出羟基与剩下的硼酸盐网络结构进行连接,在高温条件下,两个羟基中的一个O进入硼氧网络结构中,剩下的形成水释出,同时K2O的浓度相对增加。反应动力学研究表明五硼酸钾低于熔点时与水蒸汽的反应受外扩散控制;对高于熔点的动力学实验数据进行了线性拟合,获得了线性方程。

Abstract： The hydrolysis reaction of potassium pentaborate superheated steamatmosphere. Effects of temperature and steam flow is the most important factor.When the temperature is at 1173 k,B2O3/K2O of its melts is to 3.1; increase the steamflow, B2O3/K2O of melts can be down to 2.6. Undertook a preliminary study on themechanism of hydrolysis reactions, it is considered that under the action of high temperature and steam parts of boron-oxygen bond in the structure of KB5O8 cleavage and combine with H ＋ ions generated from water decomposition to form volatile HBO2. Isolated hydroxyl groups connected with the remaining borate＇s network structure. In high temperatureconditions, one oxygen of two hydroxyl groups entered the network structure of boron-oxygen, the rest being released, and K2O＇s concentration was increased. Reaction kinetic studies have shown that when potassiumpentaborate below the melting point its reacting with water vapour is control by external diffusion. We take the linear fitting of dynamic theexpefimental data under high melting point, access to the linear quation.