淀粉水热还原铬酸钠过程动力学研究

为避免传统氧化铬工艺所产生的含铬副产物对环境的污染，本文提出了用淀粉水热还原铬酸钠生产氧化铬的新工艺。在对水热还原过程的反应规律及反应机理进行分析的基础上，对淀粉水热还原铬酸钠过程的动力学进行了研究，调查了影响六价铬还原转化率的因素。结果表明，反应温度、反应物浓度和反应时间是主要因素。选择等温、恒容、不可逆反应动力学模型来描述其反应过程，其动力学方程为：r=-d［Cr(Ⅵ)］/dt=1.367×10¹³e^{-100.566×1000/RT}［Cr(Ⅵ)］［St］，即指前因子、表观活化能和总反应级数分别为1.367×10¹³L/(mol·h)、100.566kJ/mol和二级或拟二级。该反应属化学反应控制，对Cr（Ⅵ）和淀粉均表现为一级或拟一级。

Investigation of the kinetics of the hydrothermal reduction of sodium chromate with starch

In order to avoid environmental pollution caused by by-products containing chromium(Ⅵ), which are produced by conventional chromium oxide technology, this paper presented a new production process for preparing chromium oxide by hydrothermal reduction of sodium chromate using starch as a reductive. On the basic of analyzing reaction mechanism, the kinetics of hydrothermal reduction of sodium chromate by starch(St) have been studied and the affecting factors for the rate of reduction of Cr(Ⅵ) have been investigated. The results show that reaction temperature, reaction time and reactant concentration are the main factors affecting the rate of reduction of Cr(Ⅵ). A constant temperature, constant volume and irreversible reaction kinetic model was selected to describe its reaction process and the kinetic equation can be expressed as: r=-d［Cr(Ⅵ)］/dt=1.367×10¹³e^{-100.566×1000/RT}［Cr(Ⅵ)］［St］, i.e., the pre-exponential constant, apparent activation energy and overall reaction order are 1.367×10¹³L/(mol·h), 100.566kJ/mol and second-order or pseudo-second-order, respectively. The reaction is of the chemical reaction controlled type and the reaction order is first-order or pseudo-first-order with respect to Cr(Ⅵ) and starch. 