反应法去除近共沸浓度乙醇-水混合物中水的宏观动力学研究

Macro-Kinetic Study of Water Removal from Ethanol-Water Mixture near Azeotropic Concentration Using Reaction Method

针对乙醇汽油制备过程中乙醇原料的除水问题,提出了用反应法除去近共沸浓度乙醇中水的新技术路线,着重进行了近共沸乙醇-水混合物与异丁烯水合醚化反应的宏观反应动力学研究. 实验以β分子筛为催化剂,在2.0 MPa和313～363 K的条件下考察了搅拌速度、乙醇中初始水含量、烯水比和温度等因素对水的转化率和叔丁醇选择性的影响. 结果表明,乙醇对异丁烯水合反应有先促进后抑制的作用,而水对异丁烯醚化反应影响较小;水的转化率随烯水比的增大而增大,随乙醇中初始水含量的增大而减小,随着温度的升高呈现先增大后减小的趋势. 叔丁醇的选择性随初始水含量的增大而增大. 基于实验结果和Langmuir-Hinshelwood-Hougen-Watson理论,充分考虑反应体系的高度非理想性,以活度代替浓度建立了宏观反应动力学模型;采用混合进化算法对模型进行求解,结果表明模型计算值与实验值可较好地吻合.

A new method of removing water from the ethanol and water mixture near azeotropic concentration was proposed based on isobutylene （IB） hydration-etherification catalyzed by β molecular sieve. The macro-kinetic study of IB hydration-etherification was investigated under the reaction conditions of 2.0 MPa and 313 363 K. The influence of the stirring speed, initial content of water in ethanol, IB/water ratio, and reaction temperature on IB hydration-etherification was investigated. The results indicated that the presence of ethanol favored IB hydration at first, but then it inhibited the reaction. Water had little effect on the etherification between ethanol and IB. The water conversion increased with the IB/water molar ratio and decreased with the initial water content in ethanol; and it increased with the increase of temperature in lower temperature range, but decreased when the temperature was higher than 353 K. The selectivity of IB hydration increased with the initial content of water in ethanol. Under the conditions of 353 K, IB/water molar ratio of 7, and initial water content in ethanol of 10 %, the water conversion reached as high as 92.58 %. The macro-kinetic model was developed according to the Langmuir-Hinshelwood-Hougen-Watson theory and the experimental results using the Wilson liquid-phase activity to describe the non-ideality of the reactants. The calculated results using the parameters obtained from the hybrid evolutionary algorithm with multi-pattern evolution were in good agreement with the experimental data.