【作者】 张露；

【导师】 王学重；

【作者基本信息】 华南理工大学 ， 化学工程， 2021， 硕士

【摘要】 苯并三氮唑(BTA)是一种重要的精细化工产品,广泛应用于医药、农药和高分子材料等方面,具有较高的使用价值。现阶段苯并三氮唑的工业生产多采用间歇结晶的方式,存在效率低、能耗高、难以实现粒度要求等弊端。针对这些问题,尝试将苯并三氮唑的间歇结晶工艺转化为连续结晶工艺,对苯并三氮唑的连续结晶过程进行了系统的研究,为工业化生产提供基础数据。首先,对BTA的结晶热力学性质进行了研究。采用重量法测定了273.15～353.15 K条件下BTA在纯溶剂水中的溶解度,发现随着温度的升高,溶解度逐渐增大。通过Apelblat经验方程和Van’t Hoff经验方程对溶解度实验值进行拟合,发现两者均具有较好的拟合效果。经Van’t Hoff经验方程计算出BTA在纯溶剂水中溶解的摩尔焓变、摩尔熵变以及摩尔吉布斯自由能变,发现该溶解过程是吸热、熵驱动且非自发的。其次,对BTA的成核与生长动力学进行了研究。采用成像法测定了BTA在水中冷却结晶的介稳区宽度,发现介稳区宽度随着降温速率的增加变宽,随着搅拌速率的增加变窄。将介稳区宽度实验值经Nyvlt方程、自洽Nyvlt型方程和经典3D成核理论方程分别拟合,发现三者的拟合效果均较好,由此计算出表观成核级数n和质量成核速率常数k_n。采用热台显微镜法测定不同温度和过饱和度条件下的晶体生长速率,发现体系的过饱和度越大,结晶温度越高,BTA晶体的生长速率越快。在结晶热力学和动力学研究的基础上,通过ATR-UV技术对BTA-水体系的溶液浓度进行在线测量。研究紫外光谱与温度、浓度之间的关系,采用偏最小二乘法构建紫外光谱浓度预测模型,发现模型验证集的预测值与实验值的相对误差在±2.59%以内,说明模型的预测效果较佳。利用在线紫外实时监测苯并三氮唑的连续结晶过程,发现无论起始阶段晶体的浓度和粒度如何变化,合适操作条件下的连续结晶过程都会在一定的停留时间后达到稳定阶段。最后,以产品的收率和粒度为主要优化指标,开发了一种苯并三氮唑连续结晶新工艺。考察了BTA原料初始浓度、停留时间、搅拌速率和结晶温度对连续结晶产品收率和粒度分布的影响,发现原料初始浓度为0.02602 g/g、停留时间为15 min、搅拌速率为300rpm、结晶温度为24℃时,产品的收率和粒度分布均达到了理想的效果。优化后的BTA产品粒度分布较窄,在目标粒度区间30.0～60.0μm内的百分含量较高,收率从84.6%提高至91.2%,晶习完整,晶型并未发生改变,表明该连续结晶优化工艺是可行的。更多还原

【Abstract】 Benzotriazole(BTA)is an important fine chemical product,which is widely used in medicine,pesticide and polymer materials,and has a high value in use.At present,the industrial production of benzotriazole mostly adopts the way of batch crystallization,which has disadvantages such as low efficiency,high energy consumption and difficult to achieve the requirements of particle size.In response to these problems,an attempt was made to convert the batch crystallization process of benzotriazole to continuous crystallization process,and the continuous crystallization process of benzotriazole was systematically studied to provide basic data for industrial production.Firstly,the crystallization thermodynamic properties of BTA were studied.The solubility of BTA in pure solvent water at 273.15～353.15 K was measured by gravimetric method,it was found that the solubility increased gradually with the increase of temperature.The experimental values of solubility were fitted by Apelblat empirical equation and Van’t Hoff empirical equation,it was found that both of them had good fitting effects.According to the Van’t Hoff empirical equation,the molar enthalpy change,molar entropy change and molar Gibbs free energy change of BTA dissolution in pure solvent water were calculated,it was found that the dissolution process was endothermic,entropy-driven and non-spontaneous.Secondly,the nucleation and growth kinetics of BTA were studied.The width of the metastable zone of BTA cooling crystallization in water was measured by imaging method,it was found that the width of the metastable zone widened with the increase of the cooling rate and narrowed with the increase of the stirring rate.The experimental values of the metastable zone width were respectively fitted by Nyvlt equation,self-consistent Nyvlt-like equation and classical 3D nucleation theory equation,it was found that the fitting effects of the three equations were all good,therefore,the apparent nucleation order n and the mass nucleation rate constant k_n were calculated.The hot stage microscope method was used to measure the crystal growth rate under different temperature and supersaturation conditions,it was found that the greater the supersaturation of the system,the higher the crystallization temperature,and the faster the growth rate of BTA crystals.On the basis of the study of crystallization thermodynamics and kinetics,the ATR-UV technology was used to measure the solution concentration of BTA-water system online.The temperature and concentration dependent UV spectrum were studied,and the partial least squares method was used to construct a concentration prediction model of UV spectrum,it was found that the relative error between the predicted value of the model validation set and the experimental value was within±2.59%,indicating that the prediction effect of the model was better.Using online UV to monitor the continuous crystallization process of benzotriazole in real time,it was found that no matter how the initial crystal concentration and particle size changed,the continuous crystallization process would reach a steady state after a certain residence time under suitable operating conditions.Finally,a new continuous crystallization process of benzotriazole was developed with the yield and particle size of the product as the main optimization indexes.The effects of initial concentration of BTA raw material,residence time,stirring rate and crystallization temperature on the yield and particle size distribution of continuous crystallization products were investigated,it was found that when the initial concentration of raw material was 0.02602 g/g,the residence time was 15 min,the stirring rate was 300 rpm,and the crystallization temperature was 24℃,the yield and particle size distribution of the product all reached the ideal effect.The optimized BTA product had a narrow particle size distribution,with a higher percentage content in the target particle size range of 30.0～60.0μm,and the yield was increased from 84.6%to91.2%,the crystal habit was complete and the crystal form did not change,it showed that the continuous crystallization optimization process was feasible.更多还原