【作者】 杨效益；

【导师】 李瑞丰； 李秋小；

【作者基本信息】 太原理工大学 ， 化学工程与技术， 2010， 博士

【摘要】 4A沸石由于其独特的吸附性、共价载体性和良好的化学可修饰性,广泛应用于洗涤助剂、石油化工及环境保护等诸多领域。近年来随着4A沸石的应用范围越来越广,其用量也越来越大。目前工业生产普遍采用间歇法生产,其设备投资大、能耗高、产量低,产品成本高、质量不稳定。为了克服这一缺陷,本论文通过对传统的间歇晶化条件加以改进,将最关键的晶化过程连续化,实现了合成高性能4A沸石工艺条件的优化。主要内容如下:在间歇晶化条件下,通过加大反应混合物碱度、减少体系水量（即高碱度少水体系）和加入适量的表面活性剂,加快了凝胶溶解速度及晶化速度、缩短了4A沸石晶化的诱导期、加快了晶化速率、减小了平均粒径,使得整个工艺过程所需时间明显缩短,此结果为4A沸石的连续化合成提供了可能。在对自行设计、研制具有中试规模的连续晶化器进行了调试的基础上,通过正交实验的方法得到了连续晶化法合成4A沸石的的最佳工艺为:成核浆液浓度为30%、流量为2L/min,反应混合物配比n（SiO2）/n（Al₂O₃）=1.8¹.9,n（Na2O）/n（Al₂O₃）=3.2³.4,n（H2O）/n（Al₂O₃） =80¹00,晶化时间t=20min,晶化温度90℃、添加十二烷基磺酸钠（SDS）摩尔比数为0.1。通过对浆液中固体颗粒的沉降理论分析得出,在20min内沸石颗粒沉降距离为1.998×10-5mm,由于其沉降速度非常慢,所以对连续晶化过程几乎没有影响,且在实际实验过程中也未发现管道堵塞现象,实现了高性能4A沸石连续晶化的稳定中试合成。对连续晶化法合成的4A沸石产品进行了表征,结果表明:采用连续晶化法可以制备出结晶度高,粒度小且分布范围窄,钙交换能力高、速率快的高性能4A沸石;通过对连续晶化法与间歇晶化法合成的4A沸石铝离子含量、洗净力、摩损性、LCC性能对比分析表明,铝离子含量从18.34%提高到18.61%、洗净力比间歇晶化法高20%、摩损性几乎没有、LCC从39.0g/100g提高到44.2g/100g。与传统合成工艺相比,连续化工艺的料浆固含量提高85%以上,水电汽消耗及材料检修维护费用大幅降低,目前全球沸石的商业产值超过3500亿元,而4A沸石则占50%以上,若按年产20万吨4A沸石计算,合计降低成本大于2200万元/年。连续晶化法合成4A沸石的热力学过程的研究表明,连续晶化法合成过程的成核活化能En为51.1kJ·mol^-1、晶核生长活化能Ec为5.8kJ·mol^-1,晶核生长活化能与传统间歇法的相比大幅降低,晶化时间相对缩短。连续晶化法水热合成4A沸石反应体系突破了传统间歇法的典型组成,在实验中并没有观察到4A沸石转晶为方钠石,由此推测形成方钠石的原因除了由于碱度太高之外,还与晶化方式有关。对连续晶化法合成4A沸石的生长历程研究表明,连续化合成机理属液相转化机理。建立了连续晶化法合成4A沸石的生长模型,连续晶化水热条件下沸石晶粒的形成经历了前驱物溶解-成核并形成纳米小粒子（成核期）-纳米晶粒叠合生长为亚微米晶（快速生长期）这样3个阶段,称之为“第二类叠合生长模型”。连续晶化法制备4A沸石的研究,从本质上揭示连续水热条件下4A沸石晶体生长的基本规律,开辟了4A沸石形成机理和晶体生长研究的新途径,提高和发展了4A沸石的晶体生长理论,丰富了沸石合成化学的内容。不仅对降低4A沸石制备成本有着很高的实用价值,而且对有特定结构和性能的新型沸石分子筛的设计合成,特别是对实现纳米沸石制备技术研究的指导和预言具有重要的理论意义。更多还原

【Abstract】 4A zeolites have been widely used in various industries such as detergent, petrochemical, environmental protection, etc. because of their unique absorbability, ion exchange character and chemical modificable property. In recent years, with the increasingly widespread application of 4A zeolite, it has been manufactured on a greater scale. Currently the general industrial production method of 4A zeolite is batch operation, in which the investment is large and the energy consumption is high, but the output is low and the quality of the product is unstable. In order to overcome these shortages, a modified method for the traditional batch operation is introduced in this paper, by the new method the process of crystallization is changed to continuous synthesis, in which the technological conditions are optimized.Under batch crystallization conditions, the rate of gel dissolution and crystallizate was accelerated, the time of induction was shortened and the average particle size was reduced by increasing alkalinity of the reaction mixture, reducing system of water （that is less-water and high-alkalinity system）, and adding an appropriate amount of surfactant. This result provides possible for the continuous synthesize 4A zeolite. In our own designed and manufactured pilot-scale continuous crystallization reactor, the parameters such as slurry concentration, flow rate and so on were adjusted to obtain the optimal synthesis conditions of continuous synthesis through orthogonal experiments: the concentration of nucleation slurry 30%, flow 2L/min, the reaction mixture ratio of n （SiO2） / n （Al₂O₃） = 1.8 1.9, n （Na2O） / n （Al₂O₃） = 3.2 3.4, (n （H2O） / n （Al₂O₃） = 80 100, crystallization time t= 20min, the crystallization temperature is 90℃, add the dodecyl sulfonic sodium （SDS） by molar ratio of 0.1. Through the theoretical analysis, the deposition distance of zeolite particle is 1.998×10^-5mm in 20min. As the deposition is very slow, there is almost no effect on a continuous crystallization process, and in the actual experiment the phenomenon of pipe blockage has not been found. The synthesis of high-performance 4A zeolite was achieved in the pilot-scale continuous crystallization reactor.The performance of the synthetic 4A zeolite was characterized. And the results showed that the 4A zeolites with a high degree of crystallinity, small crystal size, narrow crystal size distribution, high calcium exchange capacity, fast calcium exchange rate can be produced with continuous method. In comparison with synthesis technique of batch operation, the Al³⁺ content in crystallization system under continuous synthesis was increased to 18.61% from 18.34%, the detergency was increased by 20%, the LCC of the product is increased to 44.2g/100g from 39.0g/100g, and it has little wear behavior according to the results from a series analysis.The energy consumption analysis results showed that in comparison with traditional technique, the solid content in slurry of continuous synthesis system is increased by more than 85%, and the consumption of water, steam, power and repair cost can be greatly reduced. If calculated as an annual output of 200,000 tons, the total cost reduction is greater than 22 million yuan per year.The thermodynamic study of continuous crystallization process showed that the nucleation activation energy En is 51.1kJ·mol-1 and the growth activation energy Ec is 5.8kJ ? mol-1. Compared to conventional batch method they reduced , the crystallization time is relatively shorter. Continuous crystallization system breaks through the typical composition of the traditional batch method. In the experiment, there is no sodalite formation was observed, thus we can speculate that the reasons for the formation of sodalite are not only the high degree of base, but also the way of crystallization.The results of our study showed that continuous synthesis mechanism was a liquid-phase transformation mechanism. The crystallization growth model was established for a continuous synthesis way, the crystallization process experiences three stages: collid, nanocrystalline and ultra-fine crystallite in continuous process, that was known as "Type II splicing growth model."The study about continuous process for preparation of 4A zeolite revealed the basic law of 4A zeolite crystal growth under the conditions, opened up a new way for study of formation mechanism and crystal growth of 4A zeolite, improved and developed the theory of zeolite crystal growth, enriched the content of zeolite synthetic chemistry. Therefore this study not only has a high practical value to reduce the synthetic cost of 4A zeolite, but also possesses important theoretical significance to carry out the guidance and predict of the preparation technique for zeolite of specific structure and properties.更多还原