FCC汽油深度烷基化硫转移脱硫技术的实验研究及反应机理的量子化学计算

Deep desulfurization of FCC gasoline by alkylation technology can be handled under relatively mild conditions with a minimal loss of octane number and without any hydrogen consumption, which has broad prospects for development and application in China. However, side reactions in the process lead to significant levels of coke, which will greatly reduce the catalyst lifetime. So the objective is to provide responsibly experimental and theoretical basis for the promotion and application of this desulfurization technology in our country, through a further experimental and theoretical investigation on mechanisms of representative reactions during the alkylation transfer process of thiophenic sulfurs catalyzed by two kinds of common solid acid catalysts. The study is favorable for analyzing and solving the fast deactivation problem for solid acid catalysts reasonably, as well as to improve the yield and octane number of the final gasoline product. The research results have important theoretical significance and practical value...The investigations in the project are carried out by the method of combining experiments and Quantum Chemistry Calculation. By constructing the catalyst structure model, the main and side reactions in FCC gasoline desulfurization by alkylation technique over two different solid acid catalysts have been studied from a microscopic point of view by the method of quantum chemical theory calculation, on the basis of a large number of reliable experimental data obtained by designed experiments. Then the reliability of theoretical calculations can be verified by the combination of theoretical and existing experimental results. Thus the calculation results with reliability can be used to guide the design and development of solid acid catalysts with superior performance and the optimization of reaction process. Based on the experimental and theoretical calculation results about the catalysis of MCM-41 supported phosphoric acid catalyst for FCC gasoline desulfurization by alkylation, the catalyst preparation method can be further improved. Moreover, the using technology of Amberlyst 35 for the FCC gasoline desulfurization with the addition of methanol can be optimized according to the calculated reaction mechanisms.The results are beneficial to the industrial application of the two kinds of solid acid catalysts in the alkylation process of FCC gasoline desulfurization.

FCC汽油深度烷基化硫转移技术具有反应条件温和、产品辛烷值损失小等优点。本项目通过对固体磷酸和磺酸树脂两类常用固体酸催化FCC汽油烷基化硫转移过程中各代表性主、副反应的机理和竞争关系进行深入的实验和微观理论研究，可合理分析解决此过程中催化剂易失活的问题，有助于提高产品汽油的收率和辛烷值，对该脱硫技术在我国的推广与应用具有重要的理论指导意义和实际应用价值。..采用实验和量子化学计算相结合的方法，构造催化剂模型，从分子结构的微观角度计算两固体酸催化各主要反应物的吸附及反应机理，用实验验证计算结果的可靠性，为设计性能优越的固体酸、优化反应工艺提供理论依据。最后基于实验和理论计算得到的机理，在不影响催化活性前提下进一步改进全硅MCM-41负载的固体磷酸的制备方法、优化Amberlyst 35树脂添加甲醇的催化工艺，并用实验对比验证。研究利于这两类固体酸在FCC汽油烷基化硫转移脱硫中的工业化应用。

目前我国的成品汽油以流化催化裂化(FCC)汽油为主，硫含量普遍较高。烷基化脱硫(Olefinic Alkylation of Thiophenic Sulfur，OATS)作为非加氢脱硫技术中的一种，因其脱硫效率高、反应条件温和、基本不损失产品辛烷值、投资和操作费用低等优点具有广阔的发展和应用前景。要使FCC汽油烷基化脱硫技术实现大规模工业化，就要解决好酸性催化剂选择性的问题，在不影响噻吩类硫化物烷基转化的前提下减少副反应烯烃聚合和芳烃烷基化的发生。. 本项目在设计实验获得大量可靠实验数据的基础上，采用量子化学理论计算的方法，通过建立合理的固体酸催化剂模型，从微观角度上研究固体磷酸和大孔磺酸树脂催化下FCC汽油烷基化脱硫过程中主、副反应的反应机理，最后将理论和实验结果相结合，用实验验证理论计算结果的可靠性。理论计算表明，两种固体酸催化汽油烷基化脱硫时，根据催化剂以及反应物的结构，主、副反应存在两种可能的反应机理：两步法和一步法机理，但是无论按照哪种机理进行反应均是从催化剂活性位上吸附的活化烯烃开始的，而真实汽油体系中噻吩的含量远小于烯烃，噻吩烷基化所需的活化烯烃量极少，而且相对副反应烯烃聚合，前者的反应活化能较小更易发生且反应速率更快。此外，理论计算与实验结果还表明，在两种固体酸的催化作用下，主反应硫化物与烯烃的烷基化均为放热反应，而副反应烯烃聚合均为吸热反应。. 利用主、副反应的差异以及反应体系的特殊性可通过控制催化剂表面上的总酸量来减少催化剂上剩余的未参加烷基化反应的活化烯烃量，进而达到抑制副反应烯烃聚合的目的以提高催化剂的选择性。根据所得的实验和理论结果相应地提出一些改进措施，如改进催化剂的制备方法或是在反应体系中添加适量浓度的甲醇来减少催化剂上的表面酸量，实验证明以上改进措施可以很好的提高固体酸的选择性，明显减少副反应烯烃聚合的发生，催化剂的使用寿命明显延长，从而为今后汽油烷基化脱硫技术的工业化提供必要的理论指导和实验依据。