硫醚化反应脱除FCC汽油中硫醇的反应机理及其高效催化剂研究

The mercaptans in the FCC gasoline can be removed by thioetherification reaction. No alkaline is used in the thioetherification process, so there is no problem of disposing the spent alkaline agent. Combined with widespread used technology of selective hydrodesufurization in the refinery, the loss of octane number can be decreased in the production of clean gasoline. In addition, a few of diene in the FCC gasoline can be selectively hydrogenated in the thioetherification process, contributing to holding the catalytic activity and stability of catalysts in the hydrodesulfurization process. However, there is almost no report on mechanism and catalysts about thiotherification. In this study, a series of Mo promoted-Ni/Al2O3 will be prepared. The range of acid-base properties of Al2O3 support is modified with F, Si, β-molecular sieve, K, or Mg. The catalytic performance of the catalysts with a wide range of acid-base properties and different amounts of Mo promoter in the thioetherification are studied in detail. The oxidatied and sulfided catalyst samples are characterized to detect the metal species distributions and their physical chemistry properties and to analyse the changes of the properties of the deactivated catalysts. And the relations of structure and performance will be well established. Then, the in-situ IR analyses of the thioetherification reaction and GC with PFPD detector and GC-MS analyses of products will be used to analyse the adsorption properties, reaction procedure and sulfur compounds structures and distibutions. The thioetherification reaction mechanism can be discussed on the results above. At last, combined with reaction mechanism of the diene selective hydrogenation, the high-efficiency functionalized catalysts will be designed to satisfy for a good low temperature reaction activity and an excellent activity of the diene seletive hydrogenation.

硫醚化反应脱除催化裂化(FCC)汽油中硫醇技术可完全摆脱传统Merox脱臭技术中碱渣排放问题，并在与现有的选择性加氢脱硫技术结合时，可减少生产低硫汽油过程中的辛烷值损失。同时，由于硫醚化过程中还可将FCC汽油中少量二烯烃选择性加氢，有利于保持选择性加氢脱硫催化剂的活性和寿命。目前，国内外对硫醚化反应机理和催化剂的研究报道的较少，本课题拟制备Mo改性的Ni/Al2O3催化剂，对Al2O3载体进行酸碱性和活性组分改性，并进行微反活性评价；利用一系列表征研究催化剂的物理化学性质、活性相的物种结构和失活前后催化剂结构的变化，将催化剂的物理性质与反应活性关联；再结合原位红外、色谱和质谱对催化剂活性位上物种吸附类型、反应过程、产物分布等方面来探讨硫醚化反应机理；在此基础上，结合二烯烃选择性加氢反应特点，对催化剂进行功能性设计，开发具有优异低温性能、兼顾二烯烃选择性加氢的高效硫醚化催化剂。

通过硫醚化反应过程脱除FCC汽油中硫醇的技术可解决传统汽油脱臭过程中产生碱渣的问题，还可现有的选择性加氢脱硫技术结合，生产满足国V甚至国VI标准的低硫汽油，且过程辛烷值损失极低。该过程还可将FCC 汽油中少量二烯烃选择性加氢，有利于保持后续选择性加氢脱硫催化剂的活性和寿命。本项目通过深入研究了硫醚化反应过程催化剂的物种活性结构和物化性质与反应活性关系、硫醚化反应过程机理、催化剂失活原理、催化剂改性及优化处理和催化剂寿命评价等多方面实验，表明Mo-Ni催化剂体系后，可在预硫化过程形成的2-3层MoS2堆垛条纹的Ni-Mo-S结构中心，该结构中存在的多种Ni的不饱和配体，被证实为硫醚化反应活性中心，同时具有二烯烃和烯烃加氢性能；硫醇和烯烃在硫化态Ni/Al2O3和Mo-Ni/Al2O3作用下的硫醚化反应过程，在不同温度下遵循不同的反应历程，可以归纳为两条反应路线：一是在较低温度下，硫醇和烯烃直接加成后生成硫醚；第二条是温度升高后，硫醇的C-S键断裂，形成的SH基团与反应体系中含量高的烯烃分子重新组合生成空间位阻小的硫醇后，继续与烯烃加成生成硫醚，整个反应过程的产物以空间位阻小的产物为主；催化剂失活主要由于反应过程在催化剂上的积碳引起；实验最终确定Mo-Ni/Al2O3催化剂经过F改性、水热处理和适宜条件预硫化可是催化剂具有良好的硫醚化和二烯烃加氢选择性能力。