柴油深度加氢脱硫催化剂的孔结构设计与孔道限域效应

The desulfurization efficiency on diesel oil is closely related to structure of hydrorefining catalysts. Pore confinement effect can reveal the nature of catalysis for structure sensitive catalysts and then supply valuble information for catalyst design and preparation. However, so far pore structure control and pore confinement effect has seldom been studied for diesel oil hydrorefining catalysts. In this project, alumina with different pore structure will be synthesized via different preparation methods. The catalysts for hydrocarbon refining will be prepared with the synthesized alumina as the support. The effect of pore confinement on accessibility of active sites, type and distribution of active phase will be investigated. The adsorption and reaction of model compound in different pore structures of the catalysts will also be studied. It is worthy to note that electronic modulation effect and active phase stabilization will be demonstraed. Moreover, the effect of pore confinement on hydrorefining of real diesel oil will be investigated and a mathematical model for pore confinement effect will be postulated. Finally, the highly efficient catalysts with optimum pore structure will be obtained. The innovation of this study is that the electronic modulation effect, accessibility of active sites and active site stabilization induced by pore confinement in hydrorefining process will be investigated and then the highly efficent catalysts will be designed and prepared according to the above data.

柴油的脱硫效率与加氢精制催化剂的结构密切相关。研究柴油深度加氢脱硫催化剂的限域孔道不仅能揭示敏感型催化剂的作用本质，而且可为高效催化剂设计和制备提供理论依据。但截至目前，柴油深度加氢脱硫催化剂孔结构的可控制备和孔道限域效应鲜有报道。本项目通过合成方法的设计和合成条件的控制，制备不同限域孔道的氧化铝载体和相应的加氢精制催化剂；考察催化剂限域孔道对活性中心可接近性和对活性相类型、分布和稳定性的影响；探讨不同孔道催化剂对模型化合物吸附和脱硫反应的影响规律；在此基础上，提出孔道限域在催化转化过程中的电子调制作用，确立高效加氢精制催化剂的孔道特征，构建孔道限域的理论模型；并探讨孔道限域对真实柴油馏分加氢脱硫、脱氮性能的影响。本项目的创新性在于研究柴油深度脱硫催化剂限域孔道在催化转化过程中的电子调制作用、对活性中心可接近性以及对活性相的稳定化作用，并将其作为柴油高效加氢精制催化剂设计和制备的依据。

柴油的脱硫效率与催化剂的孔道结构密切相关。探究柴油深度加氢催化剂的孔道限域效应不但可以揭示催化转化过程的电子传递现象，而且可为高效催化剂设计和开发提供理论依据。本项目通过设计合成方法、调控合成条件得到了单一介孔、双介孔和介孔-大孔等级孔道的氧化铝，并以其载体制备了不同孔道结构特征的加氢精制催化剂。探究了孔道结构对活性相堆垛结构、金属组分还原性质和价态等的影响规律，考察了噻吩、4,6-二甲基二苯并噻吩等硫化物在不同催化剂表面的吸附行为和加氢脱硫反应活性。研究发现，催化剂的限域孔道显著影响活性组分与载体的相互作用，进而影响活性相的堆垛结构，使催化剂具有不同的堆垛层数和堆垛长度、不同的边和角活性位、不同的表面四价钼含量。孔道结构对活性中心的可接近性具有重要影响，小孔有利于4,6-二甲基二苯并噻吩与边位的活性位接触，较大的孔径促进了反应物分子与角位的活性位接触。催化剂的稳定性也与孔道结构密切相关，其稳定性随孔道的变化呈现出最优值，在考察孔径范围内，孔径较小的催化剂的稳定性较优。将优势孔道催化剂用于真实柴油馏分加氢脱硫、脱氮，结果表明优势孔道催化剂的脱硫、脱氮性能均优于工业催化剂。研究明确了限域孔道在催化转化过程中的电子调制作用以及限域孔道对吸附中心、活性中心可接近性、对活性相稳定性的影响，确定了高效加氢精制催化剂的孔道特征，最终构建出了孔道限域的理论模型。该项目研究结果可为高效柴油加氢精制催化剂的设计和制备提供理论依据。