Co内嵌TiO2纳米管@分子筛胶囊型催化剂的制备及其对费托合成选择性的调控

Fischer-Tropsch synthesis is an important route for the production of clean liquid fuels from synthesis gas (CO+H2), which can be derived from non-petroleum feedstocks such as coal, natural gas, or biomass. The key challenge of research into Fischer-Tropsch synthesis is the control of catalyst selectivity. This proposal mainly focuses on the design and the controllable fabrication of Co-in-TiO2 nanotube@zeolite capsule core-shell structured composite catalyst and as well as the exploration of structure-activity relationship for Fischer-Tropsch synthesis. This study is of scientific significance and practical value, which will provide the theory basis for the design and the preparation of catalysts with high Performance. The related investigation includes as follows: (1) Through the design and the construction of Fischer-Tropsch reaction active centers (the confinement of the cobalt species within TiO2 nanotube as core) and cracking-isomerization acidic sites (mesopore zeolite membrane as shell), searching for novel preparation method of high efficiency catalysts for Fischer-Tropsch reaction, and obtaining the catalyst structure with high selectivity for direct one-step catalytic convertion of syngas into the high-grade liquid fuel with gasolene or diesel oil distillate. (2)Through investigating the influence rules of particle size and redox properties of encapsulated cobalt species, and pore size and surface acidity of mesopore zeolite membrane，and spatially sonfined effect of capsule catatlyst on the selectivity of product and the adsorbtion-desorbtion diffusion behavior of reactant and product, analyzing active site and catalytic reaction course, and providing new insight into the relationship between catalyst structure and product selectivity.

费托合成油技术是煤炭、天然气、生物质等非石油资源清洁优化利用的重要途径。产物选择性可调控性差是目前费托合成面临的主要难题，催化剂在其中起着关键作用。本项目拟开展Co-in-TiO2纳米管@分子筛胶囊型核壳结构复合催化剂的制备及其对费托合成产物选择性的调控研究。本项目的重点在于：（1）通过对胶囊型复合催化剂（核：TiO2纳米管限域组装的Co作为费托活性中心，壳：介孔分子筛膜作为裂解异构化中心）的制备化学进行研究，获得合成气高选择性地一步转化为汽油、柴油或煤油等特定碳数范围的高品位液体燃料的催化剂结构。2）研究限域组装的活性Co物种的粒子尺寸和氧化还原特性，外层分子筛膜孔径和表面酸性，以及胶囊型催化剂的空间限域效应对反应物和产物分子在催化剂表面的吸附和扩散行为的影响规律，分析催化反应中的活性中心及相关反应历程，揭示催化剂结构与费托产物选择性的构效关系，为高性能催化剂的设计和制备提供理论依据。

费托合成油技术是煤炭、天然气、生物质等非石油资源清洁优化利用的重要途径。产物选择性可调控性差是目前费托合成反应面临的主要难题，催化剂在其中起着关键作用。本项目针对催化剂结构与费托产物选择性之间的构效关系等科学问题，主要开展Co-in-TiO2纳米管@分子筛胶囊型核壳结构复合催化剂的制备及其对费托合成产物选择性的调控研究。本项目开展的主要研究内容为：1）高晶型和稳定性TiO2纳米管的制备；2）活性Co/Fe物种的限域组装；3）分级结构TiO2微球负载Co催化剂的制备；4）催化剂结构与产物选择性的构效关系研究。.本项目采用TEOS或KH570对钛酸纳米管进行表面改性，成功获得了高温稳定高结晶性的TiO2纳米管，采用超声辅助真空浸渍法获得了活性物种Co/Fe内嵌于TiO2纳米管孔道内的限域型催化剂，重点研究了TiO2纳米管结晶性，Co物种负载方法，TiO2纳米管限域、TiO2分级结构微球对费托反应性能的影响。尿素沉积沉淀（DP）方法制得的催化剂Co粒子富含在纳米管的外表面，浸渍（IMP）方法制得的催化剂Co粒子分布在纳米管内、外两个表面；相较于Co/TiO2-IMP催化剂，Co/TiO2-DP催化剂展示着两倍高的费托活性和更高的C5+选择性。Co/TiO2-IMP显示低的费托活性可归因于较强的Co-TiO2相互作用和较少可用的活性Co位。Fe-In-TiO2限域型催化剂显示出较好的碳链增长效果，C5+选择性显著增加。这一结果归因于管内限域空间对于反应物以及中间产物扩散的阻碍，提高了α烯烃的再吸附，因而提高了C5+选择性。通过本项目的研究，获得了较高选择性合成目标烃类的新型结构催化剂，探讨了催化剂结构与费托产物选择性的构效关系，揭示了费托产物选择性调变的作用机理，可为高性能催化剂的设计与制备提供理论参考。