疏水微介孔分子筛的设计及其在选择性费托合成中的应用

Due to the severe oil crisis and the tight environmental protection requirements, Fischer-Tropsch synthesis (FTS), using syngas derived from coal, natural gas, or other carbon-containing materials, has recently been received considerable attention as an alternative efficient method for synthesizing clean fuels. High selectivity for middle distillate products is one of the important directions to improve Fischer-Tropsch synthesis on the premise of high activity and stability. The breakthrough in this direction focuses on the design of the catalyst. The introduction of microporous molecular sieves to cobalt-based catalyst for Fischer-Tropsch synthesis increased the selectivity of gasoline range products, but limited that of diesel production with long-chain structure because of their smaller dynamic aperture. The introduction of mesoporous molecular sieves to cobalt-based catalysts improved mass diffusion and transportation of reactants and products, and then controlled the distribution of hydrocarbon products for Fischer-Tropsch synthesis, but their low structure stability greatly limited their industrial applications. Our study demonstrated that the introduction of hydrophobic groups to cobalt-based catalysts maked catalyst surface polarity reverse, affecting adsorption-desorption behavior of reactants and products, and improving the selectivity of the catalyst for Fischer-Tropsch synthesis. To overcome the limitations of microporous molecular sieves and mesoporous molecular sieves, and take advantage of microporous molecular sieves, mesoporous molecular sieves, and hydrophobic groups, this project plans to introduce microporous molecular sieves, mesoporous molecular sieves, and hydrophobic groups simultaneously to the cobalt-based catalyst, design and synthesize hydrophobic micro/mesoporous molecular sieve supported cobalt-based catalysts with a novel structure, study the synergistic impact law of hydrophobic, microporous, and mesoporous structure on highly selective synthesis of middle distillates, reveal the regulation mechanism of the product distribution in CO hydrogenation, and obtain highly selective catalysts for Fischer-Tropsch synthesis. The study is not only a new way to build efficient and new catalytic materials, but also explore new areas of application of the hydrophobic micro/mesoporous materials, which has a significant social and economic benefits for optimal use of China's coal resources and adjustment of energy product structure.

费托合成是将煤炭、天然气、生物质等非石油基化石燃料转化为清洁、优质 液体燃料的重要途径。而费托合成重质烃二次加工的高成本，在一定程度上制约了费托合成制备清洁中间馏分油技术的广泛应用。如何一步高选择性地获得中间馏分油是改进费托合成的重要方向之一。而这一方向的突破重点在于催化剂的设计。本项目拟将微孔分子筛、介孔分子筛和疏水基团同时引入钴基催化剂，设计合成具有新颖结构的疏水微介孔分子筛负载钴基催化剂，研究三者对 CO 加氢高选择性合成中间馏分油的协同影响规律，揭示反应过程中产物分布的调控机理，从而获得高选择性、高活性和高稳定性的费托合成催化材料。该研究不仅是构建高效新型催化材料的一条崭新途径，也是对疏水微介孔材料新领域应用的探索发展，可为我国缓解石油供需矛盾、增加能源供应提供科学依据和技术支持，同时还可促进化工、材料和能源等学科的交叉。

随着石油资源的日益匮乏和环保要求的日趋苛刻，利用费托合成技术将煤炭转化为清洁液体燃料已经引起国际催化界的高度重视。而费托合成重质烃二次加工的高成本，在一定程度上制约了费托合成制备清洁中间馏分油技术的广泛应用。因此，如何在高活性、高稳定性前提下一步高选择性地获得中间馏分油产品是改进费托合成技术的重要方向之一。而这一方向的突破重点在于催化剂的设计开发。.本项目将微孔分子筛、介孔分子筛和疏水基团同时引入钴基催化剂，设计合成具有新颖结构的疏水微介孔分子筛负载钴基催化剂，研究三者对 CO 加氢高选择性合成中间馏分油的协同影响规律，揭示反应过程中产物分布的调控机理，从而获得高选择性、高活性和高稳定性的费托合成催化材料。.研究发现，在钴基催化剂中引入微孔分子筛，利用其具有的酸性位可以在同一反应系统中裂解、异构费托反应生成的长链重质烃，提高汽油馏分的选择性；同时引入的介孔分子筛作为费托合成催化剂的载体，其规整的孔道结构，有利于反应物、产物的扩散与吸脱附，狭窄的孔径分布则有利于择型催化；催化剂表面的疏水改性有利于链增长，但同时疏水基团的空间位阻又阻碍了大分子 α - 烯烃的再吸附，这两种效应的协同作用使得中间馏分油的选择性增加。本项目实现了微孔分子筛、介孔分子筛和疏水基团三者的优势互补，达到了一步高选择性地获得中间馏分油的目标。.该研究不仅是构建高效新型催化材料的一条崭新途径，也是对疏水微介孔材料新领域应用的探索发展，可为我国缓解石油供需矛盾、增加能源供应提供科学依据和技术支持，同时还可促进化工、材料和能源等学科的交叉。