Nanostructured Core-Shell-Catalysts for Controlling the Product Distribution in Fischer-Tropsch Synthesis

通过费托合成（FTS）在钴催化剂上的合成气转化提供了各种不同链长的碳氢化合物，这需要额外的处理步骤。特别是对于使用替代碳源（例如生物质或远程天然气源）的小型分散式FT生产工厂，为了减少过程的复杂性，将FTS与一个反应装置中的加氢处理步骤相结合是有趣的。纳米结构的双功能催化剂具有特殊的应用潜力，因为它们可以在不同的反应器几何形状中使用，并且可以根据其性质以可控的方式生产。这种材料由精细分布在沸石基质中的共纳米颗粒组成。Co催化烃类链的形成，而带有酸性位点的沸石则用于裂解长链（FT产品加工，FTPA）。核-壳排列（钴核、沸石壳）确保沸石处于形成的碳氢化合物的运输路径上，并且FTS的原始产品范围可以转移到短链产品，例如可以用作液体燃料。这些双功能纳米结构催化剂的基本原理已经在材料合成和催化性能方面得到了成功的证明。然而，对获得的产物谱的控制需要对沸石基质中动力学和传输过程的相互作用有详细和定量可靠的了解。在此背景下，本项目旨在调查1的影响。2.筛分效应对大产物分子通过微孔分子筛基质的输送；FTPA中FT产物形成率与转化率之比；微孔沸石基质中的附加介孔。这些目标是通过系统地改变沸石基质的性质并将其与催化结果相关联来实现的。基础是在初步工作中开发的创新合成策略，其中纳米结构的目标材料是通过逐步合成钴核和修饰壳来构建的。这样可以最大程度地控制目标材料的特性，例如沸石基质的孔隙率和酸度。此外，钴芯的催化性能具有高度可比性，因为它们的生产方法保持不变。

The conversion of syngas over cobalt catalysts via the Fischer-Tropsch synthesis (FTS) supplies a wide range of hydrocarbons of different chain lengths, which requires an additional processing step. Especially for small-scale, decentralized FT production plants for the use of alternative carbon sources (e.g. biomass or remote natural gas sources) the combination of the FTS with a hydroprocessing step in one reaction apparatus is interesting in order to reduce the complexity of the process. Nanostructured, bi-functional catalysts have particular potential for this application because they can be used variably in different reactor geometries and can also be produced in a controlled manner with regard to their properties. Such materials consist of co-nanoparticles that are finely distributed in a zeolitic matrix. While Co catalyzes the formation of hydrocarbon chains, zeolites with acidic sites serve to crack long chains (FT product processing, FTPA). The core-shell arrangement (cobalt core, zeolite shell) ensures that the zeolite is on the transport pathway of the hydrocarbons formed and that the original product range of the FTS can be shifted to short-chain products that can be used as liquid fuels, for example.The basic principle of these bi-functional, nanostructured catalysts has already been successfully demonstrated, both in terms of material synthesis and catalytic properties. However, the control of the product spectrum obtained requires detailed and quantitatively reliable knowledge on the interaction of kinetic and transport processes in the zeolitic matrix. Against this background, the project aims to investigate the influence of 1. the sieving effect on the transport of large product molecules through the microporous zeolite matrix, 2. the ratio of FT product formation rate and conversion rate in FTPA, and 3. additional mesopores in the microporous zeolite matrix. These objectives are to be achieved by systematically varying the properties of the zeolite matrix and correlating them with the catalytic results. The basis is the innovative synthesis strategy developed in preliminary work, in which the nanostructured target materials are built up by a stepwise synthesis of the cobalt core and modification of the shell. This allows a maximum degree of controllability of the properties of the target materials, such as the porosity and acidity of the zeolite matrix. In addition, the catalytic properties of the cobalt cores are highly comparable, as their production method remains unchanged.