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

• Applicant: Professor Dr.-Ing. Robert Güttel
• Subject Area: Chemical and Thermal Process Engineering
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 430066230

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.

• DFG Programme: Research Grants