Coking and regeneration in single catalyst particles: An intra-particular approach by ad-vanced experiments, mechanistic kinetics and adaptive pore network modeling

• Applicants: Professor Dr.-Ing. Christof Hamel; Professor Dr.-Ing. Evangelos Tsotsas
• Subject Area: Chemical and Thermal Process Engineering
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 571375283

Catalyst coking is a major drawback for many reaction systems. This includes catalytic processes that will be of great importance for the energy transition and the circular economy in the future: valorization of biogenic residues, pyrolysis of plastics, catalytic conversion of pyrolysis oil or the Fischer-Tropsch synthesis. The necessity of regular catalyst regeneration has a strong influence on process design and is therefore of particular interest to industrial practitioners. Coking mechanisms are complex since coke is known to subsume a wide variety of compounds and the composition of deposits changes depending on the time on stream and conditions. Kinetics are often described as irreversible, using simplified approaches or empirical activity functions that connect main and coking reactions. No mechanistic kinetic modeling based on catalytic cycles is available, coupling directly main reactions and coke formation on valuable catalysts. This would avoid empirical activity functions and include catalyst regeneration. The complexity of coking also arises from the coupling between the kinetics of coking/regeneration and transport phenomena (mass transport). This coupling depends on the internal structure of the porous catalyst at the beginning, as well as on the evolution of this structure during its use. Structural changes are significant since pore diameters change and pores or pore junctions can be blocked. Thus, the objective of this project is an intricate coupling between the kinetics of main, coking and regeneration reactions and transport phenomena considering explicitly changes of pore structure in a transient and adaptive way. Goals refer to the development of the following: ● Mechanistic kinetic modeling of propane dehydrogenation including catalyst coking and regeneration by distinguishing different coke species at different active sites ● Kinetic description based on coupled catalytic cycles via Christiansen Mathematics ● Advanced analysis of intrinsic kinetic data in a powder profile reactor ● Quantification of intra-particular and boundary-layer profiles of concentration and temperature in a sophisticated single particle profile reactor for different particle diameters ● Advanced adaptive pore network modeling (PNM) at different levels of complexity to capture the interplay of catalytic reaction, catalyst coking/regeneration ● PNM considers the internal structure of the catalyst particle and includes changes in pore diameters or pore junctions and blockage (non-uniform spatial allocation of coke) in 3D ● Determination of transport parameters from PNM and analysis of cross-correlations of coking versus structural changes ● Pore-toparticle scale transferability for a rational design of new, superior catalysts; mathematical modeling of single catalyst particles via continuum models - The overarching developed methodology in this project will be transferable to any similar catalytic reaction, in principle.

• DFG Programme: Research Grants