NSF-DFG MISSION: Elucidating the mechanism of alcohol coupling to form acrolein using operando spatiotemporal spectrokinetics

• Applicant: Professor Dr. Raimund Horn
• Subject Area: Chemical and Thermal Process Engineering ; Technical Chemistry
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 542479366

Acrolein is an important intermediate of the chemical industry with a production volume of several hundred thousand tons per year. Acrolein synthesis is energy intensive and is based on the catalytic oxidation of propylene, which in turn is obtained by steam cracking of crude oil fractions. Goal of this research project is to investigate an alternative synthesis route to acrolein, which is the heterogeneously-catalyzed coupling of methanol and ethanol on iron molybdate catalysts. Both, methanol and ethanol can be obtained from renewable resources, making this synthesis route a potential future green alternative to today’s synthesis from fossil feedstocks. Acrolein yields are still not competitive for industrial application but could be increased based on a solid mechanistic understanding of this reaction. Goal of this research project is to understand the reaction mechanism, active sites, surface adsorbates and the structure-reactivity correlation of the catalyst. The following questions will be answered: 1.) What is the structure of the active sites, where are the active sites on the catalyst surface and how are they distributed along the reactor? 2.) What are the reaction pathways to acrolein and to the undesired side products? Which steps along these pathways are rate determining and which adsorbates are covering the catalyst surface? 3.) What is the kinetics of these steps and is it possible to increase acrolein selectivity and yield by forced periodic modulation of the reactants. To answer these questions, modern spectrokinetic measurement methods will be synergistically coupled with modern modeling methods. Molecular spectroscopy in temperature programmed and modulation excitation mode will be coupled with kinetic and spectroscopic reactor profiling to identify which active sites and surface adsorbates are kinetically relevant and how they are distributed in a plug flow reactor. The experimental kinetic and spectroscopic data lay a fundament for the development of a detailed reaction mechanism and a microkinetic reaction model using modeling tools such as Density Functional Theory, Microkinetic Modeling and Machine Learning Methods. The microkinetic model will then be used to calculate how the reactor has to be operated to achieve optimum acrolein yields. The model predictions will be experimentally verified.

• DFG Programme: Research Grants
• International Connection: USA
• Cooperation Partners: Professor Srinivas Rangarajan, Ph.D.; Professor Israel Ephraim Wachs, Ph.D.