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    NSF-DFG MISSION: Elucidating the mechanism of alcohol coupling to form acrolein using operando spatiotemporal spectrokinetics
    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.
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    CRC 1615 - Project A02: Quantitative real-time 3D electrical impedance tomography of multiphase reactors
    Project A02 develops the methodology of quantitative, real-time, 3D Electrical Impedance Tomography (EIT) for process monitoring in the SMART multiphase reactor for catalytic hydrogenolysis of glycerol. In A02, EIT will be combined with synchronized capillary sampling of multiphase flows, converting impedance data into process variables like gas-holdup, bubble size distribution and phase flow rates. An EIT measurement cell will be built featuring a higher number of electrodes (100-400) than existing systems (32) for performing EIT over a frequency range (100 kHz-1 MHz) on water/glycerol/propanediol/hydrogen flows at temperatures up to 250°C and 50 bar H2 pressure. Tailored measurement electronics and reconstruction algorithms will be developed.
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    CRC 1615 - Project C03: SMART multiphase reactor for the catalytic hydrogenolysis of glycerol
    The kinetics and process parameters of the hydrogenolysis of glycerol to 1,2-propanediol are investigated in a slurry reactor at the beginning of the funding period. The SMART reactor is simultaneously calculated, designed and subjected to a HAZOP, considering the data obtained in the slurry. The final design is worked out in detail and manufactured subsequently. After assembly, the EIT, electrowetting and further measuring and control devices are installed in the reactor. The hydrogenolysis is finally realized in the SMART reactor and the various new components are tested.
      68
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    CRC 1615 - Project B02: In situ diagnostics and control of electrowetting of carbon nanotube catalysts for application in multiphase reactors
    Electrowetting of Carbon Nanotube (CNT) Carpets carrying Ru-Cu and Ru-Fe nanoparticles will be developed as method for catalyst reactivity control inside a SMART multiphase reactor for catalytic glycerol hydrogenolysis. A miniaturized reactor module will be developed in project B02, allowing simultaneous fibre-based Raman spectroscopy and hard X-Ray measurements at PETRAIII/DESY including SAXS, XAS, XRF and TXM. Goal is to establish a functional relationship between the shift of Raman bands of the CNT's and the degree of electrowetting as measured by operando X-Ray spectroscopy. Fibre-based Raman spectroscopy can then be used for catalyst reactivity control in the SMART multiphase demonstration reactor for catalytic glycerol hydrogenolysis in project C03.
      59