Interaction of Surface and Gas Reactions in High Temperature (max ca. 1300°C) High Pressure (max. ca. 5 M Pa) Catalytic Alkane Oxidations
Final Report Abstract
Many chemical reactions at industrial scale are conducted with the aid of solid catalysts. If the reactant molecules are very stable or if the reaction produces large amounts of heat high temperatures will result in the reactor. The catalytic conversion of small saturated hydrocarbons with oxygen belong to this category. Reactions like methane oxidation to syngas, oxidative methane coupling to ethylene or oxidative dehydrogenation of ethane to ethylene occur at temperatures up to or even above 1000°C. In industrial reactors high temperatures are often paired with high pressures. These drastic conditions beg the question whether all reaction steps occur at the surface of the solid catalyst or whether some reaction steps occur also in the gas phase surrounding the catalyst. Metaphorically speaking it would be conceivable to think of the catalyst as a match lighting up and sustaining reactions in the gas phase. To explore this fundamental questions a combined experimental and simulation approach was followed in the project. On the experimental side a high-temperature high-pressure profile reactor was developed allowing for the first time simultaneous measurement of species-, temperature- and spectroscopic profiles through a catalytic reactor with sub-millimeter resolution. Fiber-based Raman Spectroscopy and Laser-Induced Fluoresence Spectroscopy were used as spectroscopic methods. The experimental profiles were compared with numerical reactor simulations using microkinetic models for catalytic and gas phase chemistry. It was found that in typical catalytic fixed bed reactors gas phase reactions are of minor importance. The voids in between catalyst pellets are too small for gas phase reactions to take place. However, if there is ample space around the catalyst for gas phase reactions to unfold such as in an empty platinum tube or around a platinum gauze gas phase reactions contribute significantly to the observed product distribution. It could be shown that the interaction between catalyst and gas phase is not only of thermal nature but also such that the catalyst produces radicals such as OH which desorb into the gas phase triggering radical chain reactions. The project was very successful leading to ten publications and one granted patent. Four PhD students graduated from the project and the PI, Prof. Dr. Raimund Horn, received the Hanns Hofmann Award in Chemical Reaction Engineering for his detailed studies of high temperature catalytic reactions.
Publications
- In-Situ Investigation of Gas Phase Radical Chemistry in the Catalytic Partial Oxidation of Methane on Pt. Catal. Today 142 (2009) 61
Geske M., Pelzer K., Horn R., Jentoft F. C., Schlögl R.
- Microwave-Assisted Self-Propagating Combustion Synthesis for Uniform Deposition of Metal Nanoparticles on Ceramic Monoliths. J. Phys. Chem. C 113 (2009) 17493
Zavyalova U., Geske M., Girgsdies F., Korup O., Horn R.
- Reactor for in-Situ Measurements of Spatially Resolved Kinetic Data in Heterogeneous Catalysis. Rev. Sci. Inst. 81 (2010) 064102
Horn R., Korup O., Geske M., Zavyalova U., Oprea I., Schlögl R.
- Lithium as Modifier for Morphology and Defect Structure of Porous Magnesium Oxide Materials Prepared by Gel Combustion Synthesis. ChemCatChem 3 (2011) 1779
Zavyalova U., Weinberg G., Frandsen W., Girgsdies F., Risse T., Dinse K. P., Schlögl R., Horn R.
- Measurement and Analysis of Spatial Reactor Profiles in High Temperature Catalysis Research. Chem. Eng. Process. 50 (2011) 998
Korup O., Mavlyankariev S., Geske M., Goldsmith C. F., Horn R.
- Carbon Formation in Catalytic Partial Oxidation of Methane on Platinum: Model Studies on a Polycrystalline Pt Foil. Catal. Today 181 (2012) 177-183
Korup O., Schlögl R., Horn R.
(See online at https://doi.org/10.1016/j.cattod.2011.04.051) - Radical Detection in Harsh Environments by Means of Laser- Induced Fluorescence using a Single Bidirectional Optical Fiber. Appl. Phys. B 109 (2012) 19-26
Schwarz H., Schlögl R., Horn R.
(See online at https://doi.org/10.1007/s00340-012-5172-9) - Catalytic Partial Oxidation of Methane on Platinum Investigated by Spatial Reactor Profiles, Spatially Resolved Spectroscopy, and Microkinetic Modeling. J. Catal. 297 (2013) 1-16
Korup O., Goldsmith C. F., Weinberg G., Geske M., Kandemir T., Schlögl R., Horn R.
(See online at https://doi.org/10.1016/j.jcat.2012.08.022) - Resolving Kinetics and Dynamics of a Catalytic Reaction inside a Fixed Bed Reactor by Combining Kinetic and Spectroscopic Profiles. Catal. Sci. Technol. 3 (2013) 169-175
Geske M., Korup O., Horn R.
(See online at https://doi.org/10.1039/c2cy20489d)
