Chemical Engineering Seminar - The heart of darkness... in heterogeneous catalysis
Event details
| Date | 01.05.2020 |
| Hour | 16:15 › 17:30 |
| Speaker | Prof. Aditya Bhan, Department of Chemical Engineering and Materials Science, University of Minnesota, USA |
| Category | Conferences - Seminars |
Note: This seminar will take place online at the following link:
https://epfl.zoom.us/j/91760958454?pwd=alhFWURSaVQ5bWtEYUhsOXZ4c2E3Zz09
Heterogeneous catalysts enable functionalization and derivatization of molecules for use as energy carriers, polymer precursors, and fine chemicals and mitigate the environmental consequences engendered in their production and consumption. With the underlying tenet that nothing is more fundamental to the understanding of catalysis than the accurate measurement and interpretation of rates of reaction, we illustrate the utility of chemical kinetics in providing insight into two catalytic systems of technological relevance.
The first part of this presentation will discuss our efforts on controlling the rate and reversibility of non-oxidative CH4 dehydroaromatization on Mo/ZSM-5. Well-dispersed carbidic Mo aggregates (MoCx) circumscribed in the pores of a medium-pore zeolite, ZSM-5, catalyze CH4 dehydroaromatization (DHA) with high benzene (>70%) and aromatic (>95%) selectivity at conversions near the ~10% equilibrium limit at ~950 K. Net benzene formation rates are limited by reaction endothermicity and approach zero as methane conversion nears the ~10% equilibrium limit. We (i) leverage the “non-selective” deactivation of MoCx/H-ZSM-5 catalysts to discern the connectivity of the methane to benzene reaction network, (ii) demonstrate Mo is the sole kinetically-relevant active site in MoCx/H-ZSM-5 catalysts, (iii) evoke and develop existing formalisms to extract intrinsic kinetic information in highly-reversible reaction systems, and (iv) circumvent thermodynamic barriers to methane DHA by in-situ H2 removal.
The second part of this presentation will describe the mechanistic origins of over-oxidation and C-C bond scission products in the partial oxidation of propylene to acrolein on mixed metal oxide catalysts. We combine transient kinetic studies, co-feed experiments of aldehydes and carboxylic acids formed as byproducts in propylene oxidation, and isotopic-labeling studies to elucidate the reaction mechanisms, identify the existence and the involvement of relevant surface intermediates, and develop an extensive reaction kinetic model describing the formation of all C2 – C6 products (> 20 C2-C6 products are formed in this chemistry at carbon selectivity as low as 0.001%), to evince the underlying mechanisms for C-C bond cleavage and formation reactions and the rates of these chemical pathways.
Practical information
- General public
- Free