Zeolite Catalysts for Light Alkane Dehydrogenation
Raul F. Lobo
University of Delaware
The chemical industry is an important contributor of greenhouse gas emissions to the atmosphere and one of the goals of my research program is to develop process alternatives that can deliver the chemical products our modern society needs while minimizing CO2 emissions. In this talk I will recent research on three classes of zeolite catalysts for light alkane dehydrogenation:
- Gallium- and zinc-containing zeolites: We have conducted an investigation of this class of materials spanning several zeolite structures (MFI, CHA and SZR), Si/Al ratios, and metal loadings and characterization techniques. This talk will summarize the salient findings of these investigations, in particular, the speciation of these metals in the zeolite pores, and the relation of these sites with catalytic rates of dehydrogenation.
- Mn-oxide supported on zeolite crystals: We discovered that Mn-containing zeolites prepared by incipient wetness impregnation (IWI) catalyze the ethane dehydrogenation reaction with high selectivity. Preparation by IWI leads to the formation of Mn2O3 nanoparticles on the external surface of the zeolite crystals and these are the location of the active sites for both ethane and propane dehydrogenation. We will compare the effect of zeolite structure and composition on catalytic activity and stability.
- Oxidative Ethane Dehydrogenation over Zeolites: B-chabazites (B-CHA) are excellent catalysts for the ODHE reaction, showing fast catalytic rates, with high selectivity towards ethylene from 500 to 600 °C. The zeolite pores stabilize surface B species leading to a negligible decrease of boron content in the spent B-CHA catalyst. A reaction network and a model for the active sites based on 11B NMR spectroscopy are proposed.