(560ep) Metal-Containing ZSM-5 Catalysts for the Dry Reforming of Methane: Exploring Synergistic Effects
Megan Hoffman, Raj Thakur, Justin Smith, Carlos A. Carrero*
Department of Chemical Engineering, Auburn University, Auburn, Alabama 36840
The abundance of natural gas in the U.S. brought by the development of new fracking technologies for its extraction has triggered a notable renaissance of the U.S. chemical manufacturing industry. Natural gas abundance and availability has made the United States one of the lowest-cost chemical producer in the world, and currently it is an appealing feedstock for producing value-added chemicals and fuels. The selective activation of C-H bonds in the most abundant component in natural gas, methane, is one of the greatest challenges in catalysis. Methane can be converted into raw materials or commodity chemicals as follow: i) indirectly via syngas or ii) directly via, for instance, selective oxidation or dehydroaromatization. Along with methane, emphasis has been placed on the utilization of CO2 to produce chemicals and fuels do to their abundance and negative impact to the environment. Both CH4 and CO2 are the main contributors of the greenhouse effect. As a result, Dry Reforming of Methane (DRM) is an attractive route to convert CH4 and CO2 into syngas with an H2/CO ratio of 1:1, which is the optimal ratio to produce liquid hydrocarbons through the Fischer-Tropsch process. However, among other factors, the multiple undesired side reactions such as methane thermal degradation, carbon monoxide disproportionation, and water gas shift has, have limited the potential application of DRM at an industrial scale. These reactions adversely affect the H2/CO ratio and the overall catalystâs performance. The major challenge to address, as a result of the mentioned side-reactions, is the rapid catalyst deactivation due to the formation of coke.
In this study, we aim to improve DRM using a series of Fe/Ni/ZSM-5 catalysts. First, various methodologies have been used to prepare these materials trying to determine the most important variables influencing the final bulk and surface structure of the catalyst. We use various characterization techniques such as N2-physisorption, X-Ray diffraction (XRD), X-Ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM), and Raman spectroscopy. Reactivity tests are performed in a home-made reaction setup equipped with various mass flow controllers, a stainless-steel reactor, a tubular furnace with a temperature controller, and a gas chromatograph (GC) for the analysis of the products. Steady-state kinetics has shown a stable catalytic activity and selectivity towards syngas for Fe/Ni/ZSM-5 compared to the Ni/ZSM-5 catalyst, indicating that Fe is suppressing the formation of coke during the reaction. We aim to determine the variables and the optimal catalyst composition to enhance the catalytic performance of conventional Ni-based catalysts. We will also perform in-situ/opernaro Raman studies to compliment the kinetic data and stablish a more conclusive structure-reactivity/selectivity/stability relationship.