Controlled Surface Segregation Leads To Efficient Coke Resistant Nickel Platinum Bimetallic Catalysts For The Dry Reforming Of Methane

Author : Teneil A. Schumacher
Publisher :
ISBN 13 : 9781085639446
Total Pages : 68 pages
Book Rating : 4.6/5 (394 download)

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Download or read book Ceria Supported Bimetallic Overlayer Catalysts to Aid in the Dry Reforming of Methane written by Teneil A. Schumacher and published by . This book was released on 2019 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: The dry reforming of methane (DRM) utilizes two abundantly available greenhouse gases, methane (CH4) and carbon dioxide (CO2), to produce industrially important syngas, hydrogen (H2) and carbon monoxide (CO), in unity. Syngas can be further treated to produce synthetic petroleum as fuels or chemicals. Most importantly, DRM serves as an important prototype reaction for sustainable chemical recycling and conversion by utilizing the major atmospheric pollutants, CH4 and CO2. It is commonly accepted that in the DRM reaction mechanism, CH4 and CO2 activate on the metal and support, respectively. Thus, the interface between the metal and the metal oxide support is also important as it provides sites to complete the reaction. Supported noble metals, such as palladium, are highly active toward the DRM reaction at high temperatures and are more resistant to carbon formation than other transition metals. However, these elements are costly for practical applications. While nickel proves to be economically favorable, deposited carbon species can accumulate on the metal which leads to loss of active sites. Furthermore, Ni is subject to sintering which also causes rapid deactivation during DRM. Previous research has shown that alloying Ni with Pd will increase catalytic activity and enhance stability against carbon formation. However, the strong Pd binding, which is required to activate CH4, also results in Pd binding too strongly to the CO and H2 products. This results in Pd surface sites being blocked and a decrease in catalytic activity. Therefore, the current global challenge for DRM is to develop thermally stable and active catalysts which can show good resistance to deactivation while minimizing use of expensive metals. Computational and experimental literature has shown that by synthesizing an overlayer of Pd on Ni (Ni@Pd), the coordination of metal atomic orbitals on the surface of a catalyst can increase. By increasing orbital coordination, the d-band center shifts down and the energy band widens. This results in a decrease of binding strength. By synthesizing a Ni@Pd overlayer, the binding strength of the overlayer metal, Pd, can be controllably decreased. By decreasing the binding strength to reactants and products, the catalyst design can then increase catalytic activity and enhance stability against carbon formation. Moreover, ceria supports provide a solution to improve the stability and catalytic performance of metal catalysts. Due to its unique redox properties, ceria may act as the active phase and remove carbon deposits on the metal by the oxidation of surface carbon to CO and prevent metal deactivation. A strong metal-support interaction between the metal and ceria can modify the structure and electronic properties of active metals which could improve the performance of metal-ceria systems. Due to ceria’s unique redox properties and oxygen storage capacities, it can better anchor the base metal as small clusters and inhibit coke formation. Furthermore, the introduction of the metal dopant, Ti, into ceria could promote its redox properties as well as enhance its thermal stability at high temperatures.