(8c) Study of the Interaction of Alkali Metals with Cobalt-Based Bimetallic Catalysts Using Density Functional Theory

The conversion of syngas to liquid hydrocarbons via Fischer-Tropsch synthesis (FTS) is  considered as an attractive emerging technology in clean energy for the present century. Despite the experimental and theoretical work, several mechanistic details for FTS remain unclear and unpredictable. To exemplify, the CO dissociation pathways remain largely unresolved [1-4]. Thus, FTS requires detailed atomic studies of the hydrocarbon formation sequence. For chemical reactions, reactant conditions and sources (i.e. Natural gas, coal, biomass) are relevant. However, in FTS, the reaction kinetics can improve with a suitable catalyst. Hence, appropriate catalysts reduce costly investments in the production or purification of syngas. Commonly used catalysts for the FTS process are 3–d transition metals such as Co, Fe, and Ru. Typically, high–surface–area supports (i.e. Silica, alumina, or zeolites) [5] are used for these catalysts. Consequently, the ability to control or engineer the catalyst surface provides leverage for controlling reaction pathways and product distribution. Indeed, catalysis already play a key role in the continuing development of clean energy conversion processes, which is essential to our standard of living [6]. Particularly, bimetallic catalysts show an increased reactivity in FTS for fuel production. Furthermore, alkali metals and transition metals have strong promoting effect in catalysts. However, the exact role and effectiveness of promoters in bimetallic catalysts is not fully elucidated. In order to increase catalyst selectivity and efficiency, it is necessary to investigate the surface structure, energies and electronic structure of catalysts and promoters using atomistic simulations. Therefore, in this research, the binding and interaction of alkali and transition metals ( Li, Na, K, Rb and Mn) with the cobalt-based (113) surface slabs have been computed using density functional theory (DFT).

[1] M. Ojeda, R. Nabar, A.U. Nilekar, A. Ishikawa, M. Mavrikakis, E. Iglesia, Journal of Catalysis, 272 (2010) 287-297.

[2] M. Zhong-Yun, C.F. Huo, X.Y. Liao, Y.W. Li, J. Wang, H. Jiao, Journal of Physical Chemistry C, 111 (2007) 4305-4314.

[3] J. Cheng, X.Q. Gong, P. Hu, C.M. Lok, P. Ellis, S. French, Journal of Catalysis, 254 (2008) 285-295.

[4] O.R. Inderwildi, S.J. Jenkins, D.A. King, Journal of Physical Chemistry C, 112 (2008) 1305-1307.

[5] S.N. Rashkeev, M.V. Glazoff, The Journal of Physical Chemistry C, 117 (2013) 4450-4458.

[6] J.J. Spivey, Catalysis Today, 100 (2005) 171-180.