----------
Will Shafer will be presenting an exit seminar titled Investigation into the Competitive Partitioning of Dissociated H2 and D2 on Activated Fischer-Tropsch Catalysts.
Abstract: Fischer-Tropsch (FT) synthesis is a complex catalytic process by which stoichiometric amounts of H2 and CO are converted into hydrocarbons [1]. Though the process has been known and utilized for close to 90 years, the mechanism occurring on the catalyst is still under scrutiny. While some authors prefer a CH2 insertion mechanism [2] and others claim a CO insertion mechanism [3], more draw the mechanism through an enol, by addition through condensation. Controversy has also arisen in the mechanism where certain academics have argued that if CH2 insertion was the favored mechanism, then no oxygenated material could be produced. From this controversy, Dry et al. [4] argued for a mechanism that involves both CH2 and CO as active surface intermediates. Since the rate-determining step remains a point of contention, a number of H2¬/D2 studies have been performed, unfortunately, with no clear conclusion. Most of these studies have examined replacing H2 with D2 ¬in the syngas over Ru [5, 6], Co [7, 8, 9], and Fe [7, 9] catalysts during F-T. However results for these experiments have varied with some displaying an inverse kinetic effect and others have displayed none. This work examines whether preferential partitioning of either H or D on activated FT metals occur; as this could be the reason why so much confusion has arisen in the kinetic isotopic switching experiments with H2 and D2.
References
1. F. Fischer, H. Tropsch, Brennst. Chem. 1923, 4, 276-285.
2. Z. Xiao-Guang, X. Yin-Sheng, G. Xie-Xian, J. Mol. Catal. 1988, 43, 381 – 394.
3. M. Zhou, K.F. Tan, A. Borgna, M. Saeys J. Phys. Chem. C. 2009, 113, 8357-8365.
4. M.E. Dry, in: G.J. Hutchings, M.S. Scurrell (Eds.) Catal. Today 1990, 6, 183-206.
5. P. Winslow, A.T. Bell, J. Catal. 1985, 91, 142-154.
6. A.T. Bell, C.S. Kellner, J. Catal. 1981, 67, 175-185.
7. M. Ojeda, A. Li, R. Nabar, A.U. Nilekar, M. Mavrikakis, E. Iglesia, J. Phys. Chem. C. 2010, 114, 19761-19770.
8. S. Zheng, Y. Liu, J. Li, B. Shi, Applied Catalysis A: General, 2007, 330, 63–68.
9. B. Shi, B. H. Davis; Applied Catalysis A: General 2004, 277 61–69.
