456523 CO2 Hydrogenation on Silica- and Titania- Supported Single-Site Heterogeneous CoII Catalyst

Wednesday, November 16, 2016: 10:00 AM
Franciscan C (Hilton San Francisco Union Square)
Juan Jimenez1, Cun Wen1, Jason Hattrick-Simpers2 and Jochen Lauterbach2, (1)Chemical Engineering, University of South Carolina, Columbia, SC, (2)Department of Chemical Engineering, University of South Carolina, Columbia, SC

Global climate change has been widely attributed to the rising amounts of CO2 in the atmosphere[1,2]. Furthermore, there exist little uses for pure carbon dioxide meaning it must be chemically upgraded into a more valuable chemical. However, one of the main difficulties with reducing CO2 via chemical conversion is the thermodynamic stability of the compound[3]. To mitigate this barrier, cobalt catalyst have been studied for the CO2 hydrogenation reaction due to their high activity and stability[4]. Literature has shown that single-site catalysts yield higher turnover frequencies than nanoparticles catalyst for both hydrogenation and oxidation reactions[5,6]. Furthermore, a unique feature of single-site catalyst is the uniformity of the active sites, which allows for a direct correlation between catalytic activity and the structure of the sites. However, to the best of our knowledge, no work has been done on the use of single-site heterogeneous catalyst for CO2 hydrogenation.

In this presentation, single-site CoII catalyst for the CO2 hydrogenation will be discussed. Single-site Co supported on silica are synthesized using methods adapted from literature[5]. Since the active site for this reaction is the highly stable CoII center, titania was also explored as a support due to its strong metal-support interaction with Co in the oxidized state[4], leading to enhanced activity compared to silica supported Co catalyst. The stability of the CoII active site comes from its tetrahedral geometry with neighboring oxygens from the oxide supports. Understanding the interactions with isolated metal ions with a uniform active site can provide insight into the mechanism of CO2 hydrogenation, which is still widely debated. In order to obtain a detailed understanding of the catalytic activity of the single-site CoII we must verify the surface species are in an isolated geometry. To this end the techniques that will be used to characterize the surface are Raman spectroscopy, diffuse reflectance UV-vis, TPR, and STEM-HAADF. These characterization techniques coupled with reaction data can correlate the activity of single-site heterogeneous CoII catalyst for CO2 hydrogenation.

References

[1] T. F. Stocker, A. Schmittner, Nature 1997, 388, 862–865.

[2] M. Meinshausen, N. Meinshausen, W. Hare, S. C. B. Raper, K. Frieler, R. Knutti, D. J. Frame, M. R. Allen, Nature 2009, 458, 1158–62.

[3] H. Arakawa, M. Aresta, J. N. Armor, M. A. Barteau, E. J. Beckman, A. T. Bell, J. E. Bercaw, C. Creutz, E. Dinjus, D. A. Dixon, et al., Chem. Rev. 2001, 101, 953–996.

[4] G. Melaet, W. T. Ralston, C.-S. Li, S. Alayoglu, K. An, N. Musselwhite, B. Kalkan, G. a. Somorjai, J. Am. Chem. Soc. 2014, 136, 2260–2263.

[5] B. Hu, A. “Bean” Getsoian, N. M. Schweitzer, U. Das, H. Kim, J. Niklas, O. Poluektov, L. A. Curtiss, P. C. Stair, J. T. Miller, et al., J. Catal. 2015, 322, 24–37.

[6] S. F. J. Hackett, R. M. Brydson, M. H. Gass, I. Harvey, A. D. Newman, K. Wilson, A. F. Lee, Angew. Chemie 2007, 119, 8747–8750.


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