(535a) Insight into Reaction Pathways in CO Hydrogenation Reactions over K/MoS2 Supported Catalysts Via Alcohol/Olefin Co-Feed Experiments

Insight into Reaction Pathways in CO Hydrogenation Reactions over K/MoS₂ Supported Catalysts via Alcohol/Olefin Co-Feed Experiments

Micaela Taborga Claure¹, Michael R. Morrill¹, Song-Hai Chai², Sheng Dai², Pradeep K. Agrawal¹, and Christopher W. Jones¹1. School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, 30332 USA
2. Chemical Science Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA

The use of supports as a means of enhancing the reactivity of K/MoS₂ catalysts has been widely investigated over a variety of oxide and carbon supports. Previous work showed that Mo-support interactions affect the product distribution. At low Mo, and K loadings, carbon supports are predominantly hydrocarbon selective, whereas hydrotalcite-derived mixed MgAl oxide (MMO) supports yield high C₂₊OH selectivity.[1,2] In this work, we seek to evaluate the effect of support on reaction pathways by evaluating changes in product distribution via alcohol and olefin co-feed experiments. Specifically, the importance of (i) CO insertion and (ii) Guerbet coupling pathways will be investigated. Early studies by Santiesteban et al. demonstrated that higher alcohols and hydrocarbons were formed via classical CO insertion pathways over K/MoS₂ catalysts.[3] However, recent studies showed that coupling reactions may also be important.[4,5]

In this work we report changes in product distribution in carbon and MMO K/MoS₂ supported catalysts via MeOH, EtOH and Ethylene co-feed experiments. Alcohol co-feed experiments were specifically targeted toward elucidating Guerbet coupling reactions as well as providing insight into the importance of CO insertion pathways. The dominant pathway is determined from the product distribution by the prominence of either the expected coupled product or the decrease in production of longer chain products as the carbon chain length increases. Similarly, ethylene co-feed experiments were used to investigate CO insertion pathways, with an increase in the next carbon chain product indicating a dominant CO insertion pathway.  Experiments over K/bulk MoS₂ were used as a control to investigate the role of the supports. Insight into the active sites for higher alcohol and hydrocarbon formation will be provided. 

References

[1] M. Taborga Claure, S.H. Chai, S. Dai, K.A. Unocic, F.M. Alamgir, P.K. Agrawal, C.W. Jones, J. Catal., 324 (2015) 88.
[2] M.R. Morrill, N.T. Thao, H. Shou, R.J. Davis, D.G. Barton, D. Ferrari, P.K. Agrawal, C.W. Jones, ACS Catal., 3 (2013) 1665.
[3] J.G. Santiesteban, C.E. Bogdan, R.G. Herman, K. Klier, in: M.J. Philips, M. Ternan (Eds.), 9th Congress on Catalysis, vol.2, Chem. Ins. Can, Ottawa, 1988, p. 561.
[4] V.P. Santos, B. van der Linden, A. Chojecki, G. Budroni, S. Corthals, H. Shibata, G.R. Meima, F. Kapteijn, M. Makkee, J. Gascon, ACS Catal., 3 (2013) 1634.
[5] J.M. Christensen, P.A. Jensen, N.C. Schiødt, A.D. Jensen, ChemCatChem, 2 (2010) 523.