Reducibility of Cobalt Supported on SBA-15 and Zirconia for Fischer-Tropsch Synthesis

2011 Spring Symposium

 
Kevin Bakhmutsky1, Noah Wieder1, Thomas Baldassare2, Michael A. Smith2 and Raymond J. Gorte1
1Department of Chemical and Biomolecular Engineering
University of Pennsylvania
2Department of Chemical Engineering
Villanova University


Abstract – High demand for petroleum and the rising costs of the crude oil feedstock have spurred a great deal of interest in the conversion of natural gas into liquid fuels via the gas-to-liquids (GTL) process. As a key step in the process, the Fischer-Tropsch synthesis (FTS) converts syngas (CO and H2) to produce hydrocarbons. Cobalt catalysts are preferentially used in the low temperature Fischer-Tropsch synthesis because of their high activity, paraffin selectivity and relative resistance to oxidation [1,2]. However, studies have shown that dispersed cobalt on catalyst supports tends to deactivate into stable cobalt (II) oxide or irreducible cobalt support mixed compounds [3-5]. This decrease of active cobalt metal sites has primarily been attributed to oxidation by water. Thermodynamic data for bulk cobalt suggests otherwise, as oxidation of cobalt at FTS operating conditions would not be expected. Coulometric titration was used to examine redox characteristics of cobalt supported on mesoporous silica and zirconia. Experimental data of cobalt constrained by pore size in a mesoporous silica support suggests that oxidation energetics of Co nanoparticles are nearly identical to those of bulk particles [6]. However, thermodynamic measurements of cobalt supported on zirconia revealed that low cobalt loading samples do appear to undergo partial oxidation at FTS conditions, unlike bulk cobalt and higher cobalt loading samples. Further experiments have suggested that the apparent distinction in redox properties is likely due to support interactions of cobalt oxide with the zirconia rather than an inherent difference in thermodynamics of bulk and dispersed cobalt.

Speaker’s Biography – Kevin Bakhmutsky completed his undergraduate studies at the Johns Hopkins University, obtaining a B.S. in Chemical Engineering in 2007. Kevin has since worked on his doctoral research at the University of Pennsylvania and is presently in his fourth year of study as a member of Dr. Raymond J. Gorte’s research group. Kevin’s thesis research focuses on catalysis and reaction engineering, with an emphasis on a thermodynamic approach to metal-support interactions.