Date of Award

5-2012

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Engineering (ME)

Department

Engineering Physics

Advisor

Robert Meulenberg

Second Committee Member

George Bernhardt

Third Committee Member

C. Thomas Hess

Abstract

The growing need for non-petroleum based fuel sources has led to an increase in research into Fischer-Tropsch synthesis (FTS), which can be used to convert biomass into fuels. Because of costs associated with FTS, design of efficient catalysts is crucial. Cobalt catalysts are effective for producing high molecular weight hydrocarbons, and have an increased lifetime when compared to other catalyst types. Cobalt metal serves as the active catalyst site, and it is therefore desirable to design catalysts with highly dispersed, easily reduced cobalt particles. To this end, Mesoporous silica supported cobalt catalysts were synthesized using the support structure MCM-41. In creating the catalysts, cobalt particles can be impregnated into the pores (Co/MCM-41), incorporated into the pore walls (Co-MCM-41), or both (Co/Co-MCM-41).

Characterization of the catalysts was performed using x-ray absorption spec-troscopy and x-ray diffraction. The catalysts were examined at three different stages in the catalyst history: after calcination, after temperature programmed reduction, and after Fischer-Tropsch synthesis. Evidence suggests that the presence of cobalt in the framework affects the reducibility of the cobalt species. The data also suggests mixed phases of cobalt metal and cobalt monoxide in the reduced and post FTS samples. The calcined samples show only the Co3O4 phase, while the post FT and post TPR show both CoO and Co metal. Unlike the other samples tested, Co/MCM-41 showed the presence of amorphous CoO after reduction. This was also the catalyst with the highest activity in the FTS reaction.

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