(92c) Fischer Tropsch Synthesis On CNT Based Catalysts

Carbon nanotubes (CNT) have been found to have extraordinary physical properties. As a result of these properties, they have been used as supports in several reactions. Recent publication have shown the utility of CNTs as supports for syngas conversion to ethanol. However, the role of CNTs in the overall reactions have not been evaluated. In this paper we present the activity of as-produced and purified CNTs towards Fischer Trospch synthesis. The results from prametric studies on Fischer Tropsch synthesis in the presence of CNT catalysts are presented. The use of as-produced CNT catalysts significantly improved the CO conversion rate per unit mass of catalyst by over 100 fold while the same value obtained when employing purified CNTs was nearly 1500 as high as an Fe-Zn-K/alumina catalyst. While it can be argued that the iron (which is used as a catalyst in the production of CNTs) may act as a catalyst, it should be noted that the amount of Fe on these catalysts (<1%) as compared to Fe (15 %) loaded on the alumina supports, shows that Fe alone cannot be responsible. In addition it was found that a;though SWNTs provided high CO conversion, the primary product was found to be methane. On the other hand MWNTs produced liquid hydrocarbons and oxygenates. This clearly demonstrates that the structure of the CNT is an important factor to the degree of CO conversion and reaction products. The product distribution from the parametric studies will be presented. It was observed that the temperature plays a key role in the liquid product distribution. It was observed that below a certain temperature, the primary products are hydrocarbons with no oxygenates. However, above this temperature, the amount of oxygenates increase reaching 100 % alcohols within a 100 oC rise in temperature. The results from studies conducted on other process parameters such as syngas composition, pressure and syngas flow rate will also be presented. This research was made possible with support, in part, by the Illinois Department of Commerce and Economic Opportunity through the Office of Coal Development and the Illinois Clean Coal Institute.