Abstract
This dissertation presents findings on the preparation and characterization of silica nanosprings (NS) supported Fe and Co catalysts for Fischer-Tropsch (FT) reactions. Silica NS with a high surface area of 400 m2/g were chosen as a new 1-dimensional nanostructured support for Fe and Co based FT catalysts and divided into three sections. Section 1 involved the preparation and characterization of Co/NS catalysts as well as to examine the effects of two different reduction temperatures on the FT catalytic performance of this Co/NS catalyst. The prepared Co/NS catalysts were characterized before the FT reaction by various analytical techniques such as surface area, X-ray diffraction, transmission electron microscopy , energy dispersive X-ray spectroscopy, temperature programmed reduction (CO and H2), X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy and thermogravimetric analysis. The activity and selectivity of all catalysts were evaluated in a quartz fixed bed micro-reactor (H2/CO of 2:1, 230-270 oC). The effect of reaction temperature on the catalytic performance of Co/NS catalyst was studied. The results showed that the catalyst reduced at a temperature of 609 oC had higher production rate of C6-C17 hydrocarbons than the catalyst reduced at 409 oC. It also was found that the Co/NS catalyst resulted in more stability compared to with conventional catalysts.
Section 2 examined the effect of three preparation techniques (impregnation, precipitation and 2-step sol-gel) and activation conditions (H2, CO or H2+CO) on catalytic performance of these Fe/NS catalysts. It was found that the Fe/NS catalyst prepared by impregnation technique and activated with CO displayed the highest CO conversion (76.6%) and a wide distribution of light hydrocarbon (C6 to C14). Moreover, the XRD and XPS results of Fe/NS catalysts showed three different Fe crystalline phases with different particle sizes.
Section 3 examined the addition of Ru, Mo, Co and Cu as promoters on the Fe/NS catalysts. It was found that the promotion of the Fe catalyst supported on NS with Ru, Mo, Co and Cu increased the CO conversion, shifted the FTS product distributions and improved the selectivity towards C6-C16 olefins instead of aromatics in unpromoted Fe/NS catalyst.
New types of Co and Fe catalysts were synthetized using silica nanosprings (NS) as a new 1-dimensional nanostructured support, and used in the Fischer-Tropsch synthesis. By using these catalysts, good activity, selectivity to C6-C16 hydrocarbons (liquid fuels) and catalytic stability have been achieved. Furthermore, the incorporation of promoters, such as Ru, Mo, Co and Cu, into these catalysts can have effect leading to both high conversion and selectivity.