Date of Award

5-2008

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Chemical Engineering

Advisor

Goodwin, Jr., James G

Abstract

Acid and metal catalysis are considerably important in the chemical industry especially, for the production of transportation fuels. Since a serious concern on the world environment has infringed on the restriction of aromatics contained in gasoline, the demand for clean high-octane branched alkanes for gasoline upgrading has significantly increased. This process involves acid catalyzed n-butane isomerization in which n-butane is converted to isobutane, a primary feedstock for the production of high-octane species. In addition, due to the unpredictable price and the limited resource of petroleum fuel derived crude oil, the attention has shifted to synthetic liquid fuels derived from other abundant energy sources such as coal and biomass. This process requires a metal catalyzed Fischer-Tropsch synthesis (FTS) to upgrade low-value coal and biomass to high value liquid fuels. However, the cost of its production is not as competitive as those obtained from oil refineries. Therefore, a highly active and durable FTS catalyst is needed.
Understanding the behavior and form of active catalytic reaction sites for hydrocarbon reaction (n-butane isomerization) and synthesis (FTS) on their respective solid acid and metal catalysts will allow us to a design of better catalysts. Sulfated zirconia (SZ) and bulk Fe catalysts have been chosen to catalyze n-butane isomerization and FTS, respectively. The present research has gained in-depth details of the constitution of the active sites of SZ at 100oC and the reaction mechanism operating for n-butane isomerization which is able to explain all apparent contradictory results reported in the literature by using olefin as a molecular probe. A highly active and stable bulk Fe FTS catalyst containing Cu and SiO2 has been also developed upon the promotion of various transition metals such as Cr, Mn, Mo, Ta, V and Zr. Cr-, Mn- and Zr-promoted Fe FTS exhibited considerable activity for both CO hydrogenation and water-gas-shift (WGS) reaction at 280oC allowing them to catalyze FTS under low H2/CO ratio syngas derived from biomass or coal. In this present work, steady-state isotopic transient kinetic analysis (SSITKA) has also been utilized to investigate the surface kinetic information about reaction on the catalysts under real reaction conditions in order to obtain how promoters influence the reactivity of catalysts at the site level.

Share

COinS