Surface spectroscopic and kinetic studies of single crystal, supported metal and metal oxide catalysts /
This dissertation deals with two separate, albeit closely
| Main Author: | |
|---|---|
| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1996.
|
| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=743267511&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | This dissertation deals with two separate, albeit closely related topics: the surface characterization of well-defined model catalysts and the corresponding catalytic activities of these surfaces. The model catalysts studied include single crystal metals and metal oxides as well as oxide-supported metal particles. The surfaces were first characterized in vacuum to determine composition and order. Next, the chemisorption properties of probe molecules such as CO and NO were studied with temperature programmed desorption (TPD) and infrared reflection absorption spectroscopy (IRAS). These techniques provide information on the heats of adsorption, adsorption sites and coverages of reactant molecules, all crucial to understanding the role of the catalyst surface during reactions. [RAS studies of CO adsorption on supported NiO(100) thin films showed that both electrostatic and chemical bonding between CO and the nonpolar oxide surface are important. Scanning tunneling microscopy (STM) and IRAS studies of copper on silica showed that the crystallographic structure of small Cu particles can be determined by relating the adsorption sites of CO (and NO) to low index single crystal facets. Establishing this link between supported particles and single crystals was crucial to relating the activities of model systems to high surface area catalysts. The activities of Pd single crystal, model thin film Pd/A'203, and high surface area supported Pd catalysts for the CO + NO reaction were found to be strongly correlated. The higher activity of large Pd particles and PD(III) was linked to the stabilization of NO relative to CO. The lower activity of smaller Pd particles and more open Pd single crystals was linked to a stronger tendency to dissociate NO and subsequently stabilize atomic nitrogen, which serves as a site blocker on these surfaces. Finally, combined IRAS and kinetics studies of the CH4 + NO reaction on Pd(110) showed that the reaction was facilitated only at large excesses of methane. This promotional effect of CH4 is due to competitive adsorption with the much more strongly bound NO. Overall, the goal of this work has been to show the viability of using surface science to model and describe environmentally important reactions that are not well understood. |
|---|---|
| Item Description: | Vita. "Major Subject: Chemistry". |
| Physical Description: | xiii, 187 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |