Degree Type

Dissertation

Date of Award

1983

Degree Name

Doctor of Philosophy

Department

Chemistry

Abstract

The reduction of nitric oxide with carbon monoxide has been investigated on the Rh(100) single crystal surface. Steady-state kinetic measurements, at 688 K and in the pressure range of 1.0 to 1800 Pa, indicate that this process proceeds via a Langmuir- Hinshelwood type mechanism and is selective towards the production of N(,2) and CO(,2). The carbon monoxide kinetic order varied continuously from +1 to -1 as the partial pressure of CO was increased from 1 to 250 Pa, at a constant NO partial pressure of 57.5 Pa. In a similar manner, the nitric oxide kinetic order varied continuously from +3/2 to -1 as the partial pressure of NO was increased from 1 to 1800 Pa, at a constant CO partial pressure of 44.0 Pa. The catalyst surface was characterized with Auger electron spectroscopy (AES), low energy electron diffraction (LEED), and thermal desorption spectroscopy (TDS). Initial Auger analysis illustrated surface contamination by sulfur, phosphorus, and boron. The sulfur and phosphorus contaminants were removed by ion bombardment with reactive ion beams of hydrogen and oxygen, respectively. The boron contaminant was identified by AES and by the formation of a boron (3 x 1) or (3 x 3) ordered overlayer. This impurity was removed via cycles of argon ion bombardment and high temperature annealing. Nitric oxide adsorbed with a high sticking coefficient and formed a c(2 x 2) ordered overlayer at saturation. The nitric oxide adsorbate dissociated upon slow step- wise heatings as indicated by the production of a surface oxide and the lack of surface nitrogen. Thermal desorption experiments indicated, however, that most of the adsorbed nitric oxide desorbed molecularly in a first order process with a peak at 401 K, during the temperature flash. Carbon monoxide adsorbs molecularly in two distinct surface sites both of which follow first order desorption kinetics, with TDS peaks at 373 and 425 K. A kinetic model was developed which is consistent with both the steady-state kinetic and surface characterization results. The kinetic data were fit to the steady-state rate law derived from this mechanism involving the;reduction of adsorbed nitrous oxide and nitrogen dioxide species by molecularly adsorbed carbon monoxide; *DOE Report IS-T-1081. This work was performed under Contract No. W-7405-Eng-82 with the Department of Energy.

DOI

https://doi.org/10.31274/rtd-180813-11918

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Ronald Eugene Hendershot

Language

en

Proquest ID

AAI8407076

File Format

application/pdf

File Size

125 pages

Share

COinS