Document Type
Thesis - University Access Only
Award Date
1998
Degree Name
Doctor of Philosophy (PhD)
Abstract
A novel method for modeling heterogeneous catalysis was developed to further facilitate the understanding of catalytic reactor mechanisms. The method employs molecular dynamics simulations, statistical mechanical, and Unity Bond Index - Quadratic Exponential Potential (UBI-QEP) calculations to calculate the rate constants for reactions on metal surfaces. The primary difficulty of molecular dynamics simulations on metal surfaces has been the lack of reliable reactive potential energy surfaces. We have overcome this through the development of the Normalized Bond Index - Reactive Potential Function (NBI-RPF), which can accurately describe the reaction of adsorbates on metal surfaces. The first calculations of rate constants for a reaction on a metal surface using molecular dynamics simulations are presented. This method is applied to the determination of the mechanism for selective hydrogenation of acetylene in an ethylene rich flow. It was determined that the selectivity for acetylene hydrogenation is attributable to the higher reactivity of acetylene versus ethylene with respect to hydrogenation by molecular hydrogen. It was shown that hydrogen transfer from the carbonaceous layer to acetylene or ethylene is insignificant in the hydrogenation process. Molecular dynamics simulations and molecular mechanics calculations were used to determine the diffusion rate constants for dimethylnaphthalene isomers is mordenite. 2,6-dimethylnaphthalene and 2,7-dimethylnaphthalene were found to have similar diffusion rate constants. Grand canonical Monte Carlo calculations were performed on the competitive adsorption of 2,6-dimethylnaphthalene and 2,7-dimethylnaphthalene in type X zeolites exchanged individually with barium, calcium, potassium, and rubidium ions, calcium exchanged MCM-22, and hydrogen form mordenite(MOR), X zeolite, Y zeolite, hypBEB, ZSM-12, and MCM-22. These calculations showed that barium exchanged X zeolite was the most selective toward 2,6-dimethylnaphthalene adsorption.
Library of Congress Subject Headings
Heterogeneous catalysis
Molecules -- Models
Format
application/pdf
Number of Pages
228
Publisher
South Dakota State University
Recommended Citation
Gialason, Jason, "Molecular Modeling of Heterogeneous Catalysis" (1998). Electronic Theses and Dissertations. 1313.
https://openprairie.sdstate.edu/etd2/1313