Degree Type

Dissertation

Date of Award

1986

Degree Name

Doctor of Philosophy

Department

Chemistry

Abstract

The results of EPR and ('31)P and ('51)V NMR experiments on vanadium-phosphorous-oxygen catalysts revealed the presence of V(III) as well as the expected V(IV) and V(V). Preparations known to be highly oxidized, such as (beta)-VOPO(,4) and B phase catalyst with P/V = 0.9, yielded NMR spectra showing only small effects of unpaired electron spin, and the EPR spin count indicated a correspondingly low concentration of V(IV). On the other hand, catalysts known to be highly reduced, such as butane-treated (VO)(,2)P(,2)O(,7) and B phase catalysts with P/V = 1.0, 1.1, gave NMR spectra with strong effects of unpaired electron spin but low EPR spin counts. Since EPR will routinely detect V(IV) but not V(III) (and no unpaired electron spins are associated with V(V)), the strong paramagnetic effects observed in the reduced catalysts must result from V(III). The catalysts examined included the model compounds (beta)-VOPO(,4) and (VO)(,2)P(,2)O(,7) before and after butane and butane treatment, precatalysts (P/V = 0.9, 1.0, 1.1) and B phase catalysts (P/V = 0.9, 1.0, 1.1) before and after butane treatment;The line broadening effects of the second order quadrupolar interaction cause loss of resolution in the NMR spectra of interesting systems, such as ('27)Al in zeolites. A multiple pulse sequence proposed to selectively average the effects of the second order quadrupolar interaction was investigated. The negative results obtained, including an echo of problematic origin, are described.

DOI

https://doi.org/10.31274/rtd-180813-6804

Publisher

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

Copyright Owner

Russell Don Walker

Language

en

Proquest ID

AAI8627158

File Format

application/pdf

File Size

112 pages

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