NMR studies of catalysts: phosphorous-31 and vanadium-51 in vanadium-phosphorous-oxygen selective oxidation catalysts and the selective averaging of the second order quadrupolar interaction in aluminosilicates

Thumbnail Image
Date
1986
Authors
Walker, Russell
Major Professor
Advisor
Committee Member
Journal Title
Journal ISSN
Volume Title
Publisher
Altmetrics
Authors
Research Projects
Organizational Units
Organizational Unit
Chemistry

The Department of Chemistry seeks to provide students with a foundation in the fundamentals and application of chemical theories and processes of the lab. Thus prepared they me pursue careers as teachers, industry supervisors, or research chemists in a variety of domains (governmental, academic, etc).

History
The Department of Chemistry was founded in 1880.

Dates of Existence
1880-present

Related Units

Journal Issue
Is Version Of
Versions
Series
Department
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.

Comments
Description
Keywords
Citation
Source
Subject Categories
Copyright
Wed Jan 01 00:00:00 UTC 1986