th  - 1987 - 51st ENC Conference

MF15
PHOSPHORUS POISONING OF THE AUTO EMISSIONS
CATALYTIC CONVERTER STUDIED BY 3xp NMR
K. R. Carduner* and R. O. Carter III
Research Staff, Ford Motor Company, Dearborn, Michigan 48121
ABSTRACT
Magic Angle Spinning 31p NNR spectroscopy is an informative
technique for the identification of solid state phosphates. The
technique is applied to study the extent and chemistry of
phosphorus poisoning of the three-way catalytic converter (TWC)
used to control auto emissions. Although it is well-known that
the source of phosphous is zinc dialklydithiophosphate (ZDPT) oil
additive, the chemistry of catalysts deactivation is only
incompletely understood and, as reveiled by the NMR, apparently
quite complex. NNR of both used and fresh catalysts indicates
that phosphorus is extraneous to the fresh catalyst and associated
with the reduced catalytic activity of the aged converter. At
least three different types of phosphorus compounds are observed
and identified by the parameters of the isotropic chemical shift
and chemical shift anisotropy as derived from the envelope of
spinning sidebands. An overview of isotropic chemical shifts and
chemical shift anisotropies of condensed phosphates is also
presented.
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