To further support the idea made above, a line scan of one of
the large particles found in used 3J1 catalyst is shown in Fig. 8a
and b. Recall that large particles in 3J1 were determined to contain
largely Ni and Pd and no Rh, as confirmed in Fig. 8b, which shows
Ni and Pd uniformly distributed throughout the particle. Note that
carbon is observed at the edge of the particle, where the presence
of the alumina support (aluminum and oxygen) is also observed.
It is therefore reasonable to postulate that carbon was deposited
primarily on the surface of the catalyst support.