The surface morphology of the fresh 3J1 catalyst showed the
presence of two groups of particles, primarily distinguished based
on their size and composition. One type of particle was observed
to be primarily Rh, and ranged in size from a few nanometers to
around 5 nm. Other particles were larger in size (10–20 nm) and
were essentially made of Ni and/or Pd, without observable Rh. On
reaction, the large particles grew in size. Addition of Rh inhibited
the growth of the large particles, whereas the addition of Pd did not
have any identifiable impact on growth of particle size. It should
also be mentioned that the growth of support alumina phase was
not seen. Recall that the peak width of support alumina did not
undergo significant change during pretreatment and activity tests.
Therefore, deactivation due to support phase collapse can be ruled
out completely.