Castner, David G.; Watson, Philip R.; Chan, Ignatius Y.

Journal of Physical Chemistry (1989), 93(8), 3188-94 CODEN: JPCHAX; ISSN: 0022-3654. English.

Co3O4 and Co supported on small (Co/SiO2-62) and large (Co/SiO2-923) pore size SiO2 were characterized by using x-ray absorption spectroscopy, XPS, anal. electron microscopy, and x-ray diffraction. These techniques are complementary and together provided a consistent, detailed description of the geometric structure and oxidation state of the catalysts. Co3O4 was the only Co species detected after calcination of all 3 samples at 450.degree.. For bulk Co3O4 the particles were octahedrally shaped and 1-5 .mu.m in size. On SiO2-62 the Co3O4 particles were 100-300 .ANG. in size and clustered together in 0.1-1-.mu.m aggregates. On SiO2-923 the Co3O4 particles were <60 .ANG. in size. Both of these supported catalysts were prepared by calcination of highly dispersed, uniformly distributed Co(NO3)2 present on the SiO2 supports. The calcination process caused both the aggregation of the Co into larger Co3O4 particles and the migration of the Co to the outer surface of the SiO2 particles.