Highly dispersed Cu and ZnO particles were successfully
deposited on alumina in a fluidized-bed reactor using the
compounds bis[bis(trimethylsilyl)amido]zinc and copper
(II)diethylamino-2-propoxide as CVD precursors. Only
with samples prepared under mild conditions using the
two-step method, were small Cu particles and large Cu
surface areas achieved, whereas the deposition of the Cu
precursor at high temperatures in one step led to the
formation of large Cu particles with diameters above 15 nm.
By repeating the two-step Cu CVD, the Cu content was
found to increase linearly, and a specific Cu surface area of
7.7 m2 g1 was obtained after 7 cycles. The Al2O3-supported
samples containing both Cu and ZnO were catalytically
active in methanol synthesis and exhibited high TOFs. The
varied sequence of the CVD of Cu and ZnO on alumina led
to catalysts with similar activities in the case of similar
specific Cu areas. The additional deposition of ZnO on a
commercial ternary catalyst resulted in a strong decrease of
the Cu surface area, but in an increase of the methanol TOF.
All samples prepared by the two-step method were also
active in the SRM.
coating relatively uniformly covered the foam surface,
as presented in Figs. 2b and 3b. The reduction with H2
led to disappearance of visible cracks. Formation of
these microstructures could be explained by complex
mass transport mechanism that occurred at elevated
temperature during the reduction. At the reduction
conditions, Ni particles gained sufficient mobility and
migrated, which resulted in formation of contacts
between particles and their growth. No agglomerates
occurred in any of the reduced samples