Rice husk ash silica as a support material for iron and ruthenium based heterogeneous catalyst
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Date
2007
Authors
Saraswathy, Balakrishnan
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Abstract
Rice husk ash silica as a support material for iron (RHA-Fe) and
ruthenium (RHA-Ru) based heterogeneous catalysts were prepared through the
sol-gel technique using an aqueous solution of metal salt in 3.0 M HNO3. The
XRD analysis showed that all samples prepared were in amorphous state. The
BET values for the RHA-Fe and RHA-Fe 700 (after calcinations) were found to
be 87.40 and 55.83 m2 g-1 respectively. The prepared RHA-Fe and RHA-Fe700
were found to be active as heterogeneous catalysts and showed high activity in
the reaction between toluene and benzyl chloride. The mono substituted
benzyltoluene was the major product and both catalysts yielded more than 92%
of this isomer. The GC shows that both the ortho and para substituted mono
isomers were present in about equal quantities. The ruthenium derivates,
RHA-Ru 700 showed very unique properties compared to the RHA-Fe samples.
The SEM micrographs of RHA-Ru 700 showed the formation of well-defined flat
elongated nano-sized rods with a smooth outer surface among the amorphous
powder. RHA-Ru had a specific surface area of ca. 65 m2 g-1, while RHA-Ru
700 had only ca. 10 m2 g-1. The decrease in specific surface area was consistent with the formation of the rod shaped crystalline phase. From the pore
distribution graphs, there were two distinct pore size distributions for RHA-Ru.
These were between 40 and 100 Å and between 150 to 400 Å respectively. All
the catalysts prepared were shown to be mesoporous except for RHA-Ru 700
which shows some crystalline state after calcination.
Description
Master
Keywords
Chemical science , Rice husk ash silica