Phase-Selective Catalysis in Emulsions Stabilized by Janus Silica-Nanoparticles
Table 2. Conversion of benzaldehyde, droplet size and interfacial area in the systems prepared with different particle concen-
trations.
Catalyst
Droplet size
mm]
Interfacial
area [m ]
Specific interfacial
area (m g part.)
Conversion of
benzaldehyde
2
2
À1
[
5
5
% Pd/Janus oil side
% Pd/Janus oil side+Janus (ratio1:1)
9.4
6.4
2.2
4.1
73
68
88%
77%
of Janus particles while keeping constant the amount tion of Pd ACHTUNGTRNENUG( NO ) to obtain a metal loading of 5 wt%. In the
3 2
[
1,13,14,19]
of catalyst. It has been previously shown
that second preparation, Pd was selectively deposited on the hy-
drophobic side. The selective deposition was conducted
increasing the particle concentration causes a de-
crease in droplet size and a consequent enhancement
in interfacial area. Therefore, in the first run, we used
0 mg of the catalyst of 5% Pd deposited on the hy-
drophobic side of the Janus particles, and in the
second one we mixed 30 mg of this catalyst with
during the initial synthesis of the Janus particles by adding a
step, i.e., 5 wt% Pd was incorporated onto the APTES-func-
tionalized Janus particles while they were still embedded in
the solidified wax. After vacuum drying, the nanoparticles
were collected as described above. Catalysts were dried
overnight at 1008C, calcined in air for 2 h at 2008C, and
stored for subsequent reaction.
3
30 mg of pristine Janus particles.
The benzaldehyde conversion obtained in each run,
together with the observed droplet size and interfacial
area are shown in Table 2.
We observe that, while the interfacial area per mass Acknowledgements
of nanoparticles slightly decreases in the second run,
the total interfacial area increases by almost a factor Funding was provided by NSF, EPSCoR 0814361, and DoE
of two. By contrast, the resulting benzaldehyde con- (DE-FG36GO88064).
version does not increase, but rather decreases almost
by the same factor as the drop in specific interfacial
area. This loss in activity could be due to the aggrega- References
tion of particles near the interface, which makes the
access of the catalytic particles to the interface less ef-
fective.
[
[
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water/wax emulsion is formed. When cooled down to room
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