英語翻譯
for HPLC was used as reaction medium (J.T.Baker,99.99%)
and H2O2 30% w/w (Merck) was used for decomposition tests,
while analyses used potassium iodide (Sigma-Aldrich),Hydra-
nal-Composite 2 (Fluka),dry methanol for KFT (Fluka),acetic
acid (Sigma-Aldrich),sodium thiosulfate penta-hydrate (99.5%,
Sigma-Aldrich),starch (Sigma-Aldrich),and potassium dichro-
mate (Riedel de Haen).Catalyst has been prepared as already¨
14reported and pre-reduced in situ before use.Preliminary tests
of H2O2 decomposition were carried out to ascertain that the
support alone does not decompose H2O2.We used pure calcined
sulfated ceria at 20 °C,1 bar for 5 h.14
Reactor Setup for the Experiments.A cocurrent,downflow
TBR was developed.In addition to the motivations already
mentioned,the TBR allows short liquid residence time if
required for selectivity.It is a steady-state reactor,so that
chemical analysis has no limitation on the sampled quantity and
does not affect the reactor operation.
The experimental reactor setup is shown schematically in
Figure 1.The reactor is made of AISI 316 stainless steel,30
cm long,1.5 cm I.D.,and internally lined with Teflon (1.15 cm
final I.D.) to prevent H2O2 decomposition due to accessible Fe3+
ions.The reactor can accommodate a catalyst bed up to 20 cm
long.An external chiller (Grant LT D6G) allows for working
temperatures between -20 and 60 °C.Three mass flow
controllers (MFC; Brooks 5850 series) are used to independently
feed the gases:N2,CO2/H2 97.5/2.5%,and O2 (AGA gas).MFC
have been calibrated on actual mass flow; volumetric flow rates
reported in the Figures are calculated with mixture densities