## 2 Results and Discussion
### Catalytic Runs: Fresh Catalysts  
The catalytic tests reported herein were carried out at 25 \({}^{\circ}\)C and 101 kPa in a semi-continuous reactor containing the catalyst suspended in the alcoholic (CH\({}_{3}\)OH) solution of the reagents (H\({}_{2}\), O\({}_{2}\)) and products (H\({}_{2}\)O\({}_{2}\), H\({}_{2}\)O). The reaction mixture was kept under stirring, which was vigorous enough to ensure the kinetic regime. The reagents (4% H\({}_{2}\), 96% O\({}_{2}\)) were continuously fed through separate mass-flow controllers at ambient pressure and temperature. Volatile species (mainly the solvent, if any) were abated with a condenser (\(-\)9 \({}^{\circ}\)C) and returned to the reactor prior to the analysis of the offgas with an on-line micro-gaschromatograph (\(\mu\)GC). This set-up allowed to monitor the consumption of H\({}_{2}\) in real time, which was taken in this work as the measure of the catalytic activity. Representative curves are illustrated in Figure 3.  
There is an initial delay (shaded area in Figure 3) between the start of the reaction (introduction of the catalyst into the reaction mixture) and the first detection of gas consumption, which we interpret as the time to the \(\mu\)GC of the off-gas. The catalysts then generally underw \begin{table}
\begin{tabular}{l c c c} \hline \hline  & **Age (weeks) a** & **Storage Atmosphere** & **Re-Activation** \\ \hline Pd/mS-pSDVB10-2A & 2 & Air (closed & none \\ Pd/\(\mu\)S-pDVB35-2A & & desiccator) & none \\ \hline Pd/mS-pSDVB10-3N & 3 & Nitrogen (dry-box) & none \\ Pd/\(\mu\)S-pDVB35-3N & & & \\ \hline Pd/mS-pSDVB10-4 AR & 4 & Air (laboratory) & H\({}_{2}\), 506 kPa, 60 \({}^{\circ}\)C \\ Pd/\(\mu\)S-pDVB35-4 AR & & & \\ \hline \end{tabular} a time from the end of the preparation and the use of the batch in the catalytic tests.  
\end{table} 
Table 2: History and coding of the catalysts’ leftovers tested after ageing. Figure 3: Kinetic plots of the overall H\({}_{2}\) consumption in the DS with Pd/mS-pSDVB10-3N (51.5 mg, diamonds; 100.3 mg, circles). and eventually reached a steady-state condition in which the apparent rate of H\({}_{2}\) consumption was constant (pseudo-zero order). The slopes of the steepest linear portions of these kinetic plots could be readily obtained and used to compare the catalytic activity. The plots in Figure 3 were obtained with different amounts of the same catalyst (51.5 and 100.3 mg) and the respective apparent rates (0.114 and 0.222 mmol\({}_{\rm H2}\cdot\)h\({}^{-1}\)) are in the same ratio as the amounts: This clearly demonstrates that the reaction is proceeding under kinetic regime, with a specific consumption rate of 23.6 mol\({}_{\rm H2}\cdot\)mol\({}_{\rm Pd}\)\({}^{-1}\cdot\)h\({}^{-1}\). In some cases, the rate of H\({}_{2}\) declined at relatively long time on-stream and a plateau was observed depending on the catalyst stability. The amount of H\({}_{2}\)O\({}_{2}\) produced was measured by indirect iodometric titration of small samples of the liquid phase periodically withdrawn from the reactor. The number of samples and their volume was small enough to have a negligible variation of the liquid-to-catalyst ratio (v/m). As the consequence, the kinetic plots of the production of H\({}_{2}\)O\({}_{2}\) are much less time-resolved than those of the H\({}_{2}\) consumption. This way of collecting the catalytic data allows to readily calculate the selectivity and is much simpler than methods based on the Karl Fischer titration of water, which require a very strict control of the interference of environmental water. Figure 4 represents the consumption of H\({}_{2}\) (top) and the production of H\({}_{2}\)O\({}_{2}\) (bottom) with time over 100 mg of the catalysts, employed shortly after their preparation. The highest apparent reaction rate was achieved with Pd/uS-pDVB35, which is not unexpected in view of its relatively high metal load (3.6%). Pd/uS-pDVB10 and Pd/C were apparently almost as active as each other, with comparable apparent rates and the same metal load (1%, \(w/w\)).