## 2 Results and Discussion
### Catalytic Runs: Aged Catalysts
However, Pd/\(\upmu\)S-pDVB35 had an induction time and the aged samples had not, but from the end of the induction time on its kinetic plot for the formation of H\({}_{2}\)O\({}_{2}\) was practically superimposable to those of Pd/\(\upmu\)S-pDVB35-3N and Pd/\(\upmu\)S-pDVB35-4 AR in the whole run and to that of Pd/\(\upmu\)S-pDVB35-2A in the first 40 min. It is also clear from Figure 8. that for reaction times longer than 1 h Pd/\(\upmu\)S-pDVB35-2A is better than the other aged catalysts and of the fresh catalyst too. All of them undergo of a decrease of selectivity with time (Table 4), but for Pd/\(\upmu\)S-pDVB35-2A this is small enough to produce a larger amount of H\({}_{2}\)O\({}_{2}\). The interpretation of the results of the ageing experiments on Pd/mS-pSDVB10 (Table 5, Figure 9) is less straightforward, because this catalyst is little active and its aged batches as well, especially at the beginning of the reaction. \begin{table}
\begin{tabular}{c c c c c} \hline  & **Catalyst** & **Pd/\(\upmu\)S-pDVB35-2A** & **Pd/\(\upmu\)S-pDVB35-3N** & **Pd/\(\upmu\)S-pDVB35-4 AR** \\ \hline \#1 & H\({}_{2}\) feed rate (\(\upmu\)mol:h\({}^{-1}\)) a & & 2452 & \\ \hline \#2 & n\({}_{\text{Pd}}\) (\(\upmu\)mol) & & 36.0 & 35.3 & 33.1 \\ \hline \#3 & \(\frac{-\partial m_{H_{2}}}{\partial t}\) (\(\upmu\)mol:h\({}^{-1}\)) & 80\({}^{\prime}\) b & 1386 (0.83) & 2124 (1.27) & 2070 (1.24) \\  & 240\({}^{\prime}\) c & 1320 & 2088 & 2034 \\ \hline \#4 & \(\frac{-\Delta n_{H_{2}O_{2}}}{\Delta t}\) (\(\upmu\)mol:h\({}^{-1}\)) d & 80\({}^{\prime}\) & 554 (0.77) & 532 (0.74) & 585 (0.81) \\  & 240\({}^{\prime}\) & 359 & 188 & 193 \\ \hline \#5 & \(R_{s,H_{2}}\) (h\({}^{-1}\)) e & 80\({}^{\prime}\) & 38.5 (0.79) & 60.2 (1.23) & 62.5 (1.28) \\  & 240\({}^{\prime}\) & 36.7 & 59.2 & 61.5 \\ \hline \#6 & \(R_{s,H_{2}O_{2}}\) (h\({}^{-1}\)) f & 80\({}^{\prime}\) & 15.4 (0.73) & 15.1 (0.72) & 17.7 (0.84) \\  & 240\({}^{\prime}\) & 10.0 & 5.3 & 5.8 \\ \hline \#7 & C (\(\%\)) g & 80\({}^{\prime}\) & 56.5 & 86.6 & 84.4 \\  & 240\({}^{\prime}\) & 53.8 & 85.2 & 83.0 \\ \hline \#8 & S (\(\%\)) h & 80\({}^{\prime}\) & 40.0 & 25.0 & 28.3 \\  & 240\({}^{\prime}\) & 27.2 & 9.0 & 9.5 \\ \hline \end{tabular}  
* ca 9.8 mmol of H\({}_{2}\) are fed per single run overall; b initial slopes (from the end of the delay+induction time to 80 min) of the curves in the top of Figure 5; c final slopes (80-240 min) of the curves in the top of Figure 5; d amount of H\({}_{2}\)O\({}_{2}\) formed (\(\Delta nH_{2}O_{2}\)) after the reaction time (\(\Delta t=80\) or 240 min) over \(\Delta t\); e calculated as the ratio of entry 3 over entry 2 in the same column; f calculated as the ratio of entry 4 over entry 2 in the same column; g calculated as the ratio of entry 3 over entry 1 in the same column; h calculated as the ratio of entry 4 over entry 3 in the same column.  
\end{table} 
Table 4: Apparent and specific rates of H\({}_{2}\) consumption and H\({}_{2}\)O\({}_{2}\) formation (values relative to the fresh catalyst in parentheses) and the respective conversions and selectivities over aged Pd/\(\upmu\)S-pDVB35 batches. Therefore, we will compare these catalysts on a quantitative basis only for relatively long reaction time. In particular, the kinetic plots in the upper part of Figure 9 show that after 120 min all the catalysts attained the steady state and converted H\({}_{2}\) at constant rates. The final rates reported in Table 5 were calculated for \(t\geq 120\) min from the slopes of the plots. The data show that ageing under oxidative conditions was detrimental to the activity (the consumption rate of H\({}_{2}\) clearly decreased with time for Pd/\(\mu\)S-pSDVB10-2A), but not to the selectivity. In this case the activity could be restored upon regeneration with a reducing agent and Pd/mS-pSDVB10-4 AR practically replicated the performance of the fresh catalyst also from the point of view of the selectivity. Pd/mS-pSDVB10-3N, which was aged under inert atmosphere, was better than Pd/mS-pSDVB10, Pd/mS-pSDVB10-2A, and Pd/mS-pSDVB10-4 AR.