using the same reaction conditions as in fig5 a and 5b was performed prior to a final co treatment t 50 u00b0 c to affect recarbonylation these data sets show for the catalyst l 3 sio 2 500 terminal and bridging co band intensities recover to their post oxidation levels which indicates that the catalyst is stable as shown in fig6 a and 6c these band intensities were also stable during ethylene hydrogenation catalysis the terminal co band wavenumber was the same before and after the second ethylene hydrogenation catalysis period fig6 a which suggests that the stability of the metal cluster was maintained in contrast the terminal co band intensity for the catalyst l 3 u2032 sio 2 500 was not stable during the second ethylene hydrogenation catalysis fig6 b as the relative intensity increased from 0 3 to 0 4 the terminal co band wavenumber observed after recarbonylation differed from the value observed prior to the second ethylene hydrogenation fig6 b these data are consistent with l 3 u2032 sio 2 500 being an unstable catalyst for ethylene hydrogenation after oxidation treatment chemical modification of activated l 3 sio 2 500 after activation the change affected by the oxidation treatment on l 3 sio 2 500 can be shown by following the decarbonylation during an oxidation treatment and recarbonylation by co treatment processes using in situ time resolved solid state ftir spectroscopy as shown in fig7 for 1988 cm u2212 1 terminal band intensity.