OXIDATION STUDIES OF PHENOLS WITH COBALT(II) ION-MODIFIED SILICA IN ALIQUID-CHROMATOGRAPHIC REACTOR

The activity of cobalt(II) ion-modified silica, a new catalyst for the oxidation of phenols with dissolved oxygen in organic solvents, has b een studied in liquid chromatographic reactors using several approache s. In this reactor mode, catalyst activity can be maintained over mont hs of repeated use while phenols are oxidized top-benzoquinones at or below 45 degrees C. This approach eliminates problems of catalyst sepa rations. Using the ideal liquid chromatographic reactor model with ine rt standard methods, the reaction is found to be first-order with resp ect to the phenolic reactants. Some pseudo-first-order rate constants have also been measured. The cobalt(II) ions bonded to silica probably function through reaction pathways similar to those of homogeneous co balt complex catalysts for phenol oxidations. However, they are stable for long periods of time under the mild reaction conditions used here and can provide separation with concerted reaction.