Catalytic wet oxidation of phenol solutions at low temperatures of 80−130 °C and space velocities
of 1−100 h-1 using Mn−Ce catalysts was studied with an emphasis on the reactive adsorption
mechanism and total organic carbon (TOC) removal. Eight catalysts (Mn/Ce = 6:4) were activated
under different conditions and promoted with alkali metals (K, Cs) or noble metals (Pt, Ru).
The compositions and physical properties of all catalysts were measured. Preliminary runs were
conducted in a batch reactor, but most experiments were carried out in a continuous-flow trickle-bed reactor. Catalysts containing mixed Mn3O4−CeO2 phases pure and promoted with alkali
metals displayed a higher activity and a higher adsorption of organic deposits on their surface.
Noble metals had little effect on process performance. The adsorption capacity of the catalysts
was found to be considerably higher than that reported for activated carbon. Furthermore,
complete regeneration of a catalyst in three consecutive tests was demonstrated under relatively
low temperature and with no loss of activity. The selectivity toward reactive adsorption was
highest on Mn−Ce−Cs catalysts. Low space velocity yielded essentially complete adsorption of
phenol, resulting in deposits on the catalyst surface. The conversion of phenol to water-soluble
oxygenates was found to increase water toxicity. The catalytic reactive adsorption−regeneration
process should become an attractive treatment method for phenol solutions and other complex
waste streams.
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