TiO2-supported gold catalysts in the catalytic wet air oxidation of succinic acid: influence of the preparation, the storage and the pre-treatment conditions

Abstract

Titania-supported gold catalysts were prepared via the so-called deposition–precipitation method, using either urea or ammonia as the precipitation agent and evaluated in the catalytic wet air oxidation of succinic acid (a model pollutant often found in the degradation pathway of phenolic compounds) at 463 K under 0.75 MPa oxygen partial pressure. The preparation parameter with the strongest impact on the gold particle size, the gold deposition yield, the chlorine removal efficiency and the gold catalyst performances was shown to be the final pH of the preparation, which strongly influenced the gold precursor speciation in solution and the interaction of the gold precursor with the titania support. Gold catalysts were shown to be very active, with about 80% of the succinic acid which is converted being directly mineralized. Furthermore, gold catalysts appeared to be somehow very selective in acetic acid with only traces of acrylic acid being intermediately produced upon succinic acid degradation. The most active catalyst was prepared via deposition–precipitation using ammonia and was shown to be only 3 times less active than the best performing ruthenium catalysts. Unfortunately, the gold catalyst rapidly deactivated upon time on stream, probably due to the intrinsic gold instability under the applied reaction conditions.