Improved γ-alumina-supported Pd and Rh catalysts for hydrodechlorination of chlorophenols

• Increasing the calcination temperature improves both the dechlorination and hydrogenation rates of Pd/γ-Al2O3.
• The activity of Rh/γ-Al2O3 is not significantly affected by calcination and reduction temperatures.
• The incorporation of Fe onto the catalysts allows development of magnetic properties.
• The monometallic and bimetallic catalysts showed a high stability with negligible Pd or Rh leaching.

The activity of monometallic (Pd or Rh) and bimetallic (iron-bearing) catalysts has been tested in the HDC of 4-chlorophenol (4-CP) in aqueous phase. The catalysts were prepared by a simple procedure consisting of incipient wetness impregnation followed by calcination and reduction at different temperatures. This allowed controlling the size, dispersion and oxidation state of the metallic nanoparticles. Increasing the temperature of calcination led to a higher dispersion of the active phase (from 21 to 46% by increasing the calcination temperature from 200 to 400 °C) and a higher ratio of zerovalent to electrodefficient palladium (M0/Mn+ values from 1.15 to 2.17) in the case of the Pd-catalysts. Those calcined in air at 400 °C and reduced with H2 at 350 °C yielded the highest values of the pseudo-first-order rate constant of 4-CP dechlorination (16.2 L h−1 gcat−1). The introduction of iron reduced the metal dispersion of both Pd and Rh but the catalysts maintained their dechlorination activity and showed magnetic properties useful for further separation from the liquid phase.

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