Active palladium catalyst preparation for hydrogenation reactions of nitrobenzene, olefin and aldehyde derivatives

• The controllable preparation of active Pd/FeOx for hydrogenation was presented.
• The washing operation is essential for the controllable catalyst preparation.
• The active catalyst possesses nano-Pd with smaller particle size.
• Over-washing results in nano-Pd particles coagulation.

A series of Pd/FeOx catalysts were prepared using co-precipitation method via controlling the washing operation after co-precipitation of the catalyst precursors. The prepared catalysts were tested by the hydrogenation reactions of nitrobenzene, benzaldehyde and styrene, respectively. The highest activity could be obtained when the catalyst precursors were washed for ten times containing ∼2.2 ppm chlorine concentration in the aqueous phase. XPS characterization suggested that a suitable Pd0/Pdδ+ ratio might be important for the high activity. TEM characterization showed that smaller nano-Pd particles can be generated and TPR characterization suggested the formation of more easily reducible Pd species when the catalyst precursors were washed for 10 times. Less or over-washing of the catalyst precursors result in coagulation of the nano-Pd particles. The washing operation, chlorine concentration, catalyst structure and catalytic performance can be related reasonably. The current results should promote the controllable preparation of active Pd-based catalysts.

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