Synthesis of rhodium-platinum bimetallic catalysts supported on SBA-15 by chemical fluid deposition for the hydrogenation of terephthalic acid in water

• Rh-Pt/SBA-15 bimetallic catalysts were synthesized by CFD method using scCO2 as a solvent.
• The Rh-Pt/SBA-15 was found to be more active in hydrogenation of TPA in water under mild conditions.
• A complete TPA conversion over Rh70Pt30/SBA-15 catalyst was obtained at 80 °C, 5 MPa of H2 in 4 h.
• Rh70Pt30/SBA-15 was also found to be suitable for hydrogenation of BPA, benzoic acid, IPA and DMP.

In this study, rhodium-platinum bimetallic catalysts supported on mesoporous silica SBA-15 (Rh-Pt/SBA-15) were synthesized by a chemical fluid deposition (CFD) method using supercritical CO2 as a solvent. Uniformly dispersed Rh-Pt nanoparticles with an average size (∼6.1 nm) smaller than the pore size of SBA-15 were obtained. The performance of the prepared catalysts in the hydrogenation of terephthalic acid (TPA) in water was investigated in spite of the poor solubility of TPA in water. The Rh-Pt/SBA-15 bimetallic catalyst synthesized at a 70:30 weight ratio of Rh to Pt (Rh70Pt30/SBA-15) exhibited a better catalytic activity than its monometallic counterparts (Rh/SBA-15 and Pt/SBA-15). A TPA conversion as high as 74.3% was achieved using the Rh70Pt30/SBA-15 bimetallic catalyst at 80 °C and 5 MPa of H2 in a 2-h reaction, whereas the conversion of TPA over the Rh/SBA-15 catalyst was found to be 24.2%, and no reaction was observed in the presence of Pt/SBA-15 catalyst. The enhanced activity of the Rh-Pt/SBA-15 catalyst was attributed to the synergistic effect of Rh and Pt in the bimetallic alloy. In the Rh-Pt/SBA-15 bimetallic catalysts, it is believed that Pt helped the adsorption of arenes on the active sites and Rh played a key role in the catalytic hydrogenation of TPA. Moreover, a complete conversion of TPA could be achieved at 80 °C and 5 MPa of H2 by increasing the reaction time to 4 h.

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