A Novel Pd Precursor Loaded γ-Al2O3 with Excellent Adsorbent Performance for Ultra-Deep Adsorptive Desulfurization of Benzene

Abstract

Fabricating highly water-soluble and chlorine-free precursors from Pd complexes remains challenging. Here, a novel Pd precursor (ammonium dinitrooxalato palladium(II) ((NH₄)₂[Pd(NO₂)₂(C₂O₄)]·2H₂O)) is synthesized to address this challenge. Additionally, a Pd/Al₂O₃ adsorbent is prepared using γ-Al₂O₃ as a base material to host Pd. The ligand action of the Pd complex forms single Pd atoms and Pd sub-nano clusters on the surface of γ-Al₂O₃. Pd/Al₂O₃-4 as an adsorbent is evaluated using the benzene ultra-deep desulfurization procedure, wherein thiophene is used as a probe molecule. The sulfur adsorption capacity of Pd/Al₂O₃-4 is 1.76 mg g⁻¹ for the ultra-deep adsorptive desulfurization of benzene at a sulfur concentration of 50 ppm. The sulfur adsorption capacity of the new Pd/Al₂O₃-4 adsorbent is 21.8% higher than that of a commercial Pd/Al₂O₃ adsorbent. In addition, the stability and durability of Pd/Al₂O₃-4 are investigated at a sulfur concentration of 1 ppm. The Pd/Al₂O₃-4 adsorbent achieves ≈100% thiophene removal after 434 h, which is 62 h more than the time required by the commercial Pd/Al₂O₃ adsorbent. The novel Pd precursor shows excellent potential for industrial applications, and the Pd/Al₂O₃-4 adsorbent can be produced on a mass scale of 500 kg per batch.