Pt-Pd bi-metal nanoparticles captured and stabilized by imine groups in a periodic mesoporous organosilica of SBA-15 for hydrogenation of nitrobenzene

Pt-Pd bi-metal nanoparticles (bi-MNPs) captured and stabilized by imine groups inside a periodic mesoporous organosilica of SBA-15 (PMO-SBA-15) and their catalytic performances in the hydrogenation of nitrobenzene were investigated. The PMO-SBA-15 was synthesized via a one-pot condensation process by hydrolysis of tetraethoxysilane (TEOS) in the presence of P123 (EO20PO70EO20) involving the assembly of triethylenetetramine silsesquioxane organic precursor. Aqueous PtCl62- and Pd2+ ions were reduced by NaBH4 to form Pt and Pd nanopaprticles, which were captured in real-time by imine groups inside the channels of the PMO-SBA-15 to obtain the sample of Pt-Pd/PMO-SBA-15. The obtained samples were characterized by TG-DTG analysis, FT-IR spectra, XRD, N-2 adsorption-desorption measurement and TEM micrograph. The results indicated that both the PMO-SBA-15 and Pt-Pd/PMO-SBA-15 retained the typical characteristics of mesoporous SBA-15 and the dispersed Pt-Pd bi-MNPs well entrapped into the channels of PMO-SBA-15 with the size of ca. 2.5 nm. The MNPs/PMO-SBA-15 was used as a catalyst for hydrogenation of nitrobenzene under 0.1 MPa H-2 at 15-60 degrees C. It was found that the bi-MNPs of Pt and Pd inside the PMO-SBA-15 were more active than the monometallic Pt or Pd nanoparticles due to the synergetic effect and the segregation behavior between Pt and Pd interaction. 100% of nitrobenzene conversion and >99% of selectivity to aniline were obtained over the Pt-Pd/PMO-SBA-15 (Pt:Pd = 1:1) catalyst. Furthermore, the Pt-Pd/PMO-SBA-15 catalyst could be recovered for reuse without significant loss of catalytic activity and selectivity. (C) 2009 Elsevier Inc. All rights reserved.