Sb对Pd基催化剂用于常压直接合成H 2 O 2 的促进效应

Abstract TiO 2 -supported Pd-Sb bimetallic catalysts were prepared and evaluated for the direct synthesis of H 2 O 2 at ambient pressure. The addition of Sb to Pd significantly enhanced catalytic performance, and a Pd 50 Sb catalyst showed the greatest selectivity of up to 73%. Sb promoted the dispersion of Pd on TiO 2 , as evidenced by transmission electron microscopy and X-ray diffraction. X-ray photoelectron spectroscopy indicated that the oxidation of Pd was suppressed by Sb. In addition, Sb 2 O 3 layers were formed and partially wrapped the surfaces of Pd catalysts, thus suppressing the activation of H 2 and subsequent hydrogenation of H 2 O 2 . In situ diffuse reflection infrared Fourier transform spectroscopy for CO adsorption suggested that Sb homogenously located on the surface of Pd-Sb catalysts and isolated contiguous Pd sites, resulting in the rise of the ratio of Pd monomer sites that are favorable for H 2 O 2 formation. As a result, the Sb modified Pd surfaces significantly enhanced the non-dissociative activation of O 2 and H 2 O 2 selectivity.