Pt supported on Zn modified silicalite-1 zeolite as a catalyst for n-hexane aromatization

Platinum (Pt) supported on Zinc (Zn) modified silicalite-1 (S-1) zeolite (denoted as Pt-Zn/S-1) was prepared by using a wetness-impregnation method and applied in the n-hexane aromatization reaction for the first time. Both Lewis and Bronsted acid sites were detected in Pt-Zn/S-1 catalyst by means of FT-IR adsorption of NH3 experiment, which were identified as mostly weak and medium ones. Besides, Pt and Zn species showed strong interaction, as revealed by the TPR (Temperature-programmed reduction) and XPS (X-ray photoelectron spectroscopy) experiments. Pt-Zn/S-1 catalyst exhibited excellent aromatization function rather than isomerization and cracking side reactions in the conversion of n-hexane. Pulse experimental study showed that 75.6% of n-hexane conversion and 76.8% of benzene selectivity were obtained over Pt-0.1 -Zn-6.0/S-1 catalyst at 550 degrees C and under atmospheric pressure. By spectroscopy tests and pulse experimental results, it was concluded that the n-hexane aromatization over Pt-Zn/S-1 catalyst follows a metal-acid bifunctional mechanism. Furthermore, with the assistance of Zn, the electron-deficient Pt species in Pt-Zn/S-1 showed good sulfur tolerance performance. (C) 2018 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved

Gold catalysts supported on the mesoporous nanoparticles composited of zirconia and silicate for oxidation of formaldehyde

Gold was loaded onto porous nanocomposite of ZrO(2) and silicate by deposition-precipitation. The resulting Au/ZrO(2)-nanocomposites are found to be superior catalysts for removal of formaldehyde from indoor air at moderate temperature by oxidation. They have large specific surface areas and allow the gold to be adequately dispersed as small nanoparticles (NPs). According to the analysis of transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), in the as-prepared catalyst, gold was well dispersed and in an oxidized state of Au(3+); and it was reduced to metallic crystals (Au(0)) during its use as catalyst. The temperature programmed desorption (TPD) results show that gold species in the two states strongly adsorb HCHO molecules at ambient temperature. The adsorbed HCHO molecules convert rapidly into formate species, as observed by the infrared spectra. The temperature programmed surface reaction (TPSR) study reveals that at temperatures below 450 K, the HCHO oxidation involves reaction between adsorbed formate species and adsorbed oxygen molecules. This explains why the gold species in both states are the active sites for HCHO oxidation, and also indicates that HCHO adsorption on the gold species and oxygen adsorption on the support are crucial steps for the oxidation. (C) 2009 Elsevier B.V. All rights reserved