AuPd/3DOM TiO2 Catalysts: Good Activity and Stability for the Oxidation of Trichloroethylene

Xing Zhang,Kunfeng Zhang,Jun Yang,Yuxi Liu,Zhuo Han,Jiguang Deng,Hongxing Dai

doi:10.3390/catal8120666

Abstract

Three-dimensionally ordered macroporous (3DOM) TiO2-supported AuPd alloy (xAuyPd/3DOM TiO2 (x = 0.87–0.91 wt%; y = 0.51–1.86)) catalysts for trichloroethylene (TCE) oxidation were prepared using the polymethyl methacrylate-templating and polyvinyl alcohol-protected reduction methods. The as-prepared materials possessed a good-quality 3DOM structure and a surface area of 49–53 m2/g. The noble metal nanoparticles (NPs) with a size of 3–4 nm were uniformly dispersed on the surface of 3DOM TiO2. The 0.91Au0.51Pd/3DOM TiO2 sample showed the highest catalytic activity with the temperature at a TCE conversion of 90% being 400 °C at a space velocity of 20,000 mL/(g h). Furthermore, the 0.91Au0.51Pd/3DOM TiO2 sample possessed better catalytic stability and moisture-resistant ability than the supported Au or Pd sample. The partial deactivation induced by H2O introduction of 0.91Au0.51Pd/3DOM TiO2 was reversible, while that induced by CO2 addition was irreversible. No significant influence on TCE conversion was observed after introduction of 100 ppm HCl to the reaction system over 0.91Au0.51Pd/3DOM TiO2. The lowest apparent activation energy (51.7 kJ/mol) was obtained over the 0.91Au0.51Pd/3DOM TiO2 sample. The doping of Au to Pd changed the TCE oxidation pathway, thus reducing formation of perchloroethylene. It is concluded that the high adsorbed oxygen species concentration, good low-temperature reducibility, and strong interaction between AuPd NPs and 3DOM TiO2 as well as more amount of strong acid sites were responsible for the good catalytic activity, stability, and water- and HCl-resistant ability of 0.91Au0.51Pd/3DOM TiO2. We believe that 0.91Au0.51Pd/3DOM TiO2 may be a promising catalyst for the oxidative elimination of chlorine-containing volatile organics.

Highlights

Chlorine-containing volatile organic compounds (CVOCs) are widely used in industries as solvents, dry-cleaning agents, degreasing agents, synthetic resins, and pharmaceuticals, which are nowadays produced in considerable amounts
It should be noted that the absence of X-ray diffraction (XRD) signals due to the noble metal phases might be associated with their low loadings
1050 cm−1, amount of the adsorption oxygen species of the supported AuPd catalysts was higher than that of the 3DOM TiO2. These results suggest that TCE could be oxidized easier and a more amount of the adsorbed oxygen species was generated on the surface of 0.91Au0.51 Pd/3DOM TiO2

Summary

Introduction

Chlorine-containing volatile organic compounds (CVOCs) are widely used in industries as solvents, dry-cleaning agents, degreasing agents, synthetic resins, and pharmaceuticals, which are nowadays produced in considerable amounts. These CVOCs are harmful to the environment and human health [1,2]. Because of its high efficiency and low operating temperatures, catalytic oxidation is considered as one of the most promising catalytic technologies [3]. Various catalysts, such as noble metals, transition-metal oxides, and perovskite-type oxides, have been developed for the oxidation of CVOCs [4,5].

Methods

Results

Conclusion