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

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.

Recent Advances in Supported Bimetallic Pd–Au Catalysts: Development and Applications in Organic Synthesis with Focused Catalytic Action Study

“…In another work, the three-dimensionally ordered macroporous (3DOM) TiO 2 supported Pd−Au (i.e., Pd 1 −Au 1 /3DOM-TiO 2 ) bimetallic catalyst prepared by poly(vinyl alcohol) protection have shown appreciable activity and stability for HDC of TCE. 99 Moreover, the photocatalytic abatement of TCE by Pd−Au BMCs also have been reported by the researchers applying plasmonic material as support for Pd−Au NPs and taking advantage of plasmonic behavior of Au. In 2017, Balint and coworkers reported a Pd−Au/TiO 2 catalyst prepared by an impregnation method for HDC of TCE which energized by solar radiation in mixture of water/methanol solvents.…”

“…Furthermore, a tandem reaction between benzyl alcohol and nitrobenzene catalyzed by Pd–Au/TiO 2 led to formation of imines and secondary amines, and Pd–Au/TiO 2 BMC mounted on polyacrylonitrile and nylon based nanofibrous membranes (PNFM) through electrospinning successfully oxidized 5-HMF to FDCA (Table , entry 13) . In addition to this, the oxidation of cinnamyl alcohol (Table , entry18), benzyl alcohol (Table , entry1–2) , and 1-phenylethanol (Table , entry 19), reduction of 4-nitrophenol (Table , entry 4), acetylene (Table , entry 12–13), , and photocatalytic HDC of TCE , have also been reported with significant enhancements in TON, TOF, and selectivity than the monometallic analogues as well other supports applied for same purpose. After TiO 2 , ceria (CeO 2 ) is the most frequently applied metal support for Pd–Au BMCs preparation because of its affordability, accessibility, acid–base properties, and the ability to bind with a large variety of metals. , Li and co-workers reported CeO 2 supported Pd 1 –Au 1 (wt %) BMC for α-alkylation of ketones with primary alcohols under visible light where unsaturated ketone formation takes place in the absence of visible light irradiation .…”

“…The latter work revealed that the catalyst with ∼7 nm Au particle size cover up to 70% with Pd was more efficient than its ∼3, ∼10 nm variants. In another work, the three-dimensionally ordered macroporous (3DOM) TiO 2 supported Pd–Au (i.e., Pd 1 –Au 1 /3DOM-TiO 2 ) bimetallic catalyst prepared by poly­(vinyl alcohol) protection have shown appreciable activity and stability for HDC of TCE . Moreover, the photocatalytic abatement of TCE by Pd–Au BMCs also have been reported by the researchers applying plasmonic material as support for Pd–Au NPs and taking advantage of plasmonic behavior of Au.…”

Advanced Nano-biotechnology for Chlorinated Volatile Compound Pollutants Control

“…Since the 20 th century, CVOCs has been produced in large quantities worldwide for use as solvents, preservatives, dry cleaning products, degreasing compounds, synthetic resins, and pharmaceuticals (Zhang et al, 2018). The generation of chlorinated hydrocarbons from leaks, spills or improper disposal led to damage large volumes of soil and groundwater in many industrial and urban areas (Dolinová et al, 2017).…”

Editorial Catalysts: Catalysis for the Removal of Gas-Phase Pollutants

“…Three-dimensionally ordered macroporous TiO 2 -supported AuPd alloy catalysts were used for trichloroethylene (TCE) oxidation. Dai et al [10] showed the high catalytic activity of some of these materials, obtaining a T 90 of 400 • C at a space velocity of 20,000 mL/(g h). They described how the supported alloys had better catalytic stability and moisture resistance than Au-or Pd-supported samples.…”