Performance of Au/TiO2 catalyst under ambient conditions

Comparison of the catalytic performance of Au/TiO2 prepared by in situ photodeposition and deposition precipitation methods for CO oxidation at room temperature under visible light irradiation

As compared with Au/TiO2-DP, the Au/TiO2-PD sample showed more electron transfer from TiO2 to Au sites, more activation of O2 induced by oxygen vacancies, and the more obvious photo-promoting effect induced by the LSPR effect.

Evaluation of Au/γ-Al2O3 nanocatalyst for plasma-catalytic decomposition of toluene

The emission of toluene into the atmosphere can seriously affect the environmental quality and endanger human health. A dielectric barrier discharge reactor filled with a small amount of Au nanocatalysts was used to decompose toluene in He and O₂ gases mixtures at room temperature and atmospheric pressure. Normally, the oxidation of toluene using Au nanocatalysts suffers from low reaction activity and facile catalyst deactivation. Herein, the effects of Au loading, calcination time and calcination temperature were systematically investigated. It was found that 0.1 wt%Au/γ-Al₂O₃ calcined at 300 °C for 5 h can keep an average size around 6 nm with good dispersion on γ-Al₂O₃ surface and display the best catalytic performance. Moreover, the influences of energy density, gas flow rate, toluene concentration and O₂ concentration on toluene degradation using 0.1 wt%Au/γ-Al₂O₃ were evaluated. It showed the best catalytic performance of near 100% conversion for toluene degradation under the reaction conditions of the energy density was 20 J/L, the gas flow rate was 300 mL/min, the concentration of toluene was 376 mg/m³ and the oxygen content was 10%. Combining experimental results and theoretical calculations, the values of reaction constant k were 8.6 × 10^-5, 3.53 × 10^-5 and 3.09 × 10^-5 m⁶/(mol*J), when O₂ concentration, power or flow rate changed, respectively. Therefore, O₂ concentration has the greatest effect on toluene decomposition compared to other factors in the presence of Au/γ-Al₂O₃.

Gold Nanoparticles as Efficient Catalysts in Organic Transformations

This review summarizes the utilization of gold nanoparticles as efficient catalysts for a variety of chemical transformations like oxidation, hydrogenation, and coupling reactions as compared to conventional catalytic materials. This review explores the gold nanoparticles-based catalysts for the liquid phase chemo-selective organic transformations which are proving to be evergreen reactions and have importance for industrial applications. Apart from organic transformation reactions, gold nanoparticles have been found to be applicable in removing the atmospheric contaminants and improving the efficiency of the fuel cells by removing the impurities of carbon monoxide.

Causes of Activation and Deactivation of Modified Nanogold Catalysts during Prolonged Storage and Redox Treatments

The catalytic properties of modified Au/TiO₂ catalysts for low-temperature CO oxidation are affected by deactivation and reactivation after long-term storage and by redox treatments. The effect of these phenomena on the catalysts was studied by HRTEM, BET, SEM, FTIR CO, XPS and H₂ TPR methods. The main cause for the deactivation and reactivation of catalytic properties is the variation in the electronic state of the supported gold, mainly, the proportion of singly charged ions Au⁺. The most active samples are those with the highest proportion of singly charged gold ions, while catalysts with a high content of trivalent gold ions are inactive at low-temperatures. Active states of gold, resistant to changes caused by the reaction process and storage conditions, can be stabilized by modification of the titanium oxide support with transition metals oxides. The catalyst modified with lanthanum oxide shows the highest stability and activity.

Enhanced degradation of p-nitrophenol in soil in a pulsed discharge plasma-catalytic system

A pulsed discharge plasma-TiO(2) catalytic (PDPTC) system was developed to investigate the degradation of p-nitrophenol (PNP) in soil. The effects of TiO(2) amount, soil pH and air moisture on PNP degradation were evaluated, and PNP degradation processes were predicted with Gaussian 03W combined with density functional theory (DFT). Experimental results showed that 88.8% of PNP could be smoothly removed in 10 min in the PDPTC system with the specific energy density of 694 J g(soil)(-1), compared with 78.1% in plasma alone system. The optimum TiO(2) amount was 2% in the present study, and higher TiO(2) amount exhibited an inhibitive effect. Alkaline soil was favorable for PNP removal. The increase of air moisture to a certain extent could enhance PNP removal. A DFT calculation presented that there was a high preference for the -ortho and -para positions with respect to the functional -OH group of PNP molecule for OH radicals attack. The main intermediates were hydroquinone, benzoquinone, catechol, phenol, benzo[d][1,2,3]trioxole, acetic acid, formic acid, NO(2)(-), NO(3)(-) and oxalic acid. The generation of hydroxylated intermediates, NO(2)(-) and NO(3)(-) suggested that the experimental results were consistent with those of the theoretical prediction.

Photocatalytic degradation of Acid Red 88 using Au-TiO(2) nanoparticles in aqueous solutions

Metal loaded semiconductors in general possess greater photocatalytic activity than pure semiconductors. Hence, with an attempt to achieve higher photocatalytic activity, Au-TiO(2) photocatalysts were prepared by deposition-precipitation method and used for the photocatalytic degradation of an azo dye (Acid Red 88; AR88). The materials were characterized by different analytical techniques. A possible mechanism for the photocatalytic degradation of AR88 by Au-TiO(2) in the absence and presence of other oxidizing agents (peroxomonosulfate (PMS), peroxodisulfate (PDS) & hydrogen peroxide (H(2)O(2))) has been proposed. The extent of mineralization of the target pollutant was also evaluated using Total Organic Carbon (TOC) analysis.