Seung Won Nahm

Property and performance of red mud-based catalysts for the complete oxidation of volatile organic compounds.

Red mud (RM) was assessed as a catalyst for the complete oxidation of volatile organic compounds (VOCs). The catalytic activity of RM was influenced by an acid treatment and the calcination temperature. Acid-treated RM (HRM) catalysts with a platinum loading (Pt/HRM) were prepared using a conventional impregnation method. Platinum catalysts supported on γ-Al2O3 (Pt/Al) were prepared for comparison. The physicochemical properties of the RM, HRM and Pt/HRM catalysts were characterized by BET analysis, ICP-AES, H2-TPD, XRD, FTIR, SEM, and FE-TEM. The acid treatment increased the BET surface area of the RM significantly, resulting in an increase in catalytic activity. Increasing the calcination temperature from 400°C to 600°C caused a decrease in its catalytic activity. Increasing the platinum loading on HRM(400) from 0.1 wt.% to 1 wt.% led to an increase in the toluene conversion, which was attributed to the better redox properties. The catalytic activities of the Pt/HRM(400) catalysts were superior to those of the Pt/Al catalysts. Benzene, toluene, o-xylene, and hexane were oxidized completely over the 1 wt.% Pt/HRM(400) catalyst at reaction temperatures less than 280°C. The presence of water vapor in the feed had a negative effect on the activity of the 1 wt.% Pt/HRM(400) catalyst.

Characterization of Pt-Based Catalyst by Consecutive Experiments of Toluene Oxidation

Catalytic oxidation of toluene was carried out to investigate the effect of consecutive run on the catalytic property and performance of 1 wt.% Pt/γ-Al2O3 and the reduced 1 wt.% Pt/γ-Al2O3. The properties were characterized by X-ray diffraction (XRD), the Brunauer Emmett Teller (BET) surface area, temperature programmed reduction (TPR), and transmission electron microscopy (TEM) analyses. In consecutive experiments the second catalytic run resulted in a significant increase of the toluene conversion compared to the first catalytic run, but the toluene conversion in the third catalytic run was similar to that of the second catalytic run. In addition, the reducing treatment of the catalyst led to an increase in the catalytic activity. The increasing catalytic activity in consecutive runs was dependent on the platinum particle size and the oxidation state of the platinum. The increase in platinum particle size during reaction and the reduction in the oxidation state of platinum by hydrogen pretreatment were responsible for the increase in the catalytic activity.

Preparations of Platinum Nanoparticles and Their Catalytic Performances.

This work investigates the effect of reducing agents and stabilizing agent on the preparation of platinum nanoparticles. We used H2PtCl6 as a precursor and hydrogen and sodium borohydride as reducing agents to prepare colloidal platinum nanoparticles. Polyvinylpyrrolidones (PVPs) is used as a stabilizing agent. Hydrogen and sodium borohydride are used as reducing agents. The prepared platinum nanoparticles are characterized by transmission electron microscopy (TEM) and X-ray diffractometer (XRD). The concentrations of the precursor and the stabilizing agent influence the size of platinum nanoparticles, while the reducing agents influence the morphologies and structures of platinum nanoparticles. Supported platinum catalysts (CPt-NaBH4, CPt-H2) are prepared from colloidal platinum nanoparticles and γ-Al2O3. For comparison, another supported platinum catalyst (IPt) is prepared by the conventional impregnation method with an aqueous H2PtCL6 solution and γ-AL2O3. The catalytic activities of CPts are superior to that of IPt on the basis of benzene conversion.

Additive effect of nano-size platinum to pretreated iron based catalyst on complete oxidation of toluene.

Catalytic oxidation of toluene (VOC) was carried out to assess the properties and catalytic activities of iron oxide catalyst promoted with nano size platinum. The properties of the prepared catalysts were characterized by the Brunauer Emmett Teller (BET) surface area method and by conducting Temperature programmed reduction (TPR), X-ray diffraction (XRD), and Tansmission electron microscopy (TEM) analyses. The experimental results showed that the addition of platinum to spent iron based catalyst shifted its conversion curve for the total oxidation of toluene to lower temperature. It was also observed that the increase in toluene conversion due to the addition of nano-size platinum was highly dependent on the surface oxygen mobility of the catalyst.