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.

Properties of Pd, Pt and Ru-Based Catalysts in Catalytic Oxidation of Methanol.

Catalytic oxidation of methanol was investigated using Pd, Pt and Ru-based catalysts. Experiment was conducted at reaction temperature of 100-220 degrees C with methanol concentration of 3000 ppm and gas hourly space velocity (GHSV) of 16,000 hr(-1). Catalysts were characterized by using Brunauer-Emmett-Teller (BET) method, X-ray diffraction (XRD), field transmission electron microscopy (FE-TEM) and temperature programmed reduction (TPR). Based on complete oxidation temperature of methanol, the activity order was: 0.16 wt% Pd /0.16 wt% Pt/0.16 wt% Ru/gamma-Al2O3 > 0.5 wt% Pt/gamma-Al2O3 > 0.5 wt% Ru/gamma-AlO3 > 0.5 wt% Pd/gamma-Al2O3. Therefore, the activity of ternary metal-based catalyst was superior to single metal-based catalyst.

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.

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.

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.

Aged nano-structured platinum based catalyst: effect of chemical treatment on adsorption and catalytic activity.

To examine the effect of chemical treatment on the adsorption and catalytic activity of nanostructured platinum based catalyst, the aged commercial Pt/AC catalyst was pretreated with sulfuric acid (H2SO4) and a cleaning agent (Hexane). Several reliable methods such as nitrogen adsorption, X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and inductively coupled plasma (ICP) were employed to characterize the aged Pt/AC catalyst and its chemically pretreated Pt/AC catalysts. The catalytic and adsorption activities of nano-structured heterogeneous Pt/AC catalyst were investigated on the basis of toluene oxidation and adsorption isotherm data. In addition, the adsorption isotherms of toluene were used to calculate the adsorption energy distribution functions for the parent catalyst and its pre-treated nano-structured Pt/AC catalysts. It was found that sulfuric acid aqueous treatment can enhance the catalytic performance of aged Pt/AC catalyst toward catalytic oxidation of toluene. It was also shown that a comparative analysis of the energy distribution functions for nano-structured Pt/AC catalysts as well as the pore size distribution provides valuable information about their structural and energetic heterogeneity.

Regeneration of spent three-way catalysts with nano-structured platinum group metals by gas and acid treatments.

The influence of physicochemical treatments on the catalytic activity of the spent nano-structured three way catalysts (TWCs) was examined to evaluate the possibility of using spent TWCs for removing VOCs. Thermal gases and acid aqueous solutions were used to regenerate the spent nano-structured TWCs. The characterization of the spent catalyst and its modified forms was carried out by using XRD, TEM, ICP, and N2 adsorption-desorption isotherms. The catalytic activity tests revealed that the spent nano-structured TWCs have a great potential for removing toxic compounds. The activities of catalysts were also found to be highly dependent on the treatment conditions. The acid aqueous treatments were very useful for improving the catalytic activity because they removed various contaminants such as fuel additives, lubricant oil additives, and metallic compounds. However, the thermal gas treated TWCs were less active than the parent TWCs. Furthermore, the activities of the catalysts treated with acids were closely connected with the remaining Pt/Al ratios.

Influence of physicochemical treatments on spent palladium based catalyst for catalytic oxidation of VOCs.

To recycle the spent catalyst for the removal of VOCs, the benzene, toluene, and xylene (BTX) complete oxidations were studied over pretreated palladium based spent catalyst in a fixed bed flow reactor system at atmospheric pressure. Two different pretreatment methods with gas (air and hydrogen) and acid aqueous solution (HCl, H(2)SO(4), HNO(3), H(3)PO(4) and CH(3)COOH) were used to investigate the catalytic activity of spent catalyst. The properties of the spent and pretreated Pd based catalyst were characterized by XRD, BET, TEM, ICP, and XPS. The results of light-off curves indicate that the catalytic activity of toluene oxidation for pretreated samples is in the order of hydrogen>air>HNO(3)>CH(3)COOH>H(2)SO(4)>H(3)PO(4)>HCl. In addition, the air and the acid aqueous pretreated catalyst activities were significantly decreased compared to that of the spent (or parent) catalyst. Moreover, hydrogen pretreated (or reduced) catalysts having mainly metallic form show the best performance in removing the toluene vapours compared to other pretreated samples. The reduction temperature made a significant difference in the catalytic performance of the spent catalyst pretreated with hydrogen. XPS results clearly supported that the palladium state of the spent catalysts pretreated at 300 degrees C was shifted more toward metallic form than other reduced catalysts. Furthermore, the results of a long-term test and catalytic activity of aromatic hydrocarbons also supported that the hydrogen pretreated spent catalyst was a good candidate for removing toxic compounds.