Pt-Al2O3 Cryogel with High Thermal Stability for Catalytic Combustion

Abstract

The cryogel catalyst of platinum on alumina was prepared from aluminum sec-butoxide and H 2 PtCl 6 through the sol-gel technique and subsequent freeze drying. The cryogel catalyst showed higher thermal stability of platinum than the corresponding xerogel or impregnation catalysts, which was ascribed to the more intimately developed platinum-alumina interaction accompanied by the encapsulation of the metal into the alumina cryogel. It was also shown that platinum accessibility was higher on the cryogel than on the xerogel despite the higher thermal stability of the metal on the formed than on the latter. For the VOC combustion, the cryogel exhibited higher activity than the xerogel and impregnation catalysts. Also for the methane combustion the cryogel showed higher activity, although it showed lower activity than the impregnation catalysts above 600°C. By the addition of ceria as an additive to the cryogel catalyst, the CH 4 combustion activity was improved especially in the temperature region above 600°C.

Thermally stable Pt-Al2O3 cryogel with high platinum concentration for catalytic combustion

“…7) It was found that the cryogel exhibited higher platinum stability and catalytic combustion activity than other catalysts. In the present paper alumina cryogel loading 5 mass platinum was prepared, and the stability and catalysis were examined in the similar manner.…”

“…The corresponding xerogel and impregnation catalysts were also prepared for comparison according to the manner as previously reported. 7) Hereafter, the impregnation catalyst using alumina cryogel (287 m 2 g -1 ) is described as Imp(cryo) whereas that using commercial alumina (Taimei Kagaku, TM-300D; 200 m 2 g -1 ) as Imp(com). The nitrogen adsorption at a liquid nitrogen temperature, X-ray powder diffraction analysis, transmission electron micrograph (TEM) image observation, CO chemisorption at room temperature, and the catalytic combustion of VOC containing acetaldehyde (67 ppm), methanol (33 ppm) and methyl formate (33 ppm) in air were carried out as previously reported.…”

“…The nitrogen adsorption at a liquid nitrogen temperature, X-ray powder diffraction analysis, transmission electron micrograph (TEM) image observation, CO chemisorption at room temperature, and the catalytic combustion of VOC containing acetaldehyde (67 ppm), methanol (33 ppm) and methyl formate (33 ppm) in air were carried out as previously reported. 7) 3. Results Figure 1 shows BET surface area, pore volume, and mean pore size of the catalysts after calcination.…”

“…3 and 4), which also agreed well with that of the 0.5 mass Pt catalyst. 7) Assuming that the mean diameter of platinum particles is 1 nm, the theoretical Pt dispersion is calculated to be ca. 73 from the Anderson's equation.…”

“…In our previous studies, the sol-gel processing and subsequent freeze drying, bringing about cryogel, successfully improved the stability of platinum (0.5 mass) on alumina at elevated temperatures. 6), 7) In the present studies, platinum-alumina cryogel with high platinum concentration (5 mass) was prepared, and the thermal stability and catalytic combustion activity were examined in comparison to those of the corresponding xerogel and two impregnation catalysts using alumina cryogel and commercial alumina as the supports.…”