Characterization of platinum–iron catalysts supported on MCM-41 synthesized with rice husk silica and their performance for phenol hydroxylation

Abstract

Mesoporous material RH-MCM-41 was synthesized with rice husk silica by a hydrothermal method. It was used as a support for bimetallic platinum−iron catalysts Pt-Fe/RH-MCM-41 for phenol hydroxylation. The catalysts were prepared by co-impregnation with Pt and Fe at amounts of 0.5 and 5.0 wt.%, respectively. The RH-MCM-41 structure in the catalysts was studied with x-ray diffraction, and their surface areas were determined by nitrogen adsorption. The oxidation number of Fe supported on RH-MCM-41 was +3, as determined by x-ray absorption near edge structure (XANES) analysis. Transmission electron microscopy (TEM) images of all the catalysts displayed well-ordered structures, and metal nanoparticles were observed in some catalysts. All the catalysts were active for phenol hydroxylation using H 2 O 2 as the oxidant at phenol : H 2 O 2 mole ratios of 2 : 1, 2 : 2, 2 : 3 and 2 : 4. The first three ratios produced only catechol and hydroquinone, whereas the 2 : 4 ratio also produced benzoquinone. The 2 : 3 ratio gave the highest phenol conversion of 47% at 70• C. The catalyst prepared by co-impregnation with Pt and Fe was more active than that prepared using a physical mixture of Pt/RH-MCM-41 and Fe/RH-MCM-41.

Mordenite modification and utilization as supports for iron catalyst in phenol hydroxylation

“…The product selectivity in the reaction catalyzed by Fe/MCM-41 could be changed by changing the reaction conditions and support acidity [6,7]. Chumee et al [9] reported that catalysts supported on RH-MCM-41 provided a faster conversion than that supported on rice husk silica [9]. The mesoporous structure of MCM-41 may facilitate the diffusion of the reactants and products.…”

Synthesis and characterization of Fe-MCM-41 from rice husk silica by hydrothermal technique for arsenate adsorption

“…Rice husk silica was extracted with HCl acid. The resulting silica product showed the amorphous silica's purity as greater than 98 wt% (Chumee et al 2009). Sodium silicate prepared from rice husk silica can be used as a source of silica to synthesize mesoporous materials such as MCM-41 (Grisdanurak et al 2003;Chiarakorn et al 2007;Chumee et al 2009).…”

“…The resulting silica product showed the amorphous silica's purity as greater than 98 wt% (Chumee et al 2009). Sodium silicate prepared from rice husk silica can be used as a source of silica to synthesize mesoporous materials such as MCM-41 (Grisdanurak et al 2003;Chiarakorn et al 2007;Chumee et al 2009). The MCM-41, with one-dimensional hexagonal mesopores (2-50 nm) and high surface area ([750 m 2 g -1 ), has attracted considerable interest for various applications, especially for gas adsorption (Grisdanurak et al 2003;Chiarakorn et al 2007).…”

“…Chiarakorn et al (2007)synthesized MCM-41 using rice husk silica under ambient conditions, which involved stirring at room temperature for 48 h. The resulting product showed wall thickness of 11.5 Å . On the other hand, Chumee et al (2009) synthesized MCM-41 by a hydrothermal technique. The product showed a significant increase in wall thickness, to 15.1 Å .…”

Influence of Rice Husk Ash on the Properties of Concrete

“…A number of possible uses for RHA include absorbents for oils and chemicals, soil ameliorants, a source of silicon, insulation powder in steel mills, as repellents in the form of "vinegar-tar" release agent in the ceramics industry, as an insulation material. More specialized applications include the use of this material as a catalyst support (Chumee et al, 2009). The main aim of this study was to determine various physical properties of RHA and important mechanical properties of concrete containing different amount of RHA.…”