Characterization of AlMCM-41 synthesized with rice husk silica and utilization as supports for platinumiron catalysts

Abstract

-RH-MCM-41 was synthesized by using silica from rice husk and further modified to increase acidity by adding Al with grafting method with Si/Al ratio of 75 and 25. The resulting materials were referred to as RH-AlMCM-41(75) and RH-AlMCM-41(25). The XRD spectra of all RH-AlMCM-41 confirmed a mesoporous structure of MCM-41. Surface areas of all RH-AlMCM-41 were in the range of 700-800 m 2 /g, lower than that of the parent RH-MCM-41, which was 1230 m 2 /g. After Al addition the Si/Al ratios of RHAlMCM-41(75) and RH-AlMCM-41(25) were higher than that of the parent RH-MCM-41. The RH-AlMCM-41 materials were used as supports for bimetallic platinum−iron catalysts, denoted as Pt-Fe/RH-AlMCM-41, with Pt and Fe amounts of 0.5 and 5.0% by weight, respectively. Results from TPR indicated that the presence of Al might assist the interaction between Pt and Fe as the reduction temperature of iron oxides shifted to a lower value. All catalysts were active for phenol hydroxylation using H 2 O 2 as an oxidant, for which the highest conversions were observed on the RH-MCM-41 material with the highest surface area. The acidity of the supports did not present a significant role in improving the catalytic performance.

Characterization and use of in natura and calcined rice husks for biosorption of heavy metals ions from aqueous effluents

“…Several technological alternatives have been associated in the literature with the use of RH and RHA: production of silica and silicon carbide, using the ashes like filler in polymers, in concrete, production of silicates, zeolite synthesis (Chumee et al, 2009) and use as an adsorbent of heavy metals in synthetic wastewater (Srivastava et al, 2006;Naiya et al, 2009;Krishnani et al, 2008;Ye et al, 2010;Bhatnagar and Sillanpaa, 2010;Ahmaruzzaman, 2010).…”

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

“…The XRD patterns of MCM-41 and Al-MCM-41 showed a decrease in intensity with a high amount of Fe added. In our previous work, the catalytic performances of bimetallic Pt-Fe catalysts with 5 wt.% Fe supported on RH-MCM-41 and Al-RH-MCM-41 were compared, and Pt-Fe/RH-MCM-41 gave a higher conversion [16]. Although it was expected that supports with higher acidity would be more active, the addition of Al resulted in a significant decrease in the surface area of MCM-41, which could explain the poorer performance.…”

Biomass, Abundant Resources for Synthesis of Mesoporous Silica Material

“…After calcination to eliminate the organics, metallic impurities such as oxides of alkali metals are removed by leaching with NaOH solution at temperatures between 100 and 200 o C for 1 h. Direct recovery of silica by precipitation from the basic solution is achieved by addition of drops of sulfuric acid to the hot basic solution, followed by thermal treatment at 110 o C [34]. Several products of commercial interest such as silicon carbide (SiC) used as semiconductors, pozzolan in cement manufacturing, and recently, sodium silicate in the preparation of silica-based mesoporous materials have been reported [35][36][37][38][39][40][41][42]. [42] demonstrated that RHA silica generated from biomass power plant can be used as silica framework for synthesis of MCM-41-type material with crystallinity characteristics and porosity similar to those synthesized from commercial silica.…”