Search

Abstract: Silica with 98% purity was prepared from rice husk by acid leaching and used as a silica source for the syntheses of zeolite beta (Beta) under hydrothermal conditions with gel Si/Al ratios of 8, 13, 15, 20, 50, 100, 150, and 200. Based on powder X-ray diffraction patterns, samples with gel Si/Al ratios of 8–20 contained only the pure phase of Beta and the highest relative crystallinity was observed in the Beta with gel Si/Al ratio of 13. This sample was further characterized by scanning electron microscopy, particle size analyzer and N2 adsorption analysis. The Beta particles were sphere shaped with the average particle size of 1.5μm and a surface area of 670m2 g−1. The samples with gel Si/Al ratios ranging from 50 to 200 showed mixed phases of Beta and ZSM-12, and the latter phase was more dominant as the Si/Al ratio increased. [Copyright &y& Elsevier]

Hierarchical fluoride-containing zeolite HY (Hie-HY(F)) is an interesting material because it tunes both a high mesoporosity and a moderate acid property, which could benefit the transformation of xylose to xylitol. Herein, we synthesized a new Hie-HY(F) by etching NH 4 Y with ammonium fluoride (NH 4 F) under ultrasonication at 60 °C for 20, 40, and 60 min. After etching with NH 4 F solution, the Hie-HY(F)s contained fluoride in the zeolite frameworks with high mesoporosity and moderate acid properties. The sonication time longer than 20 min caused the structure to collapse rather than the creation of mesoporosity. The Hie-HY(F)s were further used as supports for the Ru catalyst. When loaded with Ru precursor and calcined in air, RuO 2 phase was formed in all catalysts. The RuO 2 supported on Hie-HY(F)s had a lower reduction temperature than that on HY. Ru supported on Hie-HY(F)-20 gave the reactivity of xylose conversion to xylitol, the highest yield of 80.1 %, providing the reusability up to four cycles. [Display omitted] • Synthesis of hierarchical fluoride-containing zeolite Y (Hie-HY(F)s) was disclosed. • Hie-HY(F)s was done by etching in NH 4 F solution under sonication at various times. • Dealumination and fluorination played a crucial role in mesoporosity and acidity. • Hie-HY(F)s was used as a novel support for Ru in xylose conversion to xylitol. • Ru/Hie-HY(F)-20 gave the highest xylitol productivity, 80.1 % yield. [ABSTRACT FROM AUTHOR]

Abstract: Reducibility of 6wt.% cobalt impregnated on zeolite Y in sodium and proton form (6Co/NaY and 6Co/HY, respectively) was studied mainly by X-ray absorption spectroscopy including X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) along with other techniques such as X-ray diffraction. The results indicated that the physicochemical properties of Co strongly depended on the form of support. After calcination in air, Co2+ species were observed on both NaY and HY. After reduction in H2 at 420°C for 5h, the Co species in 6Co/NaY were partially reduced to metallic form and each Co was surrounded by other six Co atoms. On the other hand, Co species in 6Co/HY was not reducible under a similar condition and each Co was surrounded by four oxygen atoms. Because the metallic cobalt is the active form for butane hydrogenolysis, 6Co/NaY was more active than 6Co/HY at 400°C giving average conversion of 32% and 2%, respectively. [Copyright &y& Elsevier]

NaY was synthesized from fumed silica and further modified to form a composite with SBA-15. Textural properties and basicity of the composite NaY-SBA-15 were between those of the parent materials. Paraquat adsorption on NaY was 204.1 mg/g, higher than that on NaY synthesized with rice husk silica from the previous work. SBA-15 was a poor adsorbent for paraquat. Based on the weight of NaY, the adsorption capacity of analytical-grade paraquat on the NaY-SBA-15 composite was 241.5 mg/g-NaY. Moreover, the composite adsorbed blue dye from a commercial grade paraquat. Interaction between the NaY-SBA-15 and paraquat could be from C and N atoms in paraquat with oxygen atom on NaY-SBA-15. [ABSTRACT FROM AUTHOR]