14,000,000 Leading Edge Experts on the ideXlab platform

Scan Science and Technology

Contact Leading Edge Experts & Companies

Scan Science and Technology

Contact Leading Edge Experts & Companies

The Experts below are selected from a list of 87087 Experts worldwide ranked by ideXlab platform

Raul F Lobo - One of the best experts on this subject based on the ideXlab platform.

  • a general method for aluminum incorporation into high silica Zeolites prepared in fluoride media
    Chemistry of Materials, 2016
    Co-Authors: Takahiko Moteki, Raul F Lobo

    The fluoride method of Zeolite synthesis yields materials with unique characteristics such as high Si/Al ratio, large crystal size, and hydrophobic properties, and it has been advantageous for the synthesis of new pure-silica or high-silica Zeolites. It is often difficult, however, to incorporate aluminum—and thus bring about useful catalytic properties—in materials prepared through the fluorite method. In this report, we show that FAU-type Zeolites are an effective source of aluminum to the growing crystals in the high-silica LTA-type Zeolite synthesis (ITQ-29). A key advantage of using aluminosilicate Zeolite crystals as aluminum source in fluoride media was the high reproducibility and easy control of the Si/Al ratio of the product. The broad applicability of this methodology was demonstrated in the synthesis of several high-silica Zeolites in fluoride media: we report the synthesis of aluminosilicate ITQ-12 (ITW-type Zeolite). Other more conventional aluminosilicate Zeolites (CHA-, *BEA-, and STT-type...

  • investigation into the shape selectivity of Zeolite catalysts for biomass conversion
    Journal of Catalysis, 2011
    Co-Authors: Jungho Jae, Raul F Lobo, Geoffrey A Tompsett, Andrew J Foster, Karl D Hammond, Scott M Auerbach, George W Huber

    Abstract We investigate the influence of Zeolite pore size and shape selectivity on the conversion of glucose to aromatics. Zeolites having a variety of pore size and shape (small pore ZK-5, SAPO-34, medium pore Ferrierite, ZSM-23, MCM-22, SSZ-20, ZSM-11, ZSM-5, IM-5, TNU-9, and large pore SSZ-55, Beta Zeolite, Y Zeolite) were synthesized, characterized, and tested in a pyroprobe reactor coupled with GC–MS for the conversion of glucose to aromatics. The aromatic yield was a function of the pore size of the Zeolite catalyst. Small pore Zeolites did not produce any aromatics with oxygenated products (from pyrolysis of glucose), CO, CO 2 and coke as the major products. Aromatic yields were highest in the medium pore Zeolites with pore sizes in the range of 5.2–5.9 A. High coke yield, low aromatic yields, and low oxygenate yields were observed with large pore Zeolites, suggesting that the large pores facilitate the formation of coke. In addition to pore window size, internal pore space and steric hindrance play a major role for aromatic production. Medium pore Zeolites with moderate internal pore space and steric hindrance (ZSM-5 and ZSM-11) have the highest aromatic yield and the least amount of coke. The kinetic diameters of the products and reactants were estimated to determine whether the reactions occur inside the pores or at external surface sites for the different Zeolite catalysts. This analysis showed that the majority of the aromatic products and the reactants can fit inside the Zeolite pores of most of the medium and large pore Zeolites. However, in some of the smaller pore Zeolites the polycyclic aromatics may form by secondary reactions on the catalyst surface, either directly or via reaction of the smaller aromatics.

  • Zeolite and molecular sieve synthesis
    Chemistry of Materials, 1992
    Co-Authors: Mark E. Davis, Raul F Lobo

    Zeolite and molecular sieve syntheses are reviewed. The synthesis of aluminum-rich Zeolites, high-silica Zeolites, and phosphate-based molecular sieves are evaluated. Unresolved mechanistic issues are outlined and areas for exploration suggested. The ability to plan Zeolite and molecular sieve syntheses is discussed and a strategy for synthesizing a chiral Zeolite is used to demonstrate the current limitations in "designing" new molecular sieves.

Kyong-hwan Chung - One of the best experts on this subject based on the ideXlab platform.

  • highly selective catalytic properties of hzsm 5 Zeolite in the synthesis of acetyl triethyl citrate by the acetylation of triethyl citrate with acetic anhydride
    Catalysts, 2017
    Co-Authors: Kyong-hwan Chung, Sangmin Jeong, Young-kwon Park, Sang-chul Jung

    The catalytic activities of acid catalysts for the acetylation of triethyl citrate with acetic anhydride in the preparation of acetyl triethyl citrate were evaluated. Microporous Zeolites such as HZSM-5 and HY Zeolites catalysts were introduced as heterogeneous acid catalysts. HZSM-5 Zeolite catalysts showed a high conversion of triethyl citrate and excellent selectivity of acetyl triethyl citrate. The catalytic activities of HZSM-5 Zeolites were superior to those of the HY Zeolites. In particular, the selectivity of acetyl triethyl citrate on HZSM-5 Zeolites exceeded 95%. The moderate acid strength of HZSM-5 (Si/Al = 75) Zeolite led to the highest catalytic activities among the HZSM-5 Zeolite catalysts, which have various acid strengths.

  • esterification of oleic acid in soybean oil on Zeolite catalysts with different acidity
    Journal of Industrial and Engineering Chemistry, 2009
    Co-Authors: Kyong-hwan Chung, Byunggeon Park

    Abstract The catalytic activity of Zeolites was studied in the esterification of oleic acid with methanol in soybean oil. The influences of acidity and pore structure of the Zeolites were investigated in relation to conversion of the oleic acid on the Zeolite catalysts. H+ ion exchanged ZSM-5 (HMFI) and mordenite (HMOR) Zeolites conducted with different Si/Al ratio were employed to examine an influence of acidity in the reaction. Conversion of oleic acid was about 80% on HMOR Zeolites and HMFI(25) Zeolite. The conversion of oleic acid was improved as the amount of acid site increased. The amount of acid site of the Zeolites affected significantly the catalytic activity in the esterification of oleic acid.

  • removal of free fatty acid in waste frying oil by esterification with methanol on Zeolite catalysts
    Bioresource Technology, 2008
    Co-Authors: Kyong-hwan Chung, Duckrye Chang, Byunggeon Park

    The removal of free fatty acid (FFA) in waste frying oil by esterification with methanol was conducted using various Zeolite catalysts. The ZSM-5 (MFI), mordenite (MOR), faujasite (FAU), beta (BEA) Zeolites, and silicalite were employed with different Si/Al molar ratio in the reaction. The effects of acidic properties and pore structure of the Zeolite catalysts were discussed relating to the conversion of the FFA. The MFI Zeolite induced an improvement of the removal efficiency of FFA by cracking to the FFA in its pore structure due to its narrow pore mouth. The catalytic activity for FFA removal was lowered with decreasing of acid strength of the Zeolites. The strong acid sites of Zeolites induced the high conversion of FFA comparatively. The acid strength and pore structure of acidic Zeolites affected the catalytic activity in FFA removal.

Tsuneji Sano - One of the best experts on this subject based on the ideXlab platform.

  • synthesis of high silica aei Zeolites with enhanced thermal stability by hydrothermal conversion of fau Zeolites and their activity in the selective catalytic reduction of nox with nh3
    Journal of Materials Chemistry, 2015
    Co-Authors: Takushi Sonoda, Toshihiro Maruo, Yoshitaka Yamasaki, Nao Tsunoji, Yasuyuki Takamitsu, Masahiro Sadakane, Tsuneji Sano

    High-silica AEI Zeolites with Si/Al ratios of 13–20 were synthesized by FAU interZeolite conversion, in which tetraethylphosphonium (TEP) cations as a structure-directing agent (SDA) and NaF or NH4F as a fluoride source were added to the starting gels. During the thermal treatment of the AEI Zeolites, TEP cations in the zeolitic pores decomposed to yield the P-modified AEI Zeolites with various P/Al ratios. The thermal stability of the P-modified AEI Zeolite was higher than that of the non-modified AEI Zeolite synthesized using the N,N-diethyl-2,6-dimethylpiperidinium cation as an SDA. The framework structure of the P-modified AEI Zeolite was maintained after calcination at 1000 °C for 1 h, indicating an enhanced thermal stability by phosphorus modification. The catalytic performance of Cu-loaded AEI Zeolites with different P/Al ratios in the selective catalytic reduction (SCR) of NOx with NH3 was also investigated. The NO conversion was found to increase with decreasing P/Al ratio. No decrease in the NO conversion was observed after hydrothermal treatment at 900 °C for 4 h, indicating the high potential of the P-modified AEI Zeolite for NH3-SCR of NOx.

  • synthesis and thermal stability of beta Zeolite using ammonium fluoride
    Microporous and Mesoporous Materials, 2006
    Co-Authors: Hery Jon, Keiji Itabashi, Yasunori Oumi, Tsuneji Sano

    Abstract Hydrothermal synthesis of beta (BEA) Zeolite with NH4F as a fluoride source was investigated in detail. The highly crystalline BEA Zeolites with a wide range of Si/Al ratios from 10 to infinity could be easily obtained. From an evaluation of the thermal stability of BEA Zeolites synthesized with and without NH4F, it was found that the thermal stability of BEA Zeolite synthesized with NH4F is relatively higher than that of BEA Zeolite synthesized without NH4F, although the thermal stability decreases with an increase in the Al content. The addition of NaOH hardly affected the thermal stability of BEA Zeolite synthesized with NH4F. The enhanced thermal stability was attributed to much less framework defects.

  • influence of crystallinity of hzsm 5 Zeolite on its dealumination rate
    Zeolites, 1997
    Co-Authors: Tsuneji Sano, H Ikeya, T Kasuno, Zhengbao Wang, Yusuke Kawakami, Kazuo Soga

    Abstract To clarify the influence of the crystallinity (structure defect) of Zeolites on dealumination behavior, HZSM-5 Zeolites synthesized using 1-BuOH and TPABr were dealuminated under a hydrothermal atmosphere. It was found that the dealumination rate of the HZSM-5 Zeolite has apparently a third-order dependence upon the number of framework aluminums in the Zeolite structure and that, in the case of the lower water vapor pressure, below 10 kPa the dealumination rate of the HZSM-5 Zeolite synthesized using 1-BuOH is smaller than that of the Zeolite synthesized using TPABr. Taking into account the fact that the peak intensity at ca 3,740 cm −1 assigned to silanol groups is very weak in the spectrum of the HZSM-5 Zeolite from 1-BuOH as compared with that from TPABr, this seems to indicate that the dealumination rate strongly depends upon the crystallinity of Zeolite, namely, the structure defect. It was also found that the dealumination rates of the HZSM-5 Zeolites synthesized using 1-BuOH and TPABr have approximately a second-order and a 1.5-order dependence on water vapor pressure, respectively. Based on the results obtained, a plausible mechanism of the dealumination of HZSM-5 Zeolite by hydrothermal treatment was discussed.

Sang-chul Jung - One of the best experts on this subject based on the ideXlab platform.

Emmanuel I Iwuoha - One of the best experts on this subject based on the ideXlab platform.

  • alkaline hydrothermal conversion of fly ash precipitates into Zeolites 3 the removal of mercury and lead ions from wastewater
    Journal of Environmental Management, 2008
    Co-Authors: Vernon Somerset, Leslie F Petrik, Emmanuel I Iwuoha

    In this paper, the utilisation of Zeolites synthesised from fly ash (FA) and related co-disposal filtrates as low-cost adsorbent material were investigated. When raw FA and co-disposal filtrates were subjected to alkaline hydrothermal Zeolite synthesis, the Zeolites faujasite, sodalite and Zeolite A were formed. The synthesised Zeolites were explored to establish its ability to remove lead and mercury ions from aqueous solution in batch experiments, to which various dosages of the synthesised Zeolites were added. The test results indicated that when increasing synthesised Zeolite dosages of 5-20 g/L were added to the acid mine drainage (AMD) wastewater, the concentrations of lead and mercury in the wastewater were reduced accordingly. The lead concentrations were reduced from 3.23 to 0.38 and 0.17 microg/kg, respectively, at an average pH of 4.5, after the addition of raw FA Zeolite and co-disposal filtrate Zeolite to the AMD wastewater. On the other hand, the mercury concentration was reduced from 0.47 to 0.17 microg/kg at pH=4.5 when increasing amounts of co-disposal filtrate Zeolite were added to the wastewater. The experimental results had shown that the Zeolites synthesised from the co-disposal filtrates were effective in reducing the lead and mercury concentrations in the AMD wastewater by 95% and 30%, respectively.

  • alkaline hydrothermal conversion of fly ash filtrates into Zeolites 2 utilization in wastewater treatment
    Journal of Environmental Science and Health Part A-toxic\ hazardous Substances & Environmental Engineering, 2005
    Co-Authors: Vernon Somerset, Leslie F Petrik, Emmanuel I Iwuoha

    Filtrates were collected using a codisposal reaction wherein fly ash was reacted with acid mine drainage. These codisposal filtrates were then analyzed by X-ray Fluorescence spectrometry for quantitative determination of the SiO2 and Al2O3 content. Alkaline hydrothermal Zeolite synthesis was then applied to the filtrates to convert the fly ash material into Zeolites. The Zeolites formed under the experimental conditions were faujasite, sodalite, and Zeolite A. The use of the fly ash-derived Zeolites and a commercial Zeolite was explored in wastewater decontamination experiments as it was applied to acid mine drainage in different dosages. The concentrations of Ni, Zn, Cd, As, and Pb metal ions in the treated wastewater were investigated. The results of the treatment of the acid mine drainage with the prepared fly ash Zeolites showed that the concentrations of Ni, Zn, Cd, and Hg were decreased as the Zeolite dosages of the fly ash Zeolite (FAZ1) increased.