• Title/Summary/Keyword: silica support

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Supported Iron Nanoparticles on Activated Carbon, Polyethylene and Silica for Nitrate Reduction

  • Cho, Mi-Sun;Kim, E-Wha;Lee, Kyoung-Hee;Ahn, Sam-Young
    • Journal of Environmental Science International
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    • v.17 no.7
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    • pp.711-717
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    • 2008
  • The use of support materials on the nanoparticle synthesis and applications has advantages in many aspects; resisting the aggregation and gelation of nanoparticles, providing more active sites by dispersing over the supports, and facilitating a filtering process. In order to elucidate the influence of the supports on the nitrate reduction reactivity, the supported iron nanoparticles were prepared by borohydride reduction of an aqueous iron salt in the presence of supports such as activated carbon, silica and polyethylene. The reactivity for nitrate reduction decreased in the order of unsupported Fe(0) > activated carbon(AC) supported Fe(0) > polyethylene(PE) supported Fe(0) ${\ge}$ silica supported Fe(0). Rate constants decrease with increasing initial nitrate concentration implying that the reaction is limited by the surface reaction kinetics.

A Study of the Diastereoselectivity of Diels-Alder Reactions on the Ce-SiO2 as Support

  • Ziarani, Ghodsi Mohammadi;Badiei, Alireza;Miralami, Azam
    • Bulletin of the Korean Chemical Society
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    • v.29 no.1
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    • pp.47-50
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    • 2008
  • The diastereoselectivity of Diels-Alder reactions were studied on the silica surface supported with different concentrations of cerium ion as efficient Lewis acid catalysts under solvent-free conditions. The results showed that the diastereoselectivity of reaction was highly improved in these conditions. The cerium ion was grafted on silica surface by using ion exchange method.

Synthesis of CO2 Adsorbent with Various Aminosilanes and its CO2 Adsorption Behavior (다양한 아미노실란을 이용한 이산화탄소 흡착제 합성 및 흡착 특성)

  • Jeon, Jae Wan;Ko, Young Soo
    • Applied Chemistry for Engineering
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    • v.27 no.1
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    • pp.80-85
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    • 2016
  • The carbon dioxide adsorption behavior of silica with a large specific surface area and pore volume functionalized with aminosilane compounds via in-situ polymerization and functionalization method were investigated. The organosilanes include amino functional group capable of adsorbing carbon dioxide. Elemental analyzer, in situ FT-IR and thermogravimetric analyzer were used to characterize the sorbents and to determine their $CO_2$ adsorption behavior. Comparison of different aminosilane loading in the support revealed that polyaminosilane functionalization of 70% of the pore volume in the support was better in terms of the adsorption capacity and amine efficiency than that of 100% of the pore volume of the support. Furthermore, the sorbents showed a higher adsorption capacity at an adsorption temperature of $75^{\circ}C$ than at $30^{\circ}C$ due to the thermal expansion of synthesized polyaminosilanes inside the pore of silica. The N-[3-(trimethoxysilyl)propyl]ethylenediamine (2NS) sorbent with 70% of the pore volume functionalized showed the highest adsorption capacity of 9.2 wt% at $75^{\circ}C$.

Ring-opening Polymerization of L-Lactide with Silica Supported Titanium Alkoxide Catalysts

  • Kim, Eon-Ah;Shin, Eun-Woo;Yoo, Ik-Keun;Chung, Jin-Suk;Hong, Youn-Jin;Kim, Young-Jo
    • Macromolecular Research
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    • v.17 no.5
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    • pp.346-351
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    • 2009
  • $TiCl(O-i-Pr)_3/SiO_2$ and $Ti(O-i-Pr)_4/SiO_2$ were prepared by immobilizing chlorotitanium (IV) isopropoxide ($TiCl(O-i-Pr)_3$) and titanium (IV) isopropoxide ($Ti(O-i-Pr)_4$), to pretreated silica. The effect of the polymerization reaction conditions on the catalytic activity and characteristics of the resulting PLA were investigated. The catalytic conversion, molecular weight and polydispersity index (PDI) of the PLA produced on the titanium alkoxide supported catalysts increased proportionally with the reaction temperature. When the PLA was synthesized in bulk polymerization, the PLA produced with the supported catalysts had higher molecular weight than those with homogeneous catalysts. The melting temperature of the polymer produced with silica supported alkoxide catalysts was approximately $170-180^{\circ}C$.

Preparation of electro-catalysts supported on the bimodal porous carbon for polymer electrolyte fuel cell (Bimodal 다공성 탄소지지체에 담지된 고분자전해질연료전지용 전극촉매 제조)

  • Hwang, So-hee;Park, Gu-Gon;Yim, Sung-Dae;Park, Seok-Hee;Kim, Han-Sung;Yang, Tae-Hyun;Kim, Chang-Soo
    • 한국신재생에너지학회:학술대회논문집
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    • 2009.06a
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    • pp.652-655
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    • 2009
  • The bimodal porous carbons were synthesized by using imprinting method with templates of SBA-15 particle and silica sphere and applied as supporting materials for the electro-catalyst of polymer electrolyte fuel cell (PEFC). The silica spheres with diameter size of 100 nm and SBA-15 particle having 200 nm -250 nm diameter and 700 nm -900 nm length were synthesized in this work. The bimodal porous carbons (S100) were prepared by using the silica spheres and SBA-15 as templates and mesophase pitch as a carbon source. The PtRu nanoparticle of ca. 1.9 nm were supported on the bimodal porous carbon support and the resulting PtRu/S100 catalysts was tested by the cyclic voltammetry. The use of bimodal porous carbon showed in comparable electro-catalytic activities with commercial catalyst. Though unclear effects of bimodal porosity of supports could be obtained in the scope of this study, morphological advantage in electrical conductivity can be considered on the electro-catalytic activity.

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Surface Immobilizntion on Silica of Endoxylanase Produced from Recombinant Bacillus subtilis

  • Kang, Su-Cheol;Kim, Hye-Jeong;Nam, Soo-Wan;Oh, Deok-Kun
    • Journal of Microbiology and Biotechnology
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    • v.12 no.5
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    • pp.766-772
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    • 2002
  • The plasmid, pJHKJ4, containing the endoxylanase gene, was introduced into Bacillus subtilis DB 104. The recombinant cells produced 587 unit/ml of endoxylanase at 33 h. The endoxylanase was immobilized covalently on the surface of silica fur effective xylan hydrolysis. The activities of the immobilized and free endoxylanases were optimal at pH 6.5 and 10 mM $MnSO_4$. The optimal temperature of the immobilized endoxylanase was $60^{\circ}C$, whereas that of the free endoxylanase was $65^{\circ}C$. Under these optimal conditions, the activity of the immobilized endoxylanase was 1.7 times higher than that of the fee endoxylanase. From microscope photographs, the immobilized endoxylanase was found to be bounded and evenly distributed on the surface of silica, a nonporous solid support. The enzyme kinetics between the immobilized and free endoxylanases was estimated to be uncompetitive, when plotting double-reciprocal plots against xylan concentrations and endoxylanase activities. These results suggest that the higher activity of the immobilized endoxylanase may be due to increased formation of enzyme-substrate complex, because of the easy accessibility of the immobilized enzyme to the polysaccharide-xylan as a high molecular weight substrate.

Surface-functionalized Hexagonal Mesoporous Silica Supported 5-(4-Carboxyphenyl)-10,15,20-triphenyl Porphyrin Manganese(III) Chloride and Their Catalytic Activity

  • Zhang, Wei-Jie;Jiang, Ping-Ping;Zhang, Ping-Bo;Zheng, Jia-Wei;Li, Haiyang
    • Bulletin of the Korean Chemical Society
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    • v.33 no.12
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    • pp.4015-4022
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    • 2012
  • Manganese(III) 5-(4-carboxyphenyl)-10,15,20-triphenyl porphyrin chloride (Mn(TCPP)Cl) was grafted through amide bond on silica zeolite Y (HY), zeolite beta ($H{\beta}$) and hexagonal mesoporous silica (HMS). XRD, ICP-AES, $N_2$ physisorption, SEM, TEM, FTIR and thermal analysis were employed to analyse these novel heterogeneous materials. These silica supported catalysts were shown to be used for epoxidation and good shape selectivity was observed. The effect of support structure on catalytic performance was also discussed. The catalytic activity remained when the catalysts were recycled five times. The energy changes about epoxidation of alkenes by $NaIO_4$ and $H_2O_2$ were also computationally calculated to explain the different catalytic efficiency.

Effects of Platelet-Activating Factor on Tumor Necrosis $Factor-_{\alpha}$ Production by Muramyl Dipeptide- or Silica-Stimulated Alveolar Macrophages

  • Lee, Ji-Hee;Hah, Jong-Sik
    • The Korean Journal of Physiology
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    • v.30 no.1
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    • pp.77-83
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    • 1996
  • Platelet-activating factor(PAF) is a phospholipid mediator of pulmonary inflammation, and immunologic reaction. In this study, the role of PAF on tumor necrosis factor$(TNF_{-{\alpha}})$ production by rat alveolar macrophages(AM) was examined. When PAF $(10^{-12}{\sim}10{-16}\;M)$ alone was added to AM culture, $(TNF_{-{\alpha}})$ production was not significantly increased above the resting level. In contrast, the combined addition of PAF $(10^{-6}\;M)$ and muramyl dipeptide(MDP) $(1.0\;{\mu}g\ml)$ to AM cultures markedly enhanced $(TNF_{-{\alpha}})$ production with 8.2 fold increase compared with AM culture in resting state. This potentiative effect was 313% above the sum of the separate effects of PAF and MDP. To characterize MDP effects on $(TNF_{-{\alpha}})$ production, the dose-response of AM cultured with various concentrations of MDP was tested. High level of MDP $(10\;{\mu}g\ml)$ could not significantly enhance the potentiation effect on $(TNF_{-{\alpha}})$ production compared with AM cultures with low level of MDP $(0.1\;{\mu}g\ml)$, i.e. 112.5% vs 107.8%, respectively when $10^{-10}$ M of PAF was simultaneously added to the cell culture. These data support that the potentiation of TNF. g production in AM culture is mediated by PAF rather than MDf It was also evaluated whether the similar result was obtained in silica, respirable toxic particle-treated AM culture. $(TNF_{-{\alpha}})$ production was also significantly enhanced in the PAF $(10^{-6}\;M)$ and silica $(50\;{\mu}g\ml)$-added cell cultures with 4.7 fold above the value of silica alone-stimulated cells. These results indicate that PAF can potentiate $(TNF_{-{\alpha}})$ production by MDP-or silica- stimulated AM and suggest that PAF may play a potent role in lung inflammation and disease associated with microbe and occupational dust exposures.

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