• Title/Summary/Keyword: Al Hydrolysis

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A Study on the Preparation of Various Phase Alumina in High Purity by Sol-Gel Method (졸-겔법에 의한 여러 상의 고순도 Alumina 제조에 관한 연구)

  • Kyu Min Hwang;Seung Soo Park;Hee Chul Lee
    • Journal of the Korean Chemical Society
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    • v.33 no.2
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    • pp.263-270
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    • 1989
  • Aluminum alkoxide, $Al(OC_3H_7\^i)_3\;and\;Al(OC_4H_9^s)_3$, were synthesized using aluminum sheet and corresponding alcohols to prepare various phase alumina in high purity. Aluminum hydroxides were prepared by hydrolysis of synthesized Al-alkoxides and from reagent $AlCl_3$. The catalytic properties of ${\gamma}$ and ${\eta}-Al_2O_3$ prepared at various temperatures were investigated and the reaction kinetics of ${\alpha}-Al_2O_3$ formation from $Al(OH)_3$ was considered.

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Characteristic of Al(III) Hydrosis Species at Rapid Mixing Condition (급속흔화조건에서 AI(III) 가수분해종의 분포특성)

  • Jung, Chul-Woo;Son, Jung-Gi;Shon, In-Shik;Kang, Lim-Seok
    • Journal of Korean Society of Water and Wastewater
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    • v.18 no.2
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    • pp.128-136
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    • 2004
  • The overall objective of this research was to find out the role of rapid mixing conditions in the species of hydrolyzed Al(III) formed by different Al(III) coagulants. When an Al(III) salt is added to water, monomers, polymers, or solid precipitates may form. Different Al(III) coagulants (alum and PACl) show to have different Al species distribution over a rapid mixing condition. During the rapid mixing period, for alum, formation of dissolved Al(III) (monomer and polymer) increases, but for PACl, precipitates of $Al(OH)_{3(s)}$. increases rapidly. Also, for alum, higher mixing speed favoured Al(III) polymers formation over precipitates of $Al(OH)_{3(s)}$ but for PACl, higher mixing speed formed more precipitates of $Al(OH)_{3(s)}$. At A/D and sweep condition, both $Al(OH)_{3(s)}$ and dissolved Al(III) (monomer and polymer) exist, concurrent reactions by both mechanism appear to cause simultaneous precipitation.

Hydrogenation Characteristics of Aromatics in Residue Oil of Naphtha Cracking on Pt/Pd Impregnated Mesoporous Molecular Sieve (메조포러스 분자체에 담지된 Pt/Pd 촉매상에서 납사분해 잔사유의 방향족 화합물 수소화 특성)

  • Choi, Jong Hwa;Jeong, Soon Yong;Oh, Sung-Geun
    • Korean Chemical Engineering Research
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    • v.43 no.6
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    • pp.675-682
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    • 2005
  • Al containing mesoporous molecular sieve (Al-MMS) was synthesized by hydrolysis of $H_2SiF_6$ and $Al(NO_3)_3{\cdot}9H_2O$. The material obtained was characterized by XRD, $N_2$-physisorption. The specific surface area was $981m^2/g$, and the average pore size was uniformity $39{\AA}$. It was confirmed that the acidity of Al-MMS was milder than that of zeolite Y based on the results of $NH_3$-TPD. Active materials, Pt and Pd, were loaded on Al-MMS in order to examine the feasibility of using Al-MMS as a catalyst support in the hydrogenation of aromatic compounds included in the residue oil of a naphtha cracker. The hydrogenation activity of PtPd/Al-MMS has been studied by following the kinetics of the hydrogenation of naphthalene, and by comparing the kinetic parameters obtained with Pt and Pd catalysts supported on the other mesoporous material support and commercial conventional support materials. PtPd/Al-MMS catalyst shows the highest activity of hydrogenation and sulfur resistance. The high activity of PtPd/Al-MMS was confirmed again in the hydrogenation of PGO (pyrolized gas oil), which is residue oil obtained from a naphtha cracker. Therefore, PtPd/Al-MMS can be applied to the hydrogenation of aromatic compounds included in the residue oil of a commercial naphtha cracker commericially.

Fabrication and Sintering Characteristic of MgO-Al2O3-SiO2 System Ceramic Raw Materials(Mullite, Spinel and Cordierite) II. Powder and Mechanical Properties of Mg-Al Spinel Ceramics Prepared by Alkoxide (MgO-Al2O3-SiO2계 요업원료(Mullite, Spinel, Cordierite)의 제조 및 소결특성 II. Alkoxide로 제조한 Mg-Al Spinel분말 및 소결체의 특성)

  • 김창은;이홍림;안용진;김배연
    • Journal of the Korean Ceramic Society
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    • v.26 no.5
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    • pp.593-600
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    • 1989
  • Fine spinel powder was prepared from the Mg-Al double alkoxide synthesized using magnesium powder, aluminum foil and sec-butyl alcohol. This powder was compared with powder prepared by mixing two commercial alkoxides. The spinelization was started at 50$0^{\circ}C$ and was almost completed at 100$0^{\circ}C$ with a good crystallinity in the double alkoxide system. In mixed alkoxide system, homogeneous spinel powder was not obtained and MgO existed as a second phase because of solubility and hydrolysis rate differences of two alkoxides. The relative density of specimen prepared by double alkoxide was 99% and specimen prepared by mixed alkoxide was 95%. The modulus of rupture of specimens prepared by double alkoxide and mixed alkoxide was 49.9kg/$\textrm{mm}^2$ and 41.6kg/$\textrm{mm}^2$, respectively.

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Synthesis of AlON from Partially Hydrolyzed AlN Powder and its Sintering (부분 가수분해된 AlN 분말로부터 산질화 알루미늄(AlON)의 합성 및 소결)

  • 김두영;최상욱;남건태
    • Journal of the Korean Ceramic Society
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    • v.31 no.11
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    • pp.1362-1368
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    • 1994
  • The hydrolysis of aluminum nitride was increased gradually with increasing reaction time from 1 hrs to 24 hrs and/or with decreasing the addition of the reaction water from 100 mι 100mι. Amorphous aluminum hydrate, formed in the beginning of the reaction, was transformed to bayerite and to pseudoboehmite at below and above 8$0^{\circ}C$, respectively. Aluminum oxynitride was synthesized by heating the partially hydrolyzed aluminum nitride at 1$700^{\circ}C$ for 4 hrs or at 175$0^{\circ}C$ for 30 min. AlON specimen with 1 wt% of Y2O3 that was molded and then sintered pressurelessly at 190$0^{\circ}C$, exhibits 98% of the theoretical density and a translucency of 68% in the visible ray zone.

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A Study on the Preparation of $Al_2O_3-TiO_2$ Nanocomposite Powders ($Al_2O_3-TiO_2$계 Nanocomposite 분체의 합성에 관한 연구)

  • 이홍림;이호순
    • Journal of the Korean Ceramic Society
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    • v.30 no.2
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    • pp.115-122
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    • 1993
  • Transparent Al2O3 and TiO2 clear sols prepared by hydrolysis and subsequent peptization were mixed into wet gel. EDS analysis for this gel showed that wet gel was extremely homogeneous in chemical composition. Calcination of the wet gel at 120$0^{\circ}C$ for 50 minutes resulted in Al2O3-TiO2 nanocomposite powders where TiO2 particles of 101~102 nanometer were dispersed in the Al2O3 matrix. Both powders were sintered for 4 hours in the temperature range over 1500~1$650^{\circ}C$ with and without 5wt% MgO sintering aid. Among these sintered bodies, nanocomposite powder compacts sintered at 1$650^{\circ}C$ for 4 hours with 5wt% MgO showed the most dense structure with the grain size under 5${\mu}{\textrm}{m}$ and highest relative density of 98.2%.

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Effects of Some Heavy Metals(Al, Cd, Hg, and Pb) on ATP Content in Plant Leaves (식물엽의 ATP함량에 미치는 중금속(Al, Cd, Hg 및 Pb)의 영향)

  • 성민웅
    • Journal of Plant Biology
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    • v.22 no.4
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    • pp.107-113
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    • 1979
  • The present study was carried out to estimate the comparative effects of hydroponic heavy metals (Al, Cd, Hg, and Pb) on ATP content in plant leaves grown with Hoagland solution under green house condition. The two plants, kidneybean(Phaseolus vulgaris L.) and buckwheat(Fagopyrum esculentum M nch), showed similar inhibitory effect of heavy metals on ATP content in order of Hg, Cd, Pb, and Al. But the overall inhibitory effect was greater in kidneybean than in buckwheat. The affinity of heavy metals, in vitro, toward the enzyme (luciferin-luciferase) is in order of Hg, Al, Cd, and Pb, similar to that toward ATP. The results showed that the inhibitory effect of heavy metals on ATP hydrolysis is mainly due to the coordination of heavy metals with enzyme than ATP.

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Synthesis of Powder of the System Si-Al-O-N from Alkoxides II. Properties of Powders and Sintered Ceramics of Si3N4 and $\beta$-Sialon Prepared from Alkoxides (알콕사이드로부터 Si-Al-O-N계 분말합성 II. 알콕사이드로부터 합성한 Si3N4 및 $\beta$-Sialon의 분말 및 소결체의 특성)

  • 이홍림;전명철
    • Journal of the Korean Ceramic Society
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    • v.26 no.2
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    • pp.201-209
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    • 1989
  • Fine Si-Al-OH coprecipitate powders were prepared from Si- and Al-alkoxides by the hydrolysis method. $\beta$-Sialon powder was obtained from prepared Si-Al-OH coprecipitate by the simultaneous reduction and nitridation method. The syntehsized Sialon powder was pressureless sintered at 175$0^{\circ}C$ for 90 min in N2 atmosphere. The characterization of the Sialon powder was performed with XRD, BET, SEM, TEM and particle size analysis. The sinterability and mechanical properties of sintered bodies were investigated in terms of relative density, M.O.R., fracture toughness, hardness and the morphology of microstructure. The highest values of their mechanical properties were obtained for the $\beta$-Sialon ceramics at Z=1 and those values are as follows : M.O.R., KIC and HV of $\beta$-Sialon ceramics(Z=1) are 499.1 MPa, 5.9MN/m3/2 and 18.7GPa, respectively.

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Acetylcholinesterase(AChE)-Catalyzed Hydrolysis of Long-Chain Thiocholine Esters: Shift to a New Chemical Mechanism

  • Jung, Dai-Il;Shin, Young-Ju;Lee, Eun-Seok;Moon, Tae-sung;Yoon, Chang-No;Lee, Bong-Ho
    • Bulletin of the Korean Chemical Society
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    • v.24 no.1
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    • pp.65-69
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    • 2003
  • The kinetic and chemical mechanisms of AChE-catalyzed hydrolysis of short-chain thiocholine esters are relatively well documented. Up to propanoylthiocholine (PrTCh) the chemical mechanism is general acid-base catalysis by the active site catalytic triad. The chemical mechanism for the enzyme-catalyzed butyrylthiocholine(BuTCh) hydrolysis shifts to a parallel mechanism in which general base catalysis by E199 of direct water attack to the carbonyl carbon of the substrate. [Selwood, T., et al. J. Am. Chem. Soc. 1993, 115, 10477- 10482] The long chain thiocholine esters such as hexanoylthiocholine (HexTCh), heptanoylthiocholine (HepTCh), and octanoylthiocholine (OcTCh) are hydrolyzed by electric eel acetylcholinesterase (AChE). The kinetic parameters are determined to show that these compounds have a lower Michaelis constant than BuTCh and the pH-rate profile showed that the mechanism is similar to that of BuTCh hydrolysis. The solvent isotope effect and proton inventory of AChE-catalyzed hydrolysis of HexTCh showed that one proton transfer is involved in the transition state of the acylation stage. The relationship between the dipole moment and the Michaelis constant of the long chain thiocholine esters showed that the dipole moment is the most important factor for the binding of a substrate to the enzyme active site.

Synthesis of ${\alpha}$-Alumina Nanoparticles Through Partial Hydrolysis of Aluminum Chloride Vapor (염화알미늄 증기의 부분가수분해를 통한 알파 알루미나 나노입자 제조)

  • Park, Hoey Kyung;Yoo, Youn Sug;Park, Kyun Young;Jung, Kyeong Youl
    • Korean Chemical Engineering Research
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    • v.49 no.5
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    • pp.664-668
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    • 2011
  • Spherical alumina precursors represented by $AlO_xCl_y(OH)_z$, 30~200 nm in particle diameter, were prepared by partial hydrolysis of $AlCl_3$ vapor in a 500 ml reactor. Investigated on the particle morphology and size were the effects of the reaction time, the stirring speed and the reaction temperature. The particle morphology and size was insensitive to the reaction time in the range 20 to 300 s. The variation of the stirring speed from 0 to 300 and 800 rpm showed that the particle size was the largest at 0 rpm. As the temperature was varied from 180 to 190, 200, $140^{\circ}C$, the particle size showed a maximum at $190^{\circ}C$. By calcination of the as-produced particles at $1,200^{\circ}C$ for 6h with a heating rate of $10^{\circ}C$/min, ${\alpha}$-alumina particles 45 nm in surface area equivalent diameter were obtained. The particle shape after calcination turned wormlike due to sintering between neighboring particles. A rapid calcination at $1400^{\circ}C$ for 0.5 h with a higher heating rate of $50^{\circ}C$/min reduced the sintering considerably. An addition of $SiCl_4$ or TMCTS(2,4,6,8-tetramethylcyclosiloxane) to the $AlCl_3$ reduced the sintering effectively in the calcination step; however, peaks of ${\gamma}$ or mullite phase appeared. An addition of $AlF_3$ to the particles obtained from the hydrolysis resulted in a hexagonal disc shaped alumina particles.