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- 저자 : Hyun Ku Rhee ) (검색결과 272 건)
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이현구 전남대학교 촉매연구소 1997 촉매학술발표회 Vol.- No.14
분자크기가 다른 암모니아와 피리딘을 탐짐분자로 사용한 TPD와 in-situ FT-IR 분석을 통하여 12-MR 제올라이트의 산특성에 관한 정보와 함께 구조내에서의 산점의 분포에 관한 정보를 도출하였다. 12-MR 제올라이트의 dealumination에 따른 구조적인 변화는 _29Si 및 _27Al Mas NMR로 분석하였다. 12-MR의 기공크기를 요구하는 분자크기가 큰 탄화수소 전환반응의 경우 각 제올라이트내에서의 활성점의 수(산점과 금속 site의 수)뿐만 아니라 구조적 특성에 따르는 활성점의 분포도 함께 고려되어야 함을 알 수 있었다.
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우명우,이현구 순천대학교 기초과학연구소 1990 基礎科學硏究誌 Vol.1 No.-
ZSM-5 촉매를 제조하고 메탄올 전환반응에 적용하여 반응 속도에 관한 실험연구를 수행하였다. ZSM-5 촉매상에서 메탄올 전환반응에서는 많은 종류의 탄화수소들이 생성되는 데, 본 연구에서는 접촉시간을 조절하여 주로 C_2, C_3 및 C_4 탄화수소들이 생성되는 조건하에서 반응실험을 수행하였으며 lumping의 개념을 적용하여 이 경우의 반응 경로와 각 반응의 속도 상수들을 결정하였다. 이로부터 메탄올이 dimethyl ether로 변환되어 평형상태를 유지하면서 C_2 및 C_4 탄화수소들이 병행반응으로 생성되고, 생성된 C_2 및 C_4 탄화수소들로부터 C_3 탄화수소가 생성되는 것으로 추정되었다.
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Rhee, Hyun Ku,Chang, Kil Sang,Kim, Jae Youn 한국화학공학회 1989 NICE Vol.7 No.2
Various dynamical characters of continuous stirred tank reactors (CSTR) are introduced with respect to the effects of reaction types, extra thermal capacitance, periodic forcing, and coupling of CSTRs. The subject includes the classical dynamics of two-dimensional model and the variety of complex dynamics in three or higher dimensional systems such as periodic bifurcations to Locus or chaos, aperiodic oscillations on invariant Locus, and universal dynamics of alternating periodic-chaotic sequences with k 2^ν-cycles for every natural number k. Particularly this review intends to bring about the problems that the engineers must be prepared to encounter in solving various physical systems including chemically reacting systems.
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Application of Singularity Theory to a Non - Isothermal CSTR with an Autocatalytic Reaction
Rhee, Hyun Ku,Cho, Sung Min,Ko, Byung Su 한국화학공학회 1995 NICE Vol.13 No.2
The steady-state behavior is investigated for a nonisothermal, non-adiabatic CSTR in which an autocatalytic reaction takes place with kinetic scheme A+B→2B+heat, rate = k(T) C_AC_B Singularity theory is applied to find the maximal number of steady-state solutions and to determine the regions in the parameter space corresponding to these solutions. The parameter space is divided into four regions corresponding to four types of different steady-state structure and it is shown that multiple steady-states(up to three) exist for some set of parameter values.
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Rhee, Hyun Ku,Lee, Jeong Kyu 한국화학공학회 1997 Korean Journal of Chemical Engineering Vol.14 No.6
Large-pore zeolites H-Beta, H-Mordenite and H-Omega were loaded with platinum and applied for the hydroisomerization of n-hexane and n-heptane. The catalytic activity of Pt-loaded zeolite showed good correlation with the effective acidity probed by pyridine rather than with the total acidity probed by ammonia when equal amounts of metal sites are present. The selectivity to multibranched isomers over three different catalysts was found dependent upon the conversion of n-paraffin. At low conversion, the selectivity to multibranched isomers was higher over Pt-loaded zeolites with high acid strength. At high conversion level, however, the selectivity was mainly governed by the metal/acid balance. On H-Mordenite and H-Omega, large amount of strong acid sites are located in the small pore or cage. In Pt/H-MOR, the metal/acid balance was poor because there was detrimental loss of metal sites caused by isolation of Pt in the side pockets of 8-MR and/or pore blockage of the linear 12-MR channel. Even though the acidity of H-Beta was very low compared to H-MOR and H-Omega, Pt/H-Beta yielded the best performance for the hydroisomerization of n-paraffin because of better metal/acid balance in Pt/H-Beta.
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The Role of Amines in the Synthesis of Zeolites by Water - Organic Vapor Phase Transport
Rhee, Hyun Ku,Kim, Man Hoe,Jung, Man Kyu 한국화학공학회 1995 NICE Vol.13 No.6
A number of rrticles have been published to illustrate the role of amines for the synthesis of zeolites and porosils. Some of the results are contradictory on the role of amines. (n this study. the roles of amines are investigated by water-organic vapor-phase tramsport method. thic method is attractive because the dilution effects by mother liquid c:an be avoided and the composition of the synthesized zeolite is equivalent to that of the parent gel. Thus, the relation between the gel and amine can he explained clearly. In the zeodite synthesis, the templating effect of amine is less plausible, whereas the molecules with higher dipole moment and appropriate dimension such as propylamine have higher effectiveness. $quot;rhe pn$gt;torrated amines cannot work as active canons independently but amines activa.te the inactive catiuns (organic artd alkali) in the gel by means of reinforcement of the pH level in the gel.
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Synthesis of MFI - Type Zeolites Under Atmospheric Pressure
Hyun Ku Rhee,Hyung Seuk Oh,Kyoung Ku Kang,Man Hoe Kim 한국화학공학회 2001 Korean Journal of Chemical Engineering Vol.18 No.1
Silicalite and highly silicious ZSM-5 were synthesized using two reaction mixtures with different crystal growth environments, a dispersed low density mixture and a separated high density mixture, at 93 ±13℃ under the atmospheric pressure. Nucleation behavior and the transformation process of two mixtures were investigated utilizing various analytical techniques such as XRD, FT-IR, TGA, SEM, and pH measurement. During the induction period, the same intermediate phase was observed in both mixtures. The presence of this phase was found to be dependent on the degree of dilution of the reaction mixture. After the induction period, a sharp increase in both the degree of crystaliization and the pH of the reaction mixture was detected. This indicates that the pH change in the reaction mixture is closely related to the crystallization process. From these observations, a crystallization mechanism is proposed on the basis of the appearance of stable silicate species and the role of OH^- ions during the induction period. According to this mechanism, MFI-type zeolite grows by condensation reaction among the stable silicate species funned during the induction period.
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이현구 ( Hyun Ku Rhee ) 한국화학공학회 1974 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.12 No.2
A review of the literatures on the theory of chromatography is carried out by dividing the subject into four categories: (1) single soulte system, (2) multicomponent system, (3) adiabatic adsorption process, and (4) effect of diffusion and/or non-equilbrium. Each part presents a historical survey as well as a critical review of recent advances in the field. Developments in the mathematical theory of quasilinear partial differential equations are also discussed in connection with their applications to the theory of chromatography and other related fields.
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