• Membrane Journal
• /
• v.13 no.4
• /
• pp.268-282
• /
• 2003

Pervaporation-facilitated esterification with slow reaction regime was characterized by using a practical model based on non-perfect separation through membrane. A non-perfect separation in which the membrane is not perfectly permselective to water was applied to the model. Thus, membrane selectivity and membrane capability to remove water were included in the simulation model to explain how they influence the membrane-facilitated reaction process and improve the reactor performance. It was shown by simulation that in the reaction systems with non-perfect separation, reaction completion can hardly be achievable when any reactant at initial molar ratio=1 or the less abundant reactant at initial molar ratio>1 permeates through membrane, and the permeation of ester accelerates the forward reaction md increase reaction conversion at any instant through removal of product species like water. The volume change causes concentrating both reactants and products that affect the reaction with time in opposite ways; reactant-concentrating effect is dominant during the initial stage of reaction, increasing the reaction rate, and then concentrating product influences more reaction by decreasing the reaction rate.

• Membrane Journal
• /
• v.27 no.3
• /
• pp.205-215
• /
• 2017

Polymer membranes are cheap and easy in fabrication, and show a high permeability and selectivity, thus play pivotal roles in gas separation as well as water purification. However, polymer membranes typically exhibit the trade-off relation between permeability and selectivity; i.e. when the permeability is high, the selectivity is low and vice versa. Facilitated transport has been considered one of the solutions to address this issue. Over the last decades, facilitated transport concept had played an important role in preparing the membranes and providing ideal and various models for the transport. Understanding the nature of carrier, the mobility of matrix and the physico-chemical properties of polymer composites are crucial for facilitated transport. Depending on the mobility of carrier, facilitated transport membrane is classified into three; mobile carrier membrane, semi-mobile carrier membrane, fixed-site carrier membrane. Also, there are four types of reversible reaction between the carrier and the specific target; proton transfer reaction, nucleophilic addition reaction, p-complexation reaction and electrochemical reaction. The facilitated transport membranes have been applied in the separation of CO2, O2 and olefin (propylene or ethylene). In this review, major challenges surrounding facilitated transport membranes and the strategies to tackle these challenges are given in detail.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.3
• /
• pp.971-974
• /
• 2012

The facilitated diffusion effect on protein-DNA binding is studied. A rigorous theoretical approach is presented to deal with the coupling between one-dimensional and three-dimensional diffusive motions. For a simplified model, the present approach can provide numerically exact results, which are confirmed by the lattice-based Monte Carlo simulations.

• Journal of the Korean Applied Science and Technology
• /
• v.20 no.2
• /
• pp.154-164
• /
• 2003

This paper has applied a simple model to the mass transfer mechanism of Cr(VI) with crownether in a batch-type, supported liquid membrane module. Concentration at pH 3 are as follows : 0.012 kmol/$m^3{\le}$18-crown-6${\le}$0.036 kmol/$m^3$ and 20 g/$m^3{\le}$ Cr(VI)${\le}$500 g/$m^3$. The measured values of forward- and backward-reaction rate constants between Cr(VI) and 18-crown-6 were used to simulate the model with the mass conservation equation and associated boundary conditions. Comparison between the experimental and simulated facilitated factor of Cr(VI) transport led to classification of reaction regions.

• Proceedings of the Membrane Society of Korea Conference
• /
• 1999.07a
• /
• pp.15-18
• /
• 1999

A simple mathematical model for facilitated mass transport through a fixed site carrier membrane was derived by assuming an instantaneous, microscopic concentration (activity) fluctuation. The current model demonstrates that the facilitation factor depends on the extent of concentration fluctuation, the time scale ratios of diffusion to chemical reaction and the ratio of the carrier concentration to the solute solubility in matrix. The model was examined against the experimental data on oxygen transport in membranes containing metallo-porphyrin carriers, and the agreement was exceptional (within 10% error). The basic concept of this approach was applied to separate olefin from olefin/paraffin mixtures. A proprietaty carrier, developed here, resulted that the selectivity of propylene over propane was more than 120 and the propylene permeance exceed 40 gpu.

• Membrane Journal
• /
• v.17 no.2
• /
• pp.146-160
• /
• 2007

A parametric study on pervaporation-facilitated esterification was performed by using a practical model based on non-perfect separation through membrane which is not perfectly permselective to water. Thus, membrane selectivity as well as membrane capability to remove water should be taken into account in establishing the simulation model to explain how the membrane separation influence the esterification reaction process. It was shown by simulation that in the reaction systems with non-perfect separation, the permeation of reactants which are acid or/and alcohol retards the reaction by inducing the backward reaction so that reaction conversion curve is located between a reaction system coupled with pervaporation process having a perfect permselectivity to water and a reaction system without pervaporation process. The volume change of reaction system occurs as a result of the permeation through the membrane. The reaction volume change which can be characterized by the reaction ratio of $r_{\Psi}\;to\;r_{{\Psi}=1}$ affects reaction kinetics by concentrating reactants and products, respectively, with different extent with time; reactant-concentrating effect is dominant during the initial stage of reaction, resulting in facilitating the reaction, and then product-concentrating effect is exerted more on reaction, causing to slow down the reaction. When pervaporative dehydration is applied to the reaction system plays an important role in the reaction as well. The effect of timing to impose pervaporation on reaction system affected the reaction kinetics in terms of reaction rate and reaction conversion. A relationship was derived to explain membrane unit capacity and reaction parameters that will be used as a design tool to determine membrane unit capacity at a given reaction conditions or reaction parameters at a membrane unit capacity.

• Preventive Nutrition and Food Science
• /
• v.2 no.4
• /
• pp.360-367
• /
• 1997

The chemistry background of the Maillard reaction focused on pyrazines and factors affecting the reaction products were reviewed. The Maillard reaction, also called a non-enzymatic browning reaction, is quite complex and generates numerous reaction products. In processed foods, it is generally accepted as a key reaction to produce flavor components. Specially, pyrazines possess an important impact character on the roasted foods with other heterocyclic compounds. The Maillard reaction is initiated by condensation between reducing sugar and amino group, and N-glycosylamines are produced via Schiff base with dehydration of water. After the rearrangement of the N-glycosylamines, they follow transformation into deoxyhexosones which are reactive intermediates. Degradation and fragmentation are facilitated by rearranged compounds. By condensation, pyrazine, one of the final Maillard products, is generated as a relatively stable form to provide specific aromas. During the processes of the reaction, chemical or physical environmental parameters affect the formation of the products.

• Proceedings of the Membrane Society of Korea Conference
• /
• 2004.03a
• /
• pp.13-35
• /
• 2004

Metal Complexes in Macromolecules Applications of Polymer Electrolyte Membranes Facilitated Transport in Solid State Roles of Electrolytes in Solar Cells - Electrolytes :ㆍI- and $I_3$-conductor ㆍelectron barrier or hole conductor ㆍelectrochemical redox reaction media ㆍinterfacial contactor for dye, $TiO_2$ and electrode ㆍmechanical separator (omitted)

• Journal of Korean Library and Information Science Society
• /
• v.46 no.4
• /
• pp.299-324
• /
• 2015

This paper is a qualitative single case study and it was conducted for the purpose to explore change in interactive bibliotherapy experience with a middle-aged widowed spouse. A Middle-aged Widowed Spouse was taken as a research partaker. Through this research, we explored partitively the partaker's experience changes by each session during the commencing of interactive bibliotherapy and the partaker's inner/external experience change after the end of session. The result, interactive bibliotherapy facilitated and expressed the reaction of a partaker by its writing skills and reading materials including partaker's own poems. Furthermore, facilitated emotion from material and self-awareness made a partaker understand and accept itself through therapeutical interaction. In addition, those kind of changes appeared inner/external experience in life, and lasted after the end of the session. In this regard, the inner/external change appeared from a partaker means the effect of bibliotherapy, and we can notice that it is a result that facilitated through truthful reaction of counselor and texts.

• Korean Journal of Microbiology
• /
• v.40 no.3
• /
• pp.254-256
• /
• 2004

Polymerase chain reaction (PCR) is a powerful tool for precisely amplifying selected DNA sequences that have had a broad impact on genomic studies. When examining human $\alpha$- and $\beta$- tryptase genes which have 95% DNA homology, inconsistent PCR amplification of genomic sequences hampered our progress. This study suggests that long PCR technique on the original DNA digested with restriction enzymes improves both efficiency and sensitivity of PCR. These improved results seem to derived from the effective denaturation of the original genomic DNA template or reduction of formation of secondary structures that block either primer annealing or extension in PCR. Elimination of homo- or hetero-duplex products derived from highly homologous genes provides an additional advantage in this study. This communication describes how the use of restriction enzymes improved these efficiencies, and also facilitated studies of highly homologous genes including tryptase genes.