• Title/Summary/Keyword: Chemical reaction kinetics

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Kinetics of Reversible Consecutive Reactions

  • Park, Tae Jun
    • Bulletin of the Korean Chemical Society
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    • v.34 no.1
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    • pp.243-245
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    • 2013
  • Rate equations are exactly solved for the reversible consecutive reaction of the first-order and the time-dependence of concentrations is analytically determined for species in the reaction. With the assumption of pseudo first-order reaction, the calculation applies and determines the concentration of product accurately and explicitly as a function of time in the unimolecular decomposition of Lindemann and in the enzyme catalysis of Michaelis-Menten whose rate laws have been approximated in terms of reactant concentrations by the steady-state approximation.

Reaction Kinetics for the Synthesis of Diphenyl Carbonate from Dimethyl Carbonate (디메틸 카보네이트(DMC)로부터 디페닐카보네이트(DPC) 합성을 위한 반응속도론)

  • Choi, Yu-Mi;Cho, Im-Pyo;Cho, Hoon;Lee, Jin-Hong;Han, Myung-Wan
    • Korean Chemical Engineering Research
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    • v.50 no.5
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    • pp.766-771
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    • 2012
  • PC (polycarbonate) is one of the widely used engineering plastics. Polycarbonate (PC) is traditionally produced by the reaction of phosgene and bisphenol-A. This phosgene process has the disadvantage as the high toxicity and corrosiveness of phosgene. The main point of focus to overcome the disadvantage of phosgene based process has been a route through dimethyl carbonate (DMC) to diphenyl carbonate (DPC). In this paper, for the DPC synthesis reaction using PBO as a catalyst, the effect of reaction temperature, reactant ratio, catalyst concentration on the reaction yield was investigated. A kinetic model for the DPC synthesis reaction was proposed and kinetic parameters for the proposed model was determined from batch reactor experiments. The predicted results by the proposed model were in good agreement with the experimental results.

Gas Evolution Kinetics of $N_2H_4-I_2$ Reaction in a Sulfuric Acid Medium (황산 산성용액에서 기체발생에 의한 $N_2H_4-I_2$ 반응속도)

  • Choe Chuhyun
    • Journal of the Korean Chemical Society
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    • v.18 no.3
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    • pp.153-156
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    • 1974
  • The kinetics of gas evolution in the reaction between hydrazine and iodine in a sulfuric acid medium has been studied at $25^{\circ}$. The rate is first order in hydrazine and iodine concentration. The iodide ion retards the reaction whereas the effect of hydrogen ion concentration is rather complicated. The rate of gas evolution is very close to that of iodine consumption.

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Kinetics and Mechanism of the Reaction of Benzyl Bromide with Thiobenzamides (벤질브로미드와 티오벤즈아미드의 반응에 있어서의 반응속도와 반응메카니즘)

  • Hong Soon-Yung;Yoh Soo-Dong
    • Journal of the Korean Chemical Society
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    • v.16 no.5
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    • pp.284-289
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    • 1972
  • Rates of the reactions of m-and p-ring-substituted thiobenzamides with benzyl bromide in acetone have been determined by an electric conductivity method. The Hammett rule has been adopted for these reactions. It has been observed that an electron-attracting substituent accelerates the reaction while an electron-donating substituent retards the reaction, and a mechanism which accounts for the observed kinetics has been postulated. The activation energies and entropies of activation for these reactions have also been calculated.

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Nonisothermal Decomposition Reaction Kinetics, Specific Heat Capacity, Thermodynamic Properties and Adiabatic Time-to-explosion of 4-Amino-1,2,4-triazole Copper Complex

  • Ren, Yinghui;Li, Dan;Yi, Jianhua;Zhao, Fengqi;Ma, Haixia;Xu, Kangzhen;Song, Jirong
    • Bulletin of the Korean Chemical Society
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    • v.31 no.7
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    • pp.1988-1992
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    • 2010
  • 4-Amino-1,2,4-triazole copper complex (4-ATzCu) was synthesized, and its thermal behaviors, nonisothermal decomposition reaction kinetics were studied by DSC and TG-DTG techniques. The thermal decomposition reaction kinetic equation was obtained as: $d\alpha$ / dt =$10^{22.01}$ (1-$\alpha$)[-ln(1-$\alpha$)]$^{1/3}$ exp($-2.75\times10^4$ /T). The standard mole specific heat capacity of the complex was determined and the standard molar heat capacity is 305.66 $J{\cdot}mol^{-1}{\cdot}K^{-1}$ at 298.15 K. The entropy of activation $({\Delta}S^{\neq})$, enthalpy of activation $({\Delta}H^{\neq})$, and Gibbs free energy of activation $({\Delta}G^{\neq})$ are calculated as 171.88 $J{\cdot}mol^{-1}{\cdot}K^{-1}$ 225.81 $kJ{\cdot}mol^{-1}$ and 141.18 $kJ{\cdot}mol^{-1}$, and the adiabatic time-to-explosion of the complex was obtained as 389.20 s.

Kinetics of the KOH Catalyzed-Methanolysis for Biodiesel Production from Fat of Tra Catfish

  • Huong, Le Thi Thanh;Tan, Phan Minh;Hoa, Tran Thi Viet;Lee, Soo
    • Journal of the Korean Applied Science and Technology
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    • v.25 no.4
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    • pp.418-428
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    • 2008
  • Transesterification of fat of Tra catfish with methanol in the presence of the KOH catalyst yields fatty acid methyl esters (FAME) and glycerol (GL). The effects of the reaction temperature and reaction time on rate constants and kinetic order were investigated. Three regions were observed. In the initial stage, the immiscibility of the Tra fat and methanol limited the reaction rate, hence this region was controlled by the mass transfer. Subsequent to this region, produced FAME like a co-solvent made the reaction mixture homogeneous, therefore the conversion rate increased rapidly so it was controlled by the kinetic parameters of the reaction until the equilibrium was approached in the final slow region. A second-order kinetic mechanism was proposed involving second regions for the forward reaction. The rate determining step for the overall KOH catalyzed-methanolysis of Tra fat was the conversion of triglycerides (TG) to diglycerides (DG). This rate constant was increased from 0.003 to $0.019min^{-1}$ when the reaction temperature was increased from 35 to $60^{\circ}C$. Its calculated activation energy was 14.379 ($kcal.mol^{-1}$).

A Study on Chemical Effecta Through Preferential Diffusion of H2 and H in CH4-H2 Counterflow Diffusion Flames (메탄-수소 대향류확산화염에서 H2와 H의 선호확산을 통한 화학적 효과에 관한 연구)

  • Park, Jeong;Kwon, Oh-Boong;Lee, Eui-Ju;Yun, Jin-Han;Keel, Sang-In
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.31 no.12
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    • pp.1009-1016
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    • 2007
  • Numerical study on preferential diffusion effects in flame structure in $CH_4-H_2$ diffusion flames is conducted with detailed chemistry. Comparison of flame structures with mixture-averaged species diffusion and suppression of the diffusivities of $H_2$ and H was made. Discernible differences in flame structures are displayed with three species diffusion models. The behaviors of maximum flame temperatures with those species diffusion models are not explained by scalar dissipation rate but by the nature of chemical kinetics. It is seen that the modifcation of flame structure is mainly due to the preferential diffusion of H2 and thereby the nature of chemical kinetics. It is also found that the behaviors of major species with the three species diffusion models are addressed to the nature of chemical kinetics, and this is evident by examining importantly contributing reaction steps to the production and destruction of those chemical species.

Study of Kinetics of Bromophenol Blue Fading in the Presence of SDS, DTAB and Triton X-100 by Classical Model

  • Samiey, Babak;Alizadeh, Kamal;Moghaddasi, Mohammad Ali;Mousavi, Mir Fazlolah;Alzadeh, Nader
    • Bulletin of the Korean Chemical Society
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    • v.25 no.5
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    • pp.726-736
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    • 2004
  • In this paper, kinetics of reaction between Bromophenol blue (BPB) and $OH^-$, called fading, has been studied through a spectrophotometric method in the presence of nonionic Triton X-100 (TX-100), anionic sodium dodecyl sulfate (SDS) and cationic dodecyl trimethylammonium bromide (DTAB) surfactants. The influence of changes in the surfactant concentration on the observed rate constant was investigated. The results are treated quantitatively by pseudophase ion-exchange (PPIE) model and a new simple model called "classical model". The binding constants of BPB molecules to the micelles and free molecules of surfactants, their stoichiometric ratios and thermodynamic parameters of binding have been evaluated. It was found that SDS has nearly no effect on the fading rate up to 10 mM, whereas TX-100 and DTAB interact with BPB which reduce the reaction rate. By the use of fading reaction of BPB, the binding constants of SDS molecules to TX-100 micelles and their Langmuir and Freundlich adsorption isotherms were obtained and when mixtures of DTAB and TX-100 were used, no interaction was observed between these two surfactants.

Reduction Kinetics of Zinc Oxide in EAF Dust (전기로 분진중 아금산화물의 환원속도)

  • Moon Seok Min;Kim Tae Wook;Min Dong Joon
    • Resources Recycling
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    • v.11 no.4
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    • pp.37-43
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    • 2002
  • As the consumption of galvanized steels in cans and automobiles and the quantity of scraps increase, the recycling problems of EAF dust become a important problem. Valuable metals such as Fe, Zn, Pb are of continued interest to metallurgists. To recover the valuable metal and to remove the toxicity of EAF dust, high temperature smelting process is or researching as a pilot scale. The Reduction kinetics of Zn in EAF dust is so important in a view of the economic consideration of the process. In this study, the kinetics behavior of Zn in EAF dust were measured as a point of application in high temperature smelting process. The rate control step in ZnO and franklinite is revealed to be chemical reaction on the reaction surface.

Photopolymerization Kinetics of Urethane-acrylate Oligomer (우레탄-아크릴레이트 올리고머의 광경화 거동)

  • Kim, In-Beom;Song, Bong Jin;Lee, Myung Cheon
    • Applied Chemistry for Engineering
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    • v.17 no.1
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    • pp.33-36
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    • 2006
  • The kinetics of photopolymerization of urethane-acrylate oligomer which has many applications in photopolymerizable adhesives was analysed to investigate the influence of polymerization temperature and functionality of oligomer using the autocatalytic model. It was revealed that the maximum polymerization rate decreased as the polymerization temperature increased. The reaction rate constant, k, showed little change with the increase in polymerization temperature, while exponents m and n exhibited an increase. These results could be related to the diffusion and mobility restriction of reactive species during the cross-linking reaction. The decrease in photopolymerization rate with increase of temperature was mainly controlled by the reaction order n.