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1

Wyznaczenie kinetyki estryfikacji kwasu laurynowego n-heksanolem, n-oktanolem i n-dekanolem w obecności żywicy jonowymiennej Dowex 50WX8 jako katalizatora

Hamryszak Łukasz

Przemysł Chemiczny

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2024

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T. 103, nr 1

66--72

PL

Przeprowadzono badania kinetyczne procesu estryfikacji kwasu laurynowego n-heksanolem, n-oktanolem, n-dekanolem w zakresie temp. 393-413 K i dla stosunków molowych alkohol:kwas 3:1-10:1 z udziałem katalizatora heterogenicznego Dowex 50WX8 (1,5% mas.). Badania prowadzono w warunkach izotermicznych w doświadczalnym reaktorze półokresowym z ciągłym wyprowadzaniem wody. Stwierdzono, że reakcje można opisać za pomocą równania kinetycznego typu Langmuira i Hinshelwooda z reakcją powierzchniową pomiędzy kwasem laurynowym i alkoholem jako etapem limitującym. Określono parametry równania kinetycznego, wartości energii aktywacji malały w zakresie 62-54 kJ/mol w szeregu n-heksanol > n-oktanol > n-dekanol.

EN

CH₃(CH₂)₁₀COOH was esterified with CH₃(CH₂)₅OH, CH₃(CH₂)₇OH and CH₃(CH₂)₉OH at 393-413 K and at molar ratios (alc.:acid) of 3:1-10:1 in the presence of the Dowex catalyst 50WX8 (1.5% by mass). The kinetics of the studied processes were described by the detd. LangmuirHinshewood type kinetic equation, the limiting step of which was the surface reaction of CH₃(CH₂)₁₀COOH with alcohol. The activation energy decreased in the range of 62-54 kJ/mol in the alcohol series: n-hexanol > n-octanol > n-decanol.

2

Numerical study of detonation processes in rotating detonation engine and its propulsive performance

Yi Tae-Hyeong, Lou Jing, Turangan Cary Kenny, Wolanski Piotr

Transactions on Aerospace Research

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2020

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Nr 3 (260)

30--48

EN

Numerical studies on detonation wave propagation in rotating detonation engine and its propulsive performance with one- and multi-step chemistries of a hydrogen-based mixture are presented. The computational codes were developed based on the three-dimensional Euler equations coupled with source terms that incorporate high-temperature chemical reactions. The governing equations were discretized using Roe scheme-based finite volume method for spatial terms and second-order Runge-Kutta method for temporal terms. One-dimensional detonation simulations with one- and multi-step chemistries of a hydrogen-air mixture were performed to verify the computational codes and chemical mechanisms. In two-dimensional simulations, detonation waves rotating in a rectangular chamber were investigated to understand its flowfield characteristics, where the detailed flowfield structure observed in the experiments was successfully captured. Three-dimensional simulations of two-waved rotating detonation engine with an annular chamber were performed to evaluate its propulsive performance in the form of thrust and specific impulse. It was shown that rotating detonation engine produced constant thrust after the flowfield in the chamber was stabilized, which is a major difference from pulse detonation engine that generates repetitive and intermittent thrust.

PL

Przedstawiono badania numeryczne propagacji fali detonacyjnej w wirującym silniku detonacyjnym oraz jego wydajności pędnej z jedno- i wielostopniową mieszanką chemiczną na bazie wodoru. Kody obliczeniowe opracowano w oparciu o trójwymiarowe równania Eulera w połączeniu z pojęciami źródłowymi, które obejmują wysokotemperaturowe reakcje chemiczne. Obowiązujące równania zostały zdyskredytowane przy użyciu metody skończonej objętości opartej na schemacie Roe'a dla terminów przestrzennych oraz metody Runge-Kutta drugiego rzędu dla terminów czasowych. W celu weryfikacji kodów obliczeniowych i mechanizmów chemicznych przeprowadzono jednowymiarowe symulacje detonacji z jedno- i wieloetapowymi chemikaliami mieszaniny wodoru i powietrza. W symulacjach dwuwymiarowych badano fale detonacyjne obracające się w komorze prostokątnej w celu zrozumienia jej charakterystyki pola przepływu, gdzie udało się uchwycić szczegółową strukturę pola przepływu zaobserwowaną w doświadczeniach. Przeprowadzono trójwymiarowe symulacje dwufalowego wirującego silnika detonacyjnego z komorą pierścieniową w celu oceny jego właściwości pędnych w postaci ciągu i impulsu właściwego. Wykazano, że wirujący silnik detonujący wytwarza stały ciąg po ustabilizowaniu się pola przepływu w komorze, co stanowi istotną różnicę w stosunku do silnika detonującego impulsowo, który wytwarza powtarzalny i przerywany ciąg.

3

A study of the local entropy generation rate in a porous media burner

Mohammadi I., Esfahani J. A., Kim K. C.

Archives of Mechanics

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2020

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Vol. 72, nr 3

257--279

EN

In this paper, the work and performance of the premixed methane-air porous axisymmetrical burner have firstly been simulated numerically using the CFD tools. For this purpose the set of governing equations has been enriched by an additional energy equation in porous solid, and the chemical species transport has been extended onto the multi-step mechanism (GRI-2-11). This numerical model has been verified on the base of available benchmark experiments. Next, we have studied the local entropy generation problem taking into account not only classical contributions like viscous and turbulent dissipation but also, the porous combustion of gases. The results showed that the greatest portion of entropy generation in the porous medium burner is related to chemical reactions, followed by heat transfer, mass diffusion (mixing) and friction (viscous dissipation), respectively. According to the results, as the excess air ratio increases, the local entropy generation rate due to heat transfer and friction increases and the local entropy generation rate due to chemical reactions is decreased. Also, by increasing the volumetric heat transfer coefficient, the local entropy generation rate due to heat transfer decreases and the local entropy generation rate due to friction and chemical reactions increases. Also, the local entropy generation rate due to mixing does not show a significant change with the changing excess air ratio and volumetric heat transfer coefficient.

4

Investigation of the cook-off processes of HMX-based mixed explosives

Chen L., Ma X., Lu F., Wu J.

Central European Journal of Energetic Materials

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2014

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Vol. 11, no. 2

199--218

EN

In order to investigate the characteristics of the thermal reaction for two kinds of mixed explosives, PBXC-10 (HMX/TATB/Binder, 38/57/5) and JO-8 (HMX/Binder, 95/5), multi-point measured temperature cook-off tests were carried out at different heating rates. The thermal transfer and finite chemical reactions that include the β→δ transition of HMX, and the endothermic and exothermic cook-off processes were analyzed. A 3D model of the explosive cook-off test was developed to simulate the thermal and chemical behaviour in a thermal ignition. The decomposition mechanisms for HMX and TATB are described by the multistep, chemical kinetic model. The thermal properties, decomposition pathways, and chemical kinetic reaction rate constants for each component are used to develop the reaction courses at various weight percentages. The thermal decomposition reaction of a multi-component, mixed explosive can be predicted as long as the chemical kinetics model of each single-base explosive and binder are known. The phase transition of HMX has an influence on the temperature of the explosive, especially for an explosive with a high HMX content. For mixed explosives containing HMX and TATB, most of the heat release is produced by the decomposition of HMX before ignition, but TATB can delay the ignition time and decrease the reaction violence in the cook-off process.

5

Zastosowanie metody Monte Carlo do wyznaczania krzywych kinetycznych złożonych reakcji chemicznych

Gwadera M., Kupiec K.

Czasopismo Techniczne. Chemia

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2012

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R. 109, z. 2-Ch

41--52

PL

Wyznaczono przebiegi krzywych kinetycznych dla reakcji złożonych przy użyciu metody Monte Carlo. Rozważono zarówno odwracalne, jak i nieodwracalne reakcje równoległe, następcze, następczo-równoległe oraz autokatalityczne. Wykazano całkowitą zgodność wyników symulacji stochastycznych z wynikami otrzymanymi w oparciu o modele deterministyczne.

EN

Kinetic curves for multiple reactions have been determined by the means of the Monte Carlo method. Both reversible and nonreversible parallel, series, series-parallel and autocatalytic reactions have been taken under consideration. The complete consistency between results of stochastic calculations and results obtained with the use of deterministic models has been shown.

6

Corrosion at nanoscale: interface barriers and phase competition

Danielewski M., Gusak A., Wierzba B.

Ochrona przed Korozją

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2009

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nr 11

434-442

EN

The problem of simultaneous growth and competition of intermediate phases during reactive diffusion was analyzed by Gösele and Tu in 1982. In this work we reformulate old problem and propose method based on volume fixed frame of reference. It allows computing the material velocity in the reacting system in which reactions at several moving interfaces occur. All reactions lead to the lattice shift due to the difference of intrinsic diffusivities and different molar volumes. The following peculiarities are taken into account: (1) the deviation from local equilibrium at both interfaces of each moving inter-phase zone (i.e., at each side of the moving phase-boundary); (2) different mobility of the components in the interphase zone; (3) nonzero steps of molar volumes for each component from phase to phase and (5) different physicochemical properties of the interphase zones. We show the scale effect on the kinetic of the corrosion, the non-parabolic reactions, the multiphase scale growth and present the potential applications of the method.

PL

W 1982 roku Gösele i Tu analizowali problem równoczesnego wzrostu i kolejności powstawania wielofazowej zgorzeliny podczas procesu dyfuzji. W niniejszej pracy problem ten został rozwinięty i po raz pierwszy prezentujemy rozwiązanie w układzie odniesienia jakim jest sieć krystaliczna materiału. Takie podejście pozwala na wyznaczenie prędkości materiału uwzględniając wiele poruszających się granic międzyfazowych. Przesuwanie się granic faz jest wynikiem różnicy we współczynnikach dyfuzji oraz objętości molowych tworzących się faz (tlenków). W modelu wzięto pod uwagę: (1) niestechiometrię faz (po każdej stronie granicy między fazowej); (2) różne współczynniki dyfuzji składników; (3) różne objętości molowe składników oraz (4) różne właściwości fizykochemiczne granic faz. W pracy pokazany został wpływ skali na kinetykę procesu korozji, nieparaboliczność, wzrost warstw wielofazowych oraz inne możliwości aplikacyjne modelu.

7

Effect of pressure and applied voltage on the evolution of plasma characteristics for excimer laser under inhomogeneous pre-ionization conditions

Harrache Z., Amir Aid D., Mehdaoui L., Belasri A.

Journal of Technical Physics

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2008

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Vol. 49, no 1

39-52

EN

In this work, our goal is to study the effect of the total pressure and the charging voltage on the amplification and propagation of non-uniformities in volume for a XeCl laser. This study is executed by using a parallel resistor network model (PRN). In this model, the surface of discharge is divided ideally into a resistances network in parallel. The obtained results show clearly that the formation of the plasma non-uniformity in volume and on a large scale is in this case related mainly to the chemical kinetics of the laser medium, and the increase in the pressure and applied voltage discharge parameters consequently amplifies any non-uniformity.

8

Badania Ludwika Brunera (1871-1913) kinetyki chemicznej

Dolecki M.

Kwartalnik Historii Nauki i Techniki

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2007

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R. 52, nr 2

103-135

EN

In the article were discussed research works that were taken up on Polish territories by the Cracow scientist, and the first professor of Physical Chemistry - Ludwik Bruner over kinetics of homogenous and heterogenous systems. The kinetic searches of Bruner rere the crucial point in his activity. Up till now there has appeared a small number of ublications presenting the most significant achievements of the scientist. Bruner's research works over kinetics can be divided thematically into 2 main: part: -reactions velocity, photokinetics and catalysis of homogenous systems: kinetics of substitution of bromine in aromatic compounds, and addition of bromine to nonsaturated compounds, catalysis in bromination - and particularly the catalyctic action of iodine, kinetics of estrification; experiments on effect of light on the process and chemical reactions velocity -kinetics of heterogenous systems: research on the velocity of dissolution of solid bodies according to Noyes-Whitney's standard. Bruner's research works over kinetics played a significant role in the development of the scientific research on organic reactions velocity and dissolution velocity.

9

Badanie kinetyki procesu hydrolizy mocznika

Piotrowski J., Koszałka A., Simka W.

Chemia i Inżynieria Ekologiczna

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2003

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Vol. 10, nr S1

123-130

PL

Badano kinetykę procesu hydrolizy mocznika w roztworze wodnym w zakresie stężeń mocznika odpowiadającym ściekom przemysłowym 5-20 g/dm3, dla temperatur 343-363 K i czasu 0-4200 s. Wyznaczono równanie kinetyczne procesu, stałe szybkości reakcji hydrolizy oraz parametry równania Arrheniusa. Uzyskane równanie kinetyczne jest użyteczne przy projektowaniu technologii oczyszczania ścieków mocznikowych.

EN

Kinetics of urea hydrolysis process was examined. Range of urea concentration corresponded to industrial wastewater concentration of 5-20 g/dm3, temperature was 345-363 K and time 0-4200 s. Kinetic equation of the process, rate constants hydrolysis process and Arrhenius equation's parameters were determined. Results can be used during design of urea removal processes.

10

Theoretical study on the kinetics and mechanism of reactions of halogen atoms with trifluoromethanol

Brudnik K., Jodkowski J. T., Ratajczak E.

Bulletin of the Polish Academy of Sciences. Chemistry

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2003

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Vol. 51, No. 2

77-91

EN

Quantum mechanical ab initio calculations have been performed at various levels of theory to study kinetics of the reactions of fluorine, chlorine and bromine atoms with trifluoromethanol. Total energies were improved by using Gaussian-2 (G2) methodology. It is shown that the considered reactions proceed with formation of intermediate complexes. The mechanism of the reactions studied appears to be more complex and may consist of three elementary steps. The heights of the calculated energy barriers explain the differences of the reactivity of F, C1 and Br atoms towards CFsOH. The rate constants and their temperature dependence for the reactions CFsOH + X (fcx) and CFaO + HX (kfix) were calculated. The derived analytical expressions [chemical formulas] allow the description of the kinetics of the reactions under investigation. This is of considerable importance for the chemical modelling studies because of the lack of experimental measurements.

11

Kinetics of oxidative degradation of threonine by alkaline permanganate

Mavalangi S. K., Pol P. D., Nandibewoor T.

Bulletin of the Polish Academy of Sciences. Chemistry

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2003

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Vol. 51, No. 3-4

181-193

EN

The kinetics of oxidation of threonine by permanganate in alkaline medium at a constant ionic strength has been studied spectrophotometrically. The reaction between permanganate threonine in alkaline medium exhibits 1:2 stoichiometry (KMnC>4: threonine). The reaction shows first order dependence of rate on permanganate concentration and less than unit order dependence each in threonine and alkali concentrations. Reaction rate increases with an increase in ionic strength and a decrease in solvent polarity of the medium. Initial addition of reaction products did not affect the rate significantly. A mechanism involving the formation of an intermediate complex between oxidant and substrate has been proposed. The rate constants and the activation parameters for the slow step of the mechanism have been evaluated and discussed.

12

Diffusion controlled relaxation time and acceleration of velocity of sol-gel transformation for cross-linked metal alginate ionotropic gel comlexes

Khairou K. S., Al-Gethami W. M., Hassan R. M.

Bulletin of the Polish Academy of Sciences. Chemistry

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2003

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Vol. 51, No. 3-4

207-220

EN

The rate of gel-growth for spherical ionotropic metal alginate gel droplets has been studied. Experimental observations have shown that the relaxation time of the metal alginate ionotropic gel complexes of the droplet shapes decreased in the order Hg > Cd > Sn > Pb-alginates, whereas the velocity of sinking under gravitational acceleration decreases in the same order. The factors which affect the relaxation time and velocity of acceleration, such as the concentration and viscosity of the alginate sol, the nature and radius of the metal ion as well as the density and pH of the electrolyte solution have been examined. The activation energies indicated that the stability of these metal alginate gel complexes follows the order Hg > Cd > Pb ~ Sn alginates. A mechanism consistent with the experimental results has been discussed.

13

Defect structure and its mobility in pure and chromium doped cobaltous oxide

Mrowec S., Grzesik Z.

Bulletin of the Polish Academy of Sciences. Chemistry

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2003

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Vol. 51, No. 1

45-57

EN

Defect structure and the mobility of point defects in pure metal-deficient cobalt oxide (Co1-yO) and in Co1-yO-Cr(2)O(3) solid solutions have been studied as a function of temperature (1,223-1,573 K) and oxygen pressure (10-10(5)Pa) using microther-mograwimetric techniques. It has been shown that the predominant defects in pure and Cr-doped cobaltous oxide are singly ionized cation vacancies, and 3% at. of dopant is high enough to fix the concentration of predominant defects in such solid solutions on a constant level, being much higher than in pure Co(1-yO. The mobility of point defects in pure Co1-yO has been found to be concentration independent, strongly suggesting that in spite of rather high concentration no interactions and clustering of defects is to be expected. On the other hand, in Cr-doped cobaltous oxide, the defect structure is more complicated, although singly ionized cation vacancies seem to be still predominant defects.

14

Modelowanie kinetyki złożonych procesów chemicznych z użyciem sztucznych sieci neuronowych

Piotrowski K., Piotrowski J., Lipowska B.

Inżynieria i Aparatura Chemiczna

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2000

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Nr 6

12-15

PL

Zastosowano sztuczną sieć neuronową do opisu danych kinetycznych procesu inwersji azotanu(III) sodu za pomocą kwasu azotowego(V). Potwierdzono użyteczność sztucznych sieci neuronowych do numerycznego opisu kinetyki złożonych procesów chemicznych. Słowa kluczowe: sztuczna sieć neuronowa, kinetyka chemiczna, inwersja.

EN

An artificial neural network was used for the description of kinetic data of sodium nitrite inversion by nitric acid. Usefulness of artificial neural networks for numerical description of complex chemical processes was confirmed.

15

Influence of fitting and differentiation algorithms on the determination of kinetic parameters for atom formation in GFAAS

Yan-Zhong L., Xia T.

Chemia Analityczna

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2000

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Vol. 45, No. 1

83-96

EN

Different approaches for data treatment, the orthogonal polynomial regression and cubic spline function used in the calculation of kinetic parameters in GFAAS, were compared. The determination of activation energy and release order was based on the method pro-posed in our laboratory. The experimental data for thallium, obtained from probe atom-ization were utilized in the comparison. The results show that the use of polynomial regressions tends to yield larger values of kinetic order and activation energy as com-pared to that of cubic spline function, and the kinetic orders determined are less tempera-ture dependent, while the values of the order in the latter case decrease with the increase of temperature. The orders and activation energies for thallium obtained in this experi-ment are 0.33 + 0.02 and 83 š 2 kJ mol-1, 0.38 š 0.07 and 88 + 5 kJ mol'-1 and 0.17 + 0.04 and 68 š 4 kJ moP1 for 6th-order polynomial, 9th-order polynomial and cubic spline function, respectively.

PL

Porównano dwie metody w analizie danych GFAAS. Pierwsza metoda wykorzystuje wielomiany ortogonalne, a druga złożone wielomiany trzeciego stopnia. Do porównania wzięto dane uzyskane dla atomizacji talu. Otrzymane wyniki wskazują, że pierwsza metoda prowadzi do wyższych wartości energii aktywacji i rzędu reakcji oraz do-datkowo rząd reakcji tak wyznaczony jest mniej zależny od temperatury w porównaniu do drugiej reakcji. Uzyskano następujące rzędy reakcji: 0.33 š0.02 i 83 š 2 kJ mol-1; 0.38 š 0.07 i 88 š 5 kJ mol-1; 0.17 š 0.04 i 68 š 4 kJ mol-1 odpowiednio dla wielomianu 6-stopnia, 9-stopnia i złożonej funkcji 3-stopnia.

16

Blending of rate parameters for two state kinetics in renewing environments

Płonka A.

Bulletin of the Polish Academy of Sciences. Chemistry

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2000

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Vol. 48, No. 3

254-259

EN

The closed form kinetic equation and its asymptotes are discussed for the case of two distinct states of reactants for elementary first-order reaction in the renewing environments.