Numerical analysis of parameter identifiability for a mathematical model of a chemical reaction

Авторами статьи ведутся работы, направленные на разработку численного подхода к анализу параметрической идентифицируемости модели химической реакции методами анализа чувствительности для эффективного исследования и управления процессом химической реакции. Целью настоящей работы является определение параметров, подлежащих идентификации в условиях задаваемой погрешности измерений, химической реакции на примере процесса пиролиза пропана и определение незначимых параметров модели. Выполнена редукция 157-стадийной детальной схемы пиролиза пропана к 30-стадийной схеме. Предложена кинетическая модель для анализа низкотемпературного пиролиза пропана. Модель адекватно описывает выход наблюдаемых продуктов реакции при атмосферном давлении. Идентифицированы параметры кинетической модели пиролиза пропана путем решения обратной задачи химической кинетики. The authors of this paper develop a numerical approach to analyze the parametric identifiability of chemical reaction models by the methods of sensitivity analysis for the efficient study and management of chemical reaction processes. The primary objective of this paper is to determine the parameters to be identified for the propylene pyrolysis process and to determine the insignificant parameters of the model. The 157-step detailed pyrolysis scheme of propane is reduced to the 30-step scheme. A kinetic model is proposed to analyze the low-temperature pyrolysis of propane. This model adequately describes the yield of observed reaction products at atmospheric pressure. The parameters of the kinetic model of propane pyrolysis are identified by solving the inverse problem of chemical kinetics.

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Kinetics of the catalytic hydrodesulphurization reaction system; hydrogenolysis of thiophene

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19802728 ◽

1980 ◽

Vol 45 (10) ◽

pp. 2728-2741 ◽

Cited By ~ 7

Author(s):

Pavel Fott ◽

Petr Schneider

Keyword(s):

Atmospheric Pressure ◽

Active Sites ◽

Flow Reactor ◽

Kinetic Equations ◽

Reaction System ◽

Reaction Products ◽

Molybdenum Catalyst ◽

Cobalt Molybdenum Catalyst ◽

Kinetics Of ◽

Reaction Schemes

Kinetics have been studied of the reaction system taking place during the reaction of thiophene on the cobalt-molybdenum catalyst in a gradientless circulation flow reactor at 360 °C and atmospheric pressure. Butane has been found present in a small amount in the reaction products even at very low conversion. In view of this, consecutive and parallel-consecutive (triangular) reaction schemes have been proposed. In the former scheme the appearance of butane is accounted for by rate of desorption of butene being comparable with the rate of its hydrogenation. According to the latter scheme part of the butane originates from thiophene via a different route than through hydrogenation of butene. Analysis of the kinetic data has revealed that the reaction of thiophene should be considered to take place on other active sites than that of butene. Kinetic equations derived on this assumption for the consecutive and the triangular reaction schemes correlate experimental data with acceptable accuracy.

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The formation and development of oblique detonation wave with different chemical reaction models

Aerospace Science and Technology ◽

10.1016/j.ast.2021.106964 ◽

2021 ◽

pp. 106964

Author(s):

Hongbo Guo ◽

Xiongbin Jia ◽

Ningbo Zhao ◽

Shuying Li ◽

Hongtao Zheng ◽

...

Keyword(s):

Detonation Wave ◽

Chemical Reaction ◽

Oblique Detonation Wave ◽

Reaction Models

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Study of kinetics of reaction of lignin model compounds with propylene oxide

Holzforschung ◽

10.1515/hf.2008.025 ◽

2008 ◽

Vol 62 (2) ◽

pp. 169-175 ◽

Cited By ~ 3

Author(s):

Krishna K. Pandey ◽

Tapani Vuorinen

Keyword(s):

Chemical Reaction ◽

Propylene Oxide ◽

Aqueous Media ◽

Reaction Products ◽

Model Compounds ◽

Rapid Reduction ◽

Visible Absorption ◽

Lignin Model Compounds ◽

Lignin Model ◽

Kinetics Of

Abstract The etherification of phenolic groups has been found to inhibit photodegradation in wood and lignin rich pulps. The precise understanding of kinetics of chemical reaction between lignins or their model compounds and the etherifying agent is the first step for developing a viable modification procedure. In this study, we have investigated the reaction of lignin model compounds (namely, phenol and guaiacol) with propylene oxide in aqueous media. The kinetics of etherification reaction was studied under varying pH conditions in the temperature range 30–60°C. The etherified reaction products were characterized by gas chromatogram-mass spectrum (GC-MS). The extent of etherification of phenols and the rate of chemical reaction was followed by UV-Visible absorption spectroscopy. The reaction between lignin model compounds and propylene oxide was indicated by a rapid reduction in the absorbance accompanied by the development of a new band corresponding to etherified products. The reaction kinetics was investigated at pH ∼12 under the condition of excess concentration of propylene oxide. The reaction followed first order kinetics and rate constants increased linearly with an increase in the temperature and concentration of propylene oxide. The MS fragment data of reaction product support the proposed reaction scheme. The activation energy of the reaction of propylene oxide with phenol and guaiacol, calculated with the Arrhenius equation, was 56.2 kJ mol-1 and 45.4 kJ mol-1, respectively.

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Gas-phase oxidation of butene-2

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1958.0045 ◽

1958 ◽

Vol 244 (1238) ◽

pp. 331-344 ◽

Cited By ~ 6

Keyword(s):

Gas Phase ◽

Pressure Change ◽

Reaction Products ◽

Peroxide Formation ◽

Time Curve ◽

Pressure Time ◽

Initial Oxygen ◽

Gas Phase Oxidation ◽

Reactive Radicals ◽

Reaction Processes

The gas-phase thermal oxidation of butene-2 has been examined over the temperature range 289 to 395°C. No difference in behaviour of the cis and trans forms could be detected. At the higher temperatures the reaction resembled that of the oxidation of propylene in the shape of the pressure-time curve and in the identity of many of the reaction products. At the lower temperatures a decrease in pressure partly due to peroxide formation followed the induction period, and by the end of this time much of the initial oxygen had been consumed. At all temperatures excess olefin produced an apparent inhibiting effect manifested by a decreased yield of carbon monoxide and a fall-off in the maximum rate of pressure change and total pressure change. Reaction processes are discussed, and it is suggested that a peroxide precedes the formation of acetaldehyde. Branching occurs largely through reaction of acetyl radicals produced from the acetaldehyde. The inhibiting effects produced by excess olefin are attributed to the replacement of reactive radicals by the less reactive allylic-type radicals, and the addition reactions of olefin at higher olefin concentrations lead to polymerization and a low or negative overall pressure change.

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Influence of misalignments on the performance of externally occulted solar coronagraphs

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732386 ◽

2018 ◽

Vol 612 ◽

pp. A82 ◽

Cited By ~ 6

Author(s):

S. V. Shestov ◽

A. N. Zhukov

Keyword(s):

European Space Agency ◽

Numerical Approach ◽

Primary Objective ◽

Optical Elements ◽

Trade Off ◽

Space Agency ◽

Minimal Height ◽

Different Types ◽

Points Of View ◽

Quantitative Influence

Context. The ASPIICS instrument is a novel externally occulted coronagraph that will be launched on board the PROBA-3 mission of the European Space Agency. The external occulter will be placed on one satellite ~150 m ahead of the second satellite that will carry an optical instrument. During 6 h out of 19.38 h of orbit, the satellites will fly in a precise (accuracy around a few millimeters) formation, constituting a giant externally occulted coronagraph. The large distance between the external occulter and the primary objective will allow observations of the white-light solar corona starting from extremely low heights ~ 1.1R⊙. Aims. We intend to analyze influence of shifts of the satellites and misalignments of optical elements on the ASPIICS performance in terms of diffracted light. Based on the quantitative influence of misalignments on diffracted light, we provide a recipe for choosing the size of the internal occulter (IO) to achieve a trade-off between the minimal height of observations and sustainability to possible misalignments. Methods. We considered different types of misalignments and analyzed their influence from optical and computational points of view. We implemented a numerical model of the diffracted light and its propagation through the optical system and computed intensities of diffracted light throughout the instrument. Our numerical approach is based on a model from the literature that considered the axisymmetrical case. Here we extend the model to include nonsymmetrical cases and possible misalignments. Results. The numerical computations fully confirm the main properties of the diffracted light that we obtained from semi-analytical consideration. We obtain that relative influences of various misalignments are significantly different. We show that the internal occulter with RIO = 1.694 mm = 1.1R⊙ is large enough to compensate possible misalignments expected to occur in PROBA-3/ASPIICS. Besides that we show that apodizing the edge of the internal occulter leads to additional suppression of the diffracted light. Conclusions. We conclude that the most important misalignment is the tilt of the telescope with respect to the line connecting the center of the external occulter and the entrance aperture. Special care should be taken to co-align the external occulter and the coronagraph, which means co-aligning the diffraction fringe from the external occulter and the internal occulter. We suggest that the best orientation strategy is to point the coronagraph to the center of the external occulter.

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Chemical Incident Analysis Involving Storage of Fertilizer Product

Journal of the National Academy of Forensic Engineers ◽

10.51501/jotnafe.v38i1.104 ◽

2021 ◽

Vol 38 (1) ◽

Author(s):

Rogerio De Medeiros Tocantins ◽

Bettina Tomio Heckert ◽

Rafael Salum de Oliveira ◽

Hélio João Coelho ◽

Gisele Chibinski Parabocz ◽

...

Keyword(s):

Chemical Reaction ◽

Water Bodies ◽

Reaction Products ◽

Future Studies ◽

Adjacent Water ◽

Forensic Engineering ◽

Fertilizer Material ◽

The City ◽

Incident Analysis

A forensic engineering analyses of a chemical incident is presented that was classified as a self-sustaining decomposition (SSD) event, which occurred in a load of 10,000 tons of NK 21-00-21 fertilizer bulk stored inside a warehouse in the city of São Francisco do Sul in Brazil. The chemical reaction developed within the fertilizer mass and took several days to be controlled, resulting in the evacuation of thousands of residents. The water used to fight against the reaction, after having contact with the load of fertilizer material, promoted changes in adjacent water bodies, causing the death of animals (fish, crustaceans, and amphibians). The smoke from the chemical reaction products damaged the incident’s surrounding vegetation. Large SSD events are rare, with an average worldwide frequency of one every three years. Therefore, in addition to presenting a case study of this type of phenomenon, the main objective of this work is to discuss the causes that led to SSD reaction at this event, evaluate its consequences, and motivate future studies.

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