Calculation Of Kinetic Parameters Research Articles

Study on the factors influencing the thermal runaway hazards of styrene-acrylonitrile bulk copolymerization

The styrene-acrylonitrile bulk copolymerization reaction has a high risk of thermal runaway, but the factors influencing the thermal hazards of the reaction have not been adequately investigated. In this paper, the effects of different factors on the thermal runaway behavior of the styrene-acrylonitrile copolymerization are investigated using a combination of simulation and calorimetric testing. The simulation results indicate that increasing the proportion of styrene in the monomer feed significantly delays the onset of thermal runaway. The calorimetric results show that for di-tert-butyl peroxide (DTBP), azodiisobutyronitrile (AIBN) and tert-butyl peroxy benzoate (TBPB) initiators as examples, the TBPB-initiated copolymerization is found to have the maximum temperature-rising rate and pressure-rising rate. Under adiabatic runaway, the temperature and pressure change significantly with increasing TBPB concentration, indicating a great potential risk of thermal runaway. Calculation of kinetic parameters based on calorimetric data reveals thermal runaway mechanism.

DEVELOPMENT OF AN ALGORITHM FOR CALCULATING THE RATE CONSTANT OF HYDROCHLORIC ACID REACTION WITH A CARBONATE ROCK FORMATION

One of the main factors reducing acid stimulation efficiency is the intensive reaction of active acid in the immediate vicinity of the wellbore, which leads to insufficient completeness of reservoir rock dissolution in the remote reservoir zone. The reservoir hydrodynamic characteristics are not being improved properly, and the efficiency of oil production stimulation measures does not reach the planned values.To get high results of acid treatments it is necessary to achieve deep penetration of acid into the formation thickness. The reaction rate constant is used to compare the reactivity of different acid compositions and to select the most suitable acid composition for the geological and physical conditions of the treated object, which provides the highest treatment efficiency. It relates the initial substances concentrations with reaction products formation rate. To determine the reaction rate constant, a volumetric apparatus was created and methodological aspects were developed to work on it, allowing to minimize the measurement error and to achieve the greatest accuracy in determining the kinetic parameters of the reaction. But in the course of further investigations in the work of the existing algorithm for experimental data processing, a number of significant deficiencies distorting the results of calculations were revealed. The aim of the research is to develop a new improved algorithm for reaction rate constant calculation, which will improve the understanding of the process of determining the kinetic parameters of acid reaction with carbonate rock.To achieve this aim, the authors conducted a series of experiments according to the unified methodology, the results of which revealed ways to eliminate the identified deficiencies using a new algorithm. It includes obtaining and saving initial data, subsequent treatment and direct calculation of reaction kinetic parameters with results saving.The developed algorithm makes it possible to unify and automate the process of determining the kinetic parameters of the acid reaction with the formation rock, as well as to determine the reaction characteristics with higher accuracy and reduce the influence of the human factor on the research results, thus reducing the errors of the calculation results.

Coupling kinetic modeling with artificial neural networks to predict the kinetic parameters of pine needle pyrolysis

The pyrolysis behavior of biomass is critical for industrial process design, yet the complexity of pyrolysis models makes this task challenging. This paper introduces an innovative hybrid model to quantify the pyrolysis potential of pine needles, predicting the entire process of their pyrolysis behavior. Through experimental analyses and kinetic parameter calculations of pine needle pyrolysis, the study employs a kinetic model with a chemical reaction mechanism. Additionally, it introduces an improved dung beetle optimization algorithm to accurately capture the primary trends in pine needle pyrolysis. The developed artificial neural network model incorporates meta-heuristic algorithms to address process error factors. Validation is based on experimental data from TG at three different heating rates. The results demonstrate that the hybrid model exhibits strong predictive performance compared to the standalone model, with coefficients of determination (R²) of 0.9999 and 0.999 for predicting the conversion degree and conversion rate of untrained data, respectively. Additionally, the standard errors of prediction (SEP) are 0.249% and 0.449% for predicting the conversion degree and conversion rate of untrained data, respectively.

Металлотермиялық тәсілмен орта көміртекті ферромарганецті балқыту процестерінің термиялық қасиеттерін зерттеу

The purpose of this work is to study the phase transformations occurring in the charge mixture during the smelting of medium-carbon ferromanganese. The study of phase transformations occurring in the charge mixture was carried out on a device for synchronous thermal analysis Labsys Evolution TG-DTA/DSC from Setaram in dynamic mode in the tem perature range of 30-1500°С. Derivatograms were obtained for two variants of the charge mixture (Option I – manganese ore, lime, silicomanganese FeSiMn17; Option II – manganese ore, lime, converted silicomanganese) in an inert atmosphere of nitrogen. Calculation of kinet ic parameters – activation energy of endo-exothermic effects occurring at different tempera tures was made. The values of the apparent activation energy determined by the tangent of the slope angle are given.

UCST-Type Soluble Immobilized Cellulase: A New Strategy for the Efficient Degradation and Improved Recycling Performance of Wastepaper Cellulose.

This paper reports an innovative study that aims to address key issues in the efficient recycling of wastepaper cellulose. The research team utilized the temperature-responsive upper critical solution temperature (UCST) polymer P(NAGA-b-DMA) in combination with the LytA label's affinity for choline analogs. This innovative approach enabled them to successfully develop a novel soluble immobilized enzyme, P(NAGA-b-DMA)-cellulase. This new enzyme has proven highly effective, significantly enhancing the degradation of wastepaper cellulose while demonstrating exceptional stability. Compared with the traditional insoluble immobilized cellulase, the enzyme showed a significant improvement in the pH, temperature stability, recycling ability, and storage stability. A kinetic parameter calculation showed that the enzymatic effectiveness of the soluble immobilized enzyme was much better than that of the traditional insoluble immobilized cellulase. After the immobilization reaction, the Michaelis constant of the immobilized enzyme was only increased by 11.5%. In the actual wastepaper degradation experiment, the immobilized enzyme was effectively used, and it was found that the degradation efficiency of wastepaper cellulose reached 80% of that observed in laboratory conditions. This novel, thermosensitive soluble immobilized cellulase can efficiently catalyze the conversion of wastepaper cellulose into glucose under suitable conditions, so as to further ferment into environmentally friendly biofuel ethanol, which provides a solution to solve the shortage of raw materials and environmental protection problems in the paper products industry.

Evaluation of Kinetic Parameters RSG-GAS Reactor Equilibrium Silicide Core Using Continuous-Energy Monte Carlo Serpent 2 Code

The purpose of this study is to determine the kinetic parameters of the RSG-GAS equilibrium core. The calculated kinetic parameters are the effective delayed neutron fraction βeff, the neutron generation time Ʌ, and the prompt neutron lifetime ℓ since they are related to the safety of nuclear operations. The kinetic parameters were calculated using the Serpent 2 code with the ENDF/B-VII.1 and ENDF/B-VIII.0 nuclear data libraries. Calculations were performed using various adjoint-weighted methods such as Meulekamp’s method, Nauchi’s method, the Iterated Fission Probability method, and the Perturbation Technique. The calculated results of the six-group delayed neutron fraction by the Meulekamp and the IFP methods showed no significant difference. Choosing the IFP method as the reference, the maximum difference for βeff (694 pcm) is 0.73%, and the maximum difference for Ʌ and ℓ is 1.89%. The calculated kinetic parameters with ENDF/B-VII.1 and ENDF/B-VIII.0 are quite close, with a maximum difference of 0.9%. The sensitivity analysis results indicate several nuclides and reaction types that dominantly affect the βeff and Λ. The results of the kinetic parameter calculations can be used for the safety analysis of the RSG-GAS equilibrium core.

Theoretical insight of reactive oxygen species scavenging mechanism in lignin waste depolymerization products.

Apart from natural products and synthesis, phenolic compounds can be produced from the depolymerization of lignin, a major waste in biofuel and paper production. This process yields a plethora of aryl propanoid phenolic derivatives with broad biological activities, especially antioxidant properties. Due to its versatility, our study focuses on investigating the antioxidant mechanisms of several phenolic compounds obtained from renewable and abundant resources, namely, syringol (Hs), 4-allylsyringol (HAs), 4-propenylsyringol (HPns), and 4-propylsyringol (HPs). Employing the density functional theory (DFT) approach in conjunction with the QM-ORSA protocol, we aim to explore the reactivity of these compounds in neutralizing hydroperoxyl radicals in physiological and non-polar media. Kinetic and thermodynamic parameter calculations on the antioxidant activity of these compounds were also included in this study. Additionally, our research utilizes the activation strain model (ASM) for the first time to explain the reactivity of the HT and RAF mechanisms in the peroxyl radical scavenging process. It is predicted that HPs has the best rate constant in both media (1.13 × 108 M-1 s-1 and 1.75 × 108 M-1 s-1, respectively). Through ASM analysis, it is observed that the increase in the interaction energy due to the formation of intermolecular hydrogen bonds during the reaction is an important feature for accelerating the hydrogen transfer process. Furthermore, by examining the physicochemical and toxicity parameters, only Hs is not suitable for further investigation as a therapeutic agent because of potential toxicity and mutagenicity. However, overall, all compounds are considered potent HOO˙ scavengers in lipid-rich environments compared to previously studied antioxidants.

Can Re cluster complexes be an efficient catalyst for hydrogen evolution reaction? Insights from experiments and computations.

To date, researchers in chase of economic cost-efficiency are faced with the problem of developing effective catalysts for water splitting without the use of platinoids. Herein, catalytic properties of hexanuclear rhenium cluster complexes are investigated in application to the hydrogen evolution reaction (HER). A paste composite electrode containing the cluster complexes was obtained, producing a current density of 10 mA cm-2 at an extraordinarily low overpotential of 90 mV (RHE). The {Re6Se8}-based complexes have shown very favorable reaction kinetics via 102 mV dec-1 value of the Tafel slope for HER reaction within the composition of the paste electrode. Model calculations of kinetic parameters using density functional theory also support the experimental findings. This work underscores the perspectivity of rhenium cluster compounds in HER and opens a promising avenue toward the practical implementation of hydrogen production through electrochemical water splitting.

CD8α-CI-M6PR Particle Motility Assay to Study the Retrograde Motion of CI-M6PR Receptors in Cultured Living Cells.

The cation-independent mannose 6-phosphate receptors (CI-M6PR) bind newly synthesized mannose 6-phosphate (Man-6-P)-tagged enzymes in the Golgi and transport them to late endosomes/lysosomes, providing them with degradative functions. Following the cargo delivery, empty receptors are recycled via early/recycling endosomes back to the trans-Golgi network (TGN) retrogradely in a dynein-dependent motion. One of the most widely used methods for studying the retrograde trafficking of CI-M6PR involves employing the CD8α-CI-M6PR chimera. This chimera, comprising a CD8 ectodomain fused with the cytoplasmic tail of the CI-M6PR receptor, allows for labeling at the plasma membrane, followed by trafficking only in a retrograde direction. Previous studies utilizing the CD8α-CI-M6PR chimera have focused mainly on colocalization studies with various endocytic markers under steady-state conditions. This protocol extends the application of the CD8α-CI-M6PR chimera to live cell imaging, followed by a quantitative analysis of its motion towards the Golgi. Additionally, we present an approach to quantify parameters such as speed and track lengths associated with the motility of CD8α-CI-M6PR endosomes using the Fiji plugin TrackMate. Key features • This assay is adapted from the methodology by Prof. Matthew Seaman for studying the retrograde trafficking of CI-M6PR by expressing CD8α-CI-M6PR chimera in HeLa cells. • The experiments include live-cell imaging of surface-labeled CD8α-CI-M6PR molecules, followed by a chase in cells. • Allows the monitoring of real-time motion of CD8α-CI-M6PR endosomes and facilitates calculation of kinetic parameters associated with endosome trajectories, e.g., speed and distance (run lengths).

Higher precision in initial rates may be achievable: A test of a pseudo-statistical method

There has been a concerted effort at establishing the best method for the measurement of initial rates for various purposes, including the calculation of kinetic parameters, the maximum velocity (Vmax), and the Michaelis-Menten constant (KM). The objectives of this research are: 1) to derive equations without KM for the determination of the Vmax in particular and vice versa; 2) to determine the KM and Vmax with other equations other than the Michaelian equation; and 3) to subject the calculated and extrapolated kinetic parameters to pseudo-statistical remediation where necessary as a test of their viability and usefulness. The study was experimental and theoretical. It is supported by the Bernfeld method of enzyme assay. By graphical means, the Vmax and KM values for galactosidase respectively range between 163 and 185 mM/min and between 2.07 and 2.77 mg/L; the range by calculations is 177 and 214 mM/min and 2.45 and 3.311 mg/L, subject to pseudo-statistical remediation. Overall, the ranges of Vmax and KM values for alpha-amylase from both the graphical method and calculation are, respectively, 1.095 to 1.018 mM/min and 18.15 to 20.554 g/L. The equations for the determination of the KM and Vmax, which are respectively invariant with respect to each other, were rederived. The initial rates must not be characterised by a mixture of conditions that validate different quasi-steady-state assumptions if the true KM and Vmax are of interest. The new pseudo-statistical method for the remediation of error in all measurements, if necessary, is viable, useful, and robust.

Kinetic compensation effects of non-isothermal gasification in the diffusion control region

The aim of this study is to investigate the kinetic compensation effect during the non-isothermal gasification of coffee char and lignite char in a CO2 environment. The non-isothermal gasification experiments were carried out using a thermogravimetric analyzer in the temperature range of 321 K–1273 K. The activation energies (E) and pre-exponential factors (A0) of different diffusion control zones were determined, and the relationship between kinetic compensation effects and diffusion was investigated. This study shows that different kinetic parameter calculation methods have no influence on the kinetic compensation effect; intrinsic reaction or external diffusion has a very weak kinetic compensation effect, and only bed diffusion has a more obvious kinetic compensation effect. The kinetic compensation effect shows a dependence on bed diffusion.

CALCULATION OF THERMODYNAMIC AND KINETIC PARAMETERS OF CATALYTIC CRACKING REACTIONS ON LEWIS AND BRØNSTED ACID SITES

Link for citation: Nazarova G.Y., Ivashkina E.N., Maltsev V.V. Calculation of thermodynamic and kinetic parameters of catalytic cracking reactions on Lewis and Brønsted acid sites. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 7, рр. 214-225. In Rus. The relevance of the research is caused by the emerging necessity of developing a mathematical model to optimize the heterogeneous process of catalytic cracking. This tools should take into account both the chemical transformations of a wide range of hydrocarbon groups (different feedstock types), as well as the stages of adsorption, reactants diffusion, conversion of hydrocarbons on the catalyst surface, acid characteristics and pore size of the catalysts. The study of the hydrocarbon conversion patterns on Lewis or Brønsted acid sites using quantum-chemical modeling methods allow us to quantify the thermodynamic parameters of reactants adsorption, the kinetic parameters of carbocations formation and cracking on acid sites. These results are necessary to develop a mathematical model based on the of heterogeneous catalytic reaction mechanism. The aim of this work is to identify the level of quantum chemical theory and to determine the thermodynamic and kinetic parameters of reactants adsorption, carbenium ions formationand hydrocarbons cracking on Lewis and Brønsted acid sites. Methods: quantum-chemical modeling methods to optimize the molecular geometry of reactants and products of catalytic cracking reactions, calculate vibrational frequencies, thermodynamic parameters of adsorption and catalytic cracking of hydrocarbons and heteroatomic compounds with the participation of Bronsted and Lewis acid sites. Results. The chosen level of quantum-chemical theory allowed obtaining the results that are consistent with the laws of the process and the experimental reactivity of hydrocarbons in cracking reactions on acid catalysts. The thermodynamic parameters of the adsorption of C6–C16 hydrocarbons and thiophenes on Lewis and Brønsted acid sites were identified. We found that during the cracking of n-hexane on the Lewis acid site, the reaction is limited by the carbenium ion formation stage.The activation energy of this stage was 281,3 kJ/mol whereas the value for the cracking stage was 277,2 kJ/mol. Further study shows that the activation energy of carbenium ion formation from izohexane and C8–C10 alkanes with normal structure on the Lewis acid site was 257,6 and 279,2…277,9 kJ/mol. The most energetically favorable is the formation of carbocation from hexene at Brønsted acid sites (76,59 kJ/mol). The results of the work will be used to create a mathematical model of a heterogeneous process based on the Langmuir–Hinshelwood equations.

Assessment of thermokinetic behaviour of tannery sludge in slow pyrolysis process through artificial neural network

In the leather industry, tannery sludge is produced in large volume. This study investigated the thermal degradation behavior of tannery sludge using thermogravimetric analysis (TGA). The experiments were carried out in an inert atmosphere using nitrogen gas at varied heating rates of 5, 10, 20, and 40 °C/min in the temperature range of 30–900 °C. For the kinetic parameters calculation, three different models, Friedman, Kissinger-Akahira-Sunose (KAS) and the Ozawa-Flynn-Wall (OFW), were employed. The average activation energy (Ea) obtained from Friedman, KAS, and the OFW methods were 130.9 kJ mol−1, 143.14 kJ mol−1, and 147.19 kJ mol−1 respectively. Along with that, experiment of pyrolysis was accomplished in fixed bed reactor (FBR) at temperature of 400 °C. Biochar produced from FBR had a yield of about 71%. The analysis of gas chromatography-mass spectroscopy shows the different chemical compounds present in the bio-oil containing hydrocarbons (alkanes and alkenes), oxygen containing compounds (alcohols, aldehyde, ketones, esters carboxylic acids and the esters) and the nitrogen containing compounds. The kinetic assessment was complemented by distributed activation energy model (DAEM). In the pyrolysis of tannery sludge six pseudo-components were found to be involved. Furthermore, artificial neural network (ANN) was used to predict the activation energy from conversion, temperature, and the heating rate data. MLP-3-11-1 (Multilayer Perceptrons) described well the conversion behavior of tannery sludge pyrolysis.

Mechanism and kinetics of CBDA decarboxylation into CBD in hemp

Cannabidiol (CBD) is a pharmacologically active ingredient for use in medical, cosmetic, and food products. CBD forms from cannabidiolic acid (CBDA) with the process of decarboxylation by heating cannabis (Cannabis sativa L.) material. During the production of CBD-rich material, decarboxylation should be performed in precise conditions regarding temperature and time. The experiments were performed by heating hemp samples at 100, 110, 120, 130, and 140 °C for 180 min. Materials were sampled every 20 min and cannabinoid content was analyzed using HPLC, followed by calculation of kinetic parameters. Experimental results showed an exponential reduction of CBDA in the samples during heating. CBD simultaneously increased, and after a specific point, CBD started degrading. The optimal conditions were 140 °C for 30 min. At the level of molecular orbitals, reaction steps, and reaction coordinates, along with the corresponding changes in molecular energy, the molecular mechanism of CBDA decarboxylation and CBD formation was described. Computational analysis has confirmed that the mechanism of CBDA decarboxylation is a direct beta-keto acid pathway. The course of CBDA decarboxylation depends on the time, temperature, and chemical composition of the sample.

A power-modulated accelerating rate calorimetry for varying heat capacity measurement during thermal decomposition

Due to the lack of the methodology of measuring the varying specific heat capacity during the adiabatic reaction, in almost all the existing kinetic approaches for accelerating rate calorimetric data process, the specific heat capacity of the sample is considered as constant. This leads to errors in thermodynamic and kinetic parameters calculation. To overcome this shortcoming, a power-modulated accelerating rate calorimetry for varying heat capacity measurement is proposed and instrumented in this article. And the corresponding kinetics approach is presented with the varying heat capacity consideration. With the suppositional varying heat capacity setting, the validities of the proposed methodology are verified through numerical simulations. With the low mass percent di‑tert‑butyl peroxide/toluene solutions experiments, the feasibility of the developed calorimeter for varying heat capacity measurement is tested, preliminarily. In addition, the deficiencies at the present stage and improvements of this instrument are analyzed and discussed at the end of the article.

Influence of substrate concentration on kinetic parameters of alkaline phosphatase enzyme

A laboratory study was conducted in the laboratory of the Department of Soil Science and Water Resources in Agriculture and Forestry College and in the Faculty of Environment laboratory with the aim of showing the effect of temperature on the activity and effectiveness of the phosphatase enzyme and the calculation of kinetic and thermodynamic parameters (maximum velocity Vmax and concentration of the subject substance Km) and for the sake of So, it was soil chosen from Zawita forest, with sandy clay loam texture under the cover of pine trees. The soil was treated with different concentrations of Substrate subject to the enzyme (0.0125, 0.025, 0.05, 0.075, 0.1) molar and under the influence of different temperatures (10,20,30,40,50) Cᵒ.The results showed. A clear effect of the subject substance on the activity of the enzyme, as the enzyme effectiveness increased with the increase of the added concentrations of the substance. The highest efficacy value for alkaline enzyme phosphatase was V / [S] (0.6) µg P-nitrophenol gm-1. Hr-1, which resulted from the effect of concentration (100) mmol of the subject substance. While the lowest alkaline phosphatase enzyme effectiveness value V / [S] was (0.2) µg P-nitrophenol gm-1. Hr-1, which resulted from the effect of the lowest concentration of the subject substance (12.5) mmol. The results indicated thatV max value of amounted to (227.27) µg P-nitrophenol gm-1. Hr -1. while the value of Km amounted to (38.52) mmuler. The results showed an increase in enzyme phosphatase activity by increasing the incubation temperature at concentration (0.05) molar of the substrate, the highest value of the activity of the enzyme phosphatase reached V (155.47) mg P-nitrophenol gm -1 hr -1, which occurred from soil incubation at The highest temperature used in the study is (50) Cᵒ, as it was observed that the values of phosphatase enzyme effectiveness continued to increase until the highest temperature used in the study.
 

Influence of DSC Thermogram Processing Methods on the Results of Calculation of Kinetic Parameters of the Curing Reaction of a Thermoreactive Binder

Influence of DSC Thermogram Processing Methods on the Results of Calculation of Kinetic Parameters of the Curing Reaction of a Thermoreactive Binder

Production of Bio-Oil from Thermo-Catalytic Decomposition of Pomegranate Peels over a Sulfonated Tea Waste Heterogeneous Catalyst: A Kinetic Investigation

In this study, the pyrolysis procedure was used to extract oil from pomegranate peels (PP) utilizing biomass-derived sulfonated tea waste as a catalyst. FTIR, SAA, SEM, and XRD were used to characterize the catalyst. Thermo-catalytic decomposition was carried out in a salt bath reactor and the bio-oil composition was determined through GC-MS. The oil obtained from virgin PP was observed to contain compounds in the range of C5–C13, whereas from the catalyzed reaction it was found to be rich in C5–C23. For the calculation of kinetic parameters, TG analysis was performed of virgin PP and with the catalyst at different heating rates. TG/DTG indicated weight loss in four steps. The first weight loss below 100 °C is due to the physically adsorbed water molecule evaporation. The second weight loss is attributed to hemicellulose decomposition and the third one to cellulose degradation. The fourth weight loss is due to lignin degradation. Kissinger model was used for measuring the activation energy (Ea) of the decomposition reaction. The activation energy of hemicellulose, cellulose, and lignin for non-catalytic reactions was observed as 199, 249, and 299 kJmol−1, while in the case of the loaded tea waste catalyst, the Ea was reduced to 122, 163, and 207 kJmol−1, respectively, confirming the effectiveness of the catalyst. From these findings, it can be concluded that sulfonated tea waste catalyst has not only lowered the pyrolysis temperature and Ea but also brought a change in oil quality by enhancing value-added compounds in the bio-oil.

Development of a kinetic model of magnetite leaching

The object of the research is the process of magnetite leaching with nitric acid solutions, and the subject of the research is the mathematical justification of the kinetic model and the calculation of kinetic parameters. The article considers the case of leaching in the kinetic region, while magnetite is considered as a polydispersity material of spherical shape. It is proposed to use the distribution function of the number of particles N by their radius r in the form N=a∙rb, where a and b are constants. This distribution was used to derive the equation for the rate of the process W, taking into account the change in the surface of the particles depending on the degree of leaching α: W=dα/dτ=K*∙(1–α)m∙((С0(γ–α)/γ))n, where K* is the rate constant; m and n are the order of solid material and nitric acid, respectively; C0 and γ are the initial concentration of nitric acid and its stoichiometric excess. The order m is defined as m=(b+2)/(b+3), at b→∞ the order m→1. When b=0, m=2/3 is the case of the equation for a shrinking sphere. An algorithm for calculating kinetic parameters in the Excel is proposed. Experimental dependences of the degree of transformation α on time τ are approximated by a third-order equation; by differentiating the obtained equation, the values of the velocity Wexp=dα/dτ at individual points are calculated. After the logarithm of the above equation, there is the expression (γ=1): ln(Wexp)=ln(K*)+m∙ln(1–α)+n∙ln(С0(1–α)). With the help of the «LINEST» function in Excel, for a temperature of 373 K, the values of the order of m=0.93 and n=1.29 and the rate constant K*=0.08 were obtained. Calculation of kinetic parameters for different temperatures takes into account the dependence of the rate constant on temperature: ln(Wexp)=lnk0–E/R∙1/T+m∙ln(1–α)+n∙ln(C0(1–α)). As a result of the calculations, the values n=0.83; m=1.2; E/R=–10402; lnk0=25.09 were obtained. The value of the multiplier k0=exp(lnk0)=7.88∙1010, the activation energy E=–8.31∙E/R=86440 J/mol, the total reaction order n+m=2.03 was calculated. The obtained kinetic parameters were used to determine the calculated values of the rate W. The average relative error between the experimental and calculated values of the leaching rates is 10 %. The proposed method of processing experimental data using a mathematical leaching model can be used for any leaching process.

Synergistic effect of sulfonated castor oil and porous medium on kinetics of gas hydrates formation

In recent years, interest in gas hydrates has increased as they represent a potential energy source and an alternative to the current environmentally friendly method of storing and transporting natural gas. In this study, the synergistic effect of a new promoting reagent – sulfonated castor oil (SCO) – and a porous medium on the formation and decomposition of methane and methane-propane hydrates was compared to that of sodium dodecyl sulfate (SDS) using the high-pressure differential scanning calorimetry (HP-μDSC) method. DSC tests demonstrated that water conversion in the presence of SCO in a porous substrate for methane hydrates reached 95% at high water saturation, which can be attributed to improved mass transfer in the presence of surfactants. However, this value did not exceed 60% for the hydrate of methane–propane mixture, indicating that the mechanism of promotion of the sI and sII hydrates differs. According to kinetic calculations based on the Avrami equation, both SDS and SCO accelerate the formation of hydrates, but for SCO, this is possible with less supercooling. The calorimetric measurements and kinetic parameter calculations demonstrated that SCO is comparable to the well-known reagent SDS in promoting activity in porous media with varying water saturation.