Christian Devereux, Yoona Yang, Carles Martí, Judit Zádor, Michael S. Eldred, Habib N. Najm
Machine learned chemical potentials have shown great promise as alternatives to conventional computational chemistry methods to represent the potential energy of a given atomic or molecular system as a function of its geometry. However, such potentials are only as good as the data they are trained on, and building a comprehensive training set can be a costly process. Therefore, it is important to extract as much information from training data as possible without further increasing the computational cost. One way to accomplish this is by training on molecular forces in addition to energies. This allows for three additional labels per atom within the molecule. Here we develop a neural network potential energy surface for studying a hydrogen transfer reaction between two isomers of . We show that, for a much smaller training set, force training not only improves the accuracy of the model compared to only training on energies, but also provides more accurate and smoother first and second derivatives that are crucial to run dynamics and extract vibrational frequencies in the context of transition‐state theory. We also demonstrate the importance of choosing the proper force to energy weight ratio for the loss function to minimize the model test error.
{"title":"Force training neural network potential energy surface models","authors":"Christian Devereux, Yoona Yang, Carles Martí, Judit Zádor, Michael S. Eldred, Habib N. Najm","doi":"10.1002/kin.21759","DOIUrl":"https://doi.org/10.1002/kin.21759","url":null,"abstract":"Machine learned chemical potentials have shown great promise as alternatives to conventional computational chemistry methods to represent the potential energy of a given atomic or molecular system as a function of its geometry. However, such potentials are only as good as the data they are trained on, and building a comprehensive training set can be a costly process. Therefore, it is important to extract as much information from training data as possible without further increasing the computational cost. One way to accomplish this is by training on molecular forces in addition to energies. This allows for three additional labels per atom within the molecule. Here we develop a neural network potential energy surface for studying a hydrogen transfer reaction between two isomers of . We show that, for a much smaller training set, force training not only improves the accuracy of the model compared to only training on energies, but also provides more accurate and smoother first and second derivatives that are crucial to run dynamics and extract vibrational frequencies in the context of transition‐state theory. We also demonstrate the importance of choosing the proper force to energy weight ratio for the loss function to minimize the model test error.","PeriodicalId":13894,"journal":{"name":"International Journal of Chemical Kinetics","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142202387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study combines experimental and theoretical explorations. The corrosion inhibition performance of different concentrations (50, 100, 250, and 500 ppm) of folic acid in 3.5 wt% NaCl solution on Q235 steel was tested by weight loss and electrochemical test. The corrosion inhibition efficiency increased with the gradual increase of folic acid concentration and reached a maximum of 87% at 500 ppm folic acid. The experimental results for electrochemistry and weight loss are in good agreement with the simulation calculations. The adsorption of folic acid on the steel surface obeyed the Langmuir isotherm, and the adsorption process was a combination of chemisorption and physisorption. The contact angle test also yielded the maximum increase in hydrophobicity of the specimen surface at the added folic acid concentration of 500 ppm. The corrosion morphology after the addition of corrosion inhibitor was relatively flat. The adsorption orientation of folic acid molecules on the steel surface in an aqueous environment was investigated using density functional theory (DFT)/molecular dynamics (MD) simulations. The microscopic mechanism of action of folic acid corrosion inhibitors is clarified.
{"title":"Folic acid as a green inhibitor for corrosion protection of Q235 carbon steel in 3.5 wt% NaCl solution","authors":"Peng Han, Zebang Liu, Zhichao Ren, Yue Li, Zhenwei Sun, Chenyang Xu","doi":"10.1002/kin.21758","DOIUrl":"https://doi.org/10.1002/kin.21758","url":null,"abstract":"This study combines experimental and theoretical explorations. The corrosion inhibition performance of different concentrations (50, 100, 250, and 500 ppm) of folic acid in 3.5 wt% NaCl solution on Q235 steel was tested by weight loss and electrochemical test. The corrosion inhibition efficiency increased with the gradual increase of folic acid concentration and reached a maximum of 87% at 500 ppm folic acid. The experimental results for electrochemistry and weight loss are in good agreement with the simulation calculations. The adsorption of folic acid on the steel surface obeyed the Langmuir isotherm, and the adsorption process was a combination of chemisorption and physisorption. The contact angle test also yielded the maximum increase in hydrophobicity of the specimen surface at the added folic acid concentration of 500 ppm. The corrosion morphology after the addition of corrosion inhibitor was relatively flat. The adsorption orientation of folic acid molecules on the steel surface in an aqueous environment was investigated using density functional theory (DFT)/molecular dynamics (MD) simulations. The microscopic mechanism of action of folic acid corrosion inhibitors is clarified.","PeriodicalId":13894,"journal":{"name":"International Journal of Chemical Kinetics","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141871282","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Remembrance of Prof Dr Horst Hippler","authors":"Hartmut Herrmann, Craig Taatjes, Jeff Manion","doi":"10.1002/kin.21748","DOIUrl":"https://doi.org/10.1002/kin.21748","url":null,"abstract":"","PeriodicalId":13894,"journal":{"name":"International Journal of Chemical Kinetics","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141740416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the current report, both response surface methodology (RSM) and artificial neural network (ANN) were employed to develop an innovative way for removing crystal violet (CV) from aqueous media using Haloxylon salicornicum (HS) as a cost‐effective, eco‐friendly adsorbent. HS was characterized using scanning electron microscopy (SEM) and Fourier‐transform infrared (FTIR) spectroscopy. The effects of operational parameters such as adsorbent dosage, initial dye concentration, and pH on HS were studied using a central composite design (CCD). A comparative analysis of the model findings and experimental measurements revealed high correlation coefficients (R2ANN = 0.994, R2RSM = 0.971), indicating both models accurately predicted HS. The predictive performance of the ANN and RSM models was evaluated using metrics such as mean absolute deviation (MAD), mean absolute percentage error (MAPE), root mean square error (RMSE), mean square error (MSE), and the correlation coefficient (R2). The results indicate that the ANN model provides greater accuracy compared to the RSM model. The experimental data were analyzed using both linear and nonlinear forms of pseudo‐first and pseudo‐second order kinetic models (LPFO, NLPFO, LPSO, and NLPSO). Statistical error analysis was conducted to identify the best‐fitting kinetic or isotherm models for the adsorption data. The adsorption process of CV/HS was best described by NLPSO and LPSO. Additionally, the adsorption isotherms were analyzed using linear and nonlinear regression methods. The findings indicated that the linear Langmuir and Freundlich isotherms provided a more accurate fit compared to the nonlinear models, demonstrating greater effectiveness in accounting for the adsorption parameters. Thermodynamic investigations clearly demonstrate that the biosorption of CV is spontaneous and exothermic. This cost‐effective adsorbent is highly promising for treating textile wastewater.
{"title":"Remediation of cationic dye from wastewater using a new environmentally friendly adsorbent: A response surface methodology and artificial neural network modeling study","authors":"Samiya Telli, Houria Ghodbane, Aissa Laouissi, Meriem Zamouche, Yassine Kadmi","doi":"10.1002/kin.21756","DOIUrl":"https://doi.org/10.1002/kin.21756","url":null,"abstract":"In the current report, both response surface methodology (RSM) and artificial neural network (ANN) were employed to develop an innovative way for removing crystal violet (CV) from aqueous media using <jats:italic>Haloxylon salicornicum</jats:italic> (HS) as a cost‐effective, eco‐friendly adsorbent. HS was characterized using scanning electron microscopy (SEM) and Fourier‐transform infrared (FTIR) spectroscopy. The effects of operational parameters such as adsorbent dosage, initial dye concentration, and pH on HS were studied using a central composite design (CCD). A comparative analysis of the model findings and experimental measurements revealed high correlation coefficients (R2ANN = 0.994, R2RSM = 0.971), indicating both models accurately predicted HS. The predictive performance of the ANN and RSM models was evaluated using metrics such as mean absolute deviation (MAD), mean absolute percentage error (MAPE), root mean square error (RMSE), mean square error (MSE), and the correlation coefficient (<jats:italic>R</jats:italic><jats:sup>2</jats:sup>). The results indicate that the ANN model provides greater accuracy compared to the RSM model. The experimental data were analyzed using both linear and nonlinear forms of pseudo‐first and pseudo‐second order kinetic models (LPFO, NLPFO, LPSO, and NLPSO). Statistical error analysis was conducted to identify the best‐fitting kinetic or isotherm models for the adsorption data. The adsorption process of CV/HS was best described by NLPSO and LPSO. Additionally, the adsorption isotherms were analyzed using linear and nonlinear regression methods. The findings indicated that the linear Langmuir and Freundlich isotherms provided a more accurate fit compared to the nonlinear models, demonstrating greater effectiveness in accounting for the adsorption parameters. Thermodynamic investigations clearly demonstrate that the biosorption of CV is spontaneous and exothermic. This cost‐effective adsorbent is highly promising for treating textile wastewater.","PeriodicalId":13894,"journal":{"name":"International Journal of Chemical Kinetics","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141610663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the original article published in 2009, Equation (3) after correction was used to determine values of βn; hence, there are no corrections to values of βn in Table V.
{"title":"Erratum to “Rate constants and conversion ratios for aqueous-phase reactions of SO4− with CnF2n+1C(O)O− (n = 4–7) at 298 K”","authors":"Shuzo Kutsuna, Kazuhide Koike, Hisao Hori","doi":"10.1002/kin.21757","DOIUrl":"10.1002/kin.21757","url":null,"abstract":"<p>In the original article published in 2009, Equation (3) after correction was used to determine values of <i>β<sub>n</sub></i>; hence, there are no corrections to values of <i>β<sub>n</sub></i> in Table V.</p><p>We apologize for this error.</p>","PeriodicalId":13894,"journal":{"name":"International Journal of Chemical Kinetics","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/kin.21757","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141588482","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fcc‐TixAl1–xN (TiAlN) coatings synthesized via chemical vapor deposition (CVD) reduce cutting tool wear. Although CVD conditions reportedly influence coating quality, no quantitative guidelines are yet available. To quantitatively study the film‐forming mechanism of TiAlN CVD, the gas composition over the surface must be known. Therefore, we developed a gas‐phase elementary reaction model for TiAlN CVD derived from TiCl4/AlCl3/NH3. First, we constructed a novel thermodynamic dataset including molecules that contained both Ti and Al, and calculated the equilibrium composition. Thermal equilibrium calculations in the gas phase showed that the most stable species were AlCl3 and TiCl3 rather than TiCl4. An elementary reaction model was constructed based on the kinetics of the gas‐phase species that were generated. Kinetic analysis revealed that gas‐phase reactions were largely absent under our reactor conditions. The thermal equilibrium calculations indicated that TiCl4 may have given rise to TiCl3. Thus, other reaction pathways of TiCl4 to TiCl3 were explored. We calculated the reaction rate constants of 12 reactions of Ti species and added them to the model, which revealed that TiCl4 decomposed to TiCl3 via TiCl3NH2. Under our conditions, TiCl4 and TiCl3NH2 are the major Ti species and AlCl3 and AlCl2NH2 are the major Al species, which suggests that some of these species may form films. Unlike in the earlier reaction model, NH2 and H radicals were produced, which may have contributed to the surface reactions. For reactors with large Surface/Volume ratio of reactor, the effects of gas‐phase reactions should be considered. Our reaction model enables estimation of the partial pressures of reactor gas species and will therefore aid study of the TiAlN deposition mechanism.
{"title":"Theoretical study on gas‐phase reactions during chemical vapor deposition of TixAl1–xN from TiCl4, AlCl3, and NH3","authors":"Noboru Sato, Jun Yamaguchi, Masahiro Koto, Hayato Kubo, Takanori Sugiyama, Takahito Tanibuchi, Momoko Deura, Takeshi Momose, Yukihiro Shimogaki","doi":"10.1002/kin.21750","DOIUrl":"https://doi.org/10.1002/kin.21750","url":null,"abstract":"Fcc‐Ti<jats:sub>x</jats:sub>Al<jats:sub>1–x</jats:sub>N (TiAlN) coatings synthesized via chemical vapor deposition (CVD) reduce cutting tool wear. Although CVD conditions reportedly influence coating quality, no quantitative guidelines are yet available. To quantitatively study the film‐forming mechanism of TiAlN CVD, the gas composition over the surface must be known. Therefore, we developed a gas‐phase elementary reaction model for TiAlN CVD derived from TiCl<jats:sub>4</jats:sub>/AlCl<jats:sub>3</jats:sub>/NH<jats:sub>3</jats:sub>. First, we constructed a novel thermodynamic dataset including molecules that contained both Ti and Al, and calculated the equilibrium composition. Thermal equilibrium calculations in the gas phase showed that the most stable species were AlCl<jats:sub>3</jats:sub> and TiCl<jats:sub>3</jats:sub> rather than TiCl<jats:sub>4</jats:sub>. An elementary reaction model was constructed based on the kinetics of the gas‐phase species that were generated. Kinetic analysis revealed that gas‐phase reactions were largely absent under our reactor conditions. The thermal equilibrium calculations indicated that TiCl<jats:sub>4</jats:sub> may have given rise to TiCl<jats:sub>3</jats:sub>. Thus, other reaction pathways of TiCl<jats:sub>4</jats:sub> to TiCl<jats:sub>3</jats:sub> were explored. We calculated the reaction rate constants of 12 reactions of Ti species and added them to the model, which revealed that TiCl<jats:sub>4</jats:sub> decomposed to TiCl<jats:sub>3</jats:sub> via TiCl<jats:sub>3</jats:sub>NH<jats:sub>2</jats:sub>. Under our conditions, TiCl<jats:sub>4</jats:sub> and TiCl<jats:sub>3</jats:sub>NH<jats:sub>2</jats:sub> are the major Ti species and AlCl<jats:sub>3</jats:sub> and AlCl<jats:sub>2</jats:sub>NH<jats:sub>2</jats:sub> are the major Al species, which suggests that some of these species may form films. Unlike in the earlier reaction model, NH<jats:sub>2</jats:sub> and H radicals were produced, which may have contributed to the surface reactions. For reactors with large Surface/Volume ratio of reactor, the effects of gas‐phase reactions should be considered. Our reaction model enables estimation of the partial pressures of reactor gas species and will therefore aid study of the TiAlN deposition mechanism.","PeriodicalId":13894,"journal":{"name":"International Journal of Chemical Kinetics","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141572463","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Matthew S. Johnson, Hao‐Wei Pang, Allen Mark Payne, William H. Green
We present ReactionMechanismSimulator.jl (RMS), a modern differentiable software for the simulation and analysis of chemical kinetic mechanisms, including multiphase systems. RMS has already been applied to problems in combustion, pyrolysis, polymers, pharmaceuticals, catalysis, and electrocatalysis. RMS is written in Julia, making it easy to develop and allowing it to take advantage of Julia's extensive numerical computing ecosystem. In addition to its extensive library of optimized analytic Jacobians, RMS can generate and use Jacobians computed using automatic differentiation and symbolically generated analytic Jacobians. RMS is demonstrated to be faster than Cantera and Chemkin in several benchmarks. RMS also implements an extensive set of features for analyzing chemical mechanisms, including a library of easy‐to‐call plotting functions, molecular structure resolved flux diagram generation, crash analysis, traditional sensitivity analysis, transitory sensitivity analysis, and an automatic mechanism analysis toolkit. RMS implements efficient adjoint and parallel forward sensitivity analyses. We also demonstrate the ease of adding new features to RMS.
我们介绍 ReactionMechanismSimulator.jl (RMS)，这是一款用于模拟和分析化学动力学机制（包括多相系统）的现代可微分软件。RMS 已被应用于解决燃烧、热解、聚合物、制药、催化和电催化等方面的问题。RMS 是用 Julia 编写的，因此易于开发，并能利用 Julia 广泛的数值计算生态系统。除了拥有庞大的优化解析雅各布函数库外，RMS 还能生成和使用通过自动微分和符号生成的解析雅各布函数计算的雅各布函数。在多个基准测试中，RMS 的速度均优于 Cantera 和 Chemkin。RMS 还为化学机理分析提供了大量功能，包括易于调用的绘图函数库、分子结构解析通量图生成、碰撞分析、传统灵敏度分析、短暂灵敏度分析和自动机理分析工具包。RMS 实现了高效的邻接和并行前向灵敏度分析。我们还演示了为 RMS 添加新功能的便捷性。
{"title":"ReactionMechanismSimulator.jl: A modern approach to chemical kinetic mechanism simulation and analysis","authors":"Matthew S. Johnson, Hao‐Wei Pang, Allen Mark Payne, William H. Green","doi":"10.1002/kin.21753","DOIUrl":"https://doi.org/10.1002/kin.21753","url":null,"abstract":"We present ReactionMechanismSimulator.jl (RMS), a modern differentiable software for the simulation and analysis of chemical kinetic mechanisms, including multiphase systems. RMS has already been applied to problems in combustion, pyrolysis, polymers, pharmaceuticals, catalysis, and electrocatalysis. RMS is written in Julia, making it easy to develop and allowing it to take advantage of Julia's extensive numerical computing ecosystem. In addition to its extensive library of optimized analytic Jacobians, RMS can generate and use Jacobians computed using automatic differentiation and symbolically generated analytic Jacobians. RMS is demonstrated to be faster than Cantera and Chemkin in several benchmarks. RMS also implements an extensive set of features for analyzing chemical mechanisms, including a library of easy‐to‐call plotting functions, molecular structure resolved flux diagram generation, crash analysis, traditional sensitivity analysis, transitory sensitivity analysis, and an automatic mechanism analysis toolkit. RMS implements efficient adjoint and parallel forward sensitivity analyses. We also demonstrate the ease of adding new features to RMS.","PeriodicalId":13894,"journal":{"name":"International Journal of Chemical Kinetics","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141572374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This research investigates the kinetics of methylene blue (MB) discoloration using ambient air cold plasma, with a focus on the impact of agitation speed (100 and 750 rpm). The study revealed pseudo‐first‐order kinetics for MB discoloration, pinpointing optimal conditions at 35.00°C and 100 rpm. These parameters minimized half‐life times, correlated with observed kobs values. A decreasing pH trend, more pronounced at 750 rpm, was attributed to increased acidic nitrogen species (HNO3 and HNO2) production, adversely affecting dye discoloration. Concurrently, enhanced electrolyte concentration was noted from rising conductivity due to plasma production of reactive species followed by solubilization in the aqueous phase. The calculated thermodynamic activation parameters comprised: Ea = 7.96 kJ mol−1, ΔH‡ = +5.53 kJ mol−1, ΔS‡ = −253.23 J K−1 mol−1, and ΔG‡ = +79.77 kJ mol−1 (100 rpm); and Ea = 12.94 kJ mol−1, ΔH‡ = +13.78 kJ mol−1, ΔS‡ = −239.06 J K−1 mol−1, and ΔG‡ = +80.58 kJ mol−1, (750 rpm). The lowest Ea and ΔG‡ values at 100 rpm reinforced lower agitation favoring the reaction. The study demonstrated a linear decay of the reaction rate constant with the square root of ionic strength. This result, besides the negative activation entropy and moderate activation enthalpy led to a proposition to the determinant step for the transition state formation, involving an associative step between a solvated electron and the protonated substrate. The optimal dye discoloration rate and energy yield were observed at 35.00°C and 100 rpm, with values of 97.2% and 3.371 × 10−2 g kW−1 h−1, respectively.
{"title":"Effect of agitation speed on methylene blue discoloration kinetics via ambient air cold plasma","authors":"Alessandra Mbroczkoski Pereira, Péricles Inácio Khalaf","doi":"10.1002/kin.21755","DOIUrl":"https://doi.org/10.1002/kin.21755","url":null,"abstract":"This research investigates the kinetics of methylene blue (MB) discoloration using ambient air cold plasma, with a focus on the impact of agitation speed (100 and 750 rpm). The study revealed pseudo‐first‐order kinetics for MB discoloration, pinpointing optimal conditions at 35.00°C and 100 rpm. These parameters minimized half‐life times, correlated with observed <jats:italic>k<jats:sub>obs</jats:sub></jats:italic> values. A decreasing pH trend, more pronounced at 750 rpm, was attributed to increased acidic nitrogen species (HNO<jats:sub>3</jats:sub> and HNO<jats:sub>2</jats:sub>) production, adversely affecting dye discoloration. Concurrently, enhanced electrolyte concentration was noted from rising conductivity due to plasma production of reactive species followed by solubilization in the aqueous phase. The calculated thermodynamic activation parameters comprised: <jats:italic>E<jats:sub>a</jats:sub></jats:italic> = 7.96 kJ mol<jats:sup>−1</jats:sup>, <jats:italic>ΔH</jats:italic><jats:sup>‡</jats:sup> = +5.53 kJ mol<jats:sup>−1</jats:sup>, <jats:italic>ΔS</jats:italic><jats:sup>‡</jats:sup> = −253.23 J K<jats:sup>−1</jats:sup> mol<jats:sup>−1</jats:sup>, and <jats:italic>ΔG</jats:italic><jats:sup>‡</jats:sup> = +79.77 kJ mol<jats:sup>−1</jats:sup> (100 rpm); and <jats:italic>E<jats:sub>a</jats:sub></jats:italic> = 12.94 kJ mol<jats:sup>−1</jats:sup>, Δ<jats:italic>H</jats:italic><jats:sup>‡</jats:sup> = +13.78 kJ mol<jats:sup>−1</jats:sup>, <jats:italic>ΔS</jats:italic><jats:sup>‡</jats:sup> = −239.06 J K<jats:sup>−1</jats:sup> mol<jats:sup>−1</jats:sup>, and <jats:italic>ΔG</jats:italic><jats:sup>‡</jats:sup> = +80.58 kJ mol<jats:sup>−1</jats:sup>, (750 rpm). The lowest <jats:italic>E<jats:sub>a</jats:sub></jats:italic> and <jats:italic>ΔG</jats:italic><jats:sup>‡</jats:sup> values at 100 rpm reinforced lower agitation favoring the reaction. The study demonstrated a linear decay of the reaction rate constant with the square root of ionic strength. This result, besides the negative activation entropy and moderate activation enthalpy led to a proposition to the determinant step for the transition state formation, involving an associative step between a solvated electron and the protonated substrate. The optimal dye discoloration rate and energy yield were observed at 35.00°C and 100 rpm, with values of 97.2% and 3.371 × 10<jats:sup>−2</jats:sup> g kW<jats:sup>−1</jats:sup> h<jats:sup>−1</jats:sup>, respectively.","PeriodicalId":13894,"journal":{"name":"International Journal of Chemical Kinetics","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141551319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yonggang Cheng, Pedro S. F. Mendes, Parviz Yazdani, Joris W. Thybaut
Given its role as a primary side product and a potential soft oxidant in the oxidative coupling of methane (OCM), understanding the effect of CO2 co‐feeding on OCM emerges as a key milestone to optimize the process. To grasp the molecular impact of CO2, a mechanistic investigation over a La‐Sr/CaO catalyst was carried out via microkinetic modeling. Seven catalyst descriptors with a precise physico‐chemical meaning were regressed for both pure O2 and CO2 co‐feeding in order to assess eventual structural changes induced in the catalyst by the presence of CO2 in the feed. Global significance was achieved in both regressions and experimental trends were successfully reproduced by the specifically determined catalyst descriptors. CO2 co‐feeding is deemed responsible for generating a new active phase, for example, by converting metal oxides into (oxy‐)carbonates, among others, resulting in a decrease in active site density (D16) from 10 × 10−5 mol/m2 to 7 × 10−5 mol/m2. In the presence of the CO2‐induced phase, the catalyst exhibits higher attraction for unsaturated hydrocarbons as indicated by the higher initial sticking probabilities of CH3• (D11) and C2H4 (D15), which increase from 4.9 × 10−4 to 8 × 10−2 and from 2.1 × 10−2 to 3 × 10−2, respectively. Additionally, there are also lower the overall energy barriers for the activation of hydrocarbons on the catalyst, stemming from the decrease in the H abstraction enthalpy from CH4 (D1) from 14 to 6 kJ/mol. The operating conditions, in particular the O2 content, are critical in distinguishing the effect of CO2 co‐feeding. While at typical operating conditions, CO2 promotes the total oxidation of methane, in the prerequisite of reduced amount of O2, it may also act as an additional oxygen donor. This work provides molecular details on the CO2 induced changes in catalyst properties but also provides unprecedent quantified insights of the reaction mechanism underlying experimental observations.
{"title":"Microkinetic analysis of the CO2 effect on OCM over a La‐Sr/CaO catalyst","authors":"Yonggang Cheng, Pedro S. F. Mendes, Parviz Yazdani, Joris W. Thybaut","doi":"10.1002/kin.21746","DOIUrl":"https://doi.org/10.1002/kin.21746","url":null,"abstract":"Given its role as a primary side product and a potential soft oxidant in the oxidative coupling of methane (OCM), understanding the effect of CO<jats:sub>2</jats:sub> co‐feeding on OCM emerges as a key milestone to optimize the process. To grasp the molecular impact of CO<jats:sub>2</jats:sub>, a mechanistic investigation over a La‐Sr/CaO catalyst was carried out via microkinetic modeling. Seven catalyst descriptors with a precise physico‐chemical meaning were regressed for both pure O<jats:sub>2</jats:sub> and CO<jats:sub>2</jats:sub> co‐feeding in order to assess eventual structural changes induced in the catalyst by the presence of CO<jats:sub>2</jats:sub> in the feed. Global significance was achieved in both regressions and experimental trends were successfully reproduced by the specifically determined catalyst descriptors. CO<jats:sub>2</jats:sub> co‐feeding is deemed responsible for generating a new active phase, for example, by converting metal oxides into (oxy‐)carbonates, among others, resulting in a decrease in active site density (D<jats:sub>16</jats:sub>) from 10 × 10<jats:sup>−5</jats:sup> mol/m<jats:sup>2</jats:sup> to 7 × 10<jats:sup>−5</jats:sup> mol/m<jats:sup>2</jats:sup>. In the presence of the CO<jats:sub>2</jats:sub>‐induced phase, the catalyst exhibits higher attraction for unsaturated hydrocarbons as indicated by the higher initial sticking probabilities of CH<jats:sub>3</jats:sub>• (D<jats:sub>11</jats:sub>) and C<jats:sub>2</jats:sub>H<jats:sub>4</jats:sub> (D<jats:sub>15</jats:sub>), which increase from 4.9 × 10<jats:sup>−4</jats:sup> to 8 × 10<jats:sup>−2</jats:sup> and from 2.1 × 10<jats:sup>−2</jats:sup> to 3 × 10<jats:sup>−2</jats:sup>, respectively. Additionally, there are also lower the overall energy barriers for the activation of hydrocarbons on the catalyst, stemming from the decrease in the H abstraction enthalpy from CH<jats:sub>4</jats:sub> (D<jats:sub>1</jats:sub>) from 14 to 6 kJ/mol. The operating conditions, in particular the O<jats:sub>2</jats:sub> content, are critical in distinguishing the effect of CO<jats:sub>2</jats:sub> co‐feeding. While at typical operating conditions, CO<jats:sub>2</jats:sub> promotes the total oxidation of methane, in the prerequisite of reduced amount of O<jats:sub>2</jats:sub>, it may also act as an additional oxygen donor. This work provides molecular details on the CO<jats:sub>2</jats:sub> induced changes in catalyst properties but also provides unprecedent quantified insights of the reaction mechanism underlying experimental observations.","PeriodicalId":13894,"journal":{"name":"International Journal of Chemical Kinetics","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141551318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Aqueous-phase reforming (APR) is an interesting technique for generating hydrogen (H2) from biofeeds. In this work, APR of model compounds of wet biomass for H2 production was investigated. Glycerol, sorbitol, and glycine were the chosen model compounds. They represent polyols and amino acids in wet biomass such as waste sludge and microalgal biomass. The Pt/Al2O3 catalyst was preferred and it was characterized using nitrogen adsorption–desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) techniques. APR trials were performed in a continuous fixed-bed reactor. The reaction conditions chosen for this work were: temperature (T) 453–498 K, pressure (P) 1.2–2.4 MPa, feed concentration 5–15 wt%, and weight hourly space velocity (WHSV) 0.15–0.6 g reactant/(g catalyst h). The best conditions for H2 production by the APR process were found to be T = 498 K, P = 2.4 MPa, and feed concentration = 15 wt%. Among the chosen model compounds, glycerol exhibited the highest H2 selectivity (82.7%) and H2 yield (21.6%) at 498 K. The analysis of kinetic data suggested first-order reaction kinetics for all the model compounds. The values of activation energy for the reactions with glycerol (55.4 kJ/mol), sorbitol (51.6 kJ/mol), and glycine (45.7 kJ/mol) were determined. Thus, APR is a promising route for effectively producing H2-bearing gaseous products with high heating value from wet biomass.
{"title":"Hydrogen production from aqueous-phase reforming of glycerol, sorbitol, and glycine over Pt/Al2O3 catalyst in a fixed-bed reactor","authors":"Vinayak N. Kalekar, Prakash D. Vaidya","doi":"10.1002/kin.21752","DOIUrl":"10.1002/kin.21752","url":null,"abstract":"<p>Aqueous-phase reforming (APR) is an interesting technique for generating hydrogen (H<sub>2</sub>) from biofeeds. In this work, APR of model compounds of wet biomass for H<sub>2</sub> production was investigated. Glycerol, sorbitol, and glycine were the chosen model compounds. They represent polyols and amino acids in wet biomass such as waste sludge and microalgal biomass. The Pt/Al<sub>2</sub>O<sub>3</sub> catalyst was preferred and it was characterized using nitrogen adsorption–desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) techniques. APR trials were performed in a continuous fixed-bed reactor. The reaction conditions chosen for this work were: temperature (<i>T</i>) 453–498 K, pressure (<i>P</i>) 1.2–2.4 MPa, feed concentration 5–15 wt%, and weight hourly space velocity (WHSV) 0.15–0.6 g reactant/(g catalyst h). The best conditions for H<sub>2</sub> production by the APR process were found to be <i>T</i> = 498 K, <i>P</i> = 2.4 MPa, and feed concentration = 15 wt%. Among the chosen model compounds, glycerol exhibited the highest H<sub>2</sub> selectivity (82.7%) and H<sub>2</sub> yield (21.6%) at 498 K. The analysis of kinetic data suggested first-order reaction kinetics for all the model compounds. The values of activation energy for the reactions with glycerol (55.4 kJ/mol), sorbitol (51.6 kJ/mol), and glycine (45.7 kJ/mol) were determined. Thus, APR is a promising route for effectively producing H<sub>2</sub>-bearing gaseous products with high heating value from wet biomass.</p>","PeriodicalId":13894,"journal":{"name":"International Journal of Chemical Kinetics","volume":null,"pages":null},"PeriodicalIF":1.5,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141512399","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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