Pub Date : 2020-01-01DOI: 10.1177/1468678319825731
J. Vojtko, Jaroslav Durdiak, Zuzana Lukáčová-Chomisteková, P. Tomčík
Equilibrium constants and reaction rate constants for the esterification of secondary alkan-2-ols with acetic acid were measured at 60°C in 1,4-dioxane. Taft coefficients, as single parameter (without inductive effects), and two-parameter correlation (including inductive and steric effects), of the measurements were used for the prediction of esterification rate constants for secondary alkan-2-ols with monocarboxylic acids. For this prediction, previously observed results of linear correlation of rate constants for the esterification of propan-1-ol with monocarboxylic acids measured under identical experimental conditions were applied. Two parameter Taft equations for the correlation of secondary alkan-2-ols and for monocarboxylic acids were combined, resulting in an overall correlation equation usable for the prediction of reaction rates for secondary alkan-2-ols with any monocarboxylic acid. This equation was experimentally verified for the esterification of three randomly chosen alkan-2-ols with three randomly chosen monocarboxylic acids.
{"title":"Prediction of esterification rate constants for secondary alkan-2-ols based on one- and two-parameter Taft equations","authors":"J. Vojtko, Jaroslav Durdiak, Zuzana Lukáčová-Chomisteková, P. Tomčík","doi":"10.1177/1468678319825731","DOIUrl":"https://doi.org/10.1177/1468678319825731","url":null,"abstract":"Equilibrium constants and reaction rate constants for the esterification of secondary alkan-2-ols with acetic acid were measured at 60°C in 1,4-dioxane. Taft coefficients, as single parameter (without inductive effects), and two-parameter correlation (including inductive and steric effects), of the measurements were used for the prediction of esterification rate constants for secondary alkan-2-ols with monocarboxylic acids. For this prediction, previously observed results of linear correlation of rate constants for the esterification of propan-1-ol with monocarboxylic acids measured under identical experimental conditions were applied. Two parameter Taft equations for the correlation of secondary alkan-2-ols and for monocarboxylic acids were combined, resulting in an overall correlation equation usable for the prediction of reaction rates for secondary alkan-2-ols with any monocarboxylic acid. This equation was experimentally verified for the esterification of three randomly chosen alkan-2-ols with three randomly chosen monocarboxylic acids.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"88 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79894190","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}
Pub Date : 2020-01-01DOI: 10.1177/1468678319900581
P. Pakravan, Seyyed Amir Siadati
We have examined here the possibility of functionalization of the B12N12 cluster by methyl azide by means of a [2 + 3] cycloaddition reaction in analogy with the spontaneous functionalization of C20 fullerene using the same reaction. To achieve more reliable data, all possible interactions at different positions and orientations were considered by reaction channel study and potential energy surface calculations. Also, Born–Oppenheimer molecular dynamics simulations were used to find probable species which could emerge during the reactions.
{"title":"A [1 + 2] cycloaddition instead of usual [2 + 3] cycloaddition between the B12N12 cluster and methyl azide: Potential energy surface calculations and Born–Oppenheimer molecular dynamics simulations","authors":"P. Pakravan, Seyyed Amir Siadati","doi":"10.1177/1468678319900581","DOIUrl":"https://doi.org/10.1177/1468678319900581","url":null,"abstract":"We have examined here the possibility of functionalization of the B12N12 cluster by methyl azide by means of a [2 + 3] cycloaddition reaction in analogy with the spontaneous functionalization of C20 fullerene using the same reaction. To achieve more reliable data, all possible interactions at different positions and orientations were considered by reaction channel study and potential energy surface calculations. Also, Born–Oppenheimer molecular dynamics simulations were used to find probable species which could emerge during the reactions.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"41 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85237831","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}
Pub Date : 2020-01-01DOI: 10.1177/1468678320923295
Jinsong Gu, Xiuhui Lu
The mechanism of synthesis of 1,3,5-trisubstituted-1,2,4-triazoles from 3-thiopheneacetic acetic acid, 4-pyridine formamidine, and tri-fluoro ethyl hydrazine has been first investigated with B3LYP/6-311++G** method in this article. According to the potential energy profile, it can be predicted that the course of the reaction consists of six elementary reactions. The 3-thiopheneacetic acetic acid and 4-pyridine formamidine form first an intermediate product through a dehydration reaction; the intermediate product further combines with hydrogen ion to form a positive ions; the positive ion reacts with three fluorine ethyl hydrazines by a dehydration reaction to form another positive ions; then, it followed by two isomerization reactions, the final reaction with the acetate ion (Ac−) produces the final product. The research results reveal the laws of synthesis reaction of 1,3,5-trisubstituted-1,2,4-triazoles by the carboxylic acids, amidines, hydrazines, and their derivatives on theoretical level. These studies provide the systematic theoretical basis to design and synthesize new 1,3,5-trisubstituted-1,2,4-triazoles.
{"title":"A mechanistic study of 1,3,5-trisubstituted-1,2,3-triazoles by Ab initio method","authors":"Jinsong Gu, Xiuhui Lu","doi":"10.1177/1468678320923295","DOIUrl":"https://doi.org/10.1177/1468678320923295","url":null,"abstract":"The mechanism of synthesis of 1,3,5-trisubstituted-1,2,4-triazoles from 3-thiopheneacetic acetic acid, 4-pyridine formamidine, and tri-fluoro ethyl hydrazine has been first investigated with B3LYP/6-311++G** method in this article. According to the potential energy profile, it can be predicted that the course of the reaction consists of six elementary reactions. The 3-thiopheneacetic acetic acid and 4-pyridine formamidine form first an intermediate product through a dehydration reaction; the intermediate product further combines with hydrogen ion to form a positive ions; the positive ion reacts with three fluorine ethyl hydrazines by a dehydration reaction to form another positive ions; then, it followed by two isomerization reactions, the final reaction with the acetate ion (Ac−) produces the final product. The research results reveal the laws of synthesis reaction of 1,3,5-trisubstituted-1,2,4-triazoles by the carboxylic acids, amidines, hydrazines, and their derivatives on theoretical level. These studies provide the systematic theoretical basis to design and synthesize new 1,3,5-trisubstituted-1,2,4-triazoles.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"53 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91123856","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}
Pub Date : 2020-01-01DOI: 10.1177/1468678319891842
Xia An, J. Ren, Wei-Ping Hu, Xu Wu, Xianmei Xie
The production of hydrogen by steam reforming of ethanol was carried out on SBA-15-supported nano NiO catalyst synthesized by the equivalent-volume impregnation method with two different Ni sources (nickel nitrate and nickel sulfamate). The catalyst was characterized by N2 adsorption–desorption, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy to examine the physical and chemical properties. The activity tests were performed with the steam, with water/ethanol molar ratio ranging from 2:1 to 15:1, the N2 flow rate from 20 to 120 mL min−1 to determine the space-time, and the temperature range from 623 to 923 K on the two different Ni source catalysts. A favorable operating condition was established at 823 K using water/ethanol = 6 molar ratio and carrier gas (N2) flow of more than 50 mL min−1 for nickel nitrate source, but for nickel sulfamate source, the optimum temperature changed to 773 K and other conditions were the same as for the nickel nitrate source. After eliminating the influence of internal and external diffusion factors, an empirical power-law kinetic rate equation was derived from the experimental data. The non-linear regression method was used to estimate the kinetic parameter. The activation energy of the catalyst was then calculated, and the supported nickel nitrate and nickel sulfamate catalysts were 25.345 and 41.449 kJ mol−1, respectively, which was in agreement with the experimental and model-predicted results.
以两种不同镍源(硝酸镍和氨基磺酸镍)为载体，采用等体积浸渍法制备了sba -15负载的纳米NiO催化剂，进行了乙醇蒸汽重整制氢研究。采用N2吸附-脱附、x射线衍射、x射线光电子能谱和透射电镜等方法对催化剂进行了表征。在水蒸气、水/乙醇摩尔比为2:1 ~ 15:1、N2流量为20 ~ 120 mL min−1、温度为623 ~ 923 K的条件下，对两种不同Ni源催化剂进行了活性测试。硝酸镍源在823 K、水/乙醇= 6摩尔比、载气(N2)流量大于50 mL min - 1条件下具有较好的操作条件，而氨基磺酸镍源的最佳操作温度为773 K，其他条件与硝酸镍源相同。在排除内外扩散因素的影响后，由实验数据导出了经验幂律动力学速率方程。采用非线性回归方法对动力学参数进行了估计。计算了催化剂的活化能，负载型硝酸镍和氨基磺酸镍催化剂的活化能分别为25.345和41.449 kJ mol−1，与实验和模型预测结果一致。
{"title":"A highly efficient and stable Ni/SBA-15 catalyst for hydrogen production by ethanol steam reforming","authors":"Xia An, J. Ren, Wei-Ping Hu, Xu Wu, Xianmei Xie","doi":"10.1177/1468678319891842","DOIUrl":"https://doi.org/10.1177/1468678319891842","url":null,"abstract":"The production of hydrogen by steam reforming of ethanol was carried out on SBA-15-supported nano NiO catalyst synthesized by the equivalent-volume impregnation method with two different Ni sources (nickel nitrate and nickel sulfamate). The catalyst was characterized by N2 adsorption–desorption, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy to examine the physical and chemical properties. The activity tests were performed with the steam, with water/ethanol molar ratio ranging from 2:1 to 15:1, the N2 flow rate from 20 to 120 mL min−1 to determine the space-time, and the temperature range from 623 to 923 K on the two different Ni source catalysts. A favorable operating condition was established at 823 K using water/ethanol = 6 molar ratio and carrier gas (N2) flow of more than 50 mL min−1 for nickel nitrate source, but for nickel sulfamate source, the optimum temperature changed to 773 K and other conditions were the same as for the nickel nitrate source. After eliminating the influence of internal and external diffusion factors, an empirical power-law kinetic rate equation was derived from the experimental data. The non-linear regression method was used to estimate the kinetic parameter. The activation energy of the catalyst was then calculated, and the supported nickel nitrate and nickel sulfamate catalysts were 25.345 and 41.449 kJ mol−1, respectively, which was in agreement with the experimental and model-predicted results.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"23 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75202560","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}
Pub Date : 2019-11-27DOI: 10.1177/1468678319886129
A. Tahan, A. Shiroudi
Kinetic rate constants for the oxidation reaction of the hydroxyl radical with CH3SH, C2H5SH, n-C3H7SH, and iso-C3H7SH under inert (Ar) conditions over the temperature range 252–430 K have been studied theoretically using density functional theory along with various exchange–correlation functionals as well as the benchmark CBS-QB3 quantum chemical approach. Bimolecular rate constants were estimated using transition state theory and the statistical Rice–Ramsperger–Kassel–Marcus theory. Comparison with experiment confirms that in the OH addition reaction pathways leading to the related products, the first bimolecular reaction steps have effective negative activation energy barriers. Effective rate constants have been calculated according to a steady-state analysis of a two-step model reaction mechanism. As a consequence of the negative activation energies, pressures higher than 104 bar are required to reach the high-pressure limit. Both from thermodynamic and kinetic viewpoints, the most favorable process here is the oxidation reaction of hydroxyl radicals with n-C3H7SH.
{"title":"Oxidation reaction mechanism and kinetics between OH radicals and alkyl-substituted aliphatic thiols: H-abstraction pathways","authors":"A. Tahan, A. Shiroudi","doi":"10.1177/1468678319886129","DOIUrl":"https://doi.org/10.1177/1468678319886129","url":null,"abstract":"Kinetic rate constants for the oxidation reaction of the hydroxyl radical with CH3SH, C2H5SH, n-C3H7SH, and iso-C3H7SH under inert (Ar) conditions over the temperature range 252–430 K have been studied theoretically using density functional theory along with various exchange–correlation functionals as well as the benchmark CBS-QB3 quantum chemical approach. Bimolecular rate constants were estimated using transition state theory and the statistical Rice–Ramsperger–Kassel–Marcus theory. Comparison with experiment confirms that in the OH addition reaction pathways leading to the related products, the first bimolecular reaction steps have effective negative activation energy barriers. Effective rate constants have been calculated according to a steady-state analysis of a two-step model reaction mechanism. As a consequence of the negative activation energies, pressures higher than 104 bar are required to reach the high-pressure limit. Both from thermodynamic and kinetic viewpoints, the most favorable process here is the oxidation reaction of hydroxyl radicals with n-C3H7SH.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"10 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2019-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79814777","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}
Pub Date : 2019-08-22DOI: 10.1177/1468678319861319
A. Mamantov
New 1H and 13C NMR 400 MHZ spectra of the 2-Nb cation under stable ion conditions, for example, in SbF5/SO2F2/SO2ClF, −80 oC, show besides the usual 1H NMR resonances at δ 4.93, 2.82, 1.85, the never before seen singlet, δ 9.63, and doublet, δ 2.97 (J2,6 = 16.6 Hz), ratio 1.00 : 1.07, proposed to be due to resonance-stabilized bridgehead 1-Nb cationic enantiomers in equilibrium with 2-Nb cation. The corresponding 13C proton-coupled NMR spectrum, −80 oC, has a C3,5,7 triplet, δ 30.45, J(CH) = 139.14 Hz, and C4 doublet, δ 37.7, J(CH) = 154.54 Hz. The C1,2,6 absorption, δ 91.04 is relatively broad, whereas previously, at −70 oC, it was a pentuplet. The 13C proton-decoupled spectrum at −80 oC shows the C4 doublet and C3,5,7 triplet collapsed to a singlet, but the C1,2,6 resonance is still broad. Analyses support the slowing exchange between resonance stabilized enantiomeric 2-cations at ≤ –159 oC. Some future studies are proposed.
{"title":"1-Norbornyl cation may be in equilibrium with 2-norbornyl cation","authors":"A. Mamantov","doi":"10.1177/1468678319861319","DOIUrl":"https://doi.org/10.1177/1468678319861319","url":null,"abstract":"New 1H and 13C NMR 400 MHZ spectra of the 2-Nb cation under stable ion conditions, for example, in SbF5/SO2F2/SO2ClF, −80 oC, show besides the usual 1H NMR resonances at δ 4.93, 2.82, 1.85, the never before seen singlet, δ 9.63, and doublet, δ 2.97 (J2,6 = 16.6 Hz), ratio 1.00 : 1.07, proposed to be due to resonance-stabilized bridgehead 1-Nb cationic enantiomers in equilibrium with 2-Nb cation. The corresponding 13C proton-coupled NMR spectrum, −80 oC, has a C3,5,7 triplet, δ 30.45, J(CH) = 139.14 Hz, and C4 doublet, δ 37.7, J(CH) = 154.54 Hz. The C1,2,6 absorption, δ 91.04 is relatively broad, whereas previously, at −70 oC, it was a pentuplet. The 13C proton-decoupled spectrum at −80 oC shows the C4 doublet and C3,5,7 triplet collapsed to a singlet, but the C1,2,6 resonance is still broad. Analyses support the slowing exchange between resonance stabilized enantiomeric 2-cations at ≤ –159 oC. Some future studies are proposed.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"40 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2019-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81529296","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}
Pub Date : 2019-07-31DOI: 10.1177/1468678319860991
M. L. Kremer
Using [H2O2] in the molar range, the reaction with Fe2+ has two phases: in the first rapid phase, only a small fraction of the total O2 is evolved; the bulk of the gas is formed in a slow second phase. In interpretations based on the free radical model of Barb et al., the first phase has been identified with the ‘Fenton reaction’ (reaction of Fe2+with H2O2), while the second with catalytic decomposition of H2O2 by Fe3+ ions. This interpretation is not correct. A new analysis of the model shows that (1) it is a chain reaction having no termination steps and (2) the ‘Fenton part’ alone consists of two phases. It starts with rapid evolution of O2 via a five-membered chain reaction (first phase). When [Fe2+] becomes low, evolution of O2 continues in a three-membered chain reaction at a greatly reduced rate (second phase). In later stages of the second phase, Fe3+ catalysis contributes to O2 evolution. Thus, the amount of O2 formed in the rapid phase cannot be identified with the total amount formed in the ‘Fenton reaction’ but only with that formed in its first phase. Computer simulations of O2 evolution based on the model of Barb et al. and rate constants show a definite dependence of this quantity on the initial [H2O2] – in contrast to the experimentally found independence. More satisfactory, but not complete, agreement with measured data could be reached in simulations using a non-radical model. Some of the difficulty has been due to the determination of the exact position of the end of the first phase. The transition between the two phases of the reaction occurs in a short, but finite time interval. It has been shown that the quantity ‘total amount of O2 evolved in the Fenton reaction’ (subtracting the part due to Fe3+catalysis) is not accessible to experimental determination nor to theoretical calculation.
{"title":"New kinetic analysis of the Fenton reaction: Critical examination of the free radical – chain reaction concept","authors":"M. L. Kremer","doi":"10.1177/1468678319860991","DOIUrl":"https://doi.org/10.1177/1468678319860991","url":null,"abstract":"Using [H2O2] in the molar range, the reaction with Fe2+ has two phases: in the first rapid phase, only a small fraction of the total O2 is evolved; the bulk of the gas is formed in a slow second phase. In interpretations based on the free radical model of Barb et al., the first phase has been identified with the ‘Fenton reaction’ (reaction of Fe2+with H2O2), while the second with catalytic decomposition of H2O2 by Fe3+ ions. This interpretation is not correct. A new analysis of the model shows that (1) it is a chain reaction having no termination steps and (2) the ‘Fenton part’ alone consists of two phases. It starts with rapid evolution of O2 via a five-membered chain reaction (first phase). When [Fe2+] becomes low, evolution of O2 continues in a three-membered chain reaction at a greatly reduced rate (second phase). In later stages of the second phase, Fe3+ catalysis contributes to O2 evolution. Thus, the amount of O2 formed in the rapid phase cannot be identified with the total amount formed in the ‘Fenton reaction’ but only with that formed in its first phase. Computer simulations of O2 evolution based on the model of Barb et al. and rate constants show a definite dependence of this quantity on the initial [H2O2] – in contrast to the experimentally found independence. More satisfactory, but not complete, agreement with measured data could be reached in simulations using a non-radical model. Some of the difficulty has been due to the determination of the exact position of the end of the first phase. The transition between the two phases of the reaction occurs in a short, but finite time interval. It has been shown that the quantity ‘total amount of O2 evolved in the Fenton reaction’ (subtracting the part due to Fe3+catalysis) is not accessible to experimental determination nor to theoretical calculation.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"63 1","pages":"289 - 299"},"PeriodicalIF":0.7,"publicationDate":"2019-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86935824","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}
Pub Date : 2019-07-25DOI: 10.1177/1468678319862438
A. N. Pour, M. Housaindokht
The effects of metallic cobalt crystal phase on catalytic activity of cobalt catalysts in the Fischer–Tropsch synthesis were investigated in a continuous spinning basket reactor. The cobalt catalysts were prepared by impregnation of the cobalt active phase in a microemulsion system on multiwall carbon nanotube supports. A series of cobalt catalysts with different Co particle sizes was prepared by variation of the water-to-surfactant molar ratio from 2 to 12 in the microemulsion system. The X-ray diffraction results validate a complex composition of cobalt phases containing cobalt oxides and metallic cobalt with hexagonal close-packed and face-centered cubic phases. The results show that larger cobalt particles exhibit more face-centered cubic and less hexagonal close-packed metallic cobalt. The experimental results show that the catalysts with higher fractions of hexagonal close-packed phase exhibited higher conversion in the Fischer–Tropsch reaction.
{"title":"Effects of metallic cobalt crystal phase on catalytic activity of cobalt catalysts supported on carbon nanotubes in Fischer–Tropsch synthesis","authors":"A. N. Pour, M. Housaindokht","doi":"10.1177/1468678319862438","DOIUrl":"https://doi.org/10.1177/1468678319862438","url":null,"abstract":"The effects of metallic cobalt crystal phase on catalytic activity of cobalt catalysts in the Fischer–Tropsch synthesis were investigated in a continuous spinning basket reactor. The cobalt catalysts were prepared by impregnation of the cobalt active phase in a microemulsion system on multiwall carbon nanotube supports. A series of cobalt catalysts with different Co particle sizes was prepared by variation of the water-to-surfactant molar ratio from 2 to 12 in the microemulsion system. The X-ray diffraction results validate a complex composition of cobalt phases containing cobalt oxides and metallic cobalt with hexagonal close-packed and face-centered cubic phases. The results show that larger cobalt particles exhibit more face-centered cubic and less hexagonal close-packed metallic cobalt. The experimental results show that the catalysts with higher fractions of hexagonal close-packed phase exhibited higher conversion in the Fischer–Tropsch reaction.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"4 1","pages":"316 - 323"},"PeriodicalIF":0.7,"publicationDate":"2019-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79752751","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}
A nickel phosphide hydrodeoxygenation catalyst (Ni2P-O/MCM-41) was prepared using a new synthetic method. The as-prepared catalyst was evaluated in the hydrodeoxygenation of benzofuran, and the effects of reaction temperature, pressure, and the H2/liquid ratio were investigated. A pseudo first-order model was employed to describe the reaction kinetics of benzofuran hydrodeoxygenation over the Ni2P-O/MCM-41 catalyst. The reaction rate constants (k1–k5) at different temperatures were determined according to this model. At 533 K, the conversion of 2-ethylphenol in to ethylbenzene began to increase dramatically, and the yield of O-free product, ethylcyclohexane, started to increase rapidly. At 573 K, 3.0 MPa, and a H2/liquid ratio of 500 (V/V), the conversion of benzofuran over Ni2P-O/MCM-41 reached 93%, and the combined yield of O-free products was 91%. Contact time analysis indicated that demethylation was not favored over the Ni2P-O/MCM-41 catalyst.
采用新的合成方法制备了磷化镍加氢脱氧催化剂Ni2P-O/MCM-41。考察了所制备的催化剂对苯并呋喃加氢脱氧反应的影响，考察了反应温度、反应压力和H2/液比对催化剂加氢脱氧反应的影响。采用拟一阶模型描述了Ni2P-O/MCM-41催化剂上苯并呋喃加氢脱氧反应动力学。根据该模型确定了不同温度下的反应速率常数k1-k5。在533 K时，2-乙基苯酚in生成乙苯的转化率开始急剧提高，无o产物乙基环己烷的收率开始迅速提高。在573 K、3.0 MPa、H2/液比为500 (V/V)的条件下，ni2o - o /MCM-41对苯并呋喃的转化率达到93%，无o产物的总收率为91%。接触时间分析表明，Ni2P-O/MCM-41催化剂不有利于去甲基化。
{"title":"Reactivity and kinetic studies of benzofuran hydrodeoxygenation over a Ni2P-O/MCM-41 catalyst","authors":"Xueya Dai, Huaihui Song, Hualin Song, Jing Gong, Feng Li, Yanxiu Liu","doi":"10.1177/1468678319825909","DOIUrl":"https://doi.org/10.1177/1468678319825909","url":null,"abstract":"A nickel phosphide hydrodeoxygenation catalyst (Ni2P-O/MCM-41) was prepared using a new synthetic method. The as-prepared catalyst was evaluated in the hydrodeoxygenation of benzofuran, and the effects of reaction temperature, pressure, and the H2/liquid ratio were investigated. A pseudo first-order model was employed to describe the reaction kinetics of benzofuran hydrodeoxygenation over the Ni2P-O/MCM-41 catalyst. The reaction rate constants (k1–k5) at different temperatures were determined according to this model. At 533 K, the conversion of 2-ethylphenol in to ethylbenzene began to increase dramatically, and the yield of O-free product, ethylcyclohexane, started to increase rapidly. At 573 K, 3.0 MPa, and a H2/liquid ratio of 500 (V/V), the conversion of benzofuran over Ni2P-O/MCM-41 reached 93%, and the combined yield of O-free products was 91%. Contact time analysis indicated that demethylation was not favored over the Ni2P-O/MCM-41 catalyst.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"29 1","pages":"307 - 315"},"PeriodicalIF":0.7,"publicationDate":"2019-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78135749","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}
Pub Date : 2019-07-15DOI: 10.1177/1468678319860989
Huang Weijia, Ming-Hua Chen, Zhen-Tao An, Li Zhang, Zhibao Jiang
In this article, hybrid functional B3LYP method is used to construct the reactant structure of energetic components in propellant at the bhandhlyp/6-31g(d) level, and to calculate the closed-shell layer of the system. At the bhandhlyp/6-31g(d) level, the energy difference (activation energy) between the transition state and the reactant was calculated and the reaction mechanism between energetic components was analyzed. It is found that the O30 atom of RDX first breaks off from the nitro group and is easier to break away from RDX and interact with the vertex atom Al1 of the Al13 cluster. With the further separation of O30, it also acts with Al11 until it completely breaks away from N26 atom. The activation energy of this reaction is 56.448 × 103 J mol−1. The oxygen dioxide atom in ammonium perchlorate is more likely to interact with the Al11 atom of the Al13 cluster. With the reaction proceeding, the O22 atom will not completely separate from the Cl19 atom. The activation energy of the reaction is 27.830 × 103 J mol−1.
{"title":"Simulation of thermal reaction mechanism between energetic components of hydroxyl-terminated polybutadiene propellant based on quantum chemical calculation","authors":"Huang Weijia, Ming-Hua Chen, Zhen-Tao An, Li Zhang, Zhibao Jiang","doi":"10.1177/1468678319860989","DOIUrl":"https://doi.org/10.1177/1468678319860989","url":null,"abstract":"In this article, hybrid functional B3LYP method is used to construct the reactant structure of energetic components in propellant at the bhandhlyp/6-31g(d) level, and to calculate the closed-shell layer of the system. At the bhandhlyp/6-31g(d) level, the energy difference (activation energy) between the transition state and the reactant was calculated and the reaction mechanism between energetic components was analyzed. It is found that the O30 atom of RDX first breaks off from the nitro group and is easier to break away from RDX and interact with the vertex atom Al1 of the Al13 cluster. With the further separation of O30, it also acts with Al11 until it completely breaks away from N26 atom. The activation energy of this reaction is 56.448 × 103 J mol−1. The oxygen dioxide atom in ammonium perchlorate is more likely to interact with the Al11 atom of the Al13 cluster. With the reaction proceeding, the O22 atom will not completely separate from the Cl19 atom. The activation energy of the reaction is 27.830 × 103 J mol−1.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"62 1","pages":"324 - 335"},"PeriodicalIF":0.7,"publicationDate":"2019-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78149441","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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