Pub Date : 2019-03-15DOI: 10.1177/1468678319830512
Ying-ying Wang
By performing density functional theory calculations, the adsorption configurations of formic acid and possible reaction pathway for HCOOH oxidation on PtPd(111) surface are located. Results show that CO2 is preferentially formed as the main product of the catalytic oxidation of formic acid. The formation of CO on the pure Pd surface could not possibly occur during formic acid decomposition on the PtPd(111) surface owing to the high reaction barrier. Therefore, no poisoning of catalyst would occur on the PtPd(111) surface. Our results indicate that the significantly increased catalytic activity of bimetallic PtPd catalyst towards HCOOH oxidation should be attributed to the reduction in poisoning by CO.
{"title":"Theoretical study of the oxidation of formic acid on a PtPd(111) surface","authors":"Ying-ying Wang","doi":"10.1177/1468678319830512","DOIUrl":"https://doi.org/10.1177/1468678319830512","url":null,"abstract":"By performing density functional theory calculations, the adsorption configurations of formic acid and possible reaction pathway for HCOOH oxidation on PtPd(111) surface are located. Results show that CO2 is preferentially formed as the main product of the catalytic oxidation of formic acid. The formation of CO on the pure Pd surface could not possibly occur during formic acid decomposition on the PtPd(111) surface owing to the high reaction barrier. Therefore, no poisoning of catalyst would occur on the PtPd(111) surface. Our results indicate that the significantly increased catalytic activity of bimetallic PtPd catalyst towards HCOOH oxidation should be attributed to the reduction in poisoning by CO.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"77 1","pages":"67 - 73"},"PeriodicalIF":0.7,"publicationDate":"2019-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73273347","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 series of ceria promoted Ni2P catalysts were prepared and evaluated in dibenzothiophene hydrodesulfurization steam. These catalysts were characterized by X-ray diffraction, N2 adsorption–desorption, CO chemisorptions, and X-ray photoelectron spectroscopy. The results showed that the addition of ceria into the bulk Ni2P catalyst was conducive to the formation of the Ni2P phase and contributed to a higher surface area, leading to a better dispersion and smaller crystallite size of Ni2P particles. The CexNi2P catalysts showed higher dibenzothiophene hydrodesulfurization activity than Ni2P catalyst and the Ce0.09Ni2P catalyst showed the highest dibenzothiophene hydrodesulfurization activity. The Ce0.09Ni2P catalyst showed a dibenzothiophene hydrodesulfurization conversion of 94.5% at the reaction conditions of 320°C, 4.0 MPa, a H2/oil ratio of 500 (V/V), and a weight hourly space velocity of 8.0 h−1. The dibenzothiophene was mainly transformed through desulfurization pathway.
{"title":"Effect of cerium content on textural and hydrodesulfurization performance for dibenzothiophene over a bulk Ni2P catalyst","authors":"Yunwu Yu, Lianjie Liang, Chang-Wei Xu, Y.-L. Dai, Wenhao Pan, Zhao Ding, Yunxue Liu","doi":"10.1177/1468678319830798","DOIUrl":"https://doi.org/10.1177/1468678319830798","url":null,"abstract":"A series of ceria promoted Ni2P catalysts were prepared and evaluated in dibenzothiophene hydrodesulfurization steam. These catalysts were characterized by X-ray diffraction, N2 adsorption–desorption, CO chemisorptions, and X-ray photoelectron spectroscopy. The results showed that the addition of ceria into the bulk Ni2P catalyst was conducive to the formation of the Ni2P phase and contributed to a higher surface area, leading to a better dispersion and smaller crystallite size of Ni2P particles. The CexNi2P catalysts showed higher dibenzothiophene hydrodesulfurization activity than Ni2P catalyst and the Ce0.09Ni2P catalyst showed the highest dibenzothiophene hydrodesulfurization activity. The Ce0.09Ni2P catalyst showed a dibenzothiophene hydrodesulfurization conversion of 94.5% at the reaction conditions of 320°C, 4.0 MPa, a H2/oil ratio of 500 (V/V), and a weight hourly space velocity of 8.0 h−1. The dibenzothiophene was mainly transformed through desulfurization pathway.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"27 1","pages":"37 - 44"},"PeriodicalIF":0.7,"publicationDate":"2019-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88603989","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 : 2019-03-14DOI: 10.1177/1468678319825692
Zhang Jiaying
The kinetics of carbon monoxide methanation over Ni-Mo-SiO2 catalyst were studied. The model was developed based on catalyst tests carried out in a fixed-bed reactor at a reaction temperature varied from 300 °C to 450 °C under a pressure from 0.1 to 1.5 MPa with a weight hourly space velocity of 60,000 mL h−1 g−1. An orthogonal design method was adopted to select test points with temperature, pressure, and feed compositions as factors. Based on the experimental observations, a Langmuir–Hinshelwood equation kinetic model was formulated and its parameters were estimated by fitting the experimental data implemented in MATLAB. The activation energy for the formation of CH4 was 45.4 kJ mol−1 and comparing the experimental and model-predicted data showed that the proposed model gives a reasonable fit with an average absolute relative deviation of ±9.8%.
研究了Ni-Mo-SiO2催化剂上一氧化碳甲烷化反应动力学。该模型是基于在固定床反应器中进行的催化剂测试而开发的，反应温度从300°C到450°C，压力从0.1到1.5 MPa，重量每小时空间速度为60,000 mL h−1 g−1。采用正交设计法，以温度、压力、饲料成分为影响因素，选择试验点。在实验观察的基础上，建立了Langmuir-Hinshelwood方程动力学模型，并通过MATLAB实现的实验数据进行拟合，估计了模型参数。CH4生成的活化能为45.4 kJ mol−1，实验数据与模型预测数据的比较表明，模型拟合合理，平均绝对相对偏差为±9.8%。
{"title":"Kinetic study of carbon monoxide methanation over mesoporous Ni-Mo catalyst prepared by a hydrothermal method","authors":"Zhang Jiaying","doi":"10.1177/1468678319825692","DOIUrl":"https://doi.org/10.1177/1468678319825692","url":null,"abstract":"The kinetics of carbon monoxide methanation over Ni-Mo-SiO2 catalyst were studied. The model was developed based on catalyst tests carried out in a fixed-bed reactor at a reaction temperature varied from 300 °C to 450 °C under a pressure from 0.1 to 1.5 MPa with a weight hourly space velocity of 60,000 mL h−1 g−1. An orthogonal design method was adopted to select test points with temperature, pressure, and feed compositions as factors. Based on the experimental observations, a Langmuir–Hinshelwood equation kinetic model was formulated and its parameters were estimated by fitting the experimental data implemented in MATLAB. The activation energy for the formation of CH4 was 45.4 kJ mol−1 and comparing the experimental and model-predicted data showed that the proposed model gives a reasonable fit with an average absolute relative deviation of ±9.8%.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"1 1","pages":"17 - 3"},"PeriodicalIF":0.7,"publicationDate":"2019-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76492562","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 : 2019-02-01DOI: 10.1177/1468678319830487
Nazanin Beyzaie, S. Tayyari, M. Vakili, S. Beyramabadi
In this work, the mechanism of the palladium-catalysed acetoxylation of benzene C-H has been studied theoretically in detail. Based on experimental studies, a four-step mechanism for this reaction had been proposed, that is, C−H activation of benzene is the rate-determining step which forms an intermediate (k1 pathway) which is subsequently oxidized to produce a high-valent Pd intermediate (k2 pathway). Using quantum chemical calculations, all pathways were investigated, and the activation energy, activation enthalpy and activation Gibbs free energy for all steps were calculated and compared with each other. It was determined that the RDS proceeds through a square complex instead of a T-shaped complex. The activation energy related to the k2 pathway is higher than that of the RDS, and therefore, a new mechanism is proposed.
{"title":"Quantum chemical study of the mechanism of the palladium-catalysed C−H acetoxylation of benzene","authors":"Nazanin Beyzaie, S. Tayyari, M. Vakili, S. Beyramabadi","doi":"10.1177/1468678319830487","DOIUrl":"https://doi.org/10.1177/1468678319830487","url":null,"abstract":"In this work, the mechanism of the palladium-catalysed acetoxylation of benzene C-H has been studied theoretically in detail. Based on experimental studies, a four-step mechanism for this reaction had been proposed, that is, C−H activation of benzene is the rate-determining step which forms an intermediate (k1 pathway) which is subsequently oxidized to produce a high-valent Pd intermediate (k2 pathway). Using quantum chemical calculations, all pathways were investigated, and the activation energy, activation enthalpy and activation Gibbs free energy for all steps were calculated and compared with each other. It was determined that the RDS proceeds through a square complex instead of a T-shaped complex. The activation energy related to the k2 pathway is higher than that of the RDS, and therefore, a new mechanism is proposed.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"48 1-2","pages":"55 - 66"},"PeriodicalIF":0.7,"publicationDate":"2019-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1177/1468678319830487","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72470206","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 : 2018-10-01DOI: 10.3184/146867818X15319903829182
B. Hatami, A. Tavasoli, A. Asghari, Y. Zamani, A. Zamaniyan
The activities of cobalt catalysts prepared by the microemulsion impregnation method on carbon nanotubes (CNTs) and functionalised carbon nanotubes (FCNTs) supports were evaluated in the Fischer–Tropsch synthesis (FTS). The catalysts were characterised by transmission electron microscopy, X-ray diffraction and Brunauer–Emmett–Teller surface area methods. The results show that the cobalt particles in the FCNTs support are mostly located inside the tubes of the CNTs and show a narrower particle size distribution. The experimental results show that the cobalt catalyst supported on FCNTs leads to a higher CO conversion and FTS activity compared to that supported on normal CNTs. Calculated kinetic results show that the activation energies fall within the narrow range of 101.1–107.1 kJ mol−1 and the heat of hydrogen adsorption was calculated to be −40.2 and −26.2 kJ mol−1 for Co/CNTs and Co/FCNTs catalysts respectively. FCNTs, as a catalyst support of Co nanoparticles, maintain high dispersion which can be attributed to a hydrogen spillover effect of functional groups on the CNT surface.
{"title":"Intrinsic Kinetics of Fischer–Tropsch Synthesis over Co/CNTs Catalysts: Effects of Support Interaction","authors":"B. Hatami, A. Tavasoli, A. Asghari, Y. Zamani, A. Zamaniyan","doi":"10.3184/146867818X15319903829182","DOIUrl":"https://doi.org/10.3184/146867818X15319903829182","url":null,"abstract":"The activities of cobalt catalysts prepared by the microemulsion impregnation method on carbon nanotubes (CNTs) and functionalised carbon nanotubes (FCNTs) supports were evaluated in the Fischer–Tropsch synthesis (FTS). The catalysts were characterised by transmission electron microscopy, X-ray diffraction and Brunauer–Emmett–Teller surface area methods. The results show that the cobalt particles in the FCNTs support are mostly located inside the tubes of the CNTs and show a narrower particle size distribution. The experimental results show that the cobalt catalyst supported on FCNTs leads to a higher CO conversion and FTS activity compared to that supported on normal CNTs. Calculated kinetic results show that the activation energies fall within the narrow range of 101.1–107.1 kJ mol−1 and the heat of hydrogen adsorption was calculated to be −40.2 and −26.2 kJ mol−1 for Co/CNTs and Co/FCNTs catalysts respectively. FCNTs, as a catalyst support of Co nanoparticles, maintain high dispersion which can be attributed to a hydrogen spillover effect of functional groups on the CNT surface.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"124 1","pages":"262 - 273"},"PeriodicalIF":0.7,"publicationDate":"2018-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77352748","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 : 2018-10-01DOI: 10.3184/146867818X15319903829236
D. Panday, Teena Kachawa, S. Kothari
Kinetic and mechanistic studies of the oxidation of mandelic acid and nine monosubstituted mandelic acids by benzimidazolium dichromate (BIDC) in dimethyl sulfoxide are discussed with an emphasis on correlation of structure and reactivity. The reactions were of first order with respect to BIDC. However, Michaelis-Menten type kinetics were observed with respect to hydroxy acids. The reactions are catalysed by protons. The deuterium isotope effect for the oxidation of mandelic acid (kH/kD = 5.91 at 298 K) indicated an α-C-H bond cleavage in the rate-determining step. An analysis of the solvent effect showed that the role of cationsolvation is major. The reaction showed an excellent correlation with the Hammett σ values, the reaction constant being negative. Based on the kinetic data, analysis of the solvent effect and results of structure-reactivity correlation along with some non-kinetic parameters, a mechanism involving rate-determining oxidative decomposition of the complex through hydride-ion transfer via a cyclic transition state to give the corresponding oxoacid is suggested.
{"title":"Kinetics and Correlation Analysis of Reactivity in the Oxidation of Some α-Hydroxy Acids by Benzimidazolium Dichromate","authors":"D. Panday, Teena Kachawa, S. Kothari","doi":"10.3184/146867818X15319903829236","DOIUrl":"https://doi.org/10.3184/146867818X15319903829236","url":null,"abstract":"Kinetic and mechanistic studies of the oxidation of mandelic acid and nine monosubstituted mandelic acids by benzimidazolium dichromate (BIDC) in dimethyl sulfoxide are discussed with an emphasis on correlation of structure and reactivity. The reactions were of first order with respect to BIDC. However, Michaelis-Menten type kinetics were observed with respect to hydroxy acids. The reactions are catalysed by protons. The deuterium isotope effect for the oxidation of mandelic acid (kH/kD = 5.91 at 298 K) indicated an α-C-H bond cleavage in the rate-determining step. An analysis of the solvent effect showed that the role of cationsolvation is major. The reaction showed an excellent correlation with the Hammett σ values, the reaction constant being negative. Based on the kinetic data, analysis of the solvent effect and results of structure-reactivity correlation along with some non-kinetic parameters, a mechanism involving rate-determining oxidative decomposition of the complex through hydride-ion transfer via a cyclic transition state to give the corresponding oxoacid is suggested.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"6 1","pages":"300 - 314"},"PeriodicalIF":0.7,"publicationDate":"2018-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76032792","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 : 2018-10-01DOI: 10.3184/146867818X15233705894437
Hanxin Huo, Yuhui Ma
Pyrolysis of Tetra Pak waste under CO2 was investigated using a thermogravimetric/differential thermal analyser coupled with a Fourier transform infrared spectrometer. Experimental results showed that cellulose was decomposed between 270 and 390 °C, leading to the formation of aldehydes, ketones, carboxylic acids and levoglucosan. Thermal cracking of polyethylene occurred between 440 and 530 °C and the main products were aliphatic hydrocarbons. CO can be produced by the gasification of pyrolytic char by CO2 at temperatures ranging from 860–970 °C. Aluminium (Al) foil remained in a “thin layer shape” despite melting above 660 °C. CaO was generated from the decomposition of CaCO3 used as a paper filler at 722 °C. The reaction between CaO and the CO2 atmosphere during the cooling process led to the formation of new CaCO3 which was the main component of ash after gasification and was easy to separate from Al foil.
{"title":"TG/DTA-FTIR Study on Total Resource Recovery from Tetra Pak Waste by Pyrolysis under a CO2 Environment","authors":"Hanxin Huo, Yuhui Ma","doi":"10.3184/146867818X15233705894437","DOIUrl":"https://doi.org/10.3184/146867818X15233705894437","url":null,"abstract":"Pyrolysis of Tetra Pak waste under CO2 was investigated using a thermogravimetric/differential thermal analyser coupled with a Fourier transform infrared spectrometer. Experimental results showed that cellulose was decomposed between 270 and 390 °C, leading to the formation of aldehydes, ketones, carboxylic acids and levoglucosan. Thermal cracking of polyethylene occurred between 440 and 530 °C and the main products were aliphatic hydrocarbons. CO can be produced by the gasification of pyrolytic char by CO2 at temperatures ranging from 860–970 °C. Aluminium (Al) foil remained in a “thin layer shape” despite melting above 660 °C. CaO was generated from the decomposition of CaCO3 used as a paper filler at 722 °C. The reaction between CaO and the CO2 atmosphere during the cooling process led to the formation of new CaCO3 which was the main component of ash after gasification and was easy to separate from Al foil.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"138 1","pages":"229 - 235"},"PeriodicalIF":0.7,"publicationDate":"2018-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82861262","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 : 2018-10-01DOI: 10.3184/146867818X15233705894419
R. N. Mofrad, S. Sadrnezhaad, J. V. Khaki
We determined the mechanism of mechanochemical synthesis of fluorapatite from CaO, CaF2 and P2O5 by characterisation of the intermediate compounds. We used atomic absorption spectroscopy, X-ray diffraction, field emission scanning electron microscopy, FTIR spectroscopy and transmission electron microscopy to find the transitional compounds. Investigation of the binary and ternary powder mixtures revealed the appearance of H3PO4, Ca(OH)2, Ca2P2O7 and CaCO3 as the intermediate compounds. At early stages of the milling, conversions of P2O5 to H3PO4 and CaO to Ca(OH)2 occurred in the wet atmosphere. Later, a combination of Ca(OH)2 and H3PO4 formed C a2P2O7 while the unreacted CaO was converted to CaCO3 by CO2 of the ambient atmosphere. Spherical crystalline Ca10 (PO4)6F2 particles formed after 48 hours of milling due to the reaction between Ca2P2O7, CaCO3 and CaF2.
{"title":"Mechanism of Nanostructured Fluorapatite Formation from CaO, CaF2 and P2O5 Precursors by Mechanochemical Synthesis","authors":"R. N. Mofrad, S. Sadrnezhaad, J. V. Khaki","doi":"10.3184/146867818X15233705894419","DOIUrl":"https://doi.org/10.3184/146867818X15233705894419","url":null,"abstract":"We determined the mechanism of mechanochemical synthesis of fluorapatite from CaO, CaF2 and P2O5 by characterisation of the intermediate compounds. We used atomic absorption spectroscopy, X-ray diffraction, field emission scanning electron microscopy, FTIR spectroscopy and transmission electron microscopy to find the transitional compounds. Investigation of the binary and ternary powder mixtures revealed the appearance of H3PO4, Ca(OH)2, Ca2P2O7 and CaCO3 as the intermediate compounds. At early stages of the milling, conversions of P2O5 to H3PO4 and CaO to Ca(OH)2 occurred in the wet atmosphere. Later, a combination of Ca(OH)2 and H3PO4 formed C a2P2O7 while the unreacted CaO was converted to CaCO3 by CO2 of the ambient atmosphere. Spherical crystalline Ca10 (PO4)6F2 particles formed after 48 hours of milling due to the reaction between Ca2P2O7, CaCO3 and CaF2.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"76 1","pages":"201 - 210"},"PeriodicalIF":0.7,"publicationDate":"2018-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85781061","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 : 2018-10-01DOI: 10.3184/146867818X15319903829164
Enisa Selimović, T. Soldatović
The mole-ratio method was used to determine the metal–ligand stoichiometry between [ZnCl2(en)] and [ZnCl2(terpy)] (where en = 1,2-diaminoethane or ethylenediamine and terpy = 2,2′:6′,2″-terpyridine) and imidazole at pH 7.2 in the presence of different chloride concentrations. The results indicated step-wise formation of 1:1 and 1:2 complexes in the presence of 0.010 M NaCl and 1:1 complexes in the presence of 0.001 M NaCl for the [ZnCl2(en)] complex. These results are correlated with additional coordination of chlorides in the first coordination sphere and with changes in coordination geometry. In the presence of 0.001 M NaCl the five-coordinate complex anion [ZnCl3(en)]- is formed initially and then a substitution reaction with imidazole occurs. In the presence of 0.010 M NaCl the octahedral complex anion [ZnCl4(en)]2- is formed. Additional coordination of chloride in the [ZnCl2(terpy)] complex is not found and the metal–ligand stoichiometry is 1:2. The kinetics of ligand substitution reactions of zinc(II) complexes and biologically relevant nitrogen nucleophiles such as imidazole, 1,2,3-triazole and L-histidine were investigated at pH 7.2 as a function of nucleophile concentration in the presence of 0.001 M and 0.010 M NaCl. The reactions were followed under pseudo first-order conditions by UV-Vis spectrophotometry. The substitution reactions included two steps of consecutive displacement of chlorido ligands with changes only in the coordination geometry of the [ZnCl2(en)] complex. The order of reactivity of the investigated nucleophiles for the first reaction step towards both complexes was L-histidine > 1,2,3-triazole > imidazole, while in the presence of 0.010 M NaCl the most reactive ligand was 1,2,3-triazole towards the [ZnCl2(en)] complex.
采用摩尔比法测定了[ZnCl2(en)]和[ZnCl2(terpy)] (en = 1,2-二氨基乙烷或乙二胺，terpy = 2,2′:6′，2″-三吡啶)与咪唑在pH为7.2条件下的金属配体化学计量。结果表明，[ZnCl2(en)]配合物在0.010 M NaCl存在下可逐步形成1:1和1:2的配合物，在0.001 M NaCl存在下可形成1:1的配合物。这些结果与第一配位球中氯化物的附加配位以及配位几何的变化有关。在0.001 M NaCl存在下，首先形成五配位阴离子[ZnCl3(en)]-，然后与咪唑发生取代反应。在0.010 M NaCl存在下，形成八面体配合阴离子[ZnCl4(en)]2-。在[ZnCl2(terpy)]配合物中没有发现氯的额外配位，金属配体化学计量为1:2。研究了锌(II)配合物与咪唑、1,2,3-三唑和l -组氨酸等生物相关的氮亲核试剂在pH 7.2条件下，在0.001 M和0.010 M NaCl存在下，其配体取代反应的动力学与亲核试剂浓度的关系。用紫外-可见分光光度法在伪一级条件下对反应进行了跟踪。取代反应包括氯基配体连续位移的两个步骤，仅改变[ZnCl2(en)]配合物的配位几何形状。研究的亲核试剂对这两个配合物的第一步反应活性顺序为l -组氨酸> 1,2,3-三唑>咪唑，而在0.010 M NaCl存在下，对[ZnCl2(en)]配合物反应活性最高的配体是1,2,3-三唑。
{"title":"Impact of Chloride Concentration on Ligand Substitution Reactions of Zinc(II) Complexes with Biologically Relevant Nitrogen Nucleophiles","authors":"Enisa Selimović, T. Soldatović","doi":"10.3184/146867818X15319903829164","DOIUrl":"https://doi.org/10.3184/146867818X15319903829164","url":null,"abstract":"The mole-ratio method was used to determine the metal–ligand stoichiometry between [ZnCl2(en)] and [ZnCl2(terpy)] (where en = 1,2-diaminoethane or ethylenediamine and terpy = 2,2′:6′,2″-terpyridine) and imidazole at pH 7.2 in the presence of different chloride concentrations. The results indicated step-wise formation of 1:1 and 1:2 complexes in the presence of 0.010 M NaCl and 1:1 complexes in the presence of 0.001 M NaCl for the [ZnCl2(en)] complex. These results are correlated with additional coordination of chlorides in the first coordination sphere and with changes in coordination geometry. In the presence of 0.001 M NaCl the five-coordinate complex anion [ZnCl3(en)]- is formed initially and then a substitution reaction with imidazole occurs. In the presence of 0.010 M NaCl the octahedral complex anion [ZnCl4(en)]2- is formed. Additional coordination of chloride in the [ZnCl2(terpy)] complex is not found and the metal–ligand stoichiometry is 1:2. The kinetics of ligand substitution reactions of zinc(II) complexes and biologically relevant nitrogen nucleophiles such as imidazole, 1,2,3-triazole and L-histidine were investigated at pH 7.2 as a function of nucleophile concentration in the presence of 0.001 M and 0.010 M NaCl. The reactions were followed under pseudo first-order conditions by UV-Vis spectrophotometry. The substitution reactions included two steps of consecutive displacement of chlorido ligands with changes only in the coordination geometry of the [ZnCl2(en)] complex. The order of reactivity of the investigated nucleophiles for the first reaction step towards both complexes was L-histidine > 1,2,3-triazole > imidazole, while in the presence of 0.010 M NaCl the most reactive ligand was 1,2,3-triazole towards the [ZnCl2(en)] complex.","PeriodicalId":20859,"journal":{"name":"Progress in Reaction Kinetics and Mechanism","volume":"1 1","pages":"244 - 253"},"PeriodicalIF":0.7,"publicationDate":"2018-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84329255","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 : 2018-10-01DOI: 10.3184/146867818X15233705894446
M. Azarhoosh, R. Halladj, S. Askari
First, the effects of ultrasound-related variables on the crystallinity and particle size of synthesised SAPO-34 catalysts were modelled using a genetic programming (GP) method. The results confirm that GP has good predictive power. Secondly, optimisation of the ultrasound parameters was considered using a genetic algorithm (GA) to obtain SAPO-34 catalysts with high crystallinity and minimum particle size for the best performance in the methanol to light olefins process. The GP models were used as the fitness functions inside the GA. Finally, the optimum solution was validated experimentally and the results indicate that there is a good agreement between experimental and predicted values.
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