Pub Date : 2024-04-27DOI: 10.1134/s002315842401004x
T. V. Krasnyakova, D. V. Nikitenko, S. A. Mitchenko
Abstract
A new catalytic system for reductive С(sp2)–C(sp3) cross-electrophile coupling was designed: PtII iodide complexes in an acetone solution of NaI catalyze the coupling of methyl iodide with vinyl iodide to form propylene. Simultaneously, a small amount of 1,3-butadiene, the product of C(sp2)–C(sp2) coupling, is released. The total yield of the products with respect to the reacted vinyl iodide is almost quantitative. In a large excess of CH3I, the C2H3I consumption is described by the pseudo-first-order kinetics. The cross-coupling occurs as the following sequence of steps: oxidative addition of CH3I to PtII iodide complexes to form a methyl PtIV complex → reduction of the methyl PtIV complex with I– to form the corresponding PtII derivative → oxidative addition of C2H3I to the PtII derivative → reductive elimination of organyl ligands from the intermediate methyl vinyl PtIV complex.
{"title":"Catalytic C(sp2)–C(sp3) Cross-Electrophile Coupling in the PtII–NaI–С2Н3I–СН3I–Acetone System","authors":"T. V. Krasnyakova, D. V. Nikitenko, S. A. Mitchenko","doi":"10.1134/s002315842401004x","DOIUrl":"https://doi.org/10.1134/s002315842401004x","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>A new catalytic system for reductive С(<i>sp</i><sup>2</sup>)–C(<i>sp</i><sup>3</sup>) cross-electrophile coupling was designed: Pt<sup>II</sup> iodide complexes in an acetone solution of NaI catalyze the coupling of methyl iodide with vinyl iodide to form propylene. Simultaneously, a small amount of 1,3-butadiene, the product of C(<i>sp</i><sup>2</sup>)–C(<i>sp</i><sup>2</sup>) coupling, is released. The total yield of the products with respect to the reacted vinyl iodide is almost quantitative. In a large excess of CH<sub>3</sub>I, the C<sub>2</sub>H<sub>3</sub>I consumption is described by the pseudo-first-order kinetics. The cross-coupling occurs as the following sequence of steps: oxidative addition of CH<sub>3</sub>I to Pt<sup>II</sup> iodide complexes to form a methyl Pt<sup>IV</sup> complex → reduction of the methyl Pt<sup>IV</sup> complex with I<sup>–</sup> to form the corresponding Pt<sup>II</sup> derivative → oxidative addition of C<sub>2</sub>H<sub>3</sub>I to the Pt<sup>II</sup> derivative → reductive elimination of organyl ligands from the intermediate methyl vinyl Pt<sup>IV</sup> complex.</p>","PeriodicalId":682,"journal":{"name":"Kinetics and Catalysis","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2024-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140809786","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 : 2024-04-27DOI: 10.1134/s0023158424010026
V. B. Kharitontsev, M. V. Grigoriev, E. A. Tissen, P. A. Zubenko, N. Yu. Tretyakov, A. V. Elyshev
Abstract
Pyrolysis of high-density polyethylene in the presence of aluminosilicate materials containing nickel oxide has been studied. The catalytic pyrolysis of plastics makes it possible to convert polymers into chemical compounds, which can later be used as additional sources of fuels and raw materials for chemical industry or polymer production. The physicochemical parameters of the materials containing nickel oxide were determined by Fourier-transform IR spectroscopy, X-ray diffraction analysis, N2 physical adsorption method, thermogravimetric analysis, and pyrolytic gas chromatography. The chemical composition of polyethylene pyrolysis products was found to depend on the type of support used and the presence of nickel oxide in it. The presence of nickel oxide in the studied aluminosilicates increases the Lewis acidity and the content of aromatic compounds in the pyrolysis products. The activation energy of polyethylene pyrolysis in the presence of MSM-41 containing nickel oxide was calculated from the experimental data.
{"title":"Pyrolytic Decomposition of Polyethylene in the Presence of Aluminosilicate Materials Containing Nickel Oxide","authors":"V. B. Kharitontsev, M. V. Grigoriev, E. A. Tissen, P. A. Zubenko, N. Yu. Tretyakov, A. V. Elyshev","doi":"10.1134/s0023158424010026","DOIUrl":"https://doi.org/10.1134/s0023158424010026","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Pyrolysis of high-density polyethylene in the presence of aluminosilicate materials containing nickel oxide has been studied. The catalytic pyrolysis of plastics makes it possible to convert polymers into chemical compounds, which can later be used as additional sources of fuels and raw materials for chemical industry or polymer production. The physicochemical parameters of the materials containing nickel oxide were determined by Fourier-transform IR spectroscopy, X-ray diffraction analysis, N<sub>2</sub> physical adsorption method, thermogravimetric analysis, and pyrolytic gas chromatography. The chemical composition of polyethylene pyrolysis products was found to depend on the type of support used and the presence of nickel oxide in it. The presence of nickel oxide in the studied aluminosilicates increases the Lewis acidity and the content of aromatic compounds in the pyrolysis products. The activation energy of polyethylene pyrolysis in the presence of MSM-41 containing nickel oxide was calculated from the experimental data.</p>","PeriodicalId":682,"journal":{"name":"Kinetics and Catalysis","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2024-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140809784","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 : 2024-04-27DOI: 10.1134/s0023158424010038
M. A. Kipnis, P. V. Samokhin, R. S. Galkin, E. A. Volnina, N. A. Zhilyaeva
Abstract
The physicochemical and catalytic (CO2 hydrogenation) characteristics of Mo-containing catalysts were studied. The catalysts containing 8 and 15 wt % Mo oxide were prepared by impregnation of γ‑Al2O3 with ammonium paramolybdate, followed by drying and calcination at 500°C. The introduction of Mo oxide reduced the pore volume of the support and increased the average pore size, indicating that molybdenum oxide was distributed in the support pores. According to the X-ray diffraction analysis, the calcinated catalyst did not contain the crystalline MoO3 phase. According to the Raman spectra, oxygen-containing formations were present on the catalyst surface, with Mo atoms tetrahedrally and octahedrally coordinated to the oxygen atoms. The impregnated MoO3 was partially reduced with hydrogen during linear heating, starting from 320°C. The hydrogenation of CO2 (gas composition, vol %: 30.7 CO2, 68 H2, the rest was N2; 0.5 g sample) was studied under conditions of linear heating to 400°C. The main reaction was the reverse reaction of CO steam reforming. The contribution of methanation to CO2 hydrogenation was small. An increase in the temperature and pressure had a positive effect on CO2 conversion. When the pressure increased from 1 to 5 MPa, the CO content was approximately doubled. In the CO2 hydrogenation, appreciable activity (although significantly lower compared to that of Mo-containing catalysts) was also exhibited by γ-Al2O3, preliminarily heated to 400°C in an H2 flow. The activity of alumina also increased with pressure.
摘要 研究了含钼催化剂的物理化学和催化（二氧化碳加氢）特性。用对钼酸铵浸渍γ-Al2O3，然后在 500°C 下干燥和煅烧，制备了含 8 和 15 wt % 氧化钼的催化剂。氧化钼的引入减少了支撑体的孔隙体积，增加了平均孔径，表明氧化钼分布在支撑体的孔隙中。根据 X 射线衍射分析，煅烧后的催化剂不含结晶 MoO3 相。拉曼光谱显示，催化剂表面存在含氧形态，钼原子与氧原子呈四面体和八面体配位。在 320°C 开始的线性加热过程中，浸渍的 MoO3 被氢气部分还原。在线性加热至 400°C 的条件下，研究了二氧化碳的氢化（气体成分，体积百分比：30.7 CO2，68 H2，其余为 N2；0.5 克样品）。主要反应是 CO 蒸汽重整的逆反应。甲烷化对 CO2 加氢的影响很小。温度和压力的增加对 CO2 转化有积极影响。当压力从 1 兆帕增加到 5 兆帕时，CO 的含量大约增加了一倍。在 CO2 加氢过程中，在 H2 流中初步加热到 400°C 的 γ-Al2O3 也表现出明显的活性（尽管与含 Mo 催化剂相比明显较低）。氧化铝的活性也随着压力的增加而提高。
{"title":"Hydrogenation of CO2 on MoO3/Al2O3 and γ-Al2O3","authors":"M. A. Kipnis, P. V. Samokhin, R. S. Galkin, E. A. Volnina, N. A. Zhilyaeva","doi":"10.1134/s0023158424010038","DOIUrl":"https://doi.org/10.1134/s0023158424010038","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The physicochemical and catalytic (CO<sub>2</sub> hydrogenation) characteristics of Mo-containing catalysts were studied. The catalysts containing 8 and 15 wt % Mo oxide were prepared by impregnation of γ‑Al<sub>2</sub>O<sub>3</sub> with ammonium paramolybdate, followed by drying and calcination at 500°C. The introduction of Mo oxide reduced the pore volume of the support and increased the average pore size, indicating that molybdenum oxide was distributed in the support pores. According to the X-ray diffraction analysis, the calcinated catalyst did not contain the crystalline MoO<sub>3</sub> phase. According to the Raman spectra, oxygen-containing formations were present on the catalyst surface, with Mo atoms tetrahedrally and octahedrally coordinated to the oxygen atoms. The impregnated MoO<sub>3</sub> was partially reduced with hydrogen during linear heating, starting from 320°C. The hydrogenation of CO<sub>2</sub> (gas composition, vol %: 30.7 CO<sub>2</sub>, 68 H<sub>2</sub>, the rest was N<sub>2</sub>; 0.5 g sample) was studied under conditions of linear heating to 400°C. The main reaction was the reverse reaction of CO steam reforming. The contribution of methanation to CO<sub>2</sub> hydrogenation was small. An increase in the temperature and pressure had a positive effect on CO<sub>2</sub> conversion. When the pressure increased from 1 to 5 MPa, the CO content was approximately doubled. In the CO<sub>2</sub> hydrogenation, appreciable activity (although significantly lower compared to that of Mo-containing catalysts) was also exhibited by γ-Al<sub>2</sub>O<sub>3</sub>, preliminarily heated to 400°C in an H<sub>2</sub> flow. The activity of alumina also increased with pressure.</p>","PeriodicalId":682,"journal":{"name":"Kinetics and Catalysis","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2024-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140809788","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 : 2023-12-12DOI: 10.1134/s0023158423060137
D. A. Shlyapin, V. A. Borisov, V. L. Temerev, K. N. Iost, Z. A. Fedorova, P. V. Snytnikov
Abstract
Based on analysis of the catalytic properties of 4%Ru–13.6%Cs/Sibunit and 4%Ru–5.4%Ba–7.9%Cs/Sibunit in the ammonia decomposition (105 Pa, 350–470°C) and ammonia synthesis processes (6 × 105–5 × 106 Pa, 400–430°C), an analytical expression for nitrogen formation/consumption rate in the reversible reaction N2 + 3H2( rightleftharpoons ) 2NH3 has been derived to correctly describe the dependence of the chemical reaction rate on the partial pressures of the reaction mixture components for both the forward and reverse reactions. The approach used to derive the kinetic equation is based on the assumption that the adsorption sites of the ruthenium surface are filled with hydrogen, which is subsequently displaced by nitrogen during competitive interaction. Using the proposed kinetic equation, the equilibrium constants and apparent activation energies for ammonia synthesis and decomposition in the presence of 4%Ru–13.6%Cs/Sibunit and 4%Ru–5.4%Ba–7.9%Cs/Sibunit catalysts have been determined; the values are in good agreement with the published data.
{"title":"Ammonia Synthesis and Decomposition in the Presence of Supported Ruthenium Catalysts","authors":"D. A. Shlyapin, V. A. Borisov, V. L. Temerev, K. N. Iost, Z. A. Fedorova, P. V. Snytnikov","doi":"10.1134/s0023158423060137","DOIUrl":"https://doi.org/10.1134/s0023158423060137","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Based on analysis of the catalytic properties of 4%Ru–13.6%Cs/Sibunit and 4%Ru–5.4%Ba–7.9%Cs/Sibunit in the ammonia decomposition (10<sup>5</sup> Pa, 350–470°C) and ammonia synthesis processes (6 × 10<sup>5</sup>–5 × 10<sup>6</sup> Pa, 400–430°C), an analytical expression for nitrogen formation/consumption rate in the reversible reaction N<sub>2</sub> + 3H<sub>2</sub> <span>( rightleftharpoons )</span> 2NH<sub>3</sub> has been derived to correctly describe the dependence of the chemical reaction rate on the partial pressures of the reaction mixture components for both the forward and reverse reactions. The approach used to derive the kinetic equation is based on the assumption that the adsorption sites of the ruthenium surface are filled with hydrogen, which is subsequently displaced by nitrogen during competitive interaction. Using the proposed kinetic equation, the equilibrium constants and apparent activation energies for ammonia synthesis and decomposition in the presence of 4%Ru–13.6%Cs/Sibunit and 4%Ru–5.4%Ba–7.9%Cs/Sibunit catalysts have been determined; the values are in good agreement with the published data.</p>","PeriodicalId":682,"journal":{"name":"Kinetics and Catalysis","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2023-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138575238","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 : 2023-12-12DOI: 10.1134/s0023158423930031
Li Zhang, Yujing Xue, Ying Zhang
Abstract
Cu–Ni/SiO2 catalysts were prepared by coprecipitation method and used in the dehydrogenation reaction of secondary butyl alcohol to methyl ethyl ketone (MEK). The crystal structure, reduction characteristics, element valence state and dispersibility of the catalysts were investigated using X-ray diffraction (XRD), hydrogen temperature-programmed reduction (H2-TPR), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectroscopy (XPS), X-ray Auger electron spectroscopy (XAES) and high resolution transmission electron microscopy (HRTEM). The role of Ni component in the dehydrogenation reaction of secondary butyl alcohol was analyzed. The results showed that the conversion of secondary butyl alcohol increased to over 99% when using the Cu–Ni/SiO2 catalyst. The addition of nickel component to Cu/SiO2 inhibited the agglomeration of copper nanoparticles. The interaction between copper and nickel was strengthened due to the formation of the Cu–Ni compound. This resulted in change to the valence state and improved the dispersion of copper species on the catalyst surface. The Cu+/(Cu+ + Cu0) ratio increased with the addition of nickel component to Cu/SiO2, which may be responsible for the enhancement of the secondary butyl alcohol conversion. However, the addition of the nickel component increased the reduction temperature of the catalysts and deteriorated their reduction characteristics, which leads to insufficient reduction, resulting in a high content of Cu+ species remaining in the catalyst. Therefore, side reactions can occur, which are detrimental to the selectivity and yield of MEK. The selectivity to MEK can reach 98% with the Cu/SiO2 catalyst, whereas that for the Cu–Ni/SiO2 catalyst was 97%.
{"title":"Cu–Ni/SiO2 Catalysts for Dehydrogenation Reaction of Secondary Butyl Alcohol","authors":"Li Zhang, Yujing Xue, Ying Zhang","doi":"10.1134/s0023158423930031","DOIUrl":"https://doi.org/10.1134/s0023158423930031","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Cu–Ni/SiO<sub>2</sub> catalysts were prepared by coprecipitation method and used in the dehydrogenation reaction of secondary butyl alcohol to methyl ethyl ketone (MEK). The crystal structure, reduction characteristics, element valence state and dispersibility of the catalysts were investigated using X-ray diffraction (XRD), hydrogen temperature-programmed reduction (H<sub>2</sub>-TPR), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectroscopy (XPS), X-ray Auger electron spectroscopy (XAES) and high resolution transmission electron microscopy (HRTEM). The role of Ni component in the dehydrogenation reaction of secondary butyl alcohol was analyzed. The results showed that the conversion of secondary butyl alcohol increased to over 99% when using the Cu–Ni/SiO<sub>2</sub> catalyst. The addition of nickel component to Cu/SiO<sub>2</sub> inhibited the agglomeration of copper nanoparticles. The interaction between copper and nickel was strengthened due to the formation of the Cu–Ni compound. This resulted in change to the valence state and improved the dispersion of copper species on the catalyst surface. The Cu<sup>+</sup>/(Cu<sup>+</sup> + Cu<sup>0</sup>) ratio increased with the addition of nickel component to Cu/SiO<sub>2</sub>, which may be responsible for the enhancement of the secondary butyl alcohol conversion. However, the addition of the nickel component increased the reduction temperature of the catalysts and deteriorated their reduction characteristics, which leads to insufficient reduction, resulting in a high content of Cu<sup>+</sup> species remaining in the catalyst. Therefore, side reactions can occur, which are detrimental to the selectivity and yield of MEK. The selectivity to MEK can reach 98% with the Cu/SiO<sub>2</sub> catalyst, whereas that for the Cu–Ni/SiO<sub>2</sub> catalyst was 97%.</p>","PeriodicalId":682,"journal":{"name":"Kinetics and Catalysis","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2023-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138575876","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 : 2023-12-12DOI: 10.1134/s0023158423060022
L. B. Belykh, N. I. Skripov, T. P. Sterenchuk, V. V. Akimov, V. L. Tauson, M. N. Likhatski, E. A. Milenkaya, T. A. Kornaukhova, F. K. Schmidt
Abstract
The main reasons for the promoting effect of phosphorus on the properties of Pd–P/ZSM-5 catalysts during direct synthesis of H2O2 from H2 and O2 under mild conditions are considered based on the data obtained by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and inductively coupled plasma mass spectrometry (ICP MS). The introduction of phosphorus in the catalyst affects the particle size and the electronic state of palladium in the surface layer, as well as the surface concentration of the phosphate and phosphite ions. The yield of H2O2 increases when the particle size of the Pd–P catalysts decreases, when the side process of H2O2 decomposition is inhibited by the phosphate and phosphite surface ions, and when the hydrogen solubility in the solid solutions of phosphorus in palladium decreases.
{"title":"The First Application of Palladium–Phosphorus Catalysts in the Direct Synthesis of Hydrogen Peroxide: Reasons for the Promoting Action of Phosphorus","authors":"L. B. Belykh, N. I. Skripov, T. P. Sterenchuk, V. V. Akimov, V. L. Tauson, M. N. Likhatski, E. A. Milenkaya, T. A. Kornaukhova, F. K. Schmidt","doi":"10.1134/s0023158423060022","DOIUrl":"https://doi.org/10.1134/s0023158423060022","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The main reasons for the promoting effect of phosphorus on the properties of Pd–P/ZSM-5 catalysts during direct synthesis of H<sub>2</sub>O<sub>2</sub> from H<sub>2</sub> and O<sub>2</sub> under mild conditions are considered based on the data obtained by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and inductively coupled plasma mass spectrometry (ICP MS). The introduction of phosphorus in the catalyst affects the particle size and the electronic state of palladium in the surface layer, as well as the surface concentration of the phosphate and phosphite ions. The yield of H<sub>2</sub>O<sub>2</sub> increases when the particle size of the Pd–P catalysts decreases, when the side process of H<sub>2</sub>O<sub>2</sub> decomposition is inhibited by the phosphate and phosphite surface ions, and when the hydrogen solubility in the solid solutions of phosphorus in palladium decreases.</p>","PeriodicalId":682,"journal":{"name":"Kinetics and Catalysis","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2023-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138575320","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 : 2023-12-12DOI: 10.1134/s0023158423060083
Yu. V. Larichev, B. L. Moroz, P. A. Pyrjaev, V. I. Bukhtiyarov
Abstract
The advantages of using SAXS along with the masking liquid technique for determining the sizes of supported metal particles over the standard TEM and XRD methods, usually used for these purposes, were shown in the case of Au/C catalysts. Particle size distributions of gold in a wide range (1–50 nm) were obtained from the SAXS data, including for all size fractions present in the samples. The mass fractions of X-ray amorphous gold particles smaller than 4 nm (WSAXS) were determined. The oxidative treatment of the carbon support before the deposition of the metallic gold precursor complexes has a significant effect on the size distribution of gold particles in the final catalyst. A comparison of the experimental rates of CO oxidation with an excess of moist air at 40°C on Au/C catalysts with the WSAXS values found for these catalysts showed that the catalytic activity increased exponentially as WSAXS increased. The Au/C catalysts with WSAXS ≥ 80% showed high activity in the oxidation of CO.
摘要 在 Au/C 催化剂中，使用 SAXS 和掩蔽液技术确定支撑金属颗粒的尺寸比通常使用的标准 TEM 和 XRD 方法更有优势。从 SAXS 数据中获得的金的粒度分布范围很广（1-50 纳米），包括样品中存在的所有粒度分数。还测定了小于 4 纳米的 X 射线无定形金颗粒的质量分数（WSAXS）。在沉积金属金前驱体复合物之前对碳载体进行氧化处理对最终催化剂中金颗粒的尺寸分布有显著影响。将 Au/C 催化剂在 40°C 下与过量潮湿空气进行 CO 氧化的实验速率与这些催化剂的 WSAXS 值进行比较后发现，催化活性随着 WSAXS 的增加而呈指数增长。WSAXS≥ 80% 的 Au/C 催化剂在 CO 氧化过程中表现出较高的活性。
{"title":"Using SAXS for Determining the Sizes of Gold Nanoparticles in Au/C Catalysts: Advantages over Other Methods","authors":"Yu. V. Larichev, B. L. Moroz, P. A. Pyrjaev, V. I. Bukhtiyarov","doi":"10.1134/s0023158423060083","DOIUrl":"https://doi.org/10.1134/s0023158423060083","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The advantages of using SAXS along with the masking liquid technique for determining the sizes of supported metal particles over the standard TEM and XRD methods, usually used for these purposes, were shown in the case of Au/C catalysts. Particle size distributions of gold in a wide range (1–50 nm) were obtained from the SAXS data, including for all size fractions present in the samples. The mass fractions of X-ray amorphous gold particles smaller than 4 nm (<i>W</i><sub>SAXS</sub>) were determined. The oxidative treatment of the carbon support before the deposition of the metallic gold precursor complexes has a significant effect on the size distribution of gold particles in the final catalyst. A comparison of the experimental rates of CO oxidation with an excess of moist air at 40°C on Au/C catalysts with the <i>W</i><sub>SAXS</sub> values found for these catalysts showed that the catalytic activity increased exponentially as <i>W</i><sub>SAXS</sub> increased. The Au/C catalysts with <i>W</i><sub>SAXS</sub> ≥ 80% showed high activity in the oxidation of CO.</p>","PeriodicalId":682,"journal":{"name":"Kinetics and Catalysis","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2023-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138575299","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 : 2023-12-12DOI: 10.1134/s002315842393002x
Linbo Li, Yijun Du, Yao Li, Linjun Shao, Chenze Qi, Shujing Zhou, Jinjing Li
Abstract
Developing a facile and accurate method for assessing catalytic activities of supported metals can significantly promote the preparation and application of supported metal catalysts. Herein, we synthesized five MCM-41 materials functionalized with Schiff-base groups, which were employed as the supports for copper cations. The chemical structures and coordination of copper cations on the supports were characterized by Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The grafting densities were calculated by analyzing the results of thermal gravimetric analysis (TGA) and elemental analysis (EA). The microstructures of these supported copper catalysts were analyzed by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The oxidation of thioanisole to methylphenyl sulfoxide was employed to determine the catalytic activities of these supported copper catalysts while their o-Ps annihilation properties were evaluated by the positron annihilation lifetime spectroscopy. It is found that the o-Ps annihilation properties were linearly correlated with their catalytic activities. Therefore, the catalytic activities of supported copper species surrounded by different functional groups can be easily determined through o-Ps annihilation.
摘要 开发一种简便、准确的方法来评估支撑金属的催化活性，可极大地促进支撑金属催化剂的制备和应用。本文合成了五种具有希夫碱官能团的 MCM-41 材料，并将其用作铜阳离子的载体。傅立叶变换红外光谱（FT-IR）和 X 射线光电子能谱（XPS）表征了铜阳离子在载体上的化学结构和配位。通过分析热重分析（TGA）和元素分析（EA）的结果，计算了接枝密度。透射电子显微镜（TEM）和 X 射线衍射（XRD）分析了这些支撑铜催化剂的微观结构。利用硫代苯甲醚氧化成甲基苯基亚砜的过程测定了这些支撑铜催化剂的催化活性，同时利用正电子湮灭寿命光谱评估了它们的邻苯基湮灭特性。研究发现，邻苯基湮灭特性与其催化活性呈线性相关。因此，通过 o-Ps 原子湮灭可以很容易地确定被不同官能团包围的支撑铜催化剂的催化活性。
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Pub Date : 2023-12-12DOI: 10.1134/s0023158423060186
O. O. Voskresenskaya, N. A. Skorik
Abstract
The work presents an approach for studying the kinetics, mechanism, and reactivity of intermediates of a wide class of redox reactions for which the rate-limiting step is the redox decomposition of the intermediate complex. The approach was applied to the investigation of the oxidation of oxalic acid (H2Ox) by cerium(IV) in a sulfuric acid medium as part of the Belousov–Zhabotinsky oscillating reaction (BZ reaction) catalyzed by cerium ions. Experimental, mathematical, and computational methods that are typically used to study metal complexes in a stable oxidation state were kinetically generalized to variable-valence metal complexes and were used to determine the characteristics of intermediate complexes of the cerium(IV)–oxalate reaction and derive a general equation for its rate based on a set of equations describing the rapid achievement of pre-equilibrium in the system and the subsequent nonequilibrium process. A quantitative model of the process was proposed; it included two parallel reaction pathways, for which two different cerium(IV)–oxalate intermediate complexes were identified and characterized. The complexes have similar reactivity, which may be due to the similarity of the structure of their inner coordination spheres and the inner-sphere mechanism of electron transfer in the complexes. Using the developed model, a diagram of the yields of all main species of cerium(IV) under the conditions of the BZ reaction was constructed, which indicates the need to take into account the formation of intermediate complexes of the composition CeOHOx(_{n}^{{3 - 2n}}) (n = 1, 2) in the oxidation of oxalic acid under these conditions. The main difference between the presented model of the cerium(IV)–oxalate reaction as part of the BZ reaction and the previous models is the explicit consideration of the participation of intermediate complexes of cerium(IV) with oxalic acid anions and sulfate background anions in the reaction.
{"title":"Kinetics, Mechanism, and Reactivity of Intermediates of the Cerium(IV)–Oxalate Reaction in a Sulfate Medium","authors":"O. O. Voskresenskaya, N. A. Skorik","doi":"10.1134/s0023158423060186","DOIUrl":"https://doi.org/10.1134/s0023158423060186","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The work presents an approach for studying the kinetics, mechanism, and reactivity of intermediates of a wide class of redox reactions for which the rate-limiting step is the redox decomposition of the intermediate complex. The approach was applied to the investigation of the oxidation of oxalic acid (H<sub>2</sub>Ox) by cerium(IV) in a sulfuric acid medium as part of the Belousov–Zhabotinsky oscillating reaction (BZ reaction) catalyzed by cerium ions. Experimental, mathematical, and computational methods that are typically used to study metal complexes in a stable oxidation state were kinetically generalized to variable-valence metal complexes and were used to determine the characteristics of intermediate complexes of the cerium(IV)–oxalate reaction and derive a general equation for its rate based on a set of equations describing the rapid achievement of pre-equilibrium in the system and the subsequent nonequilibrium process. A quantitative model of the process was proposed; it included two parallel reaction pathways, for which two different cerium(IV)–oxalate intermediate complexes were identified and characterized. The complexes have similar reactivity, which may be due to the similarity of the structure of their inner coordination spheres and the inner-sphere mechanism of electron transfer in the complexes. Using the developed model, a diagram of the yields of all main species of cerium(IV) under the conditions of the BZ reaction was constructed, which indicates the need to take into account the formation of intermediate complexes of the composition CeOHO<i>x</i><span>(_{n}^{{3 - 2n}})</span> (<i>n</i> = 1, 2) in the oxidation of oxalic acid under these conditions. The main difference between the presented model of the cerium(IV)–oxalate reaction as part of the BZ reaction and the previous models is the explicit consideration of the participation of intermediate complexes of cerium(IV) with oxalic acid anions and sulfate background anions in the reaction.</p>","PeriodicalId":682,"journal":{"name":"Kinetics and Catalysis","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2023-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138575309","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 : 2023-12-12DOI: 10.1134/s0023158423060095
E. V. Larina, A. A. Kurokhtina, N. A. Lagoda, A. F. Schmidt
Abstract
A comparative study was made of the differential selectivity of the Sonogashira reaction with a pair of competing arylacetylenes under “ligand- and copper-free” conditions by varying nature and concentration of aryl halides and bases common to competing substrates. The change in the differential selectivity with varying nature of aryl halides is consistent with the proposal that aryl halide and arylacetylene are activated sequentially according to a mechanism that is linear in terms of chemical kinetics. The observed lack of influence of the nature and concentration of the base on the selectivity of the reaction under competition between arylacetylenes indicates that the step of their activation is virtually irreversible.
{"title":"Distinguishing Between Linear and Nonlinear (Cooperative) Mechanisms of Substrate Activation Under “Ligand- and Copper-Free” Conditions of the Sonogashira Reaction","authors":"E. V. Larina, A. A. Kurokhtina, N. A. Lagoda, A. F. Schmidt","doi":"10.1134/s0023158423060095","DOIUrl":"https://doi.org/10.1134/s0023158423060095","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>A comparative study was made of the differential selectivity of the Sonogashira reaction with a pair of competing arylacetylenes under “ligand- and copper-free” conditions by varying nature and concentration of aryl halides and bases common to competing substrates. The change in the differential selectivity with varying nature of aryl halides is consistent with the proposal that aryl halide and arylacetylene are activated sequentially according to a mechanism that is linear in terms of chemical kinetics. The observed lack of influence of the nature and concentration of the base on the selectivity of the reaction under competition between arylacetylenes indicates that the step of their activation is virtually irreversible.</p>","PeriodicalId":682,"journal":{"name":"Kinetics and Catalysis","volume":null,"pages":null},"PeriodicalIF":1.1,"publicationDate":"2023-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138575874","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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