Anatase TiO_(2)nanospindles containing 89%exposed{101}facets(TIO_(2)-101)and nanosheets with 77%exposed{001}facets(TiO_(2)-001)were hydrothermally synthesized and used as supports for Pd catalysts.The effects of the T...Anatase TiO_(2)nanospindles containing 89%exposed{101}facets(TIO_(2)-101)and nanosheets with 77%exposed{001}facets(TiO_(2)-001)were hydrothermally synthesized and used as supports for Pd catalysts.The effects of the TiO_(2)materials on the catalytic performance of Pd/TiO_(2)-101 and Pd/TiO_(2)-001 catalysts were investigated in the selective hydrogenation of acetylene to polymer-grade ethylene.The PdfTiO_(2)-101 catalyst exhibited enhanced performance in terms of acetylene conversion and ethylene yield.To understand these effects,the catalysts were characterized by H_(2)temperature-programmed desorption(H_(2)-TPD),H_(2)temperature-programmed reduction(H=-TPR),transmission electron microscopy(TEM),pulse CO chemisorption,X-ray photoelectron spectroscopy(XPS),and thermogravimetric analysis(TGA).The TEM and CO chemisorption results confirmed that Pd nanoparticles(NPs)on the TiO_(2)-101 support had a smaller average particle size(1.53 nm)and a higher dispersion(15.95%)than those on the TiO_(2)-001 support(average particle size of 4.36 nm and dispersion of 9.06%).The smaller particle size and higher dispersion of Pd on the Pd/TiO_(2)-101 catalyst provided more reaction active sites,which contributed to the improved catalytic activity of this supported catalyst.展开更多
Carbon nanotube formation exemplifies atomically precise self-assembly,where atomic interactions dynamically engineer nanoscale architectures with emergent properties that transcend classical material boundaries.Howev...Carbon nanotube formation exemplifies atomically precise self-assembly,where atomic interactions dynamically engineer nanoscale architectures with emergent properties that transcend classical material boundaries.However,elucidating the transient molecular intermediates remains a critical mechanistic frontier.This study investigates the atomic-scale nucleation process of single-walled carbon nanotubes(SWCNTs)from acetylene on iron(Fe)clusters,utilizing GFN(-x)TB-based nanoreactor molecular dynamics simulations.The simulations reveal a consistent nucleation pathway,regardless of iron cluster size(Fe_(13),Fe_(38),Fe_(55)),where the chemisorption and dissociation of acetylene molecules on the Fe clusters lead to the formation of C_(2)H and C_(2)intermediates.These species then undergo oligomerization,initiating the growth of carbon chains.As the chains cross-link and cyclize,five-membered carbon rings are preferentially formed,which eventually evolve into six-membered rings and more complex sp2-hybridized carbon networks,resembling the cap structures of nascent SWCNTs.Although the nucleation mechanism remains similar across all cluster sizes,larger clusters show enhanced catalytic activity,leading to higher molecular weight hydrocarbons and more extensive carbocyclic networks due to their higher density of active sites per reacting molecule.Crucially,the study highlights the role of C_(2)H as the key active species in the carbon network formation process.These findings offer critical insights into the initial stages of SWCNT nucleation,contributing to a deeper understanding of the mechanisms driving SWCNT growth and guiding the development of optimized synthetic strategies.展开更多
Activity on catalytic reduction of C<sub>2</sub>H<sub>2</sub> for seven Mo-Fe-S cluster compounds (I. （Et<sub>4</sub>N<sub>4</sub>）<sub>4</sub>[Mo<sub&g...Activity on catalytic reduction of C<sub>2</sub>H<sub>2</sub> for seven Mo-Fe-S cluster compounds (I. （Et<sub>4</sub>N<sub>4</sub>）<sub>4</sub>[Mo<sub>2</sub>Fe<sub>2</sub>S<sub>10</sub>]·2CH<sub>3</sub>OH, Ⅱ. Mo<sub>2</sub>Fe<sub>2</sub>S<sub>4</sub>（S<sub>2</sub>CNEt<sub>2</sub>）<sub>5</sub>·CH<sub>3</sub>CN, Ⅲ. （Bu<sub>4</sub>N）<sub>3</sub> [Mo<sub>2</sub>FeS<sub>8</sub>O]·Ⅳ·（Et<sub>4</sub>N）<sub>3</sub>[Mo<sub>2</sub>FeS<sub>8</sub>O<sub>2</sub>], V. （Et<sub>4</sub>N）<sub>2</sub>[MoFeS<sub>4</sub>（SCN）<sub>2</sub>（OCH<sub>3</sub>）<sub>2</sub>]·3CH<sub>3</sub>OH, Ⅵ. （Et<sub>4</sub>N）<sub>3</sub>[Mo<sub>2</sub>FeS<sub>8</sub>O（OCH<sub>3</sub>）<sub>2</sub>], Ⅶ. （Et<sub>4</sub>N）<sub>4</sub>Mo<sub>2</sub>Fe<sub>7</sub>S<sub>12</sub>（SPh）<sub>6</sub>·6CH<sub>3</sub>OH), three Fe-S cluster compounds （Ⅷ.（Et<sub>4</sub>N）<sub>2</sub>[Fe<sub>4</sub>S<sub>4</sub>（S<sub>2</sub>CNEt<sub>2</sub>）<sub>4</sub>], Ⅸ. （Bu<sub>4</sub>N）<sub>2</sub>[Fe<sub>4</sub>S<sub>3</sub>（SC（CH<sub>3</sub>）<sub>3</sub>）<sub>4</sub>], Ⅹ. （Bu<sub>4</sub>N）[Fe<sub>2</sub>S<sub>3</sub>（SCH<sub>2</sub>Ph）<sub>2</sub>]） and combination systems of related compounds, has been determined under anaerobic conditions at 25℃ and with KBH<sub>4</sub> as the reductant. In addition, at 15℃, under otherwise the same conditions, activity on catalytic reduction of C<sub>2</sub>H<sub>2</sub> for different constituent systems from （NH<sub>4</sub>）<sub>2</sub>MoS<sub>4</sub> and FeCl<sub>3</sub> has also been determined.展开更多
In the presence of Rh（COD）（dppe）Cl （COD=1, 5-cyclootadiene, dppe=1,2-bis-（diphenylphosphino）ethane） and CO, we studied the H/Cl exchange reaction between CH<sub>4</sub> and o-dichlorobenzene, and o...In the presence of Rh（COD）（dppe）Cl （COD=1, 5-cyclootadiene, dppe=1,2-bis-（diphenylphosphino）ethane） and CO, we studied the H/Cl exchange reaction between CH<sub>4</sub> and o-dichlorobenzene, and observed that the active species of the reaction is a complex containing dppe and carbonyl ligands. We suggest that the mechanism of exchange reaction may be described by the elementary reaction of oxidative addition and reductive elimination. In the presence of trans-PtHL<sub>2</sub>X （L=PEt<sub>3</sub>, P（n-Pr）<sub>3</sub>, P（n-Bu）<sub>3</sub>, PPh<sub>3</sub>; X=Cl<sup>-</sup>, Br<sup>-</sup>, I<sup>-</sup>, CN<sup>-</sup>） complexes, we have studied the oxidative chlorination reaction of methane. The catalytic activity was found to be related to the electron-donating properties and the cone angle of tertiary phosphine, as well as the trans-effect of X anionic ligands. In addition to the above reactions, we have also studied the insertion reaction of acetylene into C-H bond of methane catalyzed by organotransition-metal complexes containing heterocyclic chelate ligands, such as bipy, phen and TMEDA, in展开更多
文摘Anatase TiO_(2)nanospindles containing 89%exposed{101}facets(TIO_(2)-101)and nanosheets with 77%exposed{001}facets(TiO_(2)-001)were hydrothermally synthesized and used as supports for Pd catalysts.The effects of the TiO_(2)materials on the catalytic performance of Pd/TiO_(2)-101 and Pd/TiO_(2)-001 catalysts were investigated in the selective hydrogenation of acetylene to polymer-grade ethylene.The PdfTiO_(2)-101 catalyst exhibited enhanced performance in terms of acetylene conversion and ethylene yield.To understand these effects,the catalysts were characterized by H_(2)temperature-programmed desorption(H_(2)-TPD),H_(2)temperature-programmed reduction(H=-TPR),transmission electron microscopy(TEM),pulse CO chemisorption,X-ray photoelectron spectroscopy(XPS),and thermogravimetric analysis(TGA).The TEM and CO chemisorption results confirmed that Pd nanoparticles(NPs)on the TiO_(2)-101 support had a smaller average particle size(1.53 nm)and a higher dispersion(15.95%)than those on the TiO_(2)-001 support(average particle size of 4.36 nm and dispersion of 9.06%).The smaller particle size and higher dispersion of Pd on the Pd/TiO_(2)-101 catalyst provided more reaction active sites,which contributed to the improved catalytic activity of this supported catalyst.
基金supported by the National Key R&D Program of China(2022YFA1604100)the National Natural Science Foundation of China(22302220,22372187,1972157,21972160,22402218)+2 种基金the National Science Fund for Distinguished Young Scholars of China(22225206)the Fundamental Research Program of Shanxi Province(202203021222403)the Youth Innovation Promotion Association CAS(2020179)。
文摘Carbon nanotube formation exemplifies atomically precise self-assembly,where atomic interactions dynamically engineer nanoscale architectures with emergent properties that transcend classical material boundaries.However,elucidating the transient molecular intermediates remains a critical mechanistic frontier.This study investigates the atomic-scale nucleation process of single-walled carbon nanotubes(SWCNTs)from acetylene on iron(Fe)clusters,utilizing GFN(-x)TB-based nanoreactor molecular dynamics simulations.The simulations reveal a consistent nucleation pathway,regardless of iron cluster size(Fe_(13),Fe_(38),Fe_(55)),where the chemisorption and dissociation of acetylene molecules on the Fe clusters lead to the formation of C_(2)H and C_(2)intermediates.These species then undergo oligomerization,initiating the growth of carbon chains.As the chains cross-link and cyclize,five-membered carbon rings are preferentially formed,which eventually evolve into six-membered rings and more complex sp2-hybridized carbon networks,resembling the cap structures of nascent SWCNTs.Although the nucleation mechanism remains similar across all cluster sizes,larger clusters show enhanced catalytic activity,leading to higher molecular weight hydrocarbons and more extensive carbocyclic networks due to their higher density of active sites per reacting molecule.Crucially,the study highlights the role of C_(2)H as the key active species in the carbon network formation process.These findings offer critical insights into the initial stages of SWCNT nucleation,contributing to a deeper understanding of the mechanisms driving SWCNT growth and guiding the development of optimized synthetic strategies.
基金Project supported by the National Nartural Science Foundation of China
文摘Activity on catalytic reduction of C<sub>2</sub>H<sub>2</sub> for seven Mo-Fe-S cluster compounds (I. （Et<sub>4</sub>N<sub>4</sub>）<sub>4</sub>[Mo<sub>2</sub>Fe<sub>2</sub>S<sub>10</sub>]·2CH<sub>3</sub>OH, Ⅱ. Mo<sub>2</sub>Fe<sub>2</sub>S<sub>4</sub>（S<sub>2</sub>CNEt<sub>2</sub>）<sub>5</sub>·CH<sub>3</sub>CN, Ⅲ. （Bu<sub>4</sub>N）<sub>3</sub> [Mo<sub>2</sub>FeS<sub>8</sub>O]·Ⅳ·（Et<sub>4</sub>N）<sub>3</sub>[Mo<sub>2</sub>FeS<sub>8</sub>O<sub>2</sub>], V. （Et<sub>4</sub>N）<sub>2</sub>[MoFeS<sub>4</sub>（SCN）<sub>2</sub>（OCH<sub>3</sub>）<sub>2</sub>]·3CH<sub>3</sub>OH, Ⅵ. （Et<sub>4</sub>N）<sub>3</sub>[Mo<sub>2</sub>FeS<sub>8</sub>O（OCH<sub>3</sub>）<sub>2</sub>], Ⅶ. （Et<sub>4</sub>N）<sub>4</sub>Mo<sub>2</sub>Fe<sub>7</sub>S<sub>12</sub>（SPh）<sub>6</sub>·6CH<sub>3</sub>OH), three Fe-S cluster compounds （Ⅷ.（Et<sub>4</sub>N）<sub>2</sub>[Fe<sub>4</sub>S<sub>4</sub>（S<sub>2</sub>CNEt<sub>2</sub>）<sub>4</sub>], Ⅸ. （Bu<sub>4</sub>N）<sub>2</sub>[Fe<sub>4</sub>S<sub>3</sub>（SC（CH<sub>3</sub>）<sub>3</sub>）<sub>4</sub>], Ⅹ. （Bu<sub>4</sub>N）[Fe<sub>2</sub>S<sub>3</sub>（SCH<sub>2</sub>Ph）<sub>2</sub>]） and combination systems of related compounds, has been determined under anaerobic conditions at 25℃ and with KBH<sub>4</sub> as the reductant. In addition, at 15℃, under otherwise the same conditions, activity on catalytic reduction of C<sub>2</sub>H<sub>2</sub> for different constituent systems from （NH<sub>4</sub>）<sub>2</sub>MoS<sub>4</sub> and FeCl<sub>3</sub> has also been determined.
基金This work was supported by the Natural Science Foundation of China
文摘In the presence of Rh（COD）（dppe）Cl （COD=1, 5-cyclootadiene, dppe=1,2-bis-（diphenylphosphino）ethane） and CO, we studied the H/Cl exchange reaction between CH<sub>4</sub> and o-dichlorobenzene, and observed that the active species of the reaction is a complex containing dppe and carbonyl ligands. We suggest that the mechanism of exchange reaction may be described by the elementary reaction of oxidative addition and reductive elimination. In the presence of trans-PtHL<sub>2</sub>X （L=PEt<sub>3</sub>, P（n-Pr）<sub>3</sub>, P（n-Bu）<sub>3</sub>, PPh<sub>3</sub>; X=Cl<sup>-</sup>, Br<sup>-</sup>, I<sup>-</sup>, CN<sup>-</sup>） complexes, we have studied the oxidative chlorination reaction of methane. The catalytic activity was found to be related to the electron-donating properties and the cone angle of tertiary phosphine, as well as the trans-effect of X anionic ligands. In addition to the above reactions, we have also studied the insertion reaction of acetylene into C-H bond of methane catalyzed by organotransition-metal complexes containing heterocyclic chelate ligands, such as bipy, phen and TMEDA, in
