Enhancing the stability of supported noble metal catalysts emerges is a major challenge in both science and industry.Herein,a heterogeneous Pd catalyst(Pd/NCF)was prepared by supporting Pd ultrafine metal nanoparticle...Enhancing the stability of supported noble metal catalysts emerges is a major challenge in both science and industry.Herein,a heterogeneous Pd catalyst(Pd/NCF)was prepared by supporting Pd ultrafine metal nanoparticles(NPs)on nitrogen-doped carbon;synthesized by using F127 as a stabilizer,as well as chitosan as a carbon and nitrogen source.The Pd/NCF catalyst was efficient and recyclable for oxidative carbonylation of phenol to diphenyl carbonate,exhibiting higher stability than Pd/NC prepared without F127 addition.The hydrogen bond between chitosan(CTS)and F127 was enhanced by F127,which anchored the N in the free amino group,increasing the N content of the carbon material and ensuring that the support could provide sufficient N sites for the deposition of Pd NPs.This process helped to improve metal dispersion.The increased metal-support interaction,which limits the leaching and coarsening of Pd NPs,improves the stability of the Pd/NCF catalyst.Furthermore,density functional theory calculations indicated that pyridine N stabilized the Pd^(2+)species,significantly inhibiting the loss of Pd^(2+)in Pd/NCF during the reaction process.This work provides a promising avenue towards enhancing the stability of nitrogen-doped carbon-supported metal catalysts.展开更多
A variety of terminal arylacetylenes have been conveniently synthesized in good to high yields via Sonogashira coupling of aryl iodides with （trimethylsilyl）acetylene catalyzed by MCM-41-supported mercapto palladium...A variety of terminal arylacetylenes have been conveniently synthesized in good to high yields via Sonogashira coupling of aryl iodides with （trimethylsilyl）acetylene catalyzed by MCM-41-supported mercapto palladium（0） complex, followed by desilylation under mild conditions. This polymeric palladium catalyst can be reused many times without any decrease in activity.展开更多
The copolymerization of CO and styrene catalyzed by Pd/C toward the formation of polyketones(PK)was studied in the N-valeronitrile-N'-methylimidazolium hexafluorophosphate([C4CNmim]+PF-6) medium. The synthesized P...The copolymerization of CO and styrene catalyzed by Pd/C toward the formation of polyketones(PK)was studied in the N-valeronitrile-N'-methylimidazolium hexafluorophosphate([C4CNmim]+PF-6) medium. The synthesized PK was characterized by Fourier transform infrared(FTIR), elemental analysis, 13C-nuclear magnetic resonance(13C-NMR), differential scanning calorimetry(DSC), thermogravimetric analysis(TGA) and gel permeation chromatography(GPC). The supported ionic liquid film on the surface of Pd/C catalyst can prevent the products from covering the hole of active carbon due to its chemical stability and weak coordination ability with metal ions, and thus efficiently improve the catalytic activity. The effects of different amounts of ionic liquid on the catalytic activity and reusability of the catalyst and the molecular weight of PK were discussed. When the usage of ionic liquid is 10wt%(0.1 g ionic liquid / 1 g active carbon carrier) and the theoretical content of Pd2+ is 5wt%(0.05 g Pd2+/ 1 g active carbon carrier), the highest catalytic activity 2 963.64 gSTCO/(gPd·h) is achieved with the molecular weight and polydispersity index of PK as Mn=9 684, Mw=13 452 and Mw /Mn=1.389.展开更多
The efficient citral hydrogenation was achieved in aqueous media using Pd/CMS and alkali additives like K<sub>2</sub>CO<sub>3</sub>. The alkali concentrations, reaction temperature and the Pd m...The efficient citral hydrogenation was achieved in aqueous media using Pd/CMS and alkali additives like K<sub>2</sub>CO<sub>3</sub>. The alkali concentrations, reaction temperature and the Pd metal content were optimized to enhance the citral hydrogenation under aqueous media. In the absence of alkali, citral hydrogenation was low and addition of alkali promoted to ~92% hydrogenation without reduction in the selectivity to citronellal. The alkali addition appears to be altered the palladium sites. The pore size distribution reveals that the pore size of these catalysts is in the range of 0.96 to 0.7 nm. The palladium active sites are also quite uniform based on the TPR data. The catalytic parameters are correlated well with the activity data.展开更多
基金support by the National Natural Science Foundation of China(U21A20306,U20A20152)Natural Science Foundation of Hebei Province(B2022202077).
文摘Enhancing the stability of supported noble metal catalysts emerges is a major challenge in both science and industry.Herein,a heterogeneous Pd catalyst(Pd/NCF)was prepared by supporting Pd ultrafine metal nanoparticles(NPs)on nitrogen-doped carbon;synthesized by using F127 as a stabilizer,as well as chitosan as a carbon and nitrogen source.The Pd/NCF catalyst was efficient and recyclable for oxidative carbonylation of phenol to diphenyl carbonate,exhibiting higher stability than Pd/NC prepared without F127 addition.The hydrogen bond between chitosan(CTS)and F127 was enhanced by F127,which anchored the N in the free amino group,increasing the N content of the carbon material and ensuring that the support could provide sufficient N sites for the deposition of Pd NPs.This process helped to improve metal dispersion.The increased metal-support interaction,which limits the leaching and coarsening of Pd NPs,improves the stability of the Pd/NCF catalyst.Furthermore,density functional theory calculations indicated that pyridine N stabilized the Pd^(2+)species,significantly inhibiting the loss of Pd^(2+)in Pd/NCF during the reaction process.This work provides a promising avenue towards enhancing the stability of nitrogen-doped carbon-supported metal catalysts.
基金the National Natural Science Foundation of China (No.20462002)Natural Science Foundation of Jiangxi Province (No.0420015)for financial support.
文摘A variety of terminal arylacetylenes have been conveniently synthesized in good to high yields via Sonogashira coupling of aryl iodides with （trimethylsilyl）acetylene catalyzed by MCM-41-supported mercapto palladium（0） complex, followed by desilylation under mild conditions. This polymeric palladium catalyst can be reused many times without any decrease in activity.
基金Supported by the Tianjin Natural Science Foundation(No.07JCYBJC00600)
文摘The copolymerization of CO and styrene catalyzed by Pd/C toward the formation of polyketones(PK)was studied in the N-valeronitrile-N'-methylimidazolium hexafluorophosphate([C4CNmim]+PF-6) medium. The synthesized PK was characterized by Fourier transform infrared(FTIR), elemental analysis, 13C-nuclear magnetic resonance(13C-NMR), differential scanning calorimetry(DSC), thermogravimetric analysis(TGA) and gel permeation chromatography(GPC). The supported ionic liquid film on the surface of Pd/C catalyst can prevent the products from covering the hole of active carbon due to its chemical stability and weak coordination ability with metal ions, and thus efficiently improve the catalytic activity. The effects of different amounts of ionic liquid on the catalytic activity and reusability of the catalyst and the molecular weight of PK were discussed. When the usage of ionic liquid is 10wt%(0.1 g ionic liquid / 1 g active carbon carrier) and the theoretical content of Pd2+ is 5wt%(0.05 g Pd2+/ 1 g active carbon carrier), the highest catalytic activity 2 963.64 gSTCO/(gPd·h) is achieved with the molecular weight and polydispersity index of PK as Mn=9 684, Mw=13 452 and Mw /Mn=1.389.
文摘The efficient citral hydrogenation was achieved in aqueous media using Pd/CMS and alkali additives like K<sub>2</sub>CO<sub>3</sub>. The alkali concentrations, reaction temperature and the Pd metal content were optimized to enhance the citral hydrogenation under aqueous media. In the absence of alkali, citral hydrogenation was low and addition of alkali promoted to ~92% hydrogenation without reduction in the selectivity to citronellal. The alkali addition appears to be altered the palladium sites. The pore size distribution reveals that the pore size of these catalysts is in the range of 0.96 to 0.7 nm. The palladium active sites are also quite uniform based on the TPR data. The catalytic parameters are correlated well with the activity data.
