This article presents a detailed structural study of a new spherical Mg Cl2-supported Ti Cl4 Ziegler-Natta catalyst for isotactic propylene polymerization, and researches on the relationship between catalyst structure...This article presents a detailed structural study of a new spherical Mg Cl2-supported Ti Cl4 Ziegler-Natta catalyst for isotactic propylene polymerization, and researches on the relationship between catalyst structure and polymer properties. The spherical support with the chemical composition of CH3CH2 OMg OCH(CH2Cl)2 has been synthesized from a new dispersion system and is used as the supporting material to prepare Ziegler-Natta catalyst. The XRD analysis indicates that the catalyst is fully activated with δ-Mg Cl2 in the active catalyst. The far-IR spectrometric results confirm again the presence of δ-Mg Cl2 in the active catalyst. Textural property of the active catalyst exhibits high surface area coupled with high porosity. The high activity in propylene polymerization is mainly ascribed to the full activation and the porous structure of the catalyst. Scanning electron microscopy/energy dispersive spectrometer mapping results indicate a uniform titanium distribution throughout the catalyst particles. Particle size analysis shows that the catalyst has a narrow particle size distribution. The perfect spherical shape, uniform titanium distribution and narrow particle size distribution of the catalyst confirm the advantage of polymer particles production with less fines. The solid state 13 C NMR and mid-IR spectroscopic analyses indicate that there exists strong complexation between diisobutyl phthalate and Mg Cl2, which leads to the high isotacticity of polypropylene.展开更多
The Na2CO3-modified HZSM-5 zeolites were further treated by tetrapropylammonium hydroxide(TPAOH) solution. The effect of TPAOH concentration on the secondary crystallization process was investigated. The resulting sam...The Na2CO3-modified HZSM-5 zeolites were further treated by tetrapropylammonium hydroxide(TPAOH) solution. The effect of TPAOH concentration on the secondary crystallization process was investigated. The resulting samples were characterized by a complementary combination of X-ray diffraction, N2 adsorption/desorption, scanning electron microscopy, X-ray fluorescence spectroscopy, XPS, 27 Al and 29 Si magic-angle spinning nuclear magnetic resonance spectroscopy, BET and temperature-programmed desorption techniques. The results showed that the secondary crystallization of the HZSM-5 zeolite could result in migration of non-framework species from the internal channels to the zeolite surface and their transformation into framework species. The catalytic activity of these modified samples for thiophene alkylation was evaluated. Both the activity and stability of the catalysts were improved after secondary crystallization.展开更多
The electrochemical oxidation of biomass molecules coupling with hydrogen production is a promising strategy to obtain both green energy and value-added chemicals;however,this strategy is limited by the competing oxyg...The electrochemical oxidation of biomass molecules coupling with hydrogen production is a promising strategy to obtain both green energy and value-added chemicals;however,this strategy is limited by the competing oxygen evolution reactions and high energy consumption.Herein,we report a hierarchical CoNi layered double hydroxides(LDHs)electrocatalyst with abundant Ni vacancies for the efficient anodic oxidation of 5-hydroxymethylfurfural(HMF)and cathodic hydrogen evolution.The unique hierarchical nanosheet structure and Ni vacancies provide outstanding activity and selectivity toward several biomass molecules because of the finely regulated electronic structure and highly-exposed active sites.In particular,a high faradaic efficiency(FE)at a high current density(99%at 100 mA cm^(-2))is achieved for HMF oxidation,and a two-electrode electrolyzer is assembled based on the Ni vacancies-enriched LDH,which realized a continuous synthesis of highly-pure 2,5-furandicarboxylic acid products with high yields(95%)and FE(90%).展开更多
The organic compound 2,5-furandicarboxylic acid（FDCA） has been identified by the US Department of Energy（DOE） as a valuable platform chemical for a wide range of industrial applications. Currently, the most popula...The organic compound 2,5-furandicarboxylic acid（FDCA） has been identified by the US Department of Energy（DOE） as a valuable platform chemical for a wide range of industrial applications. Currently, the most popular route for FDCA synthesis is reported to be the oxidation of 5-hydroxymethylfurfural（HMF）by O_2 over the catalysis of noble metals（e.g., Au, Pt, Ru, and Pd）. However, the high costs of noble metal catalysts remain a major barrier for producing FDCA at an industrial scale. Herein, we report a transition metal-free synthesis strategy for the oxidation of HMF to FDCA under O_2 or ambient air. A simple but unprecedented process for the aerobic oxidation of HMF was carried out in organic solvents using only bases as the promoters. According to the high performance liquid chromatography（HPLC） analysis, excellent product yield（91%） was obtained in the presence of NaOH in dimethylformamide（DMF） at room temperature（25 ℃）. A plausible mechanism for the NaOH-promoted aerobic oxidation of HMF in DMF is also outlined in this paper. After the reaction, the sodium salt of FDCA particles were dispersed in the reaction mixture, making it possible for product separation and solvent reuse. The new HMF oxidation approach is expected to be a practical alternative to current ones, which depend on the use of noble metal catalysts.展开更多
Electrochemical oxidation of 5-hydroxymethylfurfural(HMF)has shown promising prospects in producing highly valuable chemicals.Herein,we report the synthesis of ultrasmall Ag nanoclusters anchored on NiColayered double...Electrochemical oxidation of 5-hydroxymethylfurfural(HMF)has shown promising prospects in producing highly valuable chemicals.Herein,we report the synthesis of ultrasmall Ag nanoclusters anchored on NiColayered double hydroxide(NiCo-LDH)nanosheet arrays(Agn@NiCo-LDH)via a facile electrodeposition strategy.The prepared Agn@NiCo-LDH nanosheet arrays exhibit excellent electrocatalytic HMF oxidation performance with a current density of 10 mA cm^(−2) at 1.29 VRHE and the Faraday efficiency of nearly 100%for 2,5-furandicarboxylic acid production.This study offers an effective approach to rationally design nanoclusters to achieve high catalytic activity for sustainable energy conversion and production.展开更多
基金the financial support by the National Natural Science Foundation of China (No. 20973022 and No. 11472048)
文摘This article presents a detailed structural study of a new spherical Mg Cl2-supported Ti Cl4 Ziegler-Natta catalyst for isotactic propylene polymerization, and researches on the relationship between catalyst structure and polymer properties. The spherical support with the chemical composition of CH3CH2 OMg OCH(CH2Cl)2 has been synthesized from a new dispersion system and is used as the supporting material to prepare Ziegler-Natta catalyst. The XRD analysis indicates that the catalyst is fully activated with δ-Mg Cl2 in the active catalyst. The far-IR spectrometric results confirm again the presence of δ-Mg Cl2 in the active catalyst. Textural property of the active catalyst exhibits high surface area coupled with high porosity. The high activity in propylene polymerization is mainly ascribed to the full activation and the porous structure of the catalyst. Scanning electron microscopy/energy dispersive spectrometer mapping results indicate a uniform titanium distribution throughout the catalyst particles. Particle size analysis shows that the catalyst has a narrow particle size distribution. The perfect spherical shape, uniform titanium distribution and narrow particle size distribution of the catalyst confirm the advantage of polymer particles production with less fines. The solid state 13 C NMR and mid-IR spectroscopic analyses indicate that there exists strong complexation between diisobutyl phthalate and Mg Cl2, which leads to the high isotacticity of polypropylene.
基金the financial support by the Natural Science Foundation of Liaoning Province of China (Grant No.201202126)the National Natural Science Foundation of China (Grant Nos. 21276253 and 21401093)
文摘The Na2CO3-modified HZSM-5 zeolites were further treated by tetrapropylammonium hydroxide(TPAOH) solution. The effect of TPAOH concentration on the secondary crystallization process was investigated. The resulting samples were characterized by a complementary combination of X-ray diffraction, N2 adsorption/desorption, scanning electron microscopy, X-ray fluorescence spectroscopy, XPS, 27 Al and 29 Si magic-angle spinning nuclear magnetic resonance spectroscopy, BET and temperature-programmed desorption techniques. The results showed that the secondary crystallization of the HZSM-5 zeolite could result in migration of non-framework species from the internal channels to the zeolite surface and their transformation into framework species. The catalytic activity of these modified samples for thiophene alkylation was evaluated. Both the activity and stability of the catalysts were improved after secondary crystallization.
基金This work was supported by the National Natural Science Foundation of China(22090031,22090030,21922501 and 21871021)Project funded by China Postdoctoral Science Foundation(2021M690319).
文摘The electrochemical oxidation of biomass molecules coupling with hydrogen production is a promising strategy to obtain both green energy and value-added chemicals;however,this strategy is limited by the competing oxygen evolution reactions and high energy consumption.Herein,we report a hierarchical CoNi layered double hydroxides(LDHs)electrocatalyst with abundant Ni vacancies for the efficient anodic oxidation of 5-hydroxymethylfurfural(HMF)and cathodic hydrogen evolution.The unique hierarchical nanosheet structure and Ni vacancies provide outstanding activity and selectivity toward several biomass molecules because of the finely regulated electronic structure and highly-exposed active sites.In particular,a high faradaic efficiency(FE)at a high current density(99%at 100 mA cm^(-2))is achieved for HMF oxidation,and a two-electrode electrolyzer is assembled based on the Ni vacancies-enriched LDH,which realized a continuous synthesis of highly-pure 2,5-furandicarboxylic acid products with high yields(95%)and FE(90%).
基金This work was supported by the SEEDS grant from the Ohio Agricultural Research and Development Center(OARDC)of the Ohio State University,Ohio,USA[grant number 2016-105].
文摘The organic compound 2,5-furandicarboxylic acid（FDCA） has been identified by the US Department of Energy（DOE） as a valuable platform chemical for a wide range of industrial applications. Currently, the most popular route for FDCA synthesis is reported to be the oxidation of 5-hydroxymethylfurfural（HMF）by O_2 over the catalysis of noble metals（e.g., Au, Pt, Ru, and Pd）. However, the high costs of noble metal catalysts remain a major barrier for producing FDCA at an industrial scale. Herein, we report a transition metal-free synthesis strategy for the oxidation of HMF to FDCA under O_2 or ambient air. A simple but unprecedented process for the aerobic oxidation of HMF was carried out in organic solvents using only bases as the promoters. According to the high performance liquid chromatography（HPLC） analysis, excellent product yield（91%） was obtained in the presence of NaOH in dimethylformamide（DMF） at room temperature（25 ℃）. A plausible mechanism for the NaOH-promoted aerobic oxidation of HMF in DMF is also outlined in this paper. After the reaction, the sodium salt of FDCA particles were dispersed in the reaction mixture, making it possible for product separation and solvent reuse. The new HMF oxidation approach is expected to be a practical alternative to current ones, which depend on the use of noble metal catalysts.
基金financially supported by the National Natural Science Foundation of China (21975013)the Fundamental Research Funds for the Central Universities。
文摘Electrochemical oxidation of 5-hydroxymethylfurfural(HMF)has shown promising prospects in producing highly valuable chemicals.Herein,we report the synthesis of ultrasmall Ag nanoclusters anchored on NiColayered double hydroxide(NiCo-LDH)nanosheet arrays(Agn@NiCo-LDH)via a facile electrodeposition strategy.The prepared Agn@NiCo-LDH nanosheet arrays exhibit excellent electrocatalytic HMF oxidation performance with a current density of 10 mA cm^(−2) at 1.29 VRHE and the Faraday efficiency of nearly 100%for 2,5-furandicarboxylic acid production.This study offers an effective approach to rationally design nanoclusters to achieve high catalytic activity for sustainable energy conversion and production.
