Copolymerization of propylene and hindered piperidine monomers was carried out over a high activity supported Ziegler-Natta catalyst, using Al(C2H5)(3) as cocatalyst. Factors which affect the copolymerization were stu...Copolymerization of propylene and hindered piperidine monomers was carried out over a high activity supported Ziegler-Natta catalyst, using Al(C2H5)(3) as cocatalyst. Factors which affect the copolymerization were studied, The copolymers exhibited high light stability without adding extra light stabilizers. A self-stabilized polypropylene was prepared.展开更多
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 composition distribution (CD) and microisotacticity distribution (ID) of propene/1-hexene copolymer synthesized by MgCl2/DIBP/TiCl4 (DIBP: diisobutyl phthalate) were determined by fractionating the copolymers acco...The composition distribution (CD) and microisotacticity distribution (ID) of propene/1-hexene copolymer synthesized by MgCl2/DIBP/TiCl4 (DIBP: diisobutyl phthalate) were determined by fractionating the copolymers according to crystallinity and characterizing the fractions by (CNMR)-C-13. The effects of two alkoxysilane donors, triethoxyphenylsilane (PTES) and dimethoxydi-tert-butylsilane (TBMS), on CD and ID of the copolymers were compared. Three main parts in the CD diagram of each copolymer were distinguished, which were correlated to active center distribution (ACD) based on three groups of different active centers. By studying the changes in l-hexene content, microisotacticity and reactivity ratio product of three typical fractions, the effects of external donor on ACD were better elucidated. It was found that TBMS shows much stronger effects on ACD than PTES. In the former system, most fractions were produced on active centers with relatively lower r(1)r(2), higher reactivity to I-hexene, and higher stereospecificity as compared to the system without external donor. It is concluded that the observed very extensive changes in ACD are mainly resulted by the formation of new types of active centers, possibly by coordination of external donor to certain positions on the catalyst.展开更多
A series of Ti/Mg supported catalysts are prepared by using ball-milled mixtures of MgCl2-ethanol adducts and NaCl as supports, and 1-hexene polymerizations catalyzed by the novel catalysts are studied. It is found th...A series of Ti/Mg supported catalysts are prepared by using ball-milled mixtures of MgCl2-ethanol adducts and NaCl as supports, and 1-hexene polymerizations catalyzed by the novel catalysts are studied. It is found that the molecular weight distribution of poly(1-hexene) becomes apparently narrower when catalysts with doped supports are used, indicating that changing the structure of the support is an effective way to regulate the active center distribution of heterogeneous Ziegler-Natta catalyst.展开更多
Different Ziegler-Natta catalysts were employed to polymerize ethylene. To investigate the influences of reaction parameters, namely Al/Ti molar ratio, hydrogen and processing parameters, i.e. ethylene pressure and te...Different Ziegler-Natta catalysts were employed to polymerize ethylene. To investigate the influences of reaction parameters, namely Al/Ti molar ratio, hydrogen and processing parameters, i.e. ethylene pressure and temperature, a Taguchi experimental design was worked out. An L27 orthogonal array was chosen to take the above-mentioned parameters and relevant interactions into account. Response surface method was the tool used to analyze the experimental design results. Al/Ti, ethylene pressure and temperature were selected as experimental design factors, and catalyst activity and polymerization yield were the response parameters. Increasing pressure, due to an increment in monomer accessibility, and rising Al/Ti, because of higher reduction in the catalysts, cause an increase in both polymerization yield and catalyst activity. Nonetheless, a higher temperature, thanks to reducing ethylene solubility in the slurry medium and partially catalyst destruction, lead to a reduction in both response parameters. A synergistic effect was also observed between temperature and pressure. All catalyst activities will reduce in the presence of hydrogen. Molecular weight also shows a decline in the presence of hydrogen as a transfer agent. However, the polydispersity index remains approximately intact. Using SEM, various morphologies, owing to different catalyst morphologies, were seen for the polyethylene.展开更多
Distribution of active centers(ACD)of ethylene or 1-hexene homopolymerization and ethylene-1-hexene copolymerization with a MgCl_2/TiCl_4 type Z-N catalyst were studied by deconvolution of the polymer molecular weight...Distribution of active centers(ACD)of ethylene or 1-hexene homopolymerization and ethylene-1-hexene copolymerization with a MgCl_2/TiCl_4 type Z-N catalyst were studied by deconvolution of the polymer molecular weight distribution into multiple Flory components.Each Flory component is thought to be formed by a certain type of active center. ACD of ethylene-1-hexene copolymer with very low 1-hexene incorporation was compared with that of ethylene homopolymer to see the effect of introducingα-olefin on ethyle...展开更多
The effects of poisoning materials on catalytic activity and isospecificity of the supported Ziegler-Natta catalyst were investigated.A minor amount of simple structure of Lewis base,i.e.,methanol,acetone,ethyl acetat...The effects of poisoning materials on catalytic activity and isospecificity of the supported Ziegler-Natta catalyst were investigated.A minor amount of simple structure of Lewis base,i.e.,methanol,acetone,ethyl acetate,was introduced into the catalyst slurry for partial poisoning catalytic active centers.It was found that the variations in deactivation power were in the order of methanol>acetone>ethyl acetate.The kinetic investigation via stopped-flow polymerization showed that poisoning compounds cau...展开更多
We report a facile coagglomeration method for preparing graphene (G)/MgCl2‐supported Ti‐based Ziegler‐Natta catalysts. The effects of graphene feed ratio on catalyst morphology and ethylene polymerization behavior ...We report a facile coagglomeration method for preparing graphene (G)/MgCl2‐supported Ti‐based Ziegler‐Natta catalysts. The effects of graphene feed ratio on catalyst morphology and ethylene polymerization behavior were examined. The synthesized catalyst exhibited very high activity for ethylene polymerization. The resultant polyethylene (PE)/G nanocomposites showed a layered morphology, and the graphene fillers were well dispersed in the PE matrix. In addition, the thermal stability and mechanical properties of PE were significantly enhanced with the introduction of a very small amount of G fillers (0.05 wt%). This work provides a facile approach to the production o fhigh‐performance PE.展开更多
文摘Copolymerization of propylene and hindered piperidine monomers was carried out over a high activity supported Ziegler-Natta catalyst, using Al(C2H5)(3) as cocatalyst. Factors which affect the copolymerization were studied, The copolymers exhibited high light stability without adding extra light stabilizers. A self-stabilized polypropylene was prepared.
基金the Sinopec Beijing Research Institute of Chemical Industry for its financial support (No. 5-12ZS0419, 5-10ZS0245, 5-12ZS0270)
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.
文摘The composition distribution (CD) and microisotacticity distribution (ID) of propene/1-hexene copolymer synthesized by MgCl2/DIBP/TiCl4 (DIBP: diisobutyl phthalate) were determined by fractionating the copolymers according to crystallinity and characterizing the fractions by (CNMR)-C-13. The effects of two alkoxysilane donors, triethoxyphenylsilane (PTES) and dimethoxydi-tert-butylsilane (TBMS), on CD and ID of the copolymers were compared. Three main parts in the CD diagram of each copolymer were distinguished, which were correlated to active center distribution (ACD) based on three groups of different active centers. By studying the changes in l-hexene content, microisotacticity and reactivity ratio product of three typical fractions, the effects of external donor on ACD were better elucidated. It was found that TBMS shows much stronger effects on ACD than PTES. In the former system, most fractions were produced on active centers with relatively lower r(1)r(2), higher reactivity to I-hexene, and higher stereospecificity as compared to the system without external donor. It is concluded that the observed very extensive changes in ACD are mainly resulted by the formation of new types of active centers, possibly by coordination of external donor to certain positions on the catalyst.
基金This work was supported by the National Natural Science Foundation of China (grant No. 20174034, 20274037).
文摘A series of Ti/Mg supported catalysts are prepared by using ball-milled mixtures of MgCl2-ethanol adducts and NaCl as supports, and 1-hexene polymerizations catalyzed by the novel catalysts are studied. It is found that the molecular weight distribution of poly(1-hexene) becomes apparently narrower when catalysts with doped supports are used, indicating that changing the structure of the support is an effective way to regulate the active center distribution of heterogeneous Ziegler-Natta catalyst.
文摘Different Ziegler-Natta catalysts were employed to polymerize ethylene. To investigate the influences of reaction parameters, namely Al/Ti molar ratio, hydrogen and processing parameters, i.e. ethylene pressure and temperature, a Taguchi experimental design was worked out. An L27 orthogonal array was chosen to take the above-mentioned parameters and relevant interactions into account. Response surface method was the tool used to analyze the experimental design results. Al/Ti, ethylene pressure and temperature were selected as experimental design factors, and catalyst activity and polymerization yield were the response parameters. Increasing pressure, due to an increment in monomer accessibility, and rising Al/Ti, because of higher reduction in the catalysts, cause an increase in both polymerization yield and catalyst activity. Nonetheless, a higher temperature, thanks to reducing ethylene solubility in the slurry medium and partially catalyst destruction, lead to a reduction in both response parameters. A synergistic effect was also observed between temperature and pressure. All catalyst activities will reduce in the presence of hydrogen. Molecular weight also shows a decline in the presence of hydrogen as a transfer agent. However, the polydispersity index remains approximately intact. Using SEM, various morphologies, owing to different catalyst morphologies, were seen for the polyethylene.
基金the Major State Basic Research Programs(No.2005CB623804).
文摘Distribution of active centers(ACD)of ethylene or 1-hexene homopolymerization and ethylene-1-hexene copolymerization with a MgCl_2/TiCl_4 type Z-N catalyst were studied by deconvolution of the polymer molecular weight distribution into multiple Flory components.Each Flory component is thought to be formed by a certain type of active center. ACD of ethylene-1-hexene copolymer with very low 1-hexene incorporation was compared with that of ethylene homopolymer to see the effect of introducingα-olefin on ethyle...
基金The authors gratefully acknowledge the Thailand Research Fund(TRF)Royal Golden Jubilee program for the financial support.
文摘The effects of poisoning materials on catalytic activity and isospecificity of the supported Ziegler-Natta catalyst were investigated.A minor amount of simple structure of Lewis base,i.e.,methanol,acetone,ethyl acetate,was introduced into the catalyst slurry for partial poisoning catalytic active centers.It was found that the variations in deactivation power were in the order of methanol>acetone>ethyl acetate.The kinetic investigation via stopped-flow polymerization showed that poisoning compounds cau...
基金supported by the National Research Foundation of Korea (NRF-2015R1D1A1A0161012)the National Natural Science Foundation of China (U1462124)~~
文摘We report a facile coagglomeration method for preparing graphene (G)/MgCl2‐supported Ti‐based Ziegler‐Natta catalysts. The effects of graphene feed ratio on catalyst morphology and ethylene polymerization behavior were examined. The synthesized catalyst exhibited very high activity for ethylene polymerization. The resultant polyethylene (PE)/G nanocomposites showed a layered morphology, and the graphene fillers were well dispersed in the PE matrix. In addition, the thermal stability and mechanical properties of PE were significantly enhanced with the introduction of a very small amount of G fillers (0.05 wt%). This work provides a facile approach to the production o fhigh‐performance PE.
