A modified rare-earth-metal catalyst system combined with quaternary ammonium salts（QASs） as cocatalysts was investigated in the alternating copolymerization of CO_2/propylene oxide（PO） to produce poly（propylene ...A modified rare-earth-metal catalyst system combined with quaternary ammonium salts（QASs） as cocatalysts was investigated in the alternating copolymerization of CO_2/propylene oxide（PO） to produce poly（propylene carbonate）（PPC）. In the presence of ZnO/SiO_2, the ZnEt_2-glycerine-Y（CCl_3OO）_3 catalyst presented higher activity for CO_2/PO copolymerization, as well as a higher molecular weight of polycarbonate, while maintaining the high carbonate content originating from the neat ZnEt_2-glycerine-Y（CCl_3OO）_3 catalyst. In the presence of QASs bearing different halide anions（F., Cl., and Br.）, the type of the halide anion had a strong influence on the activity of the catalyst for CO_2/PO alternating copolymerization. Only tetramethylammonium fluoride（TMAF） could promote the alternating copolymerization without increasing the by-product. Combined the ZnO/SiO_2 catalyst and TMAF, the catalytic activity for CO_2/PO polymerization increased dramatically compared to the basic ternary catalyst system. The improved catalyst system produced a polymer with a high carbonate unit level equivalent to that of the polycarbonate produced by the basic ZnEt_2-glycerine-Y（CCl_3OO）_3 catalyst system.展开更多
In order to investigate the influening factors of organic modification procedure and find out connections between organic modification and the properties of bentonite greases, organic montmorillonite(OMMT) thickeners ...In order to investigate the influening factors of organic modification procedure and find out connections between organic modification and the properties of bentonite greases, organic montmorillonite(OMMT) thickeners with different surfactant dosages and constituents were synthesized through intercalation reaction between sodium montmorillonite(NaM MT) and quaternary ammonium surfactants in aqueous solvents. The lubricating greases were prepared with the resulting organoclays, while the penetration and oil separation of lubricating greases were evaluated, respectively. The surface modification process of montmorillonite(MMT) was analyzed and the thickening mechanism of OMMT was discussed in this study. The experimental results showed that, with an increasing amount of surfactant, the basal spacing between the clay platelets was increasing and the structure of modifier molecules layer in the interlayer was changing from lateral bilayer to paraffin-type bilayer. The optimal properties of lubricating greases were achieved, when the structure of surfactant molecules loaded in the interlayer was the paraffin-type monolayer, which meant that the dosage of modifier was equal to 120—140 mmol/(100g). Meanwhile, it was found that the thickening performance, colloid stability, anti-wear and friction-reducing performance of lubricating greases were improved, when the surfactants were mixed with octadecyl trimethyl ammonium chloride(OTAC) and hexadecyl trimethyl ammonium chloride(HTAC). And the optimum mole ratio of two surfactants is was 1:1.展开更多
基金supported by the Pujiang Talent Projects(16PJD016)~~
文摘A modified rare-earth-metal catalyst system combined with quaternary ammonium salts（QASs） as cocatalysts was investigated in the alternating copolymerization of CO_2/propylene oxide（PO） to produce poly（propylene carbonate）（PPC）. In the presence of ZnO/SiO_2, the ZnEt_2-glycerine-Y（CCl_3OO）_3 catalyst presented higher activity for CO_2/PO copolymerization, as well as a higher molecular weight of polycarbonate, while maintaining the high carbonate content originating from the neat ZnEt_2-glycerine-Y（CCl_3OO）_3 catalyst. In the presence of QASs bearing different halide anions（F., Cl., and Br.）, the type of the halide anion had a strong influence on the activity of the catalyst for CO_2/PO alternating copolymerization. Only tetramethylammonium fluoride（TMAF） could promote the alternating copolymerization without increasing the by-product. Combined the ZnO/SiO_2 catalyst and TMAF, the catalytic activity for CO_2/PO polymerization increased dramatically compared to the basic ternary catalyst system. The improved catalyst system produced a polymer with a high carbonate unit level equivalent to that of the polycarbonate produced by the basic ZnEt_2-glycerine-Y（CCl_3OO）_3 catalyst system.
基金financially supported by the Chongqing Construction Project of Innovation Teams in Colleges and Universities-Petroleum Products Application Engineering and Technology(Project No.KJTD201342)the Chongqing Project of Innovation Research by Postgraduates(Project No.CYB16130)
文摘In order to investigate the influening factors of organic modification procedure and find out connections between organic modification and the properties of bentonite greases, organic montmorillonite(OMMT) thickeners with different surfactant dosages and constituents were synthesized through intercalation reaction between sodium montmorillonite(NaM MT) and quaternary ammonium surfactants in aqueous solvents. The lubricating greases were prepared with the resulting organoclays, while the penetration and oil separation of lubricating greases were evaluated, respectively. The surface modification process of montmorillonite(MMT) was analyzed and the thickening mechanism of OMMT was discussed in this study. The experimental results showed that, with an increasing amount of surfactant, the basal spacing between the clay platelets was increasing and the structure of modifier molecules layer in the interlayer was changing from lateral bilayer to paraffin-type bilayer. The optimal properties of lubricating greases were achieved, when the structure of surfactant molecules loaded in the interlayer was the paraffin-type monolayer, which meant that the dosage of modifier was equal to 120—140 mmol/(100g). Meanwhile, it was found that the thickening performance, colloid stability, anti-wear and friction-reducing performance of lubricating greases were improved, when the surfactants were mixed with octadecyl trimethyl ammonium chloride(OTAC) and hexadecyl trimethyl ammonium chloride(HTAC). And the optimum mole ratio of two surfactants is was 1:1.
