SalenMX has drawn much attention recently,because it is nonsensitive to moisture and effective for copolymerization of CO2 and epoxides.However,usually expensive organic metal compounds were used.A low cost procedure ...SalenMX has drawn much attention recently,because it is nonsensitive to moisture and effective for copolymerization of CO2 and epoxides.However,usually expensive organic metal compounds were used.A low cost procedure of SalenMX preparation is described that SalenAl（OPr） can be obtained by using aluminium iso-propoxide reacted with SalenH2 in tetrahydrofuran at room temperature overnight.The catalyst precursor Schiff-base SalenH2 （N,N′-Bis（salicylidene）-1,2-phenylenediamine） was synthesized by refluxing 2 equiv salicylaldehyde and 1 equiv of 1,2-phenylendiamine in methnol for a period of time.SalenH2 and SalenAl（OPr） were characterized by FT-IR,mass Spectroscopy,UV-Vis and 1H-NMR.The copolymerization of carbon dioxide and cyclohexene oxide（CHO） was carried out at 80℃ for a certain period time using 50 mg SalenAl（OPr） as catalyst.SalenAl（OPr） had been shown to be an effective catalyst for the copolymerization of CO2 and CHO along with a small quantity of byproduct cyclic carbonate.The addition of various cocatalysts,including DMAP,N-MeIm,DBU and Bu4NCl or Bu4NBr salts can greatly enhance the rate of copolymerization.The copolymers were produced with >95% carbonate linkages and <5% cyclic carbonates.The highest catalytic efficiency is 190 g copolymer per g catalyst.展开更多
Control rod is used to change the power in nuclear reactor.?Certainly, the core at any moment can be made subcritical condition and shut downs when occurring?to emergency instance in the core. The rod is grouped based...Control rod is used to change the power in nuclear reactor.?Certainly, the core at any moment can be made subcritical condition and shut downs when occurring?to emergency instance in the core. The rod is grouped based?on their function and located at different places in the core where their feature is maximized.?Two methods of control rod calibration are the asymptotic period method and the rod-drop method, which were applied in this experiment. In the first method, the reactor is made supcritical by inserting the control rod to be calibrated a certain level. The rod drop method is to determine the subcritical;at the critical state, the rod to be calibrated is dropped into the core, and the resulting decay of neutron flux is observed and related to the reactivity. In this paper, the regulating rod will be calibrated according to the reactivity in OPR-1000 that corresponds to a certain control rod insert or withdraw, and the reactivity in power reactor depends?on the integral and differential control rod group too. The core simulator OPR1000 is used to test those methods.展开更多
文摘SalenMX has drawn much attention recently,because it is nonsensitive to moisture and effective for copolymerization of CO2 and epoxides.However,usually expensive organic metal compounds were used.A low cost procedure of SalenMX preparation is described that SalenAl（OPr） can be obtained by using aluminium iso-propoxide reacted with SalenH2 in tetrahydrofuran at room temperature overnight.The catalyst precursor Schiff-base SalenH2 （N,N′-Bis（salicylidene）-1,2-phenylenediamine） was synthesized by refluxing 2 equiv salicylaldehyde and 1 equiv of 1,2-phenylendiamine in methnol for a period of time.SalenH2 and SalenAl（OPr） were characterized by FT-IR,mass Spectroscopy,UV-Vis and 1H-NMR.The copolymerization of carbon dioxide and cyclohexene oxide（CHO） was carried out at 80℃ for a certain period time using 50 mg SalenAl（OPr） as catalyst.SalenAl（OPr） had been shown to be an effective catalyst for the copolymerization of CO2 and CHO along with a small quantity of byproduct cyclic carbonate.The addition of various cocatalysts,including DMAP,N-MeIm,DBU and Bu4NCl or Bu4NBr salts can greatly enhance the rate of copolymerization.The copolymers were produced with >95% carbonate linkages and <5% cyclic carbonates.The highest catalytic efficiency is 190 g copolymer per g catalyst.
文摘Control rod is used to change the power in nuclear reactor.?Certainly, the core at any moment can be made subcritical condition and shut downs when occurring?to emergency instance in the core. The rod is grouped based?on their function and located at different places in the core where their feature is maximized.?Two methods of control rod calibration are the asymptotic period method and the rod-drop method, which were applied in this experiment. In the first method, the reactor is made supcritical by inserting the control rod to be calibrated a certain level. The rod drop method is to determine the subcritical;at the critical state, the rod to be calibrated is dropped into the core, and the resulting decay of neutron flux is observed and related to the reactivity. In this paper, the regulating rod will be calibrated according to the reactivity in OPR-1000 that corresponds to a certain control rod insert or withdraw, and the reactivity in power reactor depends?on the integral and differential control rod group too. The core simulator OPR1000 is used to test those methods.
