258 resultados para Propylene epoxidation
Resumo:
合成了二乙基锌、二正丙基锌、二正丁基锌、二异丙基锌、二异丁基锌、二仲丁基锌、苯基锌、带基锌、二环己基锌。利用不同有机锌与三氯醋酸钻及甘油组合制备了稀土三元催化剂并催化了二氧化碳和环氧丙烷的共聚合。结果表明当反应温度为80℃，二氧化碳压力为3．0MPa，烷基锌与甘油的摩尔比为2：1，稀土盐与烷基锌的摩尔比为1：20时，利用不同烷基锌制备的稀土三元催化剂的活性均显示较大值。同样聚合条件下，含有支链烷基的烷基锌制备的稀土三元催化剂的活性小于相应的含有同样主链碳原子数的正烷基锌制备的稀土催化剂，对于利用正烷基锌制备的稀土催化剂来说，随着烷基锌中烷基碳原子数的增加，催化活性减小。利用二苯基锌制备的稀土三元催化剂的活性大于利用二乙基锌制备的稀土催化剂。利用酸配和异氰酸酷对二氧化碳和环氧丙烷的共聚物进行了封端，发现封端能显著提高聚合物的热分解温度，改善聚合物的热稳定性。
Resumo:
为拓宽PPC的应用范围，本论文在CO2与PO的共聚反应中，引入第三单体缩水甘油醚（烯丙基缩水甘油醚AGE、丁基缩水甘油醚BGE和苯基缩水甘油醚GPE），制备得到不同结构和性能的二氧化碳共聚物。主要工作总结如下：1．在CO2与PO的共聚反应中，引入第三单体 AGE，合成了侧链带双键的官能化二氧化碳共聚物Pol（PO-co-CO2-co-AGE）；2．在CO2-PO-BGE的共聚反应中，控制PO／B GE的摩尔比，可制得不同结构和 性能的二氧化碳共聚物Poly（P0-co-CO2-co-BGE），其Tg为-26.8-36.1℃，大幅度拓展了二氧化碳共聚物的最低使用温度区间；3．在CO2与PO的共聚反应中，引入第三单体GPE，合成了侧链带刚性苯环的 二氧化碳共聚物Poty（PO-co-CO2-co-GPE），提高了聚合产物的热稳定性。
Resumo:
The objectives were to investigate the effect of cryoprotectants on the hatching rate of red seabream embryos. Heart-beat embryos were immersed in: five permeable cryoprotectants, dimethyl sulfoxide (DMSO), glycerol (Gly), methanol (MeOH), 1,2-propylene glycol (PG), and ethylene glycol (EG). in concentrations of 5-30% for 10, 30, or 60 min; and two non-permeable cryoprotectants: polyvinylpyrrolidone (PVP), and sucrose (in concentrations of 5-20% for 10 or 30 min). The embryos were then washed and incubated in filtered seawater until hatching occurred. The hatching rate of the embryos treated with permeable cryoprotectants decreased (P < 0.05) with increased concentration and duration of exposure. In addition, PG was the least toxic permeable cryoprotectant, followed by DMSO and EG, whereas Gly and MeOH were the most toxic. At a concentration of 15% and 30 min exposure, the hatching rate of the embryos immersed in PG was 93.3 +/- 7.0% (mean +/- S.D.), however. in DMSO. EG, Gly. and MeOH, it was 82.7 +/- 10.4, 22.0 +/- 5.7, 0.0 +/- 0.0, and 0.0 +/- 0.0%, respectively. Hatching rate of embryos treated with PVP decreased (P < 0.05) with the increase of concentration and exposure time, whereas for embryos treated with sucrose, there was no significant decrease in comparison with the control at the concentrations used. (C) 2008 Elsevier Inc. All rights reserved.
