共查询到20条相似文献，搜索用时 62 毫秒
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以H3PW12O40／TiO2为催化剂催化合成了环己酮1，2-丙二醇缩酮，探讨了H3PW12O40／TiO2对缩酮反应的催化活性，较系统地研究了酮醇物质的量比，催化剂用量，反应时间诸因素对产品收率的影响．实验表明：H3PW12O40／TiO2是合成环己酮1，2-丙二醇缩酮的良好催化剂，在n（环己酮）：n（1，2-丙二醇）=1：1．7，催化剂用量为反应物料总质量的0．5％，环己烷为带水剂，反应时间1．0h的优化条件下，环己酮1，2-丙二醇缩酮的收率可达83．7％． 相似文献
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SiO2·12WO3·26H2O/SiO2催化合成环己酮缩乙二醇 总被引：1，自引：0，他引：1
以二氧化硅负载钨硅酸为催化剂 ,通过环己酮和乙二醇反应合成了环己酮缩乙二醇 .探讨了二氧化硅负载钨硅酸对缩酮反应的催化活性 ,研究了酮醇物质的量比、催化剂用量、反应时间等对产品收率的影响 .实验表明 :二氧化硅负载钨硅酸是合成环己酮缩乙二醇的良好催化剂 .在酮醇物质的量比为 1∶1 5 ,催化剂用量为 2g/ 0 2mol环己酮 ,反应温度 1 2 5～ 1 35℃ ,4mL环己烷作带水剂 ,反应时间 40min的条件下 ,环己酮缩乙二醇的收率可达 95 4% . 相似文献
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以二氧化硅负载磷钨钼酸H3PW6Mo6O40/TiO2-WO3为催化剂,环己酮和乙二醇为原料合成环己酮乙二醇缩酮.探讨H3PW6Mo6O40/TiO2-WO3对环己酮乙二醇缩酮反应的催化活性,较系统地研究了酮醇物质的量比、催化剂用量、带水剂用量、反应时间等因素对产物收率的影响.实验表明:H3PW6Mo6O40/TiO2-WO3是合成环己酮乙二醇缩酮的良好催化剂,在n(环己酮)∶n(乙二醇)=1∶1.4,催化剂用量占反应物料总质量的1.0%,带水剂环己烷的用量为6 mL,反应时间60 min的最佳条件下,环己酮乙二醇缩酮的收率可达84.5%. 相似文献
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磷钨钼杂多酸掺杂聚苯胺催化合成丁酮1,2-丙二醇缩酮 总被引：1，自引：0，他引：1
报道了以磷钨钼杂多酸掺杂聚苯胺为催化剂,通过丁酮和1,2-丙二醇反应合成了丁酮1,2-丙二醇缩酮．系统考察了酮醇物质量比,催化剂用量,以及反应时间诸因素对产品收率的影响．确定的适宜工艺条件为n（丁酮）：n（1,2-丙二醇）=1：1．5,催化剂用量为反应物料总质量的0、8％,带水剂环己烷8mL,反应时间1、5h、在此反应条件下,丁酮1,2-丙二醇缩酮的收率可达78．1％、 相似文献
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硅钨酸催化合成丁酮乙二醇缩酮 总被引：2，自引：1，他引：2
报道了以H4SiW12O40(硅钨酸)为催化剂,通过丁酮和乙二醇反应合成了丁酮乙二醇缩酮,探讨了H4SiW12O40对缩酮反应的催化活性,较系统地研究了酮醇物质的量比,催化剂用量,反应时间诸因素对产品收率的影响.实验表明:在n(酮)∶n(醇)=1∶1.5,催化剂用量为反应物料总质量的1.5%,带水剂环己烷6 mL,反应时间1.5 h的优化条件下,丁酮乙二醇缩酮的收率可达56.9%. 相似文献
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采用溶胶-凝胶法制备了二氧化硅负载硅钨钼酸催化剂.以其为催化剂,对以丁酮和乙二醇为原料合成丁酮乙二醇缩酮的反应条件进行了研究,较系统地研究了酮醇物质的量比、催化剂用量、带水剂环己烷,反应时间对收率的影响.实验表明,二氧化硅负载硅钨钼酸催化剂是合成丁酮乙二醇缩酮的良好催化剂,在n（丁酮）∶n（乙二醇）=1∶1.4,催化剂用量为原料总质量的0.6%,环己烷作带水剂10 mL,反应时间75min的优化条件下,丁酮乙二醇缩酮的收率可达96.77%. 相似文献
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全氟磺酸树脂催化合成丁酮乙二醇缩酮的研究 总被引：1，自引：0，他引：1
以废弃的全氟磺酸树脂为催化剂,丁酮和乙二醇为原料合成了丁酮乙二醇缩酮。实验表明：当最佳醇酮摩尔比为2：1,催化剂用量为0．5g,反应时间为2h,带水剂用量为9．7mL时丁酮乙二醇缩酮的最高产率可达到87.3％。该催化剂绿色环保且易于回收,重复使用五次产率仍可达到81．1％。 相似文献
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以单质碘为催化剂用于缩酮的合成。研究了催化剂用量、酮醇摩尔比及带水剂用量对反应产率的影响。当0．1mol丙酮与0．12mol 1,2-丙二醇的混合物在50mg碘催化下，以环已烷为带水剂，回流分水50min，产品收率可达49％。 相似文献
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研究了用硫酸氢钠催化合成环已酮1，2—丙二醇缩酮，详细探索了影响缩合反应的各种因素。得出了硫酸氢钠催化合成环已酮1，2—丙二醇缩酮反应的最佳条件：以环已酮0．2摩尔为标准，酮／醇(摩尔比)为1：1．5，硫酸氢钠催化剂和带水剂环已烷的用量为反应物总质量的1．21％、总体积的41．7％，回流反应2h，环已酮1，2—丙二醇缩酮的产率达78％。 相似文献
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以二氧化硅负载Dawson型磷钨酸H6P2W18O62/SiO2为催化剂,采用环己酮和1,2-丙二醇为原料合成环己酮1,2-丙二醇缩酮.探讨H6P2W18O62/SiO2对缩酮反应的催化活性,较系统地研究了各种因素对产物收率的影响.实验表明:H6P2W18O62/SiO2是合成环己酮1,2-丙二醇缩酮的良好催化剂,在n(环己酮)∶n(1,2-丙二醇)=1∶1.5,带水剂环己烷6 mL,催化剂用量占反应物料总质量的0.6%,反应时间60 min的优化条件下,环己酮1,2-丙二醇缩酮的收率可达85.4%. 相似文献
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《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
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罗艳萍 《读与写:教育教学刊》2008,5(6)
The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity. 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献
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Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
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Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 相似文献
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RUZBEHANI Mohsen 《重庆大学学报(英文版)》2004,3(1):20-25
1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec… 相似文献
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Richard Denner 《海外英语》2007,(4):14-15
Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose. 相似文献