共查询到20条相似文献，搜索用时 48 毫秒
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SO2-4/TiO2-WO3催化剂催化合成苯甲醛乙二醇缩醛 总被引：4，自引：0，他引：4
报道了以固体超强酸SO42-／TiO2-WO3为催化剂，通过苯甲醛和乙二醇反应合成了苯甲醛乙二醇缩醛，探讨了SO42-／TiO2-WO3对缩醛反应的催化活性，较系统地研究了醛醇物质的量比，催化剂用量，反应时间诸因素对产品收率的影响．实验表明：SO42-／TiO2-WO3是合成苯甲醛乙二醇缩醛的良好催化剂，在n(醇)：n(醛)=1．25：1，催化剂用量为反应物料总质量的0．50％，环己烷为带水剂，反应时间50min的优化条件下，苯甲醛乙二醇缩醛的收率可达77．3％． 相似文献
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用固载杂多酸PW12 /SiO2 为催化剂 ,实现了肉桂酸与异戊醇反应合成肉桂酸异戊酯。最佳合成条件为 :n(酸 ) :n(醇 ) =1:2 ,催化剂用量为肉桂酸质量的 5 % ,反应时间为 3h ,产率可达 95 %。催化剂具有容易回收并可循环使用、不污染环境等优点。 相似文献
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钨硅酸催化合成乙酸辛酯 总被引：3，自引：2，他引：3
以钨硅酸为催化剂，通过乙酸和辛醇反应合成了乙酸辛酯。探讨了酸醇物质的量比、催化剂用量以及反应时间对酯化率的影响。实验结果表明：钨硅酸催化合成乙酸辛酯的最佳条件为：酸醇物质的量比1．3：1，催化剂用量0．2g／0．1mol(辛醇)，带水剂(环己烷)10mL，反应时间1h．温度100～118℃．在此条件下其酯化率可达99．30％。 相似文献
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NiSO4·6H2O催化合成肉桂酸乙酯的研究 总被引：1，自引：0，他引：1
研究了以NiSO4.6H2O为催化剂,催化以肉桂酸和乙醇为原料合成肉桂酸乙酯的反应,考察了酸醇比、催化剂用量、反应时间和反应温度等条件对肉桂酸乙酯产率的影响。实验结果表明,当酸∶醇∶催化剂=1∶6∶0.3(物质的量之比)、反应温度为90℃、反应时间为4h时,肉桂酸乙酯的产率达85.7%. 相似文献
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介绍了新型催化型TiSiW12O40/TiO2的制备方法，实验考察了以自制的该催化剂催化合成甲酸丁酯的酸醇化，催化剂用量，反应时间等因素对反应产率的影响，实验表明：在酸醇物质的量比为2．5：1，催化剂用量为反，反液的1．78％，酯化反应时间为40min，反应温度为94－98℃时，反应产率可达72．2％。 相似文献
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硫酸氢钠催化合成丁酸苄酯 总被引：2，自引：0，他引：2
研究了以硫酸氢钠为催化剂，丁酸和苄醇为原料合成丁酸苄酯，考察了影响酯化率的各种因素，确定了最佳反应条件为：丁酸用量0．1mol时，苄醇与丁酸的物质的量比为1．2，0．5g催化剂，10mL甲苯作带水剂，反应时间40min，酯化率98％以上．结果表明：硫酸氢钠是合成丁酸苄酯的优良催化剂． 相似文献
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以柠檬酸和正丁酵为原料,以纳米Sm2O3为催化剂催化合成无毒增塑剂柠檬酸三丁酯.探讨了催化剂用量、酸醇物质的量比、反应时间、反应温度对反应的影响.结果表明,纳米Sm2O3催化合成柠檬酸三丁酯的最佳条件为n(柠檬酸):n(正丁醇)=1:5.0,催化剂用量为柠檬酸质量的4.5%,反应时间为3.0h,反应温度为114～147℃,酯化率可达90.83%,并对合成的产品进行了红外光谱分析. 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