共查询到20条相似文献，搜索用时 62 毫秒
1.
本文以KOH／Al1O3为催化剂，研究了正己醛和苯甲醛交叉缩合a-丁基肉桂醛的反应，重点考察了反应温度、反应时间、反应原料摩尔配比(己醛／苯甲醛)、溶剂用量、催化剂用量、催化剂负载量诸因素对目标产物α-丁基肉桂醛产率的影响，确定了制备α-丁基肉桂醛的优化反应条件：温度70℃、时间1．5h、己醛／苯甲醛10mmol／12mmol、溶剂苯乙醇5ml、催化剂KOH／Al2O3 0．84g、催化剂负载量11．9mmol／g，得己醛的转化率为100％，α-丁基肉桂醛的选择性为83．24％，即α-丁基肉桂醛的收率为83．24％。 相似文献
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本以KF／Al2O3为催化剂，研究了柠檬醛和丙酮缩合制备假性紫罗兰酮的反应，重点考察了反应温度、反应时间、反应原料摩尔配比(柠檬醛，丙酮)、催化剂用量诸因素对反应的影响，确定了制备假性紫罗兰酮的优化反应条件：温度15℃、时间0．5h、柠檬醛，丙酮10mmol／90mmol、催化荆KF／Al2O3 1．45g，柠檬醛的转化率为97．6％，假性紫罗兰酮的选择性为100％。 相似文献
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茉莉醛是一种十分重要的合成香料,具有非常重要的应用价值。以苯甲醛和正庚醛为原料,PEG-400为相转移催化剂,氢氧化钾作碱性催化剂,乙醇为溶剂,采用相转移催化的方法制取茉莉醛。通过正交实验确定了最佳反应条件,在PEG-400的用量为4.5g,水醇体积比为2.5∶1,正庚醛的滴加速率为30滴/min,苯甲醛与正庚醛的摩尔比为1.25∶1的条件下,茉莉醛的产率达到86%。 相似文献
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以苯甲醛、乙醛为原料,在碱性条件下用羟醛缩合法合成产物肉桂醛,并分别考察了催化剂、反应温度、两种原料用量比对产物收率的影响。结果表明:在温度为25℃、催化剂为氢氧化钠、苯甲醛∶乙醛=3∶1的条件下,产品收率能达到76%。 相似文献
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本文以KF／Al2O3为催化剂,研究了柠檬醛和丙酮缩合制备假性紫罗兰酮的反应,重点考察了反应温度、反应时间、反应原料摩尔配比(柠檬醛/丙酮)、催化剂用量诸因素对反应的影响,确定了制备假性紫罗兰酮的优化反应条件:温度15℃、时间0.5h、柠檬醛／丙酮10mmol／90mmol、催化剂KF／Al2O3 1.45g,柠檬醛的转化率为97.6％,假性紫罗兰酮的选择性为100％。 相似文献
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用苯甲醛和1,2-丙二醇为原料,粉煤灰复合固体酸为催化剂合成了苯甲醛1,2-丙二醇缩醛,考察了反应物的投料比,反应时间,带水剂等对缩醛反应的影响。实验表明：较好的合成条件是11（丙二醇）：n（苯甲醛）=1．4：1（苯甲醛0．1mol）,带水剂环己烷用量15ml,回流反应2h,产物收率可达79．3％。 相似文献
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以H3 PW12 O40／TiO2－SiO2为催化剂,取代苯甲醛、乙酰乙酸乙酯和尿素为原料,无水乙醇为溶剂合成3,4－二氢嘧啶－2（1H）－酮衍生物．探讨了原料物质的量比、反应温度、催化剂用量及反应时间对收率的影响．实验表明：固定取代苯甲醛的用量为0．04 mol和无水乙醇的量为15 mL的情况下,n（取代苯甲醛）∶n（乙酰乙酸乙酯）∶n（尿素）＝1∶1．0∶1．5,催化剂的用量占反应物料总质量的1．5％,反应温度为90℃,反应时间为75 min,分别以对羟基苯甲醛、对硝基苯甲醛、茴香醛、4－氯苯甲醛、对甲氧基苯甲醛分别代替苯甲醛,产品收率为35.0％－89.2％．催化剂和合成产品分别采用IR, XRD和1 H NMR, IR, MS手段进行表征． 相似文献
8.
本文以KF/Al2O3为催化剂,研究了柠檬醛和丙酮缩合制备假性紫罗兰酮的反应,重点考察了反应温度,反应时间、反应原料摩尔配比(柠檬醛/丙酮)、催化剂用量诸因素对反应的影响,确定了制备假性紫罗兰酮的优化反应条件温度15℃、时间0.5h、柠檬醛/丙酮10mmol/90mmol、催化剂KF/Al2O3 1.45g,柠檬醛的转化率为97.6%,假性紫罗兰酮的选择性为100%. 相似文献
9.
固体超强酸TiO2／SO4^2-催化合成硬脂酸乙酯 总被引：2，自引：0，他引：2
以硬脂酸和无水乙醇为原料，固体超强酸TiO2／SO4^2-为催化剂，催化合成硬脂酸乙酯，考察了不同活化温度对催化剂催化活性的影响，原料醇酸比，反应的时间、催化剂的用量等工艺条件对酯化反应产率的影响，并用正交实验优化出较佳的合成条件，即520℃活化的催化剂催化活性最高．较佳的工艺条件是：乙醇：硬脂酸=9：1，催化剂：硬脂酸=0．09：1，反应温度为83℃，反应时间为8h．硬脂酸乙酯产率可达96．5％． 相似文献
10.
相转移催化下的交叉羟醛缩合反应 总被引：1，自引：0，他引：1
张复兴 《衡阳师范学院学报》1997,(3)
以PEG－400为相转移催化剂，用于苯甲醛与丙酮之间的交叉羟醛缩合反应，合成了二亚苄基丙酮，产率达91％。 相似文献
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邱崇丙 《唐山师范学院学报》2014,(1):21-23
汉字的六书,《说文》对“转注”一类,语焉不详。后世学者提及转注,也仅限于许慎所举出的例字。《汉字例说》一文,作者从转注的角度综合考虑,对部分现代常用字作了分析,跟传统的解释有所不同。希望能抛砖引玉,互相切磋,以推进学术研究。 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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Rachel Zupek 《海外英语》2007,(11):40-41
我们绝大部分人都同意一件事情——我们喜欢金钱。但是你对金钱的喜欢之情足够到让你创立一份事业么?.财富通常被人忽视,主要在于人们不能真正了 相似文献
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YANGShiguo 《重庆大学学报(英文版)》2004,3(1):86-88
The problem on the geometrc inequalities involving an n-dimensional simplex and its inscribed simplex is studied. Aninequality is established, which reveals that the difference between the squared circumradius of the n-dimensional simplex andthe squared distance between its circumcenter and barycenter times the squared circumradius of its inscribed simplex is not lessthan the 2(n-1)th power of n times its squared inradius, and is equal to when the simplex is regular and its inscribed siplex is atangent point one. Deduction from this inequality reaches a generalization of n-dimensional Euler inequality indicating that thecircumradius of the simplex is not less than the n-fold inradius. Another inequality is derived to present the relationship betweenthe circumradius of the n-dimensional simplex and the circumradius and inradius of its pedal simplex. 相似文献
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Rajesh Kanoi 《海外英语》2007,(1):52
Today, Sunday morning, I sit thinking and typing at my computer. My thoughts are in my homeland, India and my body is in China. The body is here and mind there for a good reason. Mr. Hu is president and I am resident and both are in each other's countries (what a difference the absence of one small letter makes!). Mr. Hu will return in a few days and I will stay on longer. 相似文献