共查询到20条相似文献，搜索用时 62 毫秒
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用磷钨酸为催化剂，以α-甲基丙烯酸和月桂醇为原料合成了α-甲基丙烯酸月桂酯，研究了杂多酸的用量，反应温度，反应时间，酸醇摩尔比等因素对酯收率的影响。结果表明：此法催化剂用量少，催化活性高，反应时间较短。酯收率较高，工艺较简单，最佳工艺条件是：醇/酸摩尔比为1.5:1，催化剂用量为反应物质量0.4%，带水剂甲苯用量为反应物质量的24%，反应温度为155℃，反应时间2h，此条件下，酯收率为85%。 相似文献
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用锗钨酸催化合成了水杨酸异戊酯,研究了催化剂用量、酸／醇摩尔比、反应温度、反应时间对酯收率的影响。当催化剂用量为反应物质量的１．３％、酸／醇摩尔比为１：２．５、反应温度为１３５～１５３℃、反应３ｈ,酯收率可超过９４％,在一定条件下催化剂可以重复使用多次。 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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李长智 《绵阳师范学院学报》2010,29(2):53-56
研究了以硫酸钛为催化剂,无水乙醇和冰乙酸为原料合成乙酸乙酯。考察了催化剂用量、原料配比、反应时间等因素对反应的影响,结果表明,催化剂用量为冰乙酸质量的10．2％,醇酸摩尔比为1．8：1,反应时间为60min是最适宜的反应条件,酯收率达69％以上。结论：硫酸钛比浓硫酸作催化剂,酯化产品纯度高。 相似文献
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以正硅酸乙酯(TEOS)为硅源,十六烷基三甲基溴化铵(CTAB)为模板剂,采用水热法合成了具有高比表面积和介孔的MCM-41材料。研究了把稀土硫酸盐固载于该材料上作为酯催化剂催化合成三醋酸甘油酯。考察了醇酸摩尔比、催化剂用量、反应时间、带水剂甲苯的用量对反应的影响,并优化了反应条件。研究结果表明,介孔固载强酸催化剂对合成三醋酸甘油酯具有优良的催化活性,在优化条件下,酯的产率高达87.7%。 相似文献
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自制了硅钨酸(H4SiW12O40)掺杂聚苯胺(PAn)催化剂H4SiW12O40／PAn．以乙酰乙酸乙酯和乙二醇为原料合成苹果酯．较系统地研究了原料摩尔比、催化剂用量、反应时间诸因素对产品收率的影响．实验表明：最佳反应条件为n(乙酰乙酸乙酯)：n(乙二醇)=1：1．5。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．上述条件下．苹果酯的收率为71．5％． 相似文献
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磷钨酸掺杂聚苯胺催化剂催化合成苹果酯-B 总被引：3，自引：0，他引：3
报道了磷钨酸掺杂聚苯胺催化剂H3PW12O40／PAn的制备，通过乙酰乙酸乙酯和1，2-丙二醇反应合成了苹果酯-B，探讨了磷钨酸掺杂聚苯胺催化剂对缩酮反应的催化活性，较系统地研究了原料量比，催化剂用量，反应时间诸因素对产品收率的影响，实验表明：磷钨酸掺杂聚苯胺催化剂是合成苹果酯-B的良好催化剂，在n(乙酰乙酸乙酯)：n(1，2-丙二醇)=1：1.5，催化刺用量为反应物料总质量的1．0％，环己烷为带水剂，反应时间50min的优化条件下，苹果酯-B的收率可达85．0％. 相似文献
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硅钨酸催化合成富马酸二甲酯 总被引：3，自引：0，他引：3
研究了以硅钨酸为催化剂，以富马酸和甲醇为原料合成富马酸二甲酯的方法。讨论了影响酯化反应的各种因素，并得出了酯化反应的最佳工艺条件：醇酸比为6：1，催化剂硅钨酸用量为酸质量的6％，15ml环己烷为带水剂，反应时间4h，酯化率达92．7％。与浓硫酸、氯化铁、硫酸氢钠催化剂作比较，实验结果表明以硅钨酸为催化剂具有催化剂用量少、重复使用效果好，反应时间短，酯收率高，方法简单等优点。 相似文献
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杂多酸作为催化剂，因其性能独特及环境污染小而引起人们广泛的关注。本文以合成的磷钨杂多酸作为催化剂，对乙酸异戊酯的合成进行了系统研究。考察了反应时间、催化剂用量、醇酸摩尔比等对酯化反应的影响。结果表明，在冰乙酸用量为0．10moL，醇酸摩尔比为1．5，催化剂用量为70mg，反应时间为90分钟且以正己烷为带水剂的条件下，酯化产率可达96．8％，乙酸异戊酯的收率达84％。并考察了催化剂的重复使用对酯化率的影响。 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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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
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正A One day a pig went to the stable(马棚)to see his good friend,an oldhorse,and was going to stay there forthenight.Night came and it was time forsleep.The pig went into the straw heap(稻草堆)and lay comfortably.A longtime passed,but the horse was stillstanding there and did not move.Thepig asked the horse why he did not go tosleep."Standing like this is the begin-ning ofsleeping,"answered the horse. 相似文献
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《今日中学生》2014,(9)
正1.Any fool can count the seeds in an apple.Only God can count all the apples in one seed.2.Happy families are all alike;every unhappy family is unhappy in its own way.3.Memories are the key not to the past,but to the future.4.Sometimes in the dark you see what you want to see.5.There is a great difference between 相似文献
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《重庆大学学报(英文版)》2014,(2)
正Scope and Policy The Journal of Chongqing University-English Edition(JCQU-E)is a peerreviewed journal publishing research articles in multiple disciplines of science and technology,covering civil and environmental engineering,chemical engineering,biotechnology,mechanical and electrical engineering,computer and data processing,mining,metallurgy,materials science,and interdisciplines thereof. 相似文献