磷钨杂多酸催化合成乙酸乙酯的研究

经实验确定了以磷钨杂多酸为催化剂、乙醇和乙酸为原料合成乙酸乙酯的最佳反应条件为酸醇比为2．0：1～2．5：1，磷钨酸用量为酸质量的2．0％～2．5％，反应时间4h，反应酯化率达94．6％以上。     

钨硅杂多酸催化合成桂皮酸正戊酯

以钨硅杂多酸为催化剂，通过桂皮酸和正戊醇酯化反应合成桂皮酸正戊酯，研究了各有关因素对桂皮酸酯化率的影响．实验证明：钨硅杂多酸是合成桂皮酸正戊酯的良好催化剂，在酸醇物质的量比为1：2．5．催化剂用量1g／0．05mol桂皮酸，带水剂苯7mL，反应时间为1．5h条件下，桂皮酸的酯化率可达99．2％．     

磷钨杂多酸催化合成乙酸异戊酯的研究

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。     

磷钨酸催化合成醋酸正丁酯的研究

以杂多酸为催化剂，合成了醋酸正丁酯，对反应条件进行了探讨。结果表明，按醇酸摩尔比3：1，催化剂用量3g，反应温度120~C，反应时间3h的反应条件，得到最佳反应结果，酯化率可达91％.     

磷钨杂多酸催化合成己酸乙酯

研究了磷钨杂多酸的制备及其催化合成己酸乙酯的情况.结果表明:磷钨杂多酸是合成己酸乙酯的良好催化剂,当酸醇物质的量比为1∶2.0,催化剂用量为0.5 g/0.1 mol己酸,甲苯为8 mL,反应时间为150 min时,酯化率可达97.2%.     

钨硅酸催化合成乙酸辛酯

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％。     

固体超强酸WO3／ZrO2催化合成乙酸正丁酯

以自制固体超强酸W03／ZrO2为催化剂,研究了合成乙酸正丁酯的最佳反应条件,实验结果证明：固体超强酸WO,／ZrO：是合成乙酸正丁酯的良好催化剂;其合成的最佳反应条件为：n（冰乙酸）：／7,（正丁醇）=1．0：1．6,催化剂用量为反应物料总质量的3．8％,在回流温度下反应时间为2．0h,在上述条件下,乙酸正丁酯的酯化率可达97．09％．     

耐寒增塑剂癸二酸二己酯的催化合成研究

以硅钨杂多酸为催化剂，癸二酸和正己醇为原料合成了癸二酸二己酯．考察了醇酸物质的量比、催化剂用量、反应时间等因素对酯化率的影响．结果表明，在适宜的条件下其酯化率可达95％以上。     

固载硅钨杂多酸催化合成戊二酸二异辛酯研究

研究了活性炭固载杂多酸催化戊二酸和异辛醇合成戊二酸二异辛酯的反应,探讨了原料配比、反应时间、催化剂用量等对酯化率的影响,当温度为120℃,醇酸摩尔比为2．5：1,反应时间为2h,催化剂用量为系统总质量的0．5％时,酯化率可达97．8％．     

氨基磺酸催化合成苯甲酸正丁酯的研究

以氨基磺酸为催化剂，催化合成了苯甲酸正丁酯，用正交实验法确定了反应的最佳条件．最佳条件为：催化剂用量为0.6g／0．1mol苯甲酸，醇酸物质的量比为2：1；回流时间为3．5—4．0h；苯甲酸的酯化率可达97．26％．该催化剂催化效果好，用量少，酯化率高，污染小，有一定的工业应用价值．     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

不同的吃喝玩乐

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/     

漏洞百出的教育

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?     

只要努力,不要后悔

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.     

浅谈移民问题

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.     

Sister Carrie, an Adherent of Desires

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.     

Improvement of one-cycle controller by use of proportional integral differential controller

1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec…     

库克斯顿城堡

城堡, 是欧洲典型的建筑之一, 每个城堡都有一个美丽的传说或是一段历史。从本期开始, 我们将推出“城堡之旅”, 带各位读者去浏览、观赏欧洲各地的城堡, 开始一段文化与历史的旅途!     

The Reader Response Approach to Teaching of English Literature

During interview with English majors, it was found that a majority of students expressed disappointment with their experience of English literature classes. Students' dislike of learning English literature appears to be the major problem of teaching English literature in China. Reader response approach is a good way to solve this problem. In this paper, I explain the rationale behind the reader response approach, such as its origin, definition, features, assumptions, and strategies. Then I illustrate how reader response approach works as a teaching strategy by presenting several teaching models. At last I evaluate its usefuiness for teachers and present the advantages of reader response approach in Chinese context.