共查询到20条相似文献，搜索用时 62 毫秒
1.
用活性炭负载硅钨酸催化剂催化柠檬酸与正丁醇酯化合成柠檬酸三丁酯.对柠檬酸与正丁醇酯化反应条件进行优化,其优化条件是:在酸醇的摩尔比为1:6.0,催化剂的负载量为18%,催化剂用量为柠檬酸质量的1.2%,反应温度为150℃,反应时间4小时,柠檬酸的酯化率达92.3%,产物经过红外光谱表征. 相似文献
2.
以柠檬酸和正丁醇为原料,硫酸铝为催化剂,合成柠檬酸三丁酯,考察了其酸醇比对酯化率的影响,并与在超声催化条件下反应对酯化率的影响进行了对比.确定了实验最佳反应条件为:以柠檬酸用量为基准,酸醇摩尔比为1∶4.0,催化剂用量为4%,在超声波振荡温度为0℃,振荡时间为20 min条件下合成柠檬酸三丁酯,酯化率为92.6%. 相似文献
3.
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
4.
以柠檬酸和异丁醇作原料,KIP209离子交换树脂为催化剂合成了柠檬酸三异丁酯（TIBC）,经单因素和正交实验考察了醇酸摩尔比、反应时间、反应温度和催化剂用量对酯化反应的影响。结果表明,合成柠檬酸三异丁酯的最佳条件为：醇酸摩尔比为4：1,反应时间4hr,反应温度150℃,催化剂用量为15%（以柠檬酸质量计）。酯化率达74.8%,且催化剂可重复使用。 相似文献
5.
用正丁醇和柠檬酸为原料,WO3/MoO3/SiO2为催化剂催化合成柠檬酸三丁酯.通过考察醇与酸的物质的量比,反应温度和反应时间,催化剂用量和溶剂用量对酯化反应的影响.确定合成柠檬酸三丁酯的最佳反应条件为n(正丁醇)/n(柠檬酸)=4.5,催化剂用量为反应物柠檬酸质量的6%,反应温度130 -140℃,反应时间3.5h,... 相似文献
6.
研究了以固体超强酸SO4 2 - /TiO2 /La3 为催化剂 ,柠檬酸和正丁醇为原料合成柠檬酸三丁酯 ,并考察了影响反应的因素。结果表明 :最适宜的反应条件为醇酸物质的摩尔比为 5 .0∶1,催化剂用量为柠檬酸用量的 0 .6% ,带水剂甲苯为正丁醇体积的 1/9,反应时间 2 .5h ,其酯化率可达 95 .6%。 相似文献
7.
8.
王建平 《洛阳师范学院学报》1999,(5)
研究了柠檬酸与正丁醇在盐类一水合硫酸氢纳,十二水合硫酸铁按催化作用下直接酯化合成柠檬酸三正丁酯的最佳条件。结果表明：酸醇摩尔比为1:6.0~7．0,催化剂用量为酸、催化剂的摩尔比为1:0．1,反应温度在110℃~135℃,反应时间为1.5h,转比率达到95％以上,产品纯度达99%。 相似文献
9.
对甲基苯磺酸催化合成乙酸仲丁酯 总被引：1，自引：0，他引：1
以对甲基苯磺酸为催化剂、对乙酸和仲丁醇间的酯化反应进行了研究,考察了催化剂用量、醇酸物质的量比和反应时间对酯化率的影响.其最佳反应条件为:乙酸用量为0.1 mol时,催化剂用量为0.4 g,仲丁醇与乙酸的物质的量之比为1.2:1,环己烷作带水剂,反应1.5 h,酯化率可达94.4%. 相似文献
10.
高锐 《蒙自师范高等专科学校学报》2009,7(2)
用CuCo2O4作催化剂催化酯化苯甲酸到苯甲酸乙酯,考察了催化剂的用量、反应温度、反应时间等对催化剂的催化酯化的影响.实验结果表明:当催化剂的用量为苯甲酸摩尔量的5%mol,在75℃条件下反应7h,苯甲酸乙酯产率可达到59.1%. 相似文献
11.
12.
13.
《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
14.
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
15.
《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
16.
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
17.
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
18.
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
19.
20.
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