共查询到20条相似文献，搜索用时 62 毫秒
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以乳酸和乙醇为原料,钨钼为催化剂催化合成乳酸乙酯.通过优化验证实验,得出最宜合成条件为:n(乳酸):n(乙醇)=1:3,钨钼催化剂为1.5g,带水剂为20ml,反应时间为30min,乳酸乙酯产率可达93.2%.该法能避免现行硫酸催化剂腐蚀设备和污染环境的弊端,并能提高反应速率和乳酸乙酯的产率,且催化剂可重复使用. 相似文献
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《浙江大学学报(A卷英文版)》2020,(3)
目的:对现有的乙醇氧化脱氢体系中Mg-Al催化剂进行改进,以期获得更高的收率和产物选择性。创新点:1.制备Cu改性的Mg-Al催化剂用于乙醇氧化脱氢反应,获得了更高的乙醛收率和选择性;2. Cu/Mg-Al催化剂制备方法简单,制备价格低廉(无需贵金属),制备条件温和(无需高温高压);3. Cu/Mg-Al催化剂在使用前无需预还原。方法:1.采用共沉淀法和浸渍法制备Cu/Mg-Al催化剂;2.通过乙醇氧化脱氢反应对催化剂进行考评,以探究Cu改性、乙醇浓度和催化剂的还原条件对催化活性的影响。结论:1.与Mg-Al催化剂相比,经由Cu改性的Mg-Al催化剂的乙醇氧化脱氢活性显著提高;在350°C,乙醛最大收率为41.8%。2.进料气中水的存在(乙醇浓度下降)会对Cu/Mg-Al的催化性能产生不利影响,使得乙醇转化率和乙醛收率下降;但在高温区间(350～400°C),这个不利影响有所减弱。3.反应前,催化剂在氢气气氛下的还原步骤对Cu/Mg-Al催化活性的影响不明显。 相似文献
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以氢为原料的燃料电池是一种洁净高效的能源.简要介绍了乙醇水蒸气重整制氢的热力学分析以及乙醇水蒸气重整的反应机理;简要概述了乙醇水蒸气重整制氢的动力学,系统论述了乙醇水蒸气重整制氢反应中的Ni系催化剂的研究进展,并展望了Ni系催化剂的研究前景. 相似文献
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以苯甲酸和乙醇为原料,4-二甲氨基吡啶为催化剂,1,3-二环己基碳二亚胺作缩合剂,加热回流合成苯甲酸乙酯,并考察了催化剂、缩合剂、酸醇比和反应时间对苯甲酸乙酯收率的影响,确定最佳工业条件为:苯甲酸、乙醇和4-二甲氨基吡啶的物质量之比为1∶3∶0.08∶1.2,并加热回流3小时. 相似文献
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用乙醇和叔丁醇在稀硫酸催化下得到乙基叔丁醚。较佳的制备条件是:乙醇和叔丁醇的摩尔比为2.5:1;催化剂硫酸的质量分数为10％,用量为乙醇的30％,产物的收率达87.5％。 相似文献
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《实验技术与管理》2020,(6)
为了提高学生的综合能力和创新思维,设计出"硅掺杂ZrO_2催化剂催化乙醇合成乙烯"的综合性实验。用共沉淀法制备了一系列不同硅掺杂量的ZrO2催化剂,采用氨气-程序升温脱附(NH3-TPD)和氮气吸脱附对催化剂进行了表征,考察了不同硅掺杂量的ZrO2催化剂对乙醇合成乙烯催化性能的影响。实验结果表明,当以氨水为沉淀剂、硝酸氧锆为锆前驱体和硅掺杂量为50%时,乙醇的转化率为99.3%,乙烯达到94.6%的最大收率。同时运用密度泛函理论方法研究了乙醇和乙烯在硅掺杂ZrO_2催化剂上的吸附。计算结果显示,相较于ZrO_2(101)催化剂,反应物乙醇在Si/ZrO_2(101)催化剂表面上吸附更为稳定,同时产物乙烯在Si/ZrO_2(101)催化剂表面上更易脱附,表明硅掺杂ZrO_2催化剂更加有利于乙烯的生成。该综合性实验将理论计算和实验相结合,使学生既能锻炼实验的基本技能,又能掌握相关理论计算的知识。 相似文献
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对羟基苯甲酸乙酯的合成 总被引：2，自引：0，他引：2
研究了以对羟基苯甲酸、乙醇为原科,氨基磺酸为催化剂,合成对羟基苯甲酸乙酯,并讨论了催化酯化的影响因素.实验结果表明,磺酸是合成对羟基苯甲酸乙酯的良好催化剂,易回收,可重复使用.最佳工艺条件为:酸醇物质的量比为1∶4,催化剂用量为反应物料总质量的10.3%,反应时间为3h,回流温度,此条件下,产品收率达90.38%. 相似文献
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固载杂多酸催化合成苯甲酸乙酯 总被引：6，自引：0，他引：6
在固载杂多酸PW1 2 SiO2 催化剂存在下 ,由苯甲酸与乙醇反应合成苯甲酸乙酯。最佳合成条件为 :n(酸 ) :n(醇 ) =1∶4 .0 ,催化剂用量为苯甲酸质量的 10 % ,反应时间为 5h ,产率可达 91%。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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杂多酸盐催化剂催化合成丁酸乙酯 总被引：2，自引：0，他引：2
首次以杂多酸盐TiSiW1 2 O40 /TiO2 为催化剂催化合成了丁酸乙酯 .结果表明 :TiSiW1 2O40 /TiO2 具有良好的催化活性 ,乙醇和正丁酸的摩尔比为 1.5∶1,催化剂用量为反应液总量的1.0 % ,酯化反应时间为 1.5h ,反应温度为 93～ 96℃ ,丁酸乙酯的产率可达 75.6 % . 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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《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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唐芳 《读与写:教育教学刊》2008,5(6)
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. 相似文献