共查询到20条相似文献，搜索用时 591 毫秒
1.
钨硅酸催化合成乙酸辛酯 总被引：3，自引：2，他引：3
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％。 相似文献
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介绍了新型催化型TiSiW12O40/TiO2的制备方法，实验考察了以自制的该催化剂催化合成甲酸丁酯的酸醇化，催化剂用量，反应时间等因素对反应产率的影响，实验表明：在酸醇物质的量比为2．5：1，催化剂用量为反，反液的1．78％，酯化反应时间为40min，反应温度为94－98℃时，反应产率可达72．2％。 相似文献
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固体超强酸S2O2-8/ZrO2-TiO2催化合成乙二酸二丁酯 总被引：5，自引：0，他引：5
制备固体超强酸催化剂S2O8^2-/ZrO2-TiO2用于合成乙二酸二丁酯，较系统地研究了该催化剂焙烧温度、用量、酸醇物质的量比、反应时间、反应温度和带水剂用量对酯化反应的影响．实验表明：S2O8^2-/ZrO2-TiO2是合成乙二酸二丁酯的良好催化剂．在催化剂焙烧温度为500℃，乙二酸为0．2mol时，酸醇的物质的量比为1：4，反应温度为130～135℃，反应时间为90min，催化剂用量为2．0g的优化条件下，乙二酸二丁酯的酯化率达95％． 相似文献
4.
固体催化剂SnCl4/C的制备及其催化酯化反应研究 总被引：1，自引：0，他引：1
制备了固体催化剂SnCl4／C，并通过乙酸苄酯的合成考察了该催化剂对酯化反应的催化情况，结果表明，固体催化剂SnCl4／C对酯化反应有很好的催化活性。适宜的反应条件为：当酸的用量为0．20mol，醇酸物质的量比为1．4，催化剂用量为1．0g，带水剂甲苯为15mL，反应时间为2．5h，反应温度为100～110℃时，酯化率达92％以上。 相似文献
5.
四氯化锡催化合成己酸异戊酯 总被引：1，自引：1，他引：1
研究了用四氯化锡催化己酸和异戊醇合成己酸异戊酯的反应。考察了酸醇摩尔比、催化剂用量、反应时间、带水剂用量等因素对酯化率的影响。优化反应条件为：催化剂用量0.5g／0．08mol己酸，酸醇摩尔比1．0：1．4，用6ml环己烷/0．08mol己酸为带水剂，反应时间120min，酯化率可达96.28％。 相似文献
6.
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
7.
以杂多酸盐TiSiW12O40-Al4(SiW12O40)3/TiO2-Al2O3为催化剂,壬酸和乙二醇为原料催化酯化合成壬酸乙二醇单酯.考察了酸醇的物质的量比、催化剂用量、反应时间、反应温度等对壬酸酯化率的影响.结果表明,合成壬酸乙二醇单酯的优化条件为:n(壬酸):n(乙二醇)=1:3,催化剂的用量为反应物总质量的4％,反应时间3.5h,反应温度90℃,在此条件下,酯化率可达94.6％以上.通过红外光谱验证了目标产物,发现该杂多酸盐催化剂对合成壬酸乙二醇单酯具有较高的催化活性,合成工艺简单,催化剂容易回收并可多次重复使用等特点. 相似文献
8.
研究了用硫酸氢钠催化合成乳酸正丁酯的反应，探讨了催化剂用量、酸醇比、反应时间及催化剂重复使用次数等因素对反应的影响。在酸醇体积比为1：3，催化剂为1．5％（w)，反应时间为2h，反应温度为120℃时，乳酸酯化率达97．2％。结果表明，在实验条件下，该催化剂具有较好的活性。 相似文献
9.
介绍了活性碳负载磷钨酸为催化剂，催化苯氧乙酸与烯丙醇的酯化反应，合成了苯氧乙酸烯丙酯。研究了反应时间、醇酸物质的量化和催化剂用量对酯收率的影响。 相似文献
10.
硫酸氢钠催化合成丁酸丁酯 总被引：1，自引：0，他引：1
以硫酸氢钠为催化剂催化正丁酸和正丁醇进行酯化反应合成了丁酸丁酯 ,讨论了反应时间、催化剂用量、酸醇摩尔比等因素对酯化率的影响 ,确定了最佳反应条件 :酸醇摩尔比 1∶1 1,催化剂用量 0 1g ,反应时间6 0min ,反应温度 12 0～ 14 0℃ ,酯化率达 98 8% . 相似文献
11.
罗艳萍 《读与写:教育教学刊》2008,5(6)
The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity. 相似文献
12.
Richard Denner 《海外英语》2007,(4):14-15
Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose. 相似文献
13.
Given a graph G,a subgraph C is called a clique of G if C is a complete subgraph of G maximal under inclusion and |C|≥2. A clique-transversal set S of G is a set of vertices of G such that S meets all cliques of G. The clique-transversal number, denoted as TC (G), is the minimum cardinality of a clique-transversal set in G. The clique-graph of G, denoted as K (G), is the graph obtained by taking the cliques of G as vertices, and two vertices are adjacent if and only if the corresponding cliques in G have nonempty intersection. Let F be a class of graphs G such that F={G|K(G) is a tree}. In this paper the graphs in F having independent clique-transversal sets are shown and thus TC (G)/|G|≤1/2 for all G ∈ F. 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
17.
陈美曦 《山东教育学院学报》2008,23(2):103-107
Different nations have different social cultures, and the social culture of every nation is developing with the development of the nation, language is greatly influenced by social culture, which enables language to possess national and historical characteristics. Word is the smallest, independent, meaningful linguistic unit of language. It can well reflect the national and historical characteristics. From synchronic aspect, the social and cultural influence on word meaning is mainly embodied in conceptual and associative meanings of word. The incorrespondence of word meaning is a phenomenon that exists in both conceptual and associative meanings of word among different languages. From diachronic aspect, the development of social culture causes some changes of word meaning to some extent. Therefore, social culture plays a key role in vocabulary learning and mastery of a language. 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
19.
《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