共查询到20条相似文献，搜索用时 61 毫秒
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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
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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
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制备固体超强酸催化剂S2O82-/TiO2-ZrO2,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:S2O82-/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
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壳聚糖硫酸盐催化合成乙酸异丁酯 总被引：2，自引：0，他引：2
以壳聚糖硫酸盐为催化剂,由冰醋酸和异丁醇合成乙酸异丁酯。探讨了催化剂用量、反应时间、反应温度、酸醇摩尔比及带水剂对酯化率的影响。实验结果表明,在催化剂用量为0.5g,反应时间为2h,酸醇摩尔比为1:1.20的条件下,产品酯化率达94.88%,且催化剂可重复使用多次。 相似文献
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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
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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
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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
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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
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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
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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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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
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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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Anton Franks 《English in Education》1999,33(2):39-49
This paper looks at the way drama works to bring a model of an arts curriculum into reality. He also shows how drama is valuable when discussed as a separate, autonomous subject in the school curriculum as opposed to one subsumed within English. He argues for a view of the arts and gives an example of a sequence of work in an English GCSE class based around Arthur Miller's play View from the Bridge. From this he draws out several strands about the relationship of the drama curriculum to the individual students and teachers, the school, and to culture. He also emphasises the primacy of performance in drama education. 相似文献