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可乐易拉罐金虫 (正式写手)
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帮忙翻译以下一段文字，谢谢啦 摘要 碳酸二甲酯（DMC）作为一种重要的有机合成中间体，广泛应用于高性能树脂、溶剂等领域。与光气法、氧化羰基化法相比，酯交换法由于具有反应条件温和、低毒、高选择性等优点，已成为DMC合成工艺研究的热点。但目前该反应体系所用催化剂在分离与重复使用等方面存在诸多不足，因此，寻找合适的催化剂及载体，提高催化剂的活性和选择性是突破DMC合成工艺研究瓶颈的关键所在。 本论文采用活性较高的甲醇与碳酸乙烯酯（EC）酯交换反应合成DMC。以碱土金属Mg的盐类Mg(NO3)2·6H2O为前躯体，通过等体积浸渍法负载活性组分MgO，分别制备了不同负载量的MgO/γ-Al2O3和MgO/NaY催化剂，恒温下于油浴加热的圆底烧瓶中催化EC与甲醇酯交换反应合成DMC。采用X射线衍射、CO2程序升温脱附和扫描电子显微镜等手段对催化剂进行了表征。 考察了不同催化剂的催化性能，发现MgO/γ-Al2O3在EC与甲醇酯交换合成DMC反应中表现出较高的DMC选择性，高负载量的MgO在γ-Al2O3的表面发生团聚造成分散度下降，因此活性下降。与γ-Al2O3载体相比，采用NaY作催化剂载体在DMC选择性上有明显区别，其活性远高于γ-Al2O3，微细NaY分子筛具有明确的孔道分布、较高的内比表面积和良好的热稳定性，且MgO/NaY催化剂重复使用效果较好，是酯交换反应过程适宜的催化剂。考察催化工艺条件，结果发现以 12%MgO/NaY为催化剂，反应温度为140 ℃，反应时间3h，n(EC):n(甲醇)为1:8，催化剂用量为5%时催化性能最佳，EC的转化率和DMC选择性均为94.3 %，且DMC的收率达到89%。 关键词：γ-Al2O3; NaY分子筛; 氧化镁; 甲醇; 碳酸乙烯酯; 碳酸二甲酯 |
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金虫 (正式写手)
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可乐易拉罐: 金币+30 2012-04-12 21:44:12
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Dimethyl carbonate (DMC) is widely used in high performance resin, solvents, etc as a kind of important synthetic organic intermediates. Compared with phosgene method and oxidation hydroformylation method, the ester exchange method has the advantages of mild reaction conditions, low toxicity and high selectivity . It has become a hot spot for DMC synthesis process research. But there are also some shortcomings for the reaction system about the separation and repetition of the catalyst ,therefore, searching for the right catalyst and carrier and improving the activity and selectivity of the catalyst are the key to break through the bottleneck for DMC synthesis process research. This paper uses ester exchange reaction to synthesize DMC by active methanol and carbonated vinyl acetate (EC) . Alkaline metal Mg of salt in Mg (NO3) 2 · 6 H2O is used as the precursor, MgO active components is loaded through the volumetric immersion method , , the different load of MgO/gamma-irradiation Al2O3 and MgO/NaY catalyst are prepared respectively . the catalysts prepared are used in ester exchange reaction under constant temperature of heating oil bath in the circle of the flask . the X-ray diffraction, CO2 temperature programming desorption and warming scanning electron microscopy means are used for characterization of the catalyst. After examining the different catalytic performance of the catalysts ,we find MgO/gamma-irradiation Al2O3 showed a higher DMC seletivity in the ester exchange reaction . high load of MgO gamma-irradiation Al2O3 in the surface of is reuinted and resulted in the decline of dispersion , so activity decreases . compared with gamma-irradiation Al2O3 carrier , the catalyst using NaY as the carrier showed higher selectivity and activity . NaY zeolite has clear distribution of holes and high specific area ,as well as the excellent thermal stability .besides , MgO/NaY catalyst can be in repeated use , so it is a good catalyst for ester exchange reaction . Investigation of catalytic process condition showed that under the condition of 12% MgO/NaY as catalyst, reaction temperature 140 ℃, reaction time 3 h, n (EC) : n (methanol) for the 1:8, catalyst for 5%, it has the best catalytic performance , the EC conversion and selectivity DMC are 94.3%, and the DMC yield reached 89%. |
3楼2012-03-30 16:54:43
可乐易拉罐
金虫 (正式写手)
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2楼2012-03-28 09:52:29
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