共查询到16条相似文献,搜索用时 46 毫秒
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通过尿素沉淀法制备了以锌基为主要活性组分的不同的复合型氧化物催化剂,考察了尿素与1,2-丙二醇(PG)合成碳酸丙烯酯(PC)反应的催化性能。用XRD,SEM,BET,CO2-TPD对催化剂进行了表征。结果表明,催化剂的强碱性位数量可能是影响催化活性的关键因素,在此基础上推出碱催化机理:较强的碱强度有利于降低中间产物羟丙基氨基甲酸酯(HPC)转化为PC的活化能。在反应温度170℃,反应时间1 h,PG/尿素摩尔比1.5,0.6 g催化剂(占尿素质量的2%),反应压力3.99×104Pa的条件下,PC收率高达99.8%。n(锌)∶n(镁)=1∶4,催化剂经过5次再生,PC收率降低了2.2%。 相似文献
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针对尿素醇解合成碳酸丙烯酯工艺,系统考察了锌盐催化体系的催化反应性能。结果显示,锌盐均表现出良好的催化活性,其中高氯酸锌的催化效果最好;高氯酸根离子强的吸电性可能是高氯酸锌催化效果好的主要原因。以高氯酸锌为催化剂,考察了不同的反应时间、催化剂用量和反应温度对合成中各反应的影响。当n(1,2-丙二醇)∶n(尿素)=4∶1、反应时间3 h、催化剂质量分数1.5%、反应温度170℃时,碳酸丙烯酯的收率可以达到94.2%。催化剂的稳定性较好,具有一定的应用前景。 相似文献
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考察了各种锌盐催化尿素和1,2-丙二醇(PG)合成碳酸丙烯酯(PC)的催化性能。几种催化剂中,氯化锌具有最佳的催化性能。以氯化锌为模板催化剂,考察了反应条件如:反应温度、反应时间和催化剂用量对催化效果的影响。结果表明,在尿素3.0 g、PG 7.62 g、反应温度170℃、反应时间3 h、催化剂用量0.4 g时,PC收率可达到82.9%。傅里叶红外表征进一步说明,催化剂的催化活性与它们活化尿素分解为异氰酸的能力有关;然后,异氰酸与催化剂作用生成中间物种,在PG的作用下最终生成PC。最后,基于以上催化测试和表征结果,提出了尿素和PG反应合成PC可能的催化反应机理。 相似文献
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对加压法二氧化碳与环氧丙烷合成碳酸丙烯酯催化剂进行了研究,实验结果表明:KI/聚乙二醇400催化体系具有很好的催化活性,可在较低温度、压力下短时间高产率的得到碳酸丙烯酯。碳酸丙烯酯得率可达99.8%以上,在一定条件下。经多次循环使用后仍有较高的活性。 相似文献
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合成离子液体溴代十八烷基甲基咪唑[C18MIM]Br,测试其在二氧化碳与环氧丙烷釜式反应中的催化性能,并研究了反应时间、反应压力和反应温度对碳酸丙烯酯产率和选择性的影响.结果显示,该离子液体具有良好的催化活性,在3 MPa、120℃反应2 h后,反应收率和产品的光学选择性都能达到99.9%. 相似文献
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在釜式反应器内考察以3种咪唑类离子液体为催化剂合成碳酸丙烯酯(PC)的催化活性及影响因素进行研究。实验结果表明,[BMIM]Br、[BMIM]BF4对上述反应具有较高的催化活性,助剂ZnBr2的加入能显著提高PO转化率。得出最适宜的反应条件为:主催化剂用量0.25%(物质的量比例,下同),n(ZnBr2)/n([BMIM]Br)=1/5,反应温度110℃,反应压力1.5 MPa条件下反应1 h,PC的收率98.29%,选择性为100%;催化剂经4次重复使用反应的转化率均在92%以上,PC的选择性均为100%。 相似文献
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Yuchen Jia Lei Lv Yingying Nie Linyu Jiao Weihua Shen Zhiqing Zhu Yunjin Fang 《加拿大化工杂志》2021,99(1):374-382
Alcoholysis of urea with 1,2‐propylene glycol (PG) is a potential industrial process for the synthesis of propylene carbonate (PC) with many advantages. However, the preparation of industrial catalysts such as Zn‐Al oxide by the co‐precipitation method will inevitably produce a large amount of salty water and building desalting equipment will increase the investment cost. The present work attempts to use a mechanically mixed catalyst consisting of commercial ZnO and Al2O3 to solve these problems. This type of catalyst was capable of catalyzing the reaction more than 5 times. The PC yield was gradually increased with each use. The best PC yield of 96.7% is comparable to the co‐precipitated Zn‐Al oxide catalysts and was achieved during the third use. In the reaction, ZnO and Al2O3 were dissolved into the reactants to form complexes, which homogenously catalyzed the reaction. It was found that the dissolved Zn and Al complex significantly influenced the PC yield and re‐precipitated in the late stage of the reaction. Furthermore, the partial dissolution of Al assisted the dissolution and precipitation of Zn, which improved the PC yield. After several dissolution‐precipitation cycles, ZnO‐Al2O3 was homogeneously mixed at the atomic scale. Interestingly, there was an adequate linear relationship between the amount of dissolved Zn and Al in each reaction, the linear correlation coefficient improved after each reaction, and the slope of the line (the ratio of dissolved Zn/Al) was 7.26 in the third use. 相似文献
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采用后嫁接法将碱性离子液体1-丁基-3-甲基咪唑的氢氧化物([Bmim]OH)分别负载到介孔硅胶、MCM-41分子筛和SBA-15分子筛上制备了非均相负载型离子液体,采用傅立叶变换红外光谱、N2吸附-脱附、元素分析和热重分析等手段对其表征,发现离子液体以共价键嫁接到硅胶上,且有较好的热稳定性。在无溶剂和温和的条件下,以非均相负载型离子液体为催化剂,研究了环氧丙烷与CO2环加成合成碳酸丙烯酯的反应,结果表明,3种非均相负载型离子液体均具有较好的催化性能,其中,[Bmim]OH/SiO2的催化性能最好,在最优条件下,环氧丙烷转化率可达99.1%,反应后催化剂经过滤即可分离回收利用,多次使用仍保持较高的反应活性。 相似文献
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Dudu Wu Wenming Chang Xia Wen Fukui Xiao Junping Li Ning Zhao Wei Wei Yuhan Sun 《Fuel Processing Technology》2008
A convenient and simple route for synthesis of methyl benzoate from dimethyl carbonate and acetophenone has been exploited for the first time in the presence of solid base catalysts. The results showed that solid base with moderate strength, such as MgO, facilitated the formation of methyl benzoate and the function of basic catalysts could mainly be attributed to the activation of ketone via the abstraction of Hα by base sites. 相似文献