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研究了水溶液中碳酸铈沉淀的陈化过程。以氯化铈、碳酸氢铵为原料制备碳酸铈颗粒,并以扫描电子显微镜观察碳酸铈颗粒的形貌与粒度。实验结果表明:当不经过陈化时,碳酸铈颗粒的粒度约为0、1μm,颗粒基本呈球状,团聚在一起;随着陈化时间的增加,碳酸铈颗粒的粒度逐渐增大;当陈化时间为10h时,碳酸铈颗粒为片状晶体,粒度约为6μm。 相似文献
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碳酸钾催化酯交换合成碳酸二丁酯的研究 总被引:7,自引:0,他引:7
研究了碳酸二甲酯(DMC)与正丁醇(n-BuOH)酯交换合成碳酸二正丁酯(DBC)的反应,筛选出合成碳酸二正丁酯的催化剂。考察了物料配比、温度和时间诸因素对反应的影响。结果表明,K2CO3具有较好的催化活性和选择性。得出了该反应最佳工艺条件:常压,反应温度140 ℃,反应时间4 h,n(DMC)∶n(n-BuOH)=1∶3。在催化剂用量为原料总质量的1%的条件下,DMC转化率为89.1%,DBC收率为86.9%,DBC选择性为97.6%,甲基丁基碳酸酯(MBC)收率为2.2%,碳酸二异丁酯(DIBC)的收率为70.0%,碳酸二叔丁酯(DTBC)收率为10.3%。 相似文献
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Kheira Marouf-Khelifa Fatiha Abdelmalek Amine Khelifa Mohamed Belhadj Ahmed Addou Jean-Louis Brisset 《Separation and Purification Technology》2006,50(3):373-379
Nitrous and nitric acids form in aqueous solutions exposed to a gliding arc discharge burning in humid air. The anions interfere when the concentration of particular solutes such as pollutants must be determined. In particular they falsify the COD measurements and spectral investigations and thus the efficiency of the plasma treatment in pollutant abatement. The nitrite anions must be thus removed, which require specific reagents. The influence of parameters such as solution pH and [reducers]/[NO2−] ratio on the reduction reaction was evaluated. The reduction of nitrite into N2 either by sulfamic acid or sodium azide is a first-order pH-dependant reaction with regard to nitrite and reducers (k1 = 2.93 × 10−1 m3 kmol−1 s−1; k2 = 6.21 × 10−1 m3 kmol−1 s−1, respectively). Sodium azide is thus more reactive than sulfamic acid. 相似文献
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In this study, anhydrous sodium carbonate is used as a catalyst to hydrolyze animal glue for core-making preparation. The structural characteristics and thermal properties of animal glue binder treated by anhydrous sodium carbonate are studied by Fourier-transform infrared spectroscopy, sodium dodecyl sulphate-polyacrylamide gel electrophoresis, gel permeation chromatography, and thermogravimetric analysis. The results show that animal glue binder treated by the anhydrous sodium carbonate has a higher tensile strength and a lower viscosity than those of untreated ones. The most effective hydrolysis process is the following. The amount of anhydrous sodium carbonate is 3 wt% to animal glue, the ratio of water to binder is 140:100, and the hydrolysis reaction should be performed at 50 °C for a reaction time of 60 min. The final tensile strength of binder reaches 2.67 MPa and the viscosity value is 1000 mPa·s. 相似文献
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Hsiang-Yu Chuang Hsi-Kuei Chen 《Journal of the Chinese Institute of Chemical Engineers》2008,39(5):457-465
The carbothermic reduction of zinc sulfide in the presence of sodium carbonate has been studied using X-ray diffractometry (XRD), thermogravimetric analysis system (TGA), atomic absorption spectrometry (AAS), inductively coupled plasma-mass spectrometry (ICP-MS), elemental analyzer (EA) and scanning electron microscopy (SEM). Experimental results of AAS indicated that the reduction in the presence of sodium carbonate proceeded significantly faster than in the presence of calcium carbonate and its sulfur fixation efficiency was acceptable. The results of XRD revealed that zinc sulfide was first transformed from β-type to α-type, then reduced to zinc vapor. The sequence of the variation of sodium containing material was found to be . A reaction mechanism is proposed to interpret the overall reaction. Results of kinetic study indicated that the rate of reduction could be increased by increasing the reaction temperature, the initial molar ratio of C/ZnS, or the initial molar ratio of Na2CO3/ZnS. The rate was also found to be increased with a decrease in sample height, size of C aggregate, size of Na2CO3 aggregate or the initial bulk density. The reduction rate, however, was found not to be influenced by the argon flow rate. An empirical expression of the initial rate of zinc yield has been determined. 相似文献
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综述了碳酸二甲酯和乙酸苯酯合成碳酸二苯酯工艺路线及其反应机理,并对该反应的催化剂体系进行了系统的概述,包括均相催化剂体系(锡和钛的有机化合物等)和多相催化剂体系(MoO3和WO3等金属氧化物)。并分析了以锡、钛以及金属氧化物作催化剂时合成碳酸二苯酯的优势和劣势;指出固载化的有机锡/有机钛与其他金属氧化物的复合化合物是今后碳酸二甲酯和乙酸苯酯合成碳酸二苯酯催化剂的重要研究方向。 相似文献
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Calcium carbonate nanoparticles (CCNP) were synthesised by precipitation from saturated sodium carbonate and calcium nitrate aqueous solutions. The effect of agitation rate, mixing time, calcium/carbonate ions concentration and temperature on particle size and morphology were investigated. Particles were characterised using X‐ray diffraction (XRD), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). Increasing the mixing time from 30 to 180 min resulted in a decrease in particles size. Mixing rate variation between 300 and 14 000 rpm decreased the particle size. Temperature increase favoured a significant growth in particle size and in the formation of aragonite beginning from 80°C. Calcium and carbonate ion concentrations are key parameters controlling the CCNP particle size. Calcite is the main polymorph obtained as revealed by XRD analysis. © 2011 Canadian Society for Chemical Engineering 相似文献
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在干燥碱式碳酸锌催化剂的作用下,以尿素和乙二醇(EG)为原料合成碳酸乙烯酯(EC)。重点考察了催化剂用量、原料配比、反应温度、反应时间对反应结果的影响。并通过GC-MS、FTIR和XRD分析,初步探索了反应机理以及碱式碳酸锌的作用机理。结果表明:当催化剂用量为尿素质量的6%,原料配比n(EG)∶n(尿素)=1∶1,反应温度160℃,反应时间3h,反应压力为0.01MPa时,碳酸乙烯酯收率达到91.64%。尿素和乙二醇合成碳酸乙烯酯的反应中,尿素首先分解生成异氰酸,异氰酸再与乙二醇反应生成中间产物2-羟乙基氨基甲酸酯(2-HEC),最后2-羟乙基氨基甲酸酯脱氨环化生成碳酸乙烯酯。所用碱式碳酸锌催化剂中存在Zn4CO3(OH)6·H2O和ZnO两种晶相,且以ZnO为主活性组分,两种晶相的协同作用提高了反应收率。 相似文献
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为利用碳酸乙烯酯固定的CO2,拓展碳酸二苯酯的合成方法,对碳酸乙烯酯酯交换合成碳酸二苯酯的反应进行了热力学分析,并考察了催化剂、反应温度、催化剂质量分数和反应时间对合成碳酸二苯酯的影响。结果表明:碳酸乙烯酯与苯酚的酯交换反应在热力学上是不可行的,而将苯酚乙酰化后可以实现由碳酸乙烯酯经酯交换合成碳酸二苯酯;不同催化剂催化酯交换反应时,n-Bu2SnO显示了最高的酯交换选择性。当反应温度为190℃,碳酸乙烯酯与乙酸苯酯的摩尔比为1∶2,n-Bu2SnO质量分数8%,反应时间10 h时,碳酸乙烯酯的转化率为15.1%,酯交换选择性64.2%,碳酸二苯酯的收率7.5%。 相似文献
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碳酸甲乙酯是一种重要的化工原料,市场潜力巨大。相对于传统制备方法,酯交换法制备碳酸甲乙酯具有明显优势。综述碳酸二甲酯酯交换反应合成碳酸甲乙酯的路线,对比碳酸二甲酯分别与乙醇和碳酸二乙酯进行反应的特点,表明碳酸二甲酯与乙醇反应需要解决产物分离的问题,而碳酸二甲酯和碳酸二乙酯酯交换反应则需要提高转化率。两种方法均具有良好的发展前景。 相似文献
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以碳酸二苯酯和异山梨醇为原料,通过熔融酯交换合成了异山梨醇型聚碳酸酯。考察了催化剂的种类及其用量、温度、压力以及原料配比对产品性能的影响。采用傅立叶变换红外光谱仪、热重分析仪和凝胶渗透色谱仪分别对产物的结构、热稳定性和分子量进行了表征。结果表明,以四乙基氢氧化铵(TEAH)为催化剂,催化剂用量为4.75×10~(–4) mol/mol异山梨醇,原料配比1∶1,缩聚温度245℃,预聚压力0.03 MPa,合成产品的特性黏度为34.61 m L/g,数均分子量为12 219,透明度良好,具有较高的热稳定性。 相似文献
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