共查询到19条相似文献,搜索用时 156 毫秒
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尿素直接醇解法合成碳酸二甲酯催化剂研究进展 总被引:5,自引:0,他引:5
综述了甲醇与尿素醇解法催化合成碳酸二甲酯所用催化剂的研究进展,尿素醇解法合成碳酸二甲酯具有原料价廉易得、工艺简单、操作条件温和、反应过程无水生成和反应产生的氨气可以回收利用等优点,具有工业化前景。 相似文献
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尿素与甲醇均相催化合成碳酸二甲酯的研究 总被引:32,自引:0,他引:32
在对尿素与甲醇合成碳酸二甲酯(DMC)反应进行热力学分析的基础上较详细地研究了乙酸锌和二丁基氧化锡对该反应的催化作用。实验表明,以乙酸锌作催化剂时,DMC收率随尿素浓度增加而增加,但随催化剂用量的增加而下降,而且以尿素浓度的影响为更强;结合观察催化剂在反应前后的色泽、形态变化和XRD分析,证明存在着乙酸锌与甲醇作用生成氧化锌、乙酸甲酯和水的副反应。水分是抑制催化剂活性的主要因素。以正交实验评价了各因素对二丁基氧化锡催化作用的影响,得到以下较佳因素水平:甲醇/尿素摩尔比44,二丁基氧化锡/尿素摩尔比0.2,反应温度180℃,反应时间6h,由极差分析该4因素的重要性次序为:反应温度>反应时间>原料摩尔比>催化剂用量。最后,就乙酸锌、二丁基氧化锡、异丙醇铝和氯化锌均对尿素和甲醇合成DMC反应有催化活性,认为该反应对Lewis酸催化反应。提出了其反应机理为甲醇在催化剂表面上发生解离吸附,形成的甲氧基进攻氨基甲酸酯的羰基碳与氨基进行交换形成碳酸二甲酯。 相似文献
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用色谱法对尿素甲醇法合成碳酸二甲酯的反应产物进行定性定量跟踪分析。讨论了温度、尿素与甲醇配比、压力等因素对合成碳酸二甲酯的影响,并确定了最佳工艺条件。 相似文献
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氧化锌催化剂在碳酸二甲酯合成中的应用研究 总被引:2,自引:0,他引:2
用低热固相配位化学反应方法、分析纯ZnO表面改性、均相沉淀法、溶胶-凝胶法、并流沉淀法和固体研磨法6种方法制备了ZnO催化剂.对这6种ZnO催化剂进行了XRD和SEM表征,筛选出最好的催化剂;比较了它们对DMC合成的活性大小的影响.结果表明:在尿素3 g,甲醇120mL,催化剂占整个反应物质量的6%,反应温度170~180℃,压力2.0~2.4 MPa,时间8 h条件下,ZnO(D)的催化活性最高,DMC的收率达到6.10%,尿素转化率为77.83%;用不同方法制备得到的ZnO催化活性顺序为ZnO(D)>ZnO(F)>ZnO(C)>ZnO(A)>ZnO(B)>ZnO(E). 相似文献
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碳酸二甲酯是重要的有机合成中间体,应用领域广泛。综述碳酸二甲酯的主要生产技术工艺,包括光气法、酯交换法、氧化羰基化法、甲醇与CO2合成法、甲醇与尿素合成法、草酸二甲酯脱羰基法等。对比各种方法的优缺点,并对未来的发展进行展望。 相似文献
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A semicontinuous process for the synthesis of methyl carbamate from urea and methanol was investigated in the autoclave without the catalyst. Some significant parameters were determined in terms of the methyl carbamate yield. The optimal reaction conditions were found at an initial molar ratio of methanol/urea of 6:1, a reaction temperature of 423 K, a flow rate of fresh methanol at 4 mL/min, a stirring speed of 800 rpm and a reaction time of 6 hours, respectively. A MC yield of 98.7 % was obtained at the optimal reaction conditions. Furthermore, the kinetics of this reaction were researched and the reaction activation energy was obtained as 110.498 kJ/mol. It was demonstrated that removing methanol containing ammonia from the autoclave and replacing it with continuously feeding fresh methanol resulted in a higher reaction rate and a high MC yield. 相似文献
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采用尿素法合成甲苯-2,4-二氨基甲酸甲酯(TDC)是一条绿色的工艺路线.其反应路径之一是以1-甲基-2,4-苯二脲(TBU)为中间产物,即2,4-二氨基甲苯(TDA)与尿素反应生成TBU,TBU再与甲醇反应得到TDC.首先对该路径进行了热力学分析,然后分别对两步反应进行了研究.对于TBU合成反应,适宜溶剂和催化剂分别为环丁砜(CBS)和乙酸锌;适宜反应条件为:反应温度130℃,反应时间7 h,n(TDA):n(Zn(OAc)2):n(Urea):n(CBS)=1:0.05:3.5:10.此时TDA转化率为54.3%,TBU选择性为73.3%.对于TDC合成反应,基于液相色谱-质谱和气相色谱分析结果,确定了反应组分.适宜的反应条件为:反应温度140℃,反应时间5 h,反应压力1.1 MPa,甲醇与TBU摩尔比为110:1.在该反应条件下,TBU转化率为100%,TDC选择性为60.4%. 相似文献
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Kinetics studies of dimethyl carbonate synthesis from urea and methanol over ZnO catalyst 总被引:1,自引:0,他引:1
Junliang Zhang Feng Wang Wei Wei Fukui Xiao Yuhan Sun 《Korean Journal of Chemical Engineering》2010,27(6):1744-1749
A kinetic experiment of dimethyl carbonate (DMC) synthesis by urea methanol over ZnO catalyst was carried out in an isothermal
fixed-bed reactor. A kinetic model based on the mole fraction was proposed and the kinetic parameters were estimated from
the experimental results. The model predictions were compared with the experimental data and fair agreements were found. The
effects of the reaction temperature (443–473 K), space time (0–4.7 h mol−1 kg
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) and urea mass percent (5–9%) in feed on DMC mole fraction were investigated. It was found that the reactions are mainly
influenced by the reaction temperature and space time rather than urea mass percent in feed. The experimental and simulated
results indicated that the reaction from MC to DMC was the rate-controlling step in the DMC synthesis process from urea and
methanol. It is important to remove the DMC and byproduct ammonia to achieve a high selectivity of DMC. This implies that
reactive distillation might be used in the DMC synthesis on an industrial scale to achieve a higher selectivity of DMC. 相似文献