草酸二甲酯催化加氢硅酸铜催化剂的研究

发布时间：2018-11-26 10:14

【摘要】：乙二醇作为一种重要的化学工业原料,被广泛的用于聚酯等行业的生产。传统的生产方式以石油为原料来生产,随着石油资源的日益匮乏,“煤制乙二醇”技术逐渐受到研究者的重视。该技术是指从煤气出发,经草酸酯选择性加氢制备乙二醇的技术。其中的关键步骤是草酸酯加氢制乙二醇。目前的铜基催化剂还未能满足工业化需求,且存在催化活性与稳定性问题。尽管国内外的研究学者对此课题进行了大量研究,并提出了不同的关于铜基催化剂活性中心的理论(Cu0或Cu+或Cu0-Cu+协同),虽然存在分歧,但可以肯定的是,探索控制催化剂表面物种的组成、价态分布的方法是开发高性能草酸酯加氢催化剂的根本途径。本文采用共沉淀法制备硅酸铜催化剂,研究了沉淀过程中活性组分与载体之间的相互作用,并考察了相应可变参数对催化剂催化性能的影响,优化了制备工艺。此外,为解决催化剂在高温条件下易烧结失活,因而添加了助剂锌以提高催化剂的热稳定性。研究结果如下：(1)在采用沉淀法制备硅酸铜催化剂的过程中,沉淀方式对铜物种的颗粒大小及在载体上的分散度有较大的影响。硝酸铜滴入硅酸按沉淀得到的催化剂性能优于硅酸钠滴入硝酸铜沉淀制得催化剂,即适宜的沉淀方式制得的催化剂活性物种分散度好,活性中心多。在沉淀过程中,沉淀速率对反应的转化率稍有影响而对目的产物的选择性影响不大。随沉淀时间的增加即沉淀速率的减慢,草酸二甲酯的转化率稍有提高。铜硅比对催化剂的催化性能影响较大,铜硅比过低,催化剂活性位少,催化活性弱；铜硅比过高则活性物种易相互聚集,颗粒长大,分布不均从而催化剂活性也会降低。实验表明较优的铜硅比为0.85：1,此时DMO转化率为90.5%,EG选择性为82.7%。(2)在进行锌改性硅酸铜催化剂研究过程中,锌元素的引入方式对催化剂有不同的影响。实验表明铜组分与锌组分同时与硅酸钠沉淀时,铜锌之间有相互作用,锌对铜物种的分散有促进作用。且锌的引入量对催化剂的性能影响较大,锌引入量少时无法起到明显效果,而引入量过多时则会包裹活性中心。所以适宜的催化剂组成为Cu0.8Zn0.2/SiO2,此时催化剂转化率为99.5%,选择性为91.5%皆为较优结果,抗失活性能测试也显示转化率为99%,活性较稳定。
[Abstract]:As an important raw material in chemical industry, ethylene glycol is widely used in the production of polyester and other industries. The traditional mode of production uses petroleum as raw material to produce. With the increasing shortage of petroleum resources, the technology of making ethylene glycol from coal has been paid more and more attention by researchers. This technology refers to the selective hydrogenation of oxalate to produce ethylene glycol from gas. The key step is the hydrogenation of oxalate to ethylene glycol. The current copper-based catalysts have not been able to meet the industrial needs, and there are problems of catalytic activity and stability. Although researchers at home and abroad have done a lot of research on this subject and put forward different theories about the active centers of copper-based catalysts (Cu0 or Cu or Cu0-Cu collaboration), although there are differences, it is certain that, The method of controlling species composition and valence distribution on the surface of catalyst is the fundamental way to develop high performance oxalate hydrogenation catalyst. In this paper, coprecipitation method was used to prepare copper silicate catalyst. The interaction between active component and carrier during precipitation was studied. The effect of variable parameters on the catalytic performance of the catalyst was investigated and the preparation process was optimized. In addition, in order to solve the problem that the catalyst is easy to be deactivated by sintering at high temperature, the additive zinc is added to improve the thermal stability of the catalyst. The results are as follows: (1) in the process of preparing copper silicate catalyst by precipitation method, the precipitation mode has a great influence on the particle size of copper species and the dispersion on the carrier. The catalytic properties of the catalyst prepared by precipitation of copper nitrate drop with silicic acid are better than that of the catalyst prepared by the precipitation of copper nitrate with sodium silicate, that is, the catalyst prepared by the appropriate precipitation method has a good dispersion of active species and more active centers. In the precipitation process, the precipitation rate had a slight effect on the conversion of the reaction, but had little effect on the selectivity of the target product. The conversion rate of dimethyl oxalate increased slightly with the increase of precipitation time. The ratio of copper to silicon has a great influence on the catalytic performance of the catalyst, the ratio of copper to silicon is too low, the activity of the catalyst is less and the catalytic activity is weak; if the ratio of copper to silicon is too high, the active species tend to aggregate mutually, the particles grow up and the distribution is uneven, thus the activity of the catalyst will also decrease. The experimental results show that the optimum copper-silicon ratio is 0.85: 1, and the DMO conversion is 90.5 and EG selectivity is 82.7%. (2) in the study of zinc modified copper silicate catalyst, The method of introducing zinc has different influence on the catalyst. The results show that when copper and zinc are precipitated with sodium silicate at the same time, there is interaction between copper and zinc, and zinc can promote the dispersion of copper species. The effect of zinc content on the performance of the catalyst is great. When the amount of zinc is low, the effect of the catalyst is not obvious, but when the amount of zinc is too much, the active center will be wrapped. Therefore, the suitable catalyst composition is Cu0.8Zn0.2/SiO2, the conversion of the catalyst is 99.5 and the selectivity of 91.5% is the best result. The deactivation resistance test also shows that the conversion is 99%, and the activity is relatively stable.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TQ223.162;O643.36

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