热处理条件对CuZnAl催化剂合成低碳醇性能的影响
发布时间：2019-02-18 08:23
【摘要】：低碳醇具有非常广泛的应用前景,可以作为清洁的液体燃料和良好的汽油添加剂,同时它还可以作为基础原料用于生产其他化学产品。在化石燃料资源日益减少的情况下,由合成气催化制备低碳醇的研究受到了人们的广泛关注。目前,对于合成气制低碳醇的研究多集中在对催化剂的改良,但效果均不尽如人意,存在诸多问题,很难实现工业应用。本课题组利用自创的完全液相法制备了不含任何碱金属及F-T组元的CuZnAl催化剂,在CO加氢实验中意外发现其具有高的低碳醇选择性,尤其是乙醇,但催化剂的重现性并不太理想,且对催化剂结构还缺乏深刻认识,因此有必要对其进行更加深入的研究。本文首先考察了高压下热处理温度对催化剂结构和性能的影响,同时研究了不同的CuZnAl比例对催化剂性能的影响,最后采用提前加热处理过的液体石蜡为热处理和反应介质,考察了其对催化剂合成低碳醇性能的影响。本文通过XRD、H_2-TPR、BET、NH_3-TPD-MS、XPS、SEM等方法对催化剂进行了表征分析,结合催化剂的活性评价数据,进一步了解了催化剂的结构和表面性质与高C_(2+)OH选择性的关系。得出以下主要结论:1.高温、高压热处理可以提高合成乙醇的选择性和稳定性。热处理条件为4.0MPa、280℃时,催化剂的乙醇选择性随着时间的推移持续提高,122 h后达到26.13%且保持稳定。2.催化剂大的比表面积、适中且稳定的Cu/Zn摩尔比、适宜含量的两种Cu_2O、比例适当的强弱酸性位,都是提高乙醇选择性和稳定性的关键因素。3.高压热处理可以抑制Cu0晶粒在反应过程中长大,加强催化剂中各组分之间的相互作用,有利于尖晶石的形成,但过多的尖晶石会弱化活性组分的作用,降低催化剂的活性。4.高压热处理下催化剂配比影响催化剂的结构与性能。较多的Al组分含量有利于尖晶石的形成,改变Cu_2O的存在形式,降低了孔径,使其有利于二甲醚的生成。Zn O晶粒的大小对催化剂的活性影响并不显著,Zn组分量的增多并没有显著促进C_(2+)OH的生成。5.预热处理后的液体石蜡在常压热处理的条件下减弱了对Cu物种的还原作用,提高了催化剂表面Cu/Zn比例,强化了Cu0-Cu+的协同作用;从而有效提高了C_(2+)OH的选择性。但在高压热处理的条件下,提前热处理液体石蜡并没有起到促进乙醇和C_(2+)OH生成的作用。
[Abstract]:Low-carbon alcohols can be used as a clean liquid fuel and a good gasoline additive, and can also be used as a basic raw material for the production of other chemical products. With the decrease of fossil fuel resources, the synthesis of low-carbon alcohols catalyzed by syngas has attracted much attention. At present, the research on synthesis of low carbon alcohol from syngas is mainly focused on the improvement of catalyst, but the effect is not satisfactory, there are many problems, it is difficult to realize industrial application. The CuZnAl catalyst without alkali metal and F-T component was prepared by a self-made complete liquid phase method. In the CO hydrogenation experiment, it was found that the catalyst had high selectivity to low carbon alcohols, especially ethanol. However, the reproducibility of the catalyst is not ideal and the structure of the catalyst is not well understood, so it is necessary to study it more deeply. In this paper, the effect of heat treatment temperature at high pressure on the structure and performance of the catalyst was investigated, and the effects of different CuZnAl ratios on the catalyst performance were studied. Finally, the heat treatment and reaction medium of the liquid paraffin treated by preheating was used as the heat treatment and reaction medium. The effect of the catalyst on the synthesis of low-carbon alcohols was investigated. In this paper, the catalyst was characterized and analyzed by means of XRD,H_2-TPR,BET,NH_3-TPD-MS,XPS,SEM and other methods. The relationship between the structure and surface properties of the catalyst and the selectivity of C _ (2) OH was further investigated. The main conclusions are as follows: 1. High temperature and high pressure heat treatment can improve the selectivity and stability of ethanol synthesis. The ethanol selectivity of the catalyst continued to increase with time when the heat treatment condition was 4.0 MPA ~ (-1) at 280 鈩，
本文编号：2425666
[Abstract]:Low-carbon alcohols can be used as a clean liquid fuel and a good gasoline additive, and can also be used as a basic raw material for the production of other chemical products. With the decrease of fossil fuel resources, the synthesis of low-carbon alcohols catalyzed by syngas has attracted much attention. At present, the research on synthesis of low carbon alcohol from syngas is mainly focused on the improvement of catalyst, but the effect is not satisfactory, there are many problems, it is difficult to realize industrial application. The CuZnAl catalyst without alkali metal and F-T component was prepared by a self-made complete liquid phase method. In the CO hydrogenation experiment, it was found that the catalyst had high selectivity to low carbon alcohols, especially ethanol. However, the reproducibility of the catalyst is not ideal and the structure of the catalyst is not well understood, so it is necessary to study it more deeply. In this paper, the effect of heat treatment temperature at high pressure on the structure and performance of the catalyst was investigated, and the effects of different CuZnAl ratios on the catalyst performance were studied. Finally, the heat treatment and reaction medium of the liquid paraffin treated by preheating was used as the heat treatment and reaction medium. The effect of the catalyst on the synthesis of low-carbon alcohols was investigated. In this paper, the catalyst was characterized and analyzed by means of XRD,H_2-TPR,BET,NH_3-TPD-MS,XPS,SEM and other methods. The relationship between the structure and surface properties of the catalyst and the selectivity of C _ (2) OH was further investigated. The main conclusions are as follows: 1. High temperature and high pressure heat treatment can improve the selectivity and stability of ethanol synthesis. The ethanol selectivity of the catalyst continued to increase with time when the heat treatment condition was 4.0 MPA ~ (-1) at 280 鈩，
本文编号：2425666
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