Abstract:

On the basis of Al₂O₃, K₂O, CaO promoters, the experimental scheme of 17 samples with univariate, bivariate, trivariate and quadruvariate components was constructed for MgO, V₂O₅, ZrO₂,WO₃ four promoters, and the effect of each variable on the performance of the catalyst was investigated by simple contrast method and characterized by SEM-EDS, H₂-TPR, N₂-TPD, XRD, BET. The results showed that the samples with the highest activity in univariate, bivariate, trivariate and quadruvariate samples contained V₂O₅, ZrO₂ or WO₃ promoters, and the outlet ammonia concentration increased to 19.06%, 24% relative increase, with each additional promoter, indicating that the catalyst activity was related to the superposition and interaction of promoters, in which ZrO₂ and MgO were beneficial to the uniform distribution of elements in the catalyst. It can increase the number of active sites of the catalyst, increase the specific surface area of the catalyst, and improve the heat resistance of the catalyst. V₂O₅ and WO₃ decreased the apparent activation energy of the catalyst, increased the number of active sites of the catalyst, and increased the electron density of α-Fe, while ZrO₂ and MgO were alkaline and V₂O₅ and WO₃ were acidic, and there was acid-base synergism between them. Therefore, the catalyst had the highest activity when MgO、V₂O₅、ZrO₂、WO₃ were added together.

Key words: Fe_1-x O, catalyst, reactivity, fixed-bed, hydrogenation, promoters, optimization

摘要：

在Al₂O₃、K₂O、CaO三个基础助催化剂基础上，针对MgO、V₂O₅、ZrO₂、WO₃四种助催化剂，分别组成单变量、双变量、三变量和四变量共17个样品的实验方案，采用简单对比法，考察各变量对催化剂性能的影响，并采用SEM-EDS、H₂-TPR、N₂-TPD、XRD、BET等进行了表征。结果表明，单变量、双变量、三变量和四变量的样品中各自具有最高活性的样品都含有V₂O₅、ZrO₂或WO₃助催化剂，且每增加一个助催化剂，出口氨浓度就提高一个百分点，达到19.06%，相对提高24%，表明催化剂活性与助催化剂的叠加及其交互作用有关，其中ZrO₂和MgO有利于催化剂中元素的均匀分布，增加催化剂的比表面积，提高催化剂的活性位数目和耐热性能；V₂O₅和WO₃降低了催化剂表观活化能、增加了α-Fe上的电子密度；ZrO₂和MgO偏碱性而V₂O₅和WO₃偏酸性，它们之间存在酸碱协同作用，所以同时加入时催化剂活性最高。

关键词: Fe_1-x O, 催化剂, 活性, 固定床, 加氢, 助催化剂, 优化