Correlations between synthesis, precursor, and catalyst structure and activity of a large set of CuO/ZnO/Al2O3 catalysts for methanol synthesis
Correlations between synthesis, precursor, and catalyst structure and activity of a large set of CuO/ZnO/Al2O3 catalysts for methanol synthesis
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DOI：
10.1016/j.jcat.2008.07.004
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发表时间：
2008-09-10
影响因子：
7.3
通讯作者：
Schueth, F.
中科院分区：
文献类型：
--
作者：
Baltes, C.;Vukojevic, S.;Schueth, F.
在严格控制pH、沉淀温度、煅烧温度等参数的条件下，采用共沉淀法系统制备了Cu/ZnO/Al2O3三元催化剂。在49倍多管高通量实验装置中测试了所有催化剂的甲醇合成活性，实验条件与商业甲醇生产路线相似，使用CO， CO2和H-2的合成气混合物。选择代表性样品进行更详细的结构和形态分析，以揭示催化剂的“制备历史”与甲醇生产率之间的相关性。在pH值为6-8、温度为70℃的条件下沉淀的前驱体所获得的催化剂的催化性能最好。XRD测量结果表明，催化剂可以根据其相进行“分组”。研究发现，一组性能最好的催化剂在煅烧前驱体中表现出未分解的Cu/Zn羟基碳酸盐残留物的特征XRD模式，从而假设这种状态下的碳酸盐物种可能会提高生产率。对这些含羟基碳酸盐催化剂的进一步研究，为了解动态老化过程及其对催化性能的影响提供了更详细的见解。经过初始相形成时间后老化20 ~ 60 min的催化剂，甲醇合成活性最高。最佳焙烧温度为250 ~ 300℃，在此条件下制备的Cu/Zn/Al羟基碳酸盐保持稳定。此外，合成气原料组成随反应条件的变化而变化，并与催化活性相关。在4.5 M Pa和245℃条件下，Cu/ZnO/Al2O3催化剂在以下气体浓度下的甲醇产率最高：H-2为50-60%，CO为30-40%，CO2为5-10%。版权所有。
Ternary Cu/ZnO/Al2O3 catalysts were systematically prepared via the coprecipitation route under strict control of parameters such as pH, precipitation temperature, and calcination temperature. All catalysts were tested with respect to their methanol synthesis activity in a 49-fold multitubular high-throughput experimentation setup under conditions similar to the commercial methanol production route, using a syngas mixture of CO, CO2, and H-2. Representative samples were chosen for a more detailed structure and morphology analysis to reveal correlations between the catalyst's "preparation history" and the methanol productivity. The best catalytic performance was observed for catalysts obtained from precursors precipitated in the pH range of 6-8 at 70 degrees C. XRD measurements allowed the "grouping" of catalysts based on their phases. It was found that a group of best-performing catalysts exhibited the characteristic XRD pattern of nondecomposed Cu/Zn hydroxy carbonate residues in the calcined precursors, leading to the assumption that carbonate species in this state may enhance productivity. Further investigations of these hydroxy carbonate-containing catalysts provided more detailed insight into the dynamic aging process and its affect on catalytic performance. The greatest methanol synthesis activity was observed for catalysts aged for 20-60 min after an initial phase formation time. The optimum calcination temperature was found to be in 250-300 degrees C. Under these conditions, the resulting Cu/Zn/Al hydroxy carbonates remained stable. In addition, the syngas feed composition was varied under reaction conditions and correlated to catalytic activities. The greatest methanol productivity over Cu/ZnO/Al2O3 catalysts was observed for the following gas concentrations: 50-60% for H-2, 30-40% for CO, and 5-10% for CO2, at 4.5 M Pa and 245 degrees C. (C) 2008 Elsevier Inc. All rights reserved.