Steam reforming of methanol using Cu-ZnO catalysts supported on nanoparticle alumina
Steam reforming of methanol using Cu-ZnO catalysts supported on nanoparticle alumina
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DOI：
10.1016/j.apcatb.2008.05.023
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发表时间：
2008-12-01
影响因子：
22.1
通讯作者：
Hagelin-Weaver, Helena E.
中科院分区：
文献类型：
--
作者：
Jones, Samuel D.;Neal, Luke M.;Hagelin-Weaver, Helena E.
以纳米氧化铝为载体，负载铜、锌前驱体制备了甲醇水蒸气重整催化剂。将结果与市售的铜、氧化锌和氧化铝催化剂的结果进行比较。程序升温还原，BET比表面积测量，和N2 O分解用于表征催化剂表面。用XRD研究了催化剂的体相结构，用XPS测定了催化剂表面物种的化学状态。纳米颗粒负载的催化剂实现了与商业参比催化剂相似的转化率，但温度略高。然而，纳米颗粒负载的催化剂在给定的温度和时空下也表现出比参比催化剂显著更低的CO选择性。此外，纳米颗粒负载的催化剂的转换频率高于商业催化剂，这意味着表面铜的活性更高。已确定高氧化铝浓度最终降低催化活性以及促进不期望的CH 2 O形成。较低的催化活性可能是由于强烈的Cu-Al 2 O3相互作用，这导致Cu物种不容易被还原。此外，氧化铝载体的酸性似乎促进了CH 2 O的形成，其在低Cu浓度下不会重整为CO2和H-2。本研究中存在的CO水平高于可以通过逆水煤气变换（WGS）反应解释的水平。虽然焦化不是显著的失活途径，但ZnO迁移到催化剂表面（或Cu迁移到催化剂本体）确实解释了催化活性的永久损失。Cu 2 O存在于废纳米颗粒催化剂上，并且可能Cu+/Cu-0比率对于催化活性和CO选择性都是重要的。(C)2008 Elsevier B. V.保留所有权利。
Methanol steam reforming was studied over several catalysts made by deposition of copper and zinc precursors onto nanoparticle alumina. The results were compared to those of a commercially available copper, zinc oxide and alumina catalyst. Temperature programmed reduction, BET surface area measurements, and N2O decomposition were used to characterize the catalyst surfaces. XRD was used to study the bulk structure of the catalysts, and XPS was used to determine the chemical states of the surface species. The nanoparticle-supported catalysts achieved similar conversions as the commercial reference catalyst but at slightly higher temperatures. However, the nanoparticle-supported catalysts also exhibited a significantly lower CO selectivity at a given temperature and space time than the reference catalyst. Furthermore, the turnover frequencies of the nanoparticle-supported catalysts were higher than that of the commercial catalyst, which means that the activity of the surface copper is higher. It was determined that high alumina concentrations ultimately decrease catalytic activity as well as promote undesirable CH2O formation. The lower catalytic activity may be due to strong Cu-Al2O3 interactions, which result in Cu species which are not easily reduced. Furthermore, the acidity of the alumina support appears to promote CH2O formation, which at low Cu concentrations is not reformed to CO2 and H-2. The CO levels present in this study are above what can be explained by the reverse water-gas-shift (WGS) reaction. While coking is not a significant deactivation pathway, migration of ZnO to the surface of the catalyst (or of Cu to the bulk of the catalyst) does explain the permanent loss of catalytic activity. CU2O is present on the spent nanoparticle catalysts and it is likely that the Cu+/Cu-0 ratio is of importance both for the catalytic activity and the CO selectivity. (C) 2008 Elsevier B.V. All rights reserved.