Elucidating the role of Cu species in the oxidative carbonylation of methanol to dimethyl carbonate on CuY: An in situ spectroscopic and catalytic study
Elucidating the role of Cu species in the oxidative carbonylation of methanol to dimethyl carbonate on CuY: An in situ spectroscopic and catalytic study
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DOI：
10.1016/j.apcata.2010.05.009
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发表时间：
2010-07-15
影响因子：
5.5
通讯作者：
Bentrup, Ursula
中科院分区：
文献类型：
--
作者：
Engeldinger, Jana;Domke, Christine;Bentrup, Ursula
通过用硝酸铜溶液对商用 NH4-Y 沸石进行初湿浸渍并在空气中于 400 摄氏度下煅烧而获得不同 Cu 含量的 CuY 催化剂，通过原位 FTIR 研究来表征 Cu 物种并阐明其在甲醇氧化羰基化中的具体作用。 CO 的吸附用于检查 Cu(I) 物质的状态，而酸度则通过吡啶吸附来表征。根据 Cu 含量，观察到 2160 和 2146 cm(-1) 处的特征 Cu(I)-CO 谱带的不同强度比，这提供了有关超笼附近不同位置的 Cu(I) 阳离子分布的信息。不同强度的路易斯位点是通过引入位于超级笼中的 Cu(I)/Cu(II) 阳离子产生的 Cu 来创建的。MeOH 通过形成甲氧基物质以离解方式吸附在优选的 Cu(I) 路易斯位点上，无需额外供应氧气。甲氧基物质和 CO 吸附在相同的 Cu 位点上。在有氧和无氧的情况下，MeOH 和 CO 同时吸附时会形成氧化产物（碳酸单甲酯、碳酸二甲酯、CO2），这表明 CuO 聚集体的晶格氧参与了氧化过程，并指向 Mars-van-Krevelen 机制。另外还发现，在较高的铜负载量下，吸附的甲酸盐物质更加明显。 CO 与吸附的甲氧基物质反应，主要形成碳酸单甲酯，而同时存在的类甲酸盐物质则促进碳酸二甲酯的形成。这暗示了吸附的碳酸酯类物质对于碳酸二甲酯形成的特定作用。人们发现高 Cu 负载量是有益的，因为超级笼中额外形成的 CuO、团聚体有利于甲醇的氧化和氧代羰基化反应，并增强碳酸二甲酯的形成，催化测试也证实了这一点。 (c) 2010 Elsevier B.V. 保留所有权利。
CuY catalysts with varied Cu content obtained by incipient-wetness-impregnation of commercial NH4-Y zeolite with copper nitrate solution and calcination at 400 degrees C in air were examined by in situ FTIR investigations to characterize the Cu species and elucidate their specific role in the oxidative carbonylation of methanol. The adsorption of CO was applied to check the state of Cu(I) species whereas the acidity was characterized by pyridine adsorption. Depending on the Cu content different intensity ratios of the characteristic Cu(I)-CO bands at 2160 and 2146 cm(-1) were observed which give information about the distribution of Cu(I) cations at different positions near the supercage. Lewis sites of different strengths are created by introduction of Cu resulting from Cu(I)/Cu(II) cations positioned in the super cages.MeOH adsorbs dissociatively on preferable Cu(I) Lewis sites by formation of methoxy species without additional supply of oxygen. Methoxy species and CO adsorb at the same Cu sites. Oxygenated products (monomethyl carbonate, dimethyl carbonate, CO2) are formed during simultaneous adsorption of MeOH and CO with and without oxygen which indicates a participation of lattice oxygen of CuO aggregates in the oxidation process and points to a Mars-van-Krevelen mechanism. Adsorbed formate species more pronounced at higher Cu loadings were additionally found. CO reacts with adsorbed methoxy species by formation of mainly monomethyl carbonate whereas the simultaneous presence of formate-like species promotes the formation of dimethyl carbonate. This implicates a specific role of adsorbed carbonate-like species for dimethyl carbonate formation. High Cu loadings were found to be beneficial because the additional formation of CuO, agglomerates in the super cages favors oxidation and oxocarbonylation reactions of methanol and enhances the formation of dimethyl carbonate which was also confirmed by the catalytic tests. (c) 2010 Elsevier B.V. All rights reserved.