An infrared and inelastic neutron scattering spectroscopic investigation on the interaction of η-alumina and methanol
An infrared and inelastic neutron scattering spectroscopic investigation on the interaction of η-alumina and methanol
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DOI：
10.1039/b505974g
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发表时间：
2005-01-01
影响因子：
3.3
通讯作者：
Lennon, D
中科院分区：
文献类型：
--
作者：
McInroy, AR;Lundie, DT;Lennon, D
用红外光谱（漫反射和透射）和非弹性中子散射（INS）光谱研究了工业上重要的甲醇与η-氧化铝催化剂的相互作用。红外光谱和INS光谱一起表明，化学吸附的甲氧基是唯一的表面物种存在。通过对η-氧化铝（110）上的甲氧基进行定期DFT计算来确认分配。吸附的甲氧基形成二甲醚的热转化也遵循INS，DFT计算协助分配。在漫反射光谱中观察到约2600 cm（-1）的强特征。这条带在氧化铝/甲醇吸附系统的大量文献中描述得很差，其观察结果提出了在该特定催化剂表面上存在新的表面物种的可能性。INS测量确定，2600 cm（-1）特征可归属于甲基岩石与甲基变形模式的组合带。这一分配得到加强的中子散射强度在一个特定的能量作为动量转移的函数，这证实了这种特殊的吸附甲氧基功能产生的二级跃迁的分析。在模型化合物Al（OCH 3）（3）中观察到类似的行为。漫反射光谱中2600 cm（-1）峰的异常红外强度是C-H伸缩和组合模的不同吸收系数的结果。催化剂研究的影响进行了讨论。
The industrially important interaction of methanol with an eta-alumina catalyst has been investigated by a combination of infrared spectroscopy (diffuse reflectance and transmission) and inelastic neutron scattering ( INS) spectroscopy. The infrared and INS spectra together show that chemisorbed methoxy is the only surface species present. Confirmation of the assignments was provided by a periodic DFT calculation of methoxy on eta-alumina ( 110). The thermal conversion of adsorbed methoxy groups to form dimethylether was also followed by INS, with DFT calculations assisting assignments. An intense feature about 2600 cm(-1) was observed in the diffuse reflectance spectrum. This band is poorly described in the extensive literature on the alumina/methanol adsorption system and its observation raised the possibility of a new surface species existing on this particular catalyst surface. INS measurements established that the 2600 cm(-1) feature could be assigned to a combination band of the methyl rock with the methyl deformation modes. This assignment was reinforced by an analysis of the neutron scattering intensity at a particular energy as a function of momentum transfer, which confirmed this particular adsorbed methoxy feature to arise from a second order transition. Similar behaviour was observed in the model compound Al(OCH3)(3). The anomalous infrared intensity of the 2600 cm(-1) peak in the diffuse reflectance spectrum is a consequence of the different absorption coefficients of the C-H stretch and the combination mode. The implications for catalyst studies are discussed.