In situ FTIR studies of propene adsorption over Ag- and Cu-exchanged Y zeolites
In situ FTIR studies of propene adsorption over Ag- and Cu-exchanged Y zeolites
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DOI：
10.1016/j.micromeso.2011.04.040
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发表时间：
2012
影响因子：
5.2
通讯作者：
F. Benaliouche;Y. Boucheffa;F. Thibault-Starzyk
中科院分区：
文献类型：
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作者：
F. Benaliouche;Y. Boucheffa;F. Thibault-Starzyk
采用固态离子交换(SSIE)技术制备了银、铜交换型HY沸石。得到了从低交换量到高交换量的不同金属载量的样品。通过元素分析、粉末X-射线衍射仪和氮气吸附测孔仪对交换沸石的组成和结构进行了研究。用吡啶吸附的傅里叶变换红外光谱(FTIR)对其酸性进行了研究。用原位傅里叶变换红外光谱研究了室温下丙烯在银和铜分子筛上的吸附。X射线衍射分析表明，即使在高交换度的情况下，离子交换后的沸石结构仍保持较好的稳定性。孔隙率测量表明，银、铜交换度的增加导致了孔体积和比表面积的减小，这在银交换沸石中表现得更为明显。对两种交换金属的酸度评价表明，两种金属的Brnsted酸度显著降低，Lewis酸度略有增加，在交换度较高时更为明显。在室温下，HY分子筛上具有较高数量的Brnsted酸中心有利于丙烯的瞬时齐聚反应。丙烯分子与Cu2+的相互作用比与Ag+的作用更强。FTIR谱中CC伸展带的形状至少包括两个重叠的带，这表明丙烯CC键可能与多种丙烯键的Ag+、Cu2+和Cu+中心相互作用。
Ag- and Cu-exchanged forms of HY zeolite are prepared by the solid-state ion exchange (SSIE) technique. Samples with different metal loadings ranging from low to high exchange are obtained. Both compositional and structural investigations of the exchanged zeolites are performed by elemental analysis, powder X-ray diffraction (XRD), and nitrogen adsorption porosimetry. The acidity investigation is carried out by using the Fourier transform infrared spectroscopy (FTIR) of pyridine adsorption. Propene adsorption over the Ag- and Cu-exchanged zeolites is studied at room temperature by using in situ FTIR spectroscopy. XRD analysis shows good conservation of the zeolitic structure after ionic exchange even at high exchange degree. Porosity measurements indicate that the increase of Ag and Cu exchange degrees leads to a decrease of the porous volumes and the specific surface areas, which is more pronounced for Ag-exchanged zeolites. The acidity evaluation for both exchanged metals shows an important decrease of Brønsted acidity and a slight increase of Lewis acidity, which are more noticeable at high degree of exchange. Instantaneous oligomerization of propene on HY zeolite at room temperature is favored by the relatively high amount of Brønsted acid sites. The propene molecules interact more strongly with Cu2+than with Ag+. The shape of the CC stretching band of the FTIR spectra involves at least two overlapping bands indicating that the propene CC bond may interact with several kinds of Ag+, Cu2+and Cu+sites of various propene bonding.