UPPA-UFR Sciences & Techniques BP1155, Pau, France.
Phys Chem Chem Phys. 2011 Jun 21;13(23):11430-7. doi: 10.1039/c1cp20086k. Epub 2011 May 18.
Reliable experimental IR and theoretical approaches, both investigating CO adsorption on NaY faujasites, are supporting that CO capture occurs through the completion of the vacant coordination of Na(+) cations located in the accessible S(II) sites. As a result, carbonyl adsorbed species are formed by the capture of one, two or three CO molecules and are experimentally discernable by their respective IR positions that are down-shifted by an average 11-12 cm(-1) value for each captured CO molecule. DFT analysis is proposed for comparison and reproduces well the observed experimental shift of the ν(CO) positions of the different polycarbonyls of interest. In addition, the effect of Si or Al composition surrounding the SII Na(+) cation is investigated and results suggest that polycarbonyls that are formed might be in connection with the acidic strength of the cationic sites. This combined study completes and improves the understanding of the complex issue of CO adsorption at 80 K widely used as a model to explain how physical adsorption takes place in NaY faujasites working as an efficient industrial adsorbent in gas separation or gas purification processes.
可靠的实验红外光谱和理论方法都表明，CO 在 NaY 型沸石上的吸附是通过填充位于可及 S(II)位的 Na(+)阳离子的空位配位来完成的。因此，通过捕获一个、两个或三个 CO 分子形成了羰基吸附物种，并且可以通过它们各自的红外位置来实验区分，这些位置因每个捕获的 CO 分子而平均向低波数移动 11-12cm(-1)。提出了 DFT 分析进行比较，并很好地再现了实验观察到的不同感兴趣的多羰基 ν(CO)位置的位移。此外，还研究了围绕 SII Na(+)阳离子的 Si 或 Al 组成的影响，结果表明形成的多羰基可能与阳离子位的酸性强度有关。这项综合研究完善并提高了对 CO 在 80K 下吸附的复杂问题的理解，这一模型广泛用于解释 NaY 型沸石作为气体分离或气体净化过程中高效工业吸附剂的物理吸附是如何发生的。
