https://scholars.lib.ntu.edu.tw/handle/123456789/611482
標題: | Atomistic Investigations of the Effects of Si/Al Ratio and Al Distribution on the Adsorption Selectivity of n-Alkanes in Br?nsted-Acid Zeolites | 作者: | Yang C.-T. Janda A. Bell A.T. Lin L.-C. LI-CHIANG LIN |
關鍵字: | Adsorption;Atoms;Catalytic cracking;Equilibrium constants;Hexane;Intelligent systems;Monte Carlo methods;Paraffins;Zeolites;Adsorption selectivity;Comprehensive comparisons;Computational approach;Configurational-bias monte carlo;Equilibrium adsorption constant;Implications for futures;Selectivity ratio;Spatial proximity;Aluminum | 公開日期: | 2018 | 卷: | 122 | 期: | 17 | 起(迄)頁: | 9397-9410 | 來源出版物: | Journal of Physical Chemistry C | 摘要: | The adsorption of n-alkanes onto Br?nsted-acid sites is a key step in the catalytic cracking of alkanes. Employing configurational-bias Monte Carlo simulations, we have investigated how the ratio of equilibrium adsorption constants for central C-C bonds relative to terminal bonds of n-alkanes (i.e., the adsorption selectivity ratio) in Br?nsted-acid zeolites is influenced by the Si/Al ratio and the Al distribution. A new computational approach was implemented, and the developed force field was validated by a comprehensive comparison between simulation results and experimental data for a number of Br?nsted-acid zeolites. While the adsorption selectivity seems to be relatively insensitive to the Si/Al ratio, our results reveal that the Al distribution plays a crucial role in determining the adsorption selectivity. Changes in the Al distribution result in a change of as much as 2-fold in the adsorption selectivity ratio for n-hexane. The selectivity generally shows larger variations with respect to Al distribution in zeolites with a larger Si/Al ratio. The two factors identified by this work that substantially influence the selectivity ratio are the siting of Al atoms among T-sites and their spatial proximity, and an atomic-level understanding of each of these effects was achieved. The siting of Al atoms at more or less selective T-sites significantly influences the overall selectivity ratio, and Al atoms in close proximity can synergistically enhance the adsorption of central C-C bonds, leading to a higher selectivity ratio relative to isolated Al atoms. We anticipate that these results will have important implications for future large-scale computational screenings and the development of advanced synthesis approaches to target certain Al distributions in zeolites. ? 2018 American Chemical Society. |
URI: | https://www.scopus.com/inward/record.uri?eid=2-s2.0-85046644088&doi=10.1021%2facs.jpcc.7b11190&partnerID=40&md5=dfae5a06459636a20e6fd62a1871b77e https://scholars.lib.ntu.edu.tw/handle/123456789/611482 |
DOI: | 10.1021/acs.jpcc.7b11190 |
顯示於: | 化學工程學系 |
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