Adsorption and Diffusion of Alkanes in Na-MOR: Modeling the Effect of the Aluminum Distribution

Ban, Shuai; Vlugt, Thijs J. H.

doi:10.1021/ct900315r

Cited by 7 publications

(3 citation statements)

References 44 publications

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“…This might prevent the synthesis of zeolite. As shown in the literature, − the distribution of Al atoms in certain types of zeolites can affect the adsorption properties such as adsorption loading, diffusion, and so forth. However, at very high Al contents (i.e., Si/Al ratio < 3), the effect of the distribution of Al atoms is expected to be small.…”

Section: Simulation Methodology and Computational Detailsmentioning

confidence: 99%

In Silico Screening of Zeolites for High-Pressure Hydrogen Drying

Erdős

Geerdink

Martín-Calvo

et al. 2021

ACS Appl. Mater. Interfaces

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According to the ISO 14687-2:2019 standard, the water content of H2 fuel for transportation and stationary applications should not exceed 5 ppm (molar). To achieve this water content, zeolites can be used as a selective adsorbent for water. In this work, a computational screening study is carried out for the first time to identify potential zeolite frameworks for the drying of high-pressure H2 gas using Monte Carlo (MC) simulations. We show that the Si/Al ratio and adsorption selectivity have a negative correlation. 218 zeolites available in the database of the International Zeolite Association are considered in the screening. We computed the adsorption selectivity of each zeolite for water from the high-pressure H2 gas having water content relevant to vehicular applications and near saturation. It is shown that due to the formation of water clusters, the water content in the H2 gas has a significant effect on the selectivity of zeolites with a helium void fraction larger than 0.1. Under each operating condition, five most promising zeolites are identified based on the adsorption selectivity, the pore limiting diameter, and the volume of H2 gas that can be dried by 1 dm3 of zeolite. It is shown that at 12.3 ppm (molar) water content, structures with helium void fractions smaller than 0.07 are preferred. The structures identified for 478 ppm (molar) water content have helium void fractions larger than 0.26. The proposed zeolites can be used to dry 400–8000 times their own volume of H2 gas depending on the operating conditions. Our findings strongly indicate that zeolites are potential candidates for the drying of high-pressure H2 gas.

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Section: Simulation Methodology and Computational Detailsmentioning

confidence: 99%

In Silico Screening of Zeolites for High-Pressure Hydrogen Drying

Erdős

Geerdink

Martín-Calvo

et al. 2021

ACS Appl. Mater. Interfaces

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“…但受计算成本限制其应用仍局限在小沸石体系和短时长的模拟, 并且至今其中原子的运动轨迹模拟仍与经典的分子动力学一样遵循牛顿第二定律 [19] , 通过解原子核坐标的微分方程来实现位移. 因此传统的分子动力学方法(MD)和蒙特卡洛方法(MC) [20] , 仍以其较低的计算成本在沸石分子筛这样的复杂大体系中广泛应用, 特别集中在吸附和扩散行为的研究 [21] 中 . 分子模拟(MD/MC) 方法在晶体生长机制的研究中 [22] 常被应用于晶胞结构较为简单的金属晶体 [22a] 、离子晶体 [22b,22c] 体系势能计算方法参照林德昌的工作 [24] , 采用 pcff 力场参数 [25] , atom-based 方法计算库仑力和范德华力, 截断半径 12.5 Å, 长程 vdW 矫正 [26] 我们曾报道过三甲苯的超声洗脱择优取向 MFI 沸石晶体样品的实验结果 [7b] , 推测有吸附质处于沸石晶体接近孔道开口处的孔道浅层位置, 它所起的作用可能与 Casci [16] 所报道的六甲基己双胺一样、遏制了晶面的生长.…”

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Growth Mechanism Study onb-axis Oriented MFI Zeolite with MD Simulation

Hui¹,

Guo²,

Wang³

et al. 2012

Acta Chim. Sinica

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Co-templating role in the growth of b-axis oriented siliceous MFI type zeolite crystals was studied by molecular dynamic (MD) simulation. A siliceous supercell consisting of 2×2×2 unit cell is adopted as the inner part of the simulated structure for the zeolite. The crystal structures, adopted as simulated growing part of the zeolite, are four cleavage surface models along a or b axis individually, which cleaved from a supercell consisting of 1×1×2 unit cell and the Si-O hanging bonds are saturated by H atoms. The dynamic behaviors of two templates (n-propylamine and hexamethylene tetramine) in the cages of channel intersections and the opening channel windows were investigated with NVT MD simulations in 450 K for 5×10 5 fs each run, using pcff forcefields. The simulations were performed by Discover module from Accelrys Material Studio. The interaction energies between the templates and the zeolite, and the average values of coordinates imaging the trajectories of the templates in times of whole MD simulation, are used as two indicators for investigating the dynamic adsorption sites and the size match with the channel wall for the templates. The results indicate: (1) hexamethylene tetramine (HMTA) molecule is hold at the opening window of the channel along a axis (site I) and extruded out of the opening window of channel along b axis (site III) to nearby crystal-growing site (site IV); (2) mean-squared-displacement (MSD) analysis reveals that strong interaction exists between n-propylamine molecule and the zeolite because of the fact that N-atom is sticking to the adsorption site while other atoms of the molecule are rotating and moving with freedom. On the other hand, all atoms of HMTA molecule are almost frozen in the constrained space of the channel cage. As an evidently deduction, n-propylamine molecules play a major directing role in the formation and the growth of the zeolite crystals, while HMTA molecules promote the growth of the crystal surface along a axis and impede the growth of the crystal surface along b axis.

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“…However, many applications involve zeolites containing also framework-aluminium and their accompanying charge compensating cations. It is known that the diffusivity in such systems can be very different compared to the all-silica form [44,45], mostly related to the existence of strong and weak adsorption sites [46]. Although the RSM has been applied successfully to all-silica systems, it is an intriguing question up to which extent the RSM can be applied in aluminium containing systems.…”

Section: Application Rsm To Aluminium Containing Zeolitic Systemsmentioning

confidence: 99%