Power plant post-combustion carbon dioxide capture: An opportunity for membranes

Merkel, Timothy C.; Lin, Haiqing; Wei, Xiaotong; Baker, Richard W.

doi:10.1016/j.memsci.2009.10.041

Cited by 1,391 publications

(1,290 citation statements)

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“…29 In Figure 2, most of the data points in the CO 2 /N 2 Robeson plot are concentrated in a narrow band of permeation selectivity values and indicates a general positive correlation between CO 2 permeability and CO 2 /N 2 permeation selectivity. On the other hand, the data points for the CO 2 /CH 4 Robeson plots are spread across a wider range of selectivity values with less meaningful correlations being found between permeability and selectivity. Because both CO 2 and N 2 molecules are nonpolar with quadruple moments, linear, and have comparable kinetic diameters, the diffusion properties of the two gas molecules are similar.…”

Section: ■ Results and Discussionmentioning

confidence: 92%

“…Upon increasing the pressure, the gas uptake begins to saturate; thus, the adjusted permeability value based upon GCMC-IAST becomes smaller at pressures outside of the linear Henry regime. Because CO 2 /N 2 separation occurs at a lower pressure compared to CO 2 /CH 4 separation, the overall shift in the data points in the Robeson plots (indicating decrease in CO 2 permeability) in Figure 2c becomes more apparent for CO 2 / CH 4 .…”

Section: ■ Results and Discussionmentioning

confidence: 95%

“…Figure 1 also illustrates that the zeolite data points for CO 2 and N 2 are concentrated in the highly diffusive region (i.e., D S > 10 −9 m 2 /s), whereas CH 4 data points are scattered across a wider range of D S values. Because the kinetic diameter of CH 4 is larger than both CO 2 and N 2 , there exists more structures with relatively smaller diffusion coefficients for CH 4 . Also, due to the long-range electrostatic interactions present for the nonpolar CO 2 and N 2 molecules with quadruple moments, the likelihood of finding structures with a relatively high energy barrier remains small as the contributions of the nonlocal interactions spread across the entire channel.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…23 From the reduced set, we selected over 87 000 zeolite structures that have orthogonal unit cells to facilitate calculations. Similar work has been conducted by Haldoupis et al, but their approach was limited to computing diffusion coefficients of spherical molecules such as CH 4 . 24 Our method can compute diffusion coefficients of both spherical and nonspherical molecules within a single structure in just a few seconds, providing the speed-up required to screen thousands of different structures.…”

Section: ■ Introductionmentioning

confidence: 96%

“…At this point, it is important to emphasize that the ideal material for a separation depends on the actual process requirements. We use our screening approach to illustrate this point with a simple model that mimics the separation of CH 4 from CO 2 at conditions typical of a natural gas reservoir. The increase in efficiency of our method allows us to screen many materials and identify the optimal structures for an entire class of materials.…”

Section: ■ Introductionmentioning

confidence: 99%

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Large-Scale Screening of Zeolite Structures for CO₂ Membrane Separations

Kim

Abouelnasr²,

Lin³

et al. 2013

J. Am. Chem. Soc.

111

114

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ABSTRACT:We have conducted large-scale screening of zeolite materials for CO 2 /CH 4 and CO 2 /N 2 membrane separation applications using the free energy landscape of the guest molecules inside these porous materials. We show how advanced molecular simulations can be integrated with the design of a simple separation process to arrive at a metric to rank performance of over 87 000 different zeolite structures, including the known IZA zeolite structures. Our novel, efficient algorithm using graphics processing units can accurately characterize both the adsorption and diffusion properties of a given structure in just a few seconds and accordingly find a set of optimal structures for different desired purity of separated gases from a large database of porous materials in reasonable wall time. Our analysis reveals that the optimal structures for separations usually consist of channels with adsorption sites spread relatively uniformly across the entire channel such that they feature well-balanced CO 2 adsorption and diffusion properties. Our screening also shows that the top structures in the predicted zeolite database outperform the best known zeolite by a factor of 4−7. Finally, we have identified a completely different optimal set of zeolite structures that are suitable for an inverse process, in which the CO 2 is retained while CH 4 or N 2 is passed through a membrane. ■ INTRODUCTIONElevated CO 2 concentrations in the atmosphere are considered to be the primary cause of global warming. 1 Because of the ever-increasing amount of CO 2 emissions and our continuing reliance on fossil fuels, it remains imperative to search for various methods to mitigate the emission process. Among many suggested solutions, carbon capture and sequestration (CCS) is emerging as a viable technique: 2 CCS consists of utilizing materials to capture CO 2 emissions from point sources such as electric power plants, cement and steel plants, or natural gas field and injecting the adsorbed CO 2 molecules to geological reservoirs. Some of the main barriers for the large-scale implementation of CCS are the energy requirements and cost of the capture process.The currently available technology uses amines to selectively absorb CO 2 . These amines are very efficient in absorption of CO 2 , but the regeneration of the amine solution is relatively energy intensive. Alternative technologies, such as adsorption by adsorbents 3 or separations using membranes, 4 have the potential to significantly reduce the energy costs. Both technologies depend on the development of novel materials that have optimal properties for a given separation, with important classes of materials being nanoporous solids, such as zeolites and metal−organic frameworks. 3,5−8 By changing the pore topology and chemical composition, one could, in principle, synthesize millions of different materials, making it difficult to experimentally characterize and test all these materials. This gives a great opportunity for molecular simulations to identify the optimal materials in silico and gui...

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Section: ■ Results and Discussionmentioning

confidence: 92%

Section: ■ Results and Discussionmentioning

confidence: 95%