The 7th Industrial Fluid Properties Simulation Challenge

Objective

The 7th Industrial Fluid Properties Simulation Challenge (IFPSC) will focus on predicting adsorption isotherms of n-perfluorohexane (n-C₆F₁₄) in BCR-704 Faujasite type zeolite.

Timeline

March, 2012 - Challenge problem announced

Friday, September 21, 2012 - Challenge final entries due

Background

Zeolite adsorbents are used in a variety of applications due to their high surface area and ability to adsorb or desorb sorbates depending upon the applied conditions. Applications include the removal of volatile organic compounds and toxic gases from air and storage of corrosive chemicals during shipping.

With increasing numbers of applications, the ability to predict the performance of zeolites for a wide range of adsorbents would be very valuable in pre-optimizing systems and reducing product development time. Molecular simulation techniques, in principle, could be ideal for predicting adsorption in zeolites with various chemistry.

Although adsorption in porous media has been an area of extensive activity in the field of molecular simulation (e.g. in zeolites [1,2], metal-organic frameworks [3,4], nanotubes [5], and other porous carbons [6,7]), it has not yet been the focus of the IFPSC. Organizing a simulation challenge to assess the capability of molecular simulation methods and force fields to accurately predict adsorption in porous media for practically relevant and moderately complex chemical systems is of interest in order to benchmark the state-of-the-art capability in this important application area.

Studies of adsorption equilibria by molecular simulation employing both Monte Carlo [8-10] and molecular dynamics [11,12] techniques have become relatively common. However, applying these methods to study adsorption equilibria using force fields (potential energy models) developed for bulk phase conditions remains an open issue. General, transferable force fields that are reasonably accurate over a wide range of state conditions in the bulk are not necessarily transferable to the adsorbed phase. Moreover, active sites on the surface of the adsorbent can dramatically affect the adsorption behavior.

The focus of the current challenge is to assess the potential of molecular simulation methods to predict organic sorbate adsorption isotherms. Specifically, the challenge will focus on predicting the adsorption isotherms of n-perfluorohexane in BCR-704 Faujasite type zeolite.

The certified reference material BCR-704 Faujasite type zeolite will be used in the experimental benchmark studies. The BCR-704 zeolite material is supplied by the Institute of Reference Materials and Measurement (IRMM) and can be obtained from Sigma-Aldrich.

Argon and Nitrogen adsorption isotherm studies have been carried out to characterize the BCR-704 zeolite. The adsorption studies have been carried out by the industry-leading company Quantachrome Corporation. The results of the argon and nitrogen studies will be provided to Challenge entrants to aid in validating simulation models. The adsorption and isotherm data will be provided via a posting on the IFPSC web-site no-later then the end of March 2012.

Elemental analysis has also been carried out on BCR-704 Faujasite type zeolite and is reported in IRMM report EUR 21065 Certification of the Specific Micropore Volume and the Median Micropore Width of Two Microporous Reference Materials According to Draft-DIN 66135-4, BCR-704, BCR-705 (see section 3.2.2). Argon adsorption studies are also reported. Details of an FAU type framework can be found in database of zeolite stuctures from the Structure Commission of the International Zeolite Association (link). Elemental analysis studies are also in progress at 3M Company and will be reported on the IFPSC web-site when completed.

The experimental benchmark adsorption studies for n-perfluorohexane (n-C₆F₁₄) in BCR-704 zeolite will also be carried out by Quantachrome Corporation. n-perfluorohexane (n-C₆F₁₄) is a high performance material produced by 3M Company.

Challenge

For n-perfluorohexane (n-C₆F₁₄), compute adsorption isotherms in BCR-704 zeolite at a temperature of 293K and at relative pressures of 0.01, 0.05, 0.1, 0.2, 0.4, 0.6, and 0.8. The relative pressure is defined as that relative to the bulk saturation pressure predicted by the model for the given temperature (293K in this case).

Rules of the Game

Any theory/modeling/simulation method can be used. However, only submissions that rely primarily on molecular modeling and simulation methods will be scored and judged for the Challenge competition. Submissions employing correlative or alternative methods are also encouraged, however, but only to demonstrate the capabilities of these approaches. Presentation and publication of papers employing alternative approaches will be considered for acceptance in the IFPSC Challenge Special Session at the Fall 2012 National AIChE meeting and in the subsequent journal special proceedings.
Any force field (or other model parameterization) previously published in the open literature prior to the announcement of this challenge is acceptable.
Force fields (or other models) may be parameterized using any other published physical property data but not via new or previously unpublished experimental studies including n-perfluorohexane adsorption isotherms in BCR-704 zeolite.
The experimental bulk saturation pressure for n-C₆F₁₄ at 293K used to calculate relative pressures was 0.24 bar [13]. This data can be used to aid in developing and validating the theory/modeling/simulation method. The relative pressures for reporting challenge results, however, must be based on the bulk saturation pressure predicted by the model.
The bulk saturation pressure predicted by the model must be reported.
Estimates of the uncertainty must be included.

Challenge Scoring

Challenge champions along with 1st, 2nd, and 3rd runners-up will be awarded. Entries will be scored by comparing the predicted adsorption isotherm data to experimentally measured data. For adsorption isotherms, the amount of perfluorohexane experimentally adsorbed at the defined set of pressures will be compared to the amounts predicted at the same pressures.

Full credit will be awarded for a prediction that falls within the experimental uncertainty. A weighted scale of partial credit will be awarded for predictions with an absolute deviation above the minimum threshold and a maximum of 25%. No points will be awarded for prediction above the maximum deviation.

Other Entry Guidelines

Entries are to be submitted to contest@ifpsc.org on or before the deadline
A submission for this challenge problem is to be in the form of a manuscript suitable for submission to a refereed, archival, scientific journal. The manuscript must contain sufficient detail about the simulation or other method and about the force field (if simulation) so that an experienced simulator could reproduce the results without requiring access to proprietary information. In particular, all potential parameters and molecule geometry parameters must be explicitly specified in the manuscript. The results are to be reported in SI units.
An analysis of the uncertainty in the calculated results is required and must be included in the manuscript.
Entries are expected to present results that are statistically significant and to present sufficient supporting evidence to establish this quality. Also, the scientific reasoning behind any new (unpublished) force field parameterizations must be explicitly and precisely expressed in the entry. If there is a consensus among the judges that an entry is of poor quality (uses a method commonly accepted to be fundamentally flawed, presents results that are not statistically significant, fails to provide sufficient supporting data and details, violates the various rules and guidelines established for the competition, or for any other reason that the work would unlikely be accepted in any peer-reviewed scientific journal in the field), that entry will be rejected and will not be considered in the judging.
Entries that represent collaborations between multiple research groups are welcomed.

Also, see the list of Frequently Asked Questions: link

References

[1] A. H. Fuchs and A. K. Cheetham, J. Phys. Chem. B, 105, 7375 (2001).

[2] B. Smit and T. L. M. Maesen, Chem. Rev., 108, 4125 (2008).

[3] S. Keskin, J. Liu, R. B. Rankin, J. K. Johnson, and D. S. Sholl, Ind. Eng. Chem. Res., 48, 2355 (2008).

[4] T. Düren, Y.-S. Bae, and R. Q. Snurr, Chem. Soc. Rev., 38, 1237 (2009).

[5] W. Shi and J. K. Johnson, Phys. Rev. Lett., 91, 015504 (2003).

[6] G. M. Davies and N. A. Seaton, AIChE J., 46, 1753 (2000).

[7] M. B. Sweatman and N. Quirke, Mol. Simul., 31, 667 (2005).

[8] G.E. Norman and V.S. Filinov, High Temp. (USSR), 7, 216 (1969).

[9] S.C. McGrother and K.E. Gubbins, Mol. Phys., 97, 955 (1999).

[10] D. Frenkel and B. Smit, Understanding Molecular Simulation, Academic Press, San Diego (2002).