(784c) A MULTI-Functional Membrane Reactor System for the Destruction of Chemical Warfare Agents

The possibility of use of chemical weapons has increased in recent years, both as a result of potential terrorist attacks as well as of ongoing international conflicts. The successful application of a flow-through catalytic membrane reactor (FTCMR) as an individual protection (IP) system for the destruction of dimethyl methylphosphonate (DMMP), which is known as a chemical precursor (and used to simulate its characteristics) for Sarin (GB), a toxic chemical warfare agent (CWA) was previously investigated and reported by this group¹.

In this current effort, a novel hybrid system is being developed that combines the FTCMR with a surface-flow membrane system (SFMS). The main advantage of this hybrid system, combining the SFMS (capable of the physical removal of a large fraction of the CWA from contaminated air streams) and the FTCMR (which completely oxidizes the remaining amount) is the continuous CWA destruction for extended time periods which are appropriate for both IP and collective protection (CP) applications.

As part of the study, the effect of the DMMP concentration in the feed on its complete combustion in the FTCMR was investigated. The studies indicate that the protection (complete conversion) time is a function of the DMMP concentration, with longer times observed for the lower concentrations, and shorter protection times associated with the higher concentrations. These observations validate the role for the FTCMR as a second stage in a hybrid system, following a bulk-toxin removal SFMS first stage. We also investigate the performance of the SFMS. Experiments indicate that a high removal rate can be achieved with a proper choice of (feed rate/membrane surface area) and the sweep ratio. The pressure ratio (P/P_s) limit for the DMMP removal is << 1, supporting the proposed SFMS concept for the effective removal of condensable toxins, i.e., steady-state adsorption/desorption via nanoporous carbon membrane films, as opposed to the traditional batch-wise adsorption with subsequent regeneration. The low (P/P_s) limits indicate that the selected carbon membrane provides a favorable isotherm relationship; with an optimal selection of (feed rate/membrane surface area) and sweep ratio, a high degree of removal can be achieved, so that only trace residual amounts may require further catalytic degradation in the FTCMR. The performance of the combined system is currently under investigation, and experimental results and the modeling of the system performance will be presented at the meeting.

References:

1.  Motamedhashemi, M.M.Y., Egolfopoulos, F.N., and Tsotsis, T.T., “Application of a Flow-Through Catalytic Membrane Reactor (FTCMR) for the Destruction of a Chemical Warfare Simulant,” J. Membrane Sci., 376, 119, 2011.