A flow-through membrane reactor for destruction of a chemical warfare simulant

The possibility of the use of chemical weapons has been increased in recent years both as a result of potential terrorist attacks and of ongoing international conflicts. The focus of our research is the development of a novel, hybrid catalytic membrane reactor system, which consists of a flow-through catalytic membrane reactor (FTCMR) integrated with a surface-flow based membrane separator (SFMS). The combined system has been shown to achieve complete oxidation of chemical warfare agents (CWA) at trace levels, and is appropriate for use in integrated individual protection (IP) systems as well as collective protection (CP) systems for civil and military applications.;As a part of this research, a catalytic tubular alumina membrane is prepared via impregnation with chloroplatinic acid solutions, and is utilized in a FTCMR for the catalytic oxidation of dimethyl methylphosphonate (DMMP) in air. DMMP is known as a chemical precursor for the more toxic gas Sarin (GB), and has been widely used to simulate its characteristics.;In this Thesis experiments are reported for different DMMP feed concentrations (150-1000 ppm) and reactor temperatures (373-573K), which demonstrate the potential advantage of the FTCMR in the complete catalytic oxidation of this important CWA simulant. Complete destruction of low and high concentrations of DMMP was achieved at lower temperatures compared to the values obtained in this study for a wall-coated plug-flow (monolith) reactor containing the same amount of catalytic metal.;A mathematical model has also been developed in order to provide a better understanding of the fundamental transport phenomena underpinning the FTCMR operation. It makes use of the Dusty Gas Model (DGM), which incorporates in an appropriate fashion continuum and Knudsen diffusion, and viscous flow as the mechanisms for gas transport through the porous membrane being utilized in the FTCMR. In the first application, the model is used for identifying the advantages of the FTCMR concept compared to the wall-coated catalytic monolith, and also for investigating some of the limitations, which may exist in applying this concept for the complete oxidation of chemical warfare simulants. The results of the model support the superiority of the FTCMR concept over the more conventional (plug-flow) monolith reactor.;During the FTCMR experiments it was found that one of the challenges associated with the catalytic destruction of DMMP is catalytic membrane deactivation via active site coverage and pore-blockage. Therefore, in the second application, the model is extended to incorporate the effect of catalyst deactivation and pore-blockage, on the performance of the FTCMR. The model is successfully applied to determine from experimental data important parameters such as the reaction rate constants and the poisoning and pore plugging factors. The simulation results also confirm the experimental observations in that the protection time provided by the FTCMR is a function of the DMMP concentration in the feed, pointing out that an appropriate role for the FTCMR to play is as a second stage in a hybrid system, following a bulk-toxin removal unit in the first stage. The main advantage of the proposed hybrid system, combining a surface-flow membrane (SFM) separation unit (which is capable of continuously physically removing a large portion of the CWA from contaminated air streams) with the FTCMR, is that it completely destructs the CWA that remains with a lower rate of pore blockage, thus resulting in the continuous CWA destruction for extended time periods, which are appropriate for both IP and CP applications.