Nanocrystalline zeolites simulant

Nanociystalline zeolites (ciystal sizes of less than 100 nm) are porous aluminosilicate nanomaterials with increased surface areas relative to conventional micron-sized zeolites. Nanocrystalline zeolites are potentially useful for CWA decontamination applications because of their enhanced absorptive and catalytic properties. This chapter describes FTIR and solid state NMR studies of the thermal reactivity of two CWA simulants, 2-CEES (2 chloroethyl sulfide) and DMMP (dimethylmethylphosphonate) on nanocrystalline zeohtes, such as NaZSM-5 (sihcalite, purely siliceous form of ZSM-5) and NaY, with crystal sizes of approximately 25 nm. 

Nanocrystalline zeolites, NaY and NaZSM-5 and silicalite, synthesized by us, were evaluated for the decontamination of the CWA simulants, DMMP (15) and 2-CEES (16,17). The increased surface area and external surface reactivity of nanocrystalline zeolites provides potential advantages for CWA decontamination that are not found in conventional zeolite materials. The adsorption capacity and the thermal oxidation of these simulants on nanociystalline zeolites was investigated using FTIR spectroscopy and solid state NMR spectroscopy and the reactivity on different materials was compared. 

Adsorption and thermal oxidation of a mustard gas simulant on nanocrystalline zeolites. 

The 2-CEES molecule has a chemical stracture similar to mustard gas (Figure 1) without one chlorine atom but it is significantly less toxic. Zawadski and Parsons have shown that 2-CEES and mustard gas have very similar crystal stractures (18), therefore it is expected that 2-CEES will closely mimic the reactivity of mustard gas. FTIR spectroscopy and flow reactor measurements were used to investigate the adsorption, desorption and thermal oxidation of the mustard gas simulant, 2-CEES, on nanocrystalline zeolites. Thermal oxidation reactivity of 2-CEES on nanociystalUne NaZSM-5 (15 nm) is compared to that on nanociystalline silicalite-1 (23 nm) and NaY(22 nm) (16). 

The use of nanocrystalline NaY for the thermal reaction of DMMP was evaluated thus taking advantage of the inherent reactivity of Y zeolites and the enhanced properties of the nanocrystalline form of Y zeohtes. Nanocrystalline NaY with a ciystal size of 30 nm was evaluated for the adsorption and thermal reaction of the VX simulant, DMMP. FTIR and solid state P NMR spectroscopy were used to identify the gas phase and adsorbed species formed during the adsorption and reaction of DMMP in nanociystalline NaY. DMMP adsorbs molecularly on nanocrystalline NaY at room temperamre. 

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