Nanocrystalline zeolites oxidation

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). 

Since aluminum was hypothesized to be responsible for the increased reactivity of nanocrystalline NaZSM-5 relative to silicalite, the 2-CEES reactivity on nanocrystalline NaY, which has a much lower Si/Al ratio than ZSM-5, was evaluated. The 2-CEES thermal oxidation activity of several different nanocrystalline zeolites was compared as shown in Figure 3. The amounts of selected products (CH4, CO2, CO and SO2) formed on nanocrystalline NaY(22 nm), NaZSM-5(15 nm) and silicalite-1 (23 nm) is... 

The thermal decomposition of 2-CEES on nanocrystalhne zeohtes was probed by FTIR spectroscopy. Comparison of the reactivy of nanocrystaUine NaZSM-5, silicalite and NaY indicated that NaZSM-5 was most effective for 2-CEES thermal oxidation and that external surface silanol sites were important to the zeolite reactivity. The adsorption and reaction of DMMP on nanocrystalline NaY was investigated using FTIR and sohd state NMR spectroscopy. External surface silanol and EFAL sites were implicated in the thermal oxidation of DMMP on nanocrystaUine NaY. Thus, the nanocrystalline zeolites can be envisioned as new bifunctional catalyst materials with active sites on the external surface playing an important role in the intrinsic reactivity of the material. Future studies will focus on optimizing the activity of nanocrystaUine zeolites for CWA decontamination apphcations by taUoring the surface properties. 

XRD patterns of the prepared samples V-Mo-Zeolite are similar to that of zeolites which suggests that the metal species (i.e. oxide, cations,...) are well dispersed through the zeolites structure and the absence of bulk phases in the XRD patterns implies that for these samples the molybdenum and vanadium oxides are present in either a nanocrystalline state or as a small crystallites which measured less than 4 nm in diameter. Furthermore, XRD and FTIR (1500-400 cm 1) showed no significant damage of the zeolite host structure after exchange and thermal treatment except for the sample V2MoMor. 

Numerous reports of heterogeneous catalysis active for alkylaromatic oxidations have appeared. These include an encapsulation of metal ions by zeolites or polymers [92-95]. Non-Co, Pd-based heterogeneous catalysts have been discovered by BP researchers [96-98]. Very recently, nanocrystalline ceria (Ce02) has been discovered to be a highly active heterogeneous catalyst for oxidation of pX in water to TA [99,100]. 

The weak Raman scattering from water allows the direct observation of the oxide species in the aqueous phase, the nanocrystalline nucleation seeds, and the solid phases present during zeolite synthesis, which are not as readily detectable with x-ray diffraction (XRD). The transformation of aluminosilicate gel to zeolite A was investigated with Raman spectroscopy by several researchers [150,179,180], but one outstanding investigation also... 

The conversion of rapeseed oil on Mo oxide and Ni-modified nanocrystalline ZSM-5 zeolites [167] resulted in the total deoxygenation of the vegetable oil. The major products were light olefins C -Cj and aromatic hydrocarbons. Ni/HZSM-5 catalysts demonstrate a higher selectivity to light olefins, whereas Mo/HZSM-5 catalysts are more selective to aromatics ... 

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