Nanocrystalline zeolites

Figure 4.10 SEM image of nanocrystalline zeolite taken with field emission SEM operated at 0.5 kV. Sample prep was by dispersing powder in isopropyl alcohol and placing a droplet of the suspended powder on a standard TEM grid. Sample is uncoated.

Castagnola and Dutta investigated the use of nanocrystalline zeolites with high surface area as hosts [18]. The strategy to increase photochemical efficiency was... 

Figure 24. Photolytic charge separation with nanocrystalline zeolite (a) correlation of percentage crystallinity of nanocrystals (shown in parentheses) with PVS" production (b) comparison of the rate of PVS " radical generation for nanocrystalline zeolite X and micronsized zeolite Y.

M. Camhlor, A. Corma, and S. Valencia, Characterization of Nanocrystalline Zeolite Beta. Microporous Mesoporous Mater, 1998, 25, 59-74. 

Chemical recycling of polyolefins (catalytic cracking) Nanocrystalline zeolites (ZSM-5 P-zeolite) Nanocrystalline zeolites have shown an excellent catalytic performance compared with conventional zeolites [73]... 

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. 

Table 1. External and Internal Surface Areas of Nanocrystalline Zeolites...

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. 

Tauflqurrahmi, N., A. R. Mohamed, and S. Bhatia. 2011. Production of Biofuel from Waste Cooking Palm Oil Using Nanocrystalline Zeolite as Catalyst Process Optimization Studies. Bioresource Technology 102 (22) 10686-10694. 

S.C. Larsen (2007) J. Phys. Chem. C, vol. Ill, p. 18464 Nanocrystalline zeolites and zeolite stmcmres Synthesis, characterization, and applications . 

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