Catalysts, nanocomposite

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Table 7. As can be seen, both Dowex and Deloxan led to poor enantioselec-tivities, which further decreased after catalyst recovery. Better results, which are comparable with those obtained in homogeneous phase, were obtained with Nation (Table 7) [53], although it was necessary to carry out the reaction at 60 °C due to the low copper content in the soHd. This low copper level is a consequence of the low surface area of this polymer (< 0.02 m g ) and, for this reason, a nafion-silica nanocomposite was used as the support [53]. With this catalyst, the reaction took place at room temperature and with similar enantioselectivity (Table 7).

Mineralization of Indigo Carmine at Neutral pH Using a Nanocomposite as a Heterogeneous Photo-Fenton Catalyst... 

To determine the stability of the Fe-B nanocomposite as a heterogeneous photo Fenton catalyst, the Fe concentrations in solution after 120 minutes were measured by ICP. The results obtained indicate that the Fe concentration in solution after 20 minutes reaction is less than 1 mg/L, which is negligible. 

The resulting M°/CFP nanocomposites with M = Pd, Pt, Ag and Au exhibit in general satisfactory handiness in the laboratory atmosphere and chemical stability under operational conditions, re-usability, mechanical robustness (under proper conditions), plain filterability. Their reactivity is quite comparable to that of conventional M°/ S (S = carbon, inorganic support) catalysts. M°/CFP are to be employed in the liquid phase. 

Figure 5 shows the Z-contrast scanning transmission electron microscope (STEM) image of a Ru/Sn02 nanocomposite catalyst prepared by the assembly process [18]. A combined EDX analysis, using an electron beam of... 

The catalytic activity of the Ru/Sn02 nanocomposite was eight times higher than that of the most effective Ru metal catalyst reported previously [56]. An o-CAN selectivity over 99.9% at a substrate conversion of 100% was obtained over the Ru/Sn02 catalyst. This selectivity was comparable to the result reported for a boride-modified PVP-Ru colloidal catalyst [56,57], and was better than that of the PVP-Ru catalyst with the same Ru nanoparticles. The Sn02 nanoparticles remarkably promoted both the catalytic activity and selectivity of the Ru nanoclusters. An extremely low dechlorination rate of o-CAN in the absence of o-CNB was observed over this catalyst, which was 20-fold lower than that over the PVP-Ru colloidal catalyst, and was 73-fold lower when compared with a Ru/Si02 nanocomposite catalyst. 

It should be mentioned that the structure of carbon supports could have significant influence on the electro-catalytic properties of the nanocomposite catalysts. Recently, Pt/Ru nanoclusters prepared by the alkaline EG method were impregnated into a synthesized carbon support with highly ordered mesoporous. Although the Pt/ Ru nanoclusters can be well dispersed in the pores of this carbon substrate, the long and narrow channels in this material seem not suitable for the application in... 

Mizukoshi Y, Sato K, Konno TJ, Masahashi N, Tanabe S (2008) Magnetically retrievable palladium/maghemite nanocomposite catalysts prepared by sonochemical reduction method. Chem Lett 37 922-923... 

Ge, J.P., Zhang, Q., Zhang, T.R. and Yin, Y.D. (2008) Core-satellite nanocomposite catalysts protected by a porous silica shell controllable reactivity, high stability, and magnetic recyclability. Angewandte Chemie International Edition, 47 (46), 8924-8928. 

Figure 5.6 Sol-gel nanocomposites are composed of an entrapped catalyst and an organically modified Si02 based matrix. Reproduced with permission from [60].

Zhang, J.C., Li, Q. and Cao, W.L. (2005) Preparation of Ti02-MoOj nanocomposite photo-catalyst by supercritical fluid dry method. Journal of Environmental Sciences, 17 (China), 350-352. 

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