Cyclohexane is the only product detected in the hydrogenation of benzene [28], suggesting that the partially hydrogenated intermediates were only transient. The hydrogenation of styrene, employing the current nanocomposites Pt/GE, was on the side chain instead. The hydrogenation after 1 h could convert >99% of styrene to ethylbenzene. Benzene hydrogenation is an ideal reaction for such studies as it has been investigated extensively on single-crystalline Pt

surfaces. Because this reaction has been shown to produce only cyclohexane on Pt(100) and both cyclohexene and cyclohexane on Pt(111), thus, PARP inhibitor suitable for probing nanoparticle shape-dependent reaction selectivity in catalysis [27]. The Pd, Pt, and Ru species were investigated selleck products on the γ-Al2O3 supported catalysts Selleck GSI-IX for hydrogenation of styrene, and the group VIII metals were the best choices. The hydrogenation of styrene activity of metal catalysts on the supported alumina material followed the order Pd > Pt > Ru [29]. Also, the benzene hydrogenation catalytic activity of the CNT-supported metallic nanoparticles increases in the order Pd/CNT < Au/CNT < Rh/CNT < Pt/CNT < Pd-Rh/CNT.

For the CNT-supported single metallic nanoparticle catalysts, this order follows generally the same trend as the typical catalytic activities of transition metals known for hydrogenation of benzene, i.e., Co < Pd < Ni < Pt < Ru < Rh [11]. The reason for this order is not known in the literature, but the solvent has been shown to play a role on the hydrogenation of monocyclic arenes in the conventional heterogeneous catalytic system using transition metals as catalysts. The difference in enthalpy of vaporization among the transition metals has also been related to their difference in catalytic activity [11]. The hydrogenation results of Pt/GE nanocomposites were shown in Table 3. Table 3 The results for hydrogenation of styrene from Pt/ G and commercial catalysts   Metal (wt%) Size (nm) Reaction condition Product (%)         Styrene Ethylbezene Urease Ethycyclohexane Pt/GE 12 14.6 100°C,140 psi,1

h 3.21 96.79 – Pt/C 10 2 ~ 5 Same – >99 – Pd/C 10 3 ~ 5 Same – >99 –   Metal (wt%) Size (nm) Reaction condition   Product (%)   Styrene Ethylbezene Ethycyclohexane Pt/GE 12 14.6 100°C,1520 psi,1 h – 99.66 0.34 Pt/C 10 2 ~ 5 Same 59.69 40.31 – Pd/C 10 3 ~ 5 Same – 99.87 0.13 Conclusions The low H2 pressure hydrogenation reaction condition exhibited a catalytic activity in the order Pd/C to Pt/C > Pt/GE. However, the high H2 pressure hydrogenation reaction condition gave an order of Pd/C > Pt/GE > Pt/C. The hydrogenation activity of Pt/GE was better than the commercial Pt/C but a little less than that of the commercial Pd/C. Acknowledgment The authors would like to thank Academia Sinica and National Central University for financially supporting this work. References 1. Burda C, Chen XB, Narayanan R, El-Sayed MA: The chemistry and properties of nanocrystals of different shapes.