Metal supported platinum catalysts from

Time courses of dehydrogenation activities with carbon-supported platinum catalyst under superheated liquid-film conditions in laboratory-scale continuous operation. Catalyst platinum nanoparticles supported on granular activated carbon (Pt/C, 5 wt-metal%), 1.1 g. Feed rate of tetralin 0.5 mL/min (superheated liquid-film conditions). Reaction conditions boiling and refluxing by heating at 240°C and cooling at 25°C. (Reproduced from Hodoshima, Sv Shono, A., Satoh, Kv and Saito, Yv Chem. Eng. Trans8,183-188, 2005. With permission.)... 

As well as increased selectivity, the other main advantage of the ionic liquid systems is the ability to recycle the reaction medium without loss of solvent. To facilitate the recycle, the reaction mixture was simply extracted with diethyl ether resulting in a mass recovery > 99 %. The extraction was performed with the catalyst in-situ and no catalyst was found to traverse into the extractant phase either as particulate matter or as the result of leaching of the metal from the support. As shown in Table 1, a drop in activity for the platinum catalyst, from a conversion of 82% to 36 % after 4 hours reaction, was observed on the first recycle when using [emim][NTf2]. 

In the synthesis of supported platinum catalysts, chloride complexes of platinum (IV) are commonly used as precursors. Their sorption on the alumina surface occurs from aqueous solutions and implies the involvement of OH groups of the support surface. Therewith, two main mechanisms of the interaction between metal complex and support are considered, implementation of each mechanism depending both on the chemical composition of a complex (degree of hydrolysis) and the ratio of various OH groups (Belskaya et al., 2008, 2011 Bourikas, 2006 Lycourghiotis, 2009). The first mechanism consists in the formation of outer sphere complexes it implies electrostatic interaction between chloroplatinate and alumina surface, which is protonated and positively charged at low pH of the solution ... 

Recently, it is reported that Xi02 particles with metal deposition on the surface is more active than pure Ti02 for photocatalytic reactions in aqueous solution because the deposited metal provides reduction sites which in turn increase the efficiency of the transport of photogenerated electrons (e ) in the conduction band to the external sjistem, and decrease the recombination with positive hole (h ) in the balance band of Xi02, i.e., less defects acting as the recombination center[l,2,3]. Xhe catalytic converter contains precious metals, mainly platinum less than 1 wt%, partially, Pd, Re, Rh, etc. on cordierite supporter. Xhus, in this study, solutions leached out from wasted catalytic converter of automobile were used for precious metallization source of the catalyst. Xhe XiOa were prepared with two different methods i.e., hydrothermal method and a sol-gel method. Xhe prepared titanium oxide and commercial P-25 catalyst (Deagussa) were metallized with leached solution from wasted catalytic converter or pure H2PtCl6 solution for modification of photocatalysts. Xhey were characterized by UV-DRS, BEX surface area analyzer, and XRD[4]. 

Finally, clays can be used as supports for other catalysts such as platinum metal or aluminum chloride, largely to facilitate recovery of the catalyst from a liquid after reaction (e.g., by filtration). 

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