Support mesoporous carbon

Sano N, Yamamoto T, Takemori I, Kim S-I, Eiad-ua A, Yamamoto D, Nakaiwa M (2006) Degradation of phenol by simultaneous use of gas-phase corona discharge and catalyst-supported mesoporous carbon gels. Ind Eng Chem Res 45 2897-2900... 

Fig. 3. Pt/C catalysts (4% wt.). (a) Support commercial activated charcoal (b) support mesoporous carbon xerogel.

In this study, we have synthesized Pt supported mesoporous carbons by carbonization of a mixture of neutral surfactants (P123), R complex and resorcinol resin. The eatalytic properties of this composite in selective oxidation of CO in hydrogen rich condition have been studied. 

Kuppan, B. Selvam, E Platinum-supported mesoporous carbon (Pt/CMK-3) as anodic catalyst for direct methanol fuel-cell applications The effect of preparation and deposition methods. Prog. Nat. Sci. Mater. Int. 22 (2012), pp. 616-624. 

Selvam, P. Kuppan, B. Synthesis, characterization and electrocatalytic properties of nano-platinum-supported mesoporous carbon molecular sieves, Pt/NCCR-41. Catal. Today 198 (2012), pp. 85-91. 

The sitosterol hydrogenation and deactivation kinetics was determined in a shaking constant-pressure batch reactor by using the new type of synthetic support material (mesoporous carbon Sibunit) for palladium (4wt% Pd) [55]. 

Mesoporous carbon materials were prepared using ordered silica templates. The Pt catalysts supported on mesoporous carbons were prepared by an impregnation method for use in the methanol electro-oxidation. The Pt/MC catalysts retained highly dispersed Pt particles on the supports. In the methanol electro-oxidation, the Pt/MC catalysts exhibited better catalytic performance than the Pt/Vulcan catalyst. The enhanced catalytic performance of Pt/MC catalysts resulted from large active metal surface areas. The catalytic performance was in the following order Pt/CMK-1 > Pt/CMK-3 > Pt/Vulcan. It was also revealed that CMK-1 with 3-dimensional pore structure was more favorable for metal dispersion than CMK-3 with 2-dimensional pore arrangement. It is eoncluded that the metal dispersion was a critical factor determining the catalytic performance in the methanol electro-oxidation. 

Exo- and Endocyclic C=C Double Bond with Highly Mesoporous Carbon Supported Pd... 

Highly mesoporous carbon supported Pd catalysts were prepared using sodium formate and hydrogen for the reduction of the catalyst precursors. These catalysts were tested in the enantioselective hydrogenation of isophorone and of 2-benzylidene-l-benzosuberone. The support and the catalysts were characterized by different methods such as nitrogen adsorption, hydrogen chemisorption, SEM, XPS and TPD. 

The object of the present study was to use in the above mentioned hydrogenations improved carbon supported catalysts, which could compete with the Pd black catalyst. Carbon materials are common supports, their surface properties can be modified easily and it is possible to prepare carbons with different proportion of micro-, meso- and macropores, which can be key factors influencing their performances. A highly mesoporous carbon was synthesised and used as support of Pd catalysts in the enantioselective hydrogenations. To our knowledge this is the first report on the use of highly mesoporous carbon for the preparation of Pd catalysts for liquid-phase hydrogenation. 

The anchoring and the reduction methods of precious metal precursors influence the particle size, the dispersion and the chemical composition of the catalyst. The results of SEM and H2 chemisorption measurements are summarised in Table 3. The XPS measurements indicate that the catalysts have only metallic Pd phase on their surface. The reduction of catalyst precursor with sodium formate resulted in a catalyst with lower dispersion than the one prepared by hydrogen reduction. The mesoporous carbon supported catalysts were prepared without anchoring agent, this explains why they have much lower dispersion than the commercial catalyst which was prepared in the presence of a spacing and anchoring agent (15). 

Table 4 Enantiomeric excesses in the enantioselective hydrogenation of isophorone and 2-benzyl- 1-benzosuberone on highly mesoporous carbon supported Pd catalysts.

The smaller surface area values of the catalysts indicate that the palladium blocks some part of the surface of this mesoporous carbon. The decreased amount of the CO-yielding complexes on the catalyst surface compared to that of the carbon support indicates that the palladium is attached to CO generating groups. The increased concentration of C02 containing complexes on the catalysts surfaces can be due to the steps of the preparation. To clarify this it needs further experiments. 

The reduction of the catalyst precursor with sodium formate resulted in a lower Pd dispersion than the catalyst prepared by hydrogen reduction, the particle size is much larger in the former catalyst. The mesoporous carbon supported Pd catalysts are near to those of Pd on titania with respect to their enantiodifferentiating ability. Besides the metal dispersion, the availability of the Pd surface in the pores for the large modifier molecules seems to be the determining factor of the enantioselectivity. 

The interesting properties of the mesoporous carbon supported Pd need further studies. 

Alternative support materials are being investigated to replace carbon black as support in order to provide higher corrosion resistance and surface area. These supports can be classified into (i) carbon nanotubes and fibers (ii) mesoporous carbon and (iii) multi-layer graphene and they are presented in detail in the following section. 

Despite the advantages offered by CNTs and CNFs, there are still many obstacles (cost, synthesis methods) to overcome to allow large-scale production. Another type of catalyst support material is mesoporous carbon that provides high surface area and conductivity [100, 141]. It can be classified into ordered (OMC) and disordered (DOMC) mesoporous carbon [100], OMCs have been extensively used as catalyst support materials for fuel cells [140,142-146], The large surface area and 3D connected monodis-persed mesospheres facilitate diffusion of the reactants, making them very attractive materials as catalyst supports [100]. 

Park, I.-S. Choi, S. Y. Ha, J., High-performance titanium dioxide photocataiyst on ordered mesoporous carbon support. Chem.Phys. Lett. 2008,456 198-201. 

Liu, B. Zeng, H. C., Carbon Nanotubes Supported Mesoporous Mesocrystals of Anatase Ti02. Chem. Mater. 2008,20 2711-2718. 

Over the last decade, novel carbonaceous and graphitic support materials for low-temperature fuel cell catalysts have been extensively explored. Recently, fibrous nanocarbon materials such as carbon nanotubes (CNTs) and CNFs have been examined as support materials for anodes and cathodes of fuel cells [18-31], Mesoporous carbons have also attracted considerable attention for enhancing the activity of metal catalysts in low-temperature DMFC and PEMFC anodes [32-44], Notwithstanding the many studies, carbon blacks are still the most common supports in industrial practice. 

However, despite the growing use of this type of carbon material to enhance electrode performance, hydrogen storage, or other applications mentioned above, the development of hybrid mesoporous carbon materials with supramolecular functionalities has not seen much activity yet. Since this interesting and biocompatible support platform offers plenty of room for exploration in the context of this book, progress is soon expected here. 

Air diffusion electrodes In fuel cells and in air-breathing batteries, a mesoporous carbon electrode is made up of two layers an outer layer composed of carbon powder and a hydrophobic (nonwettable) binder, typically PTFE. This enables the access of gas to the inner layer, where the binder is selected to be both a hydrophilic (wettable) and an ion-conducting ionomer, to support (rather than impair if the binder was nonconducting) the ionic conductivity of the porous electrode. The catalyst particles are dispersed in-between the carbon particles. Thus, a very tortuous interface between the two layers is formed. The reacting gas approaches this interface, forming three phase points of contact providing a high active surface area. See also - air electrode. 

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