Parasuraman Selvam

Glyceric acid is one of the important intermediates of glycerol oxidation. However, it is extremely difficult to achieve high glyceric acid selectively as the reaction follows a complex pathway with the formation of a variety of undesired products. In this context, periodic mesoporous carbon-supported gold catalysts show promise for selective formation of the targeted product. Therefore, in this investigation, an effort has made to study the effect of particle size and shape of a series of carbon supported with varied sized/shaped gold catalysts on the liquid-phase oxidation of glycerol. Further, the role played by the surface of gold-nanoparticles has prompted us to investigate in detail the isotropic (nanocube/nanosphere) and anisotropic (nanoslabs/nanorods) gold supported onto both activated/amorphous carbon (Au/AC) and ordered mesoporous carbon (Au/CMK-3) towards glycerol oxidation. It was observed that the CMK-3 supported gold nanocube exhibited the highest yield towards glyceric acid with an excellent stability in terms of recyclability/reusability.

Ordered nanoporous carbons having very high surface area are of great technological interest for the development of catalytic, electrocatalytic and hydrogen-storage systems. These carbons with various structures, e.g. CMK-1, CMK-3, NCCR-41, etc., have been synthesized by carbonization of sucrose, furfuryl alcohol and other suitable carbon containing precursors within the pores of nanoporous silicate molecular sieves. The inorganic templates were then removed by etching with HF, followed by filtration, washing and heat treatment to obtain the nanoporous carbons and nitrogen containing carbons. In the present study, ordered nanoporous carbon, designated as NCCR-56, was prepared using IITM-56 silica as the hard template and sucrose as the carbon source. This carbon was then used as a support for the preparation of mono dispersed gold nanoparticles (Au/NCCR-56), which shows promise for glycerol oxidation of reaction.

Platinum-supported ordered mesoporous carbon catalysts were prepared employing colloidal platinum reduced by four different reducing agents, viz., paraformaldehyde, sodium borohydride, ethylene glycol and hydrogen, and deposited over ordered mesoporous carbon (CMK-3) synthesized by silica hard template (SBA-15). The resulting platinum nanoparticles supported mesoporous carbon, designated as Pt/CMK-3, catalysts were tested for the electocata-lytic oxidation of methanol. The effect of the various reduction methods on the influence of particle size vis-à-vis on the electrocatalytic effect is investigated. All the catalysts were systematically characterized by XRD, BET and TEM. The results of the synthetic methods, characterization techniques and the electrocatalytic performance indicate that the Pt/CMK-3 catalysts are superior to that prepared with activated carbon (Pt/AC) as well as with that of the commercial platinum-supported carbon catalyst (Pt/E-TEK). In particular, the catalyst, Pt/CMK-3, prepared using paraformaldehyde reduced platinum showed much higher activity and long-term stability as compared to the other reducing methods.

In this investigation, we report the synthesis and characterization of mesoporous carbon with disordered MCM-41 type structure by carbonization of sucrose within the pores of siliceous MCM-41. The silica template was removed by a standard procedure, viz., etching with HF, followed by filtration, washing and heat treatment, to obtain the mesoporous carbon. The resulting mesoporous carbon, designated as NCCR-41, was then used as a support for the preparation of highly uniform and well-dispersed nano-sized platinum nanoparticles. The supported catalysts with narrow size distribution of the active platinum, referred as Pt/NCCR-41, show excellent electrocatalytic activity for methanol oxidation reaction in comparison with platinum supported activated carbon (Pt/AC) as well as commercial carbon (Pt/E-TEK) catalysts. © 2012 Elsevier B.V.