Proc. Indian Acad. Sci. (Chem. Sci.), Vol. 108, No. 3, June 1996, p. 343. © Printed in India.

Investigation of the oxidative stability of fullerene soots and the catalytic activity of palladium dispersed on them

ARUNABHA DATTA*, RAVINDRA Y KELKAR, HANIF I KHWAJA and MONIKA DATTA t* ÷

Alchemie Research Centre, P.O. Box 155, Thane-Belapur Road, Thane 400601, India tDepartment of Chemical Technology, University of Bombay, Matunga, Bombay 400 019, India + On leave from Delhi University as a Fellow of the Jawaharalal Nehru Centre for Advanced Scientific Research, Bangalore, India

In spite of the tremendous interest in fullerenes and in C6o , in particular, there have been few reported studies on the nature of the Kratschmer-Huffman (K-H) soot prepared by the contact arc vaporization of graphite. At the same time, although the reduction of fullerenes, both chemically and electrochemically, has been well studied, their oxidation behaviour is less well understood. We have shown recently, through in situ FTIR studies that C6o, which is oxidatively less stable than graphite, undergoes total oxidation at elevated temperatures through the formation of an intermediate anhydride. It was also shown that the K-H soot both before and after extraction with solvents such as toluene and trichlorobenzene (TCB) is, quite surprisingly, oxidatively less stable than C6o inspire of being more graphite-like in nature. The K-H soot after extraction with solvents has been variously described as consisting of giant fullerenes (up to C4oo) or bucky tubes. Although the exact nature of the K-H soot is still not clear, it is evident from these studies as well as from our investigation of their oxidative stability, that the K-H soot, even after extraction of the soluble fullerenes from it by solvents, is very different from that of the other known forms of carbon. Consequently, since fullerenes are known to be very good electron acceptors and carbon is a very important catalyst support, we have studied the nature of palladium dispersed on K-H soot both before and after extraction with toluene and TCB. The samples were prepared by dispersing Pd(NO3) 2 on the soot samples followed by reduction with formaldehyde. It was found that the dispersed palladium was present on the soot samples in a mixture of oxidation states whereas, under identical conditions, the palladium dispersed on activated carbon is present exclusively as Pd °. The dispersed palladium was found to selectively catalyse the oxidation of one of the components of soot. In addition the Pd/soot samples are active catalysts for the disproportionation of cinnamyl alcohol to cinnamaldehyde and dihydrocinnamylalcohol giving conversions of up to 75 % under conditions where a commercial Pd/C catalyst is virtually inactive.

* For correspondence

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