The structure and selectivity of supported metal particles j.m. domínguez

This chapter characterizes particles of Pt supported on graphite by using weak beam electron microscopy and correlates the particle shape with the kinetics data for the conversion of neopentane. This reaction is of the “demanding” type as the activity is influenced by the particle size and more general by the mode of catalyst preparation. This system appears to be very convenient for the correlation sought because the reaction has the metal as sole site of catalytic activity. The preparation of Pt/C catalyst is made by using materials of high purity. The support is a graphite LONZA - LT10, type ex-anthracite, with 99.9% of carbon, as reported by the supplier. The activity data of the neopentane conversion over a Pt/C catalyst is collected in a differential reactor flow system coupled with a Varian Aerograph 1200 chromatograph. When observed in bright field microscopy, the Pt clusters show two main profiles, hexagonal and elongated hexagonal. The data plot represents a very encouraging correlation between the particle shape and crystallography with selectivity for isomerization data, which proves that the electron microscopy is indeed a very powerful technique to obtain such data.