Abstract:
A series of alkaline doped multiwall carbon nanotubes, CNTOM (with M = Li, Na, K, Cs) has been prepared
by wetness impregnation with alkaline acetates and subsequent pyrolysis of commercial multiwall
carbon nanotubes previously oxidized with nitric acid, characterized by different physico-chemical techniques
and tested as catalysts in the Knoevenagel condensation between benzaldehyde and different
active methylene compounds. As determined by different techniques, caesium has been incorporated in
a less extent than the rest of alkalines. The SBET values decrease in the CNTOM with respect to the raw
material, mainly due to the blockage of micropores and small mesopores by the metallic phase formed.
As deduced from PZC values, the character of the surface of nanotubes changes from acid for the oxidized
sample to basic for the alkaline doped nanotubes, the basic character decreasing with the size of the
alkaline cation. The order of activity observed in the Knoevenagel condensation between benzaldehyde
and ethyl cyanoacetate seems to be correlated mainly with the amount of basic centres, CNTOCs being
the less active catalyst due to its lower metal content. Conversion values of benzaldehyde...