Efficient semihydrogenation of the C-C triple bond using palladium on pumice as catalyst

An efficient semihydrogenation of C-C triple bonds was achieved using palladium on pumice as the catalyst with a metal loading of 3% wt. The results obtained showed better selectivity when compared with Pd/C and better activity when compared with Lindlar's catalyst. Hydrogenation of sterically hindered alkynes is slow on Pd/pumice. The selectivity with respect to alkenes is probably due to the presence of sodium ions in the pumice structure that increases the electron density on the supported metal. (C) 1999 Elsevier Science Ltd. All rights reserved.