Palladium catalyst is the most used among precious metal catalysts for diversified purposes. The palladium catalyst is widely used for synthesis of specialty chemicals because many reactions can take place by the catalyst at a lower temperature and pressure with a minimal quantity and minimal side reaction, especially in the hydrogenation of olefins and aromatic nitro compounds, as compared with sponge Ni metal (Raney type Ni) catalyst. It is also used for a dehalogenation and a carbonylation.