Preparation of silica-supported Pd nanoparticle catalysts by an alcohol reduction method and evaluation of their catalytic properties in the dechlorination of an aromatic chloride

摘要

Reduction of a Pd(II) precursor in refluxing 2-propanol, ethanol, or methanol in the presence of dissolved NaOH afforded silica-supported Pd catalysts designated Pd/SiO2(Pr), Pd/SiO2(Et), and Pd/SiO2(Me), respectively. Pd/SiO2(Pr) consisted of metallic Pd particles (average particle size, 5.1 nm) dispersed in the porous structure of SiO2, whereas the Pd particles on Pd/SiO2(Et) and Pd/SiO2(Me) were larger. The catalytic activity of Pd/SiO2(Pr) in the dechlorination of 2,4,6-trichloroanisole in a solution of 2-propanol containing NaOH was greatly enhanced by the addition of methanol; the optimum rate occurred at 1 % v/v methanol. The activity of Pd/SiO2(Et) was also enhanced by methanol but to a lesser extent than that of Pd/SiO2(Pr). In contrast, Pd/SiO2(Me) exhibited no activity even in the presence of methanol.