Influence of the Dispersionfo Metallic Particles on the Reaction of Triphenylarsine with Alumina-Supported Nickel

摘要

The hydrogenolysis of triphenylarsine with alumina-supported nickel catalysts with various particle sizes was studied at tempera-tures ranging from 303 to 443 K umder 12 bar of hydrogen. The reac-tion initially takes place sefrdivelv on the surface of the nickel par-ticles and leads to the successive hydrogenolysis of —As—Ph bonds with benzene and cwckulieimue formation. At 303 K, the reaction stops when the Ni particles are completely covered with grafted— As—Ph fragments. The quantity of fixed arsenic increases with the dispersion of the nuetid particles. It is proposed that more As—Ph fragments (per metallic atom) are grafted onto edge atoms than onto face aimun .1 due Ni particles. When the reaction is performed at higher temperature, the As atoms migrate inside the nickel par-ticles early mud lam an intermetallic compound. At 373 K, the Ni_5As_2 phase, very poorly crystallized, is obtained. At 443 K, the reaction leath I. a uicil-crystallized phase NiAs. The dispersion of the catalyst has no influence on the nature of the formed intermetal-lic species. However, the formation rate of these species increases with the dispersion of the catalysts.