Effect of hydrogen on carbon deposition catalyzed by copper-nickel alloys

Abstract

Carbon deposition from benzene onto cold-rolled sheets of copper-nickel alloys was studied at temperatures ranging from 570 to 700 °C, in atmospheres of hydrogen, helium, and their mixtures. The deposition rate onto pure nickel was higher in hydrogen than in helium, whereas that onto 80% nickel alloy was higher in helium-rich atmosphere than in hydrogen. In hydrogen-rich atmospheres, the deposition proceeded at a constant rate, which changed reversibly with the composition of the atmosphere. In helium, the deposition rate decreased gradually. Hydrogen seems to affect the catalytic deposition in two ways: (i) by removing surface carbon film which hinders the catalytic action of metal surface, and (ii) by removing the chemisorbed species which are the precursor of the deposition.