ACTIVATION OF HYDROGEN AT 79°K
BY
SUPPORTED COPPER
4587
Activation of Hydrogen at 79°K by Supported Copperla by J. E. Benson,lb Arden B. Walters,lO and M. Boudart'd Bepurtment of Chemical Engineering, Stanford University, Stanford, California 94506
(Received June 24, 1968)
A new catalyst containing 500 ppm of copper on magnesium oxide has been found to activate molecular hydrogen at 79°K as evidenced by its ability to catalyze the Hz-D~exchange at that temperature at a rate per surface atom comparable to that measured on metallic nickel. This catalyst is poisoned by adsorption of hydrogen at higher temperature. The nature of the surface sites responsible for the exchange is discussed.
Introduction Active catalytic centers associated with electronic defects induced by irradiation of silica gel with aluminum impurities were discovered by Kohn2 and studied in detail by various worker^.^-^ Similar centers have been investigated by Lunsford and Leland6.7 on magnesia with iron impurities. Several workers,s-10 whose results have remained unpublished, have also described a catalyst which resembles those of Kohn and Lunsford in its unexpected ability to catalyze the hydrogen-deuterium exchange a t liquid nitrogen temperature as well as in its deactivation by hydrogen adsorbed at higher temperatures. The catalyst consisted of 5 mol % copper supported on magnesia, activated without irradiation by reduction and evacuation a t high temperature. I n view of the recent findings with irradiated catalysts, it became imperative to confirm and expand the previous results with special attention to the absence of impurities such as nickel that might be introduced during the preparation of the catalysts.
Experimental Section All chemicals used were of high purity. The gases used were hydrogen (produced electrolytically) and deuterium (99.5% D2, obtained from the Matheson Co.). Both hydrogen and deuterium were purified by diffusion through palladium alloys prior to their use. Grade A helium was obtained from General Dynamics. Catalysts containing 5.0 and 0.05 mol yocopper on magnesia were prepared by impregnating Mallinckrodt analytical reagent grade magnesia with a cupric nitrate solution prepared by dissolving ASARCO copper metal (99,999+% Cu,
