The influence on selectivity of the environment of catalyst sitesII. Modification of cobalt and nickel hydrogenation catalysts by the action of sulfur and other nonmetals

Abstract

The effect of the presence of sulfur on the activity and selectivity of nickel and cobalt powders has been investigated by examination of 1,3-butadiene hydrogenation at 100 °C. Nickel and cobalt surfaces devoid of sulfur give preferential 1-butene formation by 1:2 addition (type A behavior), whereas surfaces contaminated by sulfur, in sufficient quantity and suitably incorporated, give preferential 2-butene formation with a hightrans:cis ratio (type B behavior). Sulfur-contaminated catalysts have been prepared by the reduction of (CoO + CoS) and analogous nickel mixtures, by the adsorption of thiophen and of hydrogen sulfide on nominally clean cobalt powders, and by transfer of sulfur from a contaminated alumina support. The electronic effects on surface sites of sulfur present in an ad-layer and of sulfur incorporated in the surface are distinguishable. Contamination by phosphorus, arsenic, selenium, bromine, and chlorine (but not oxygen) gives type B catalysts similar to those obtained by contamination with sulfur. The effect was not permanent in the case of halogen contamination. This work (i) interprets our previous reports of the existence of “two forms” of nickel and of cobalt, (ii) established 1,3-butadiene hydrogenation as a test reaction for the determination of the extent of contamination of nickel or cobalt catalysts by sulfur and some other nonmetals, and (iii) provides a method for the modification of catalyst selectivity in that the balance of 1:2 and 1:4 addition in 1,3-alkadiene hydrogenation can be controlled.