Hydrogenation of Butadiene for the Characterization of Co-Mo Sulfide Catalysts.

Abstract

Hydrogenation of butadiene was conducted at 473K on Co, Mo and Co-Mo sulfide catalysts supported on NaY and Al2O3 as a probe-reaction to characterize the active metal species in the binary sulfide catalysts at a relatively high temperature. The distributions of butene were considerably different as compared among Mo and Co sulfides; Mo sulfide catalysts providing almost an equilibrium-distribution of butenes, and Co sulfide catalysts showing 1-butene-rich compositions. With NaY-supported Co-Mo binary sulfide catalysts, prepared by using metal carbonyls as precursors, the butene distribution was Co-like, clearly indicating that the hydrogenation occurred on the Co sites, in spite of the simultaneous presence of the same amounts of the Co and Mo sulfide clusters. In the case of an Al2O3-supported Mo sulfide catalyst decorated with Co sulfide species, using Co-carbonyl, it is suggested that most of the Mo sulfide sites are modified by the Co species, although some Mo sites are used for the reaction. Comparing the distributions of butene in the hydrogenation of butadiene with that in the isomerization of 1-butene, it is concluded that the isomerization of butenes takes place on Mo sulfide sites in the presence of butadiene, while the isomerization on Co sites is significantly retarded by the presence of butadiene.