Chemisorption studies of promoted solid-state HDS catalysts

Abstract

Oxygen pulse chemisorption measurements were made on a series of model HDS catalysts synthesized from solid-state reactions of elemental starting materials. Three different promoter atoms having the following catalyst stoichiometries were used in this study: P2xMo1-xS2 for the Co and Fe samples and PxMo1-xS2 for the Ni series. Four samples from each promoter family were studied and the P/(P + Mo) weight percent ratio varied from 0.030 to 0.355. All catalysts displayed Arrhenius type behavior in the HDS of thiophene and it was found that O2 chemisorption uptakes could be correlated with the HDS activity of these solid-state model catalysts. Pulse chemisorption experiments revealed that the more active samples adsorbed increased amounts of O2; hence activity normalizations using O2 uptake resulted in a consolidation of the Arrhenius plots so that the individual data points merged into a narrow band on the plot. Oxygen activity normalizations also revealed that on a per mole of O2 basis, the model catalysts gave thiophene HDS turnover frequencies similar to those found on an industrial HDS catalyst. CO chemisorption experiments were run on a select number of samples and similar trends were observed.