Effect of Sulphur and Silicon in Fuels on an Automotive Reforming Catalyst

Abstract

The effect of sulphur on a rhodium reformer catalyst was determined in the partial oxidation of n-heptane. The yield loss of the catalyst upon sulphur addition appeared to almost instantaneous and not progressive in time (i.e. it reaches a plateau). Up to ppm levels, the direct yield loss appeared to be linearly related to the sulphur level in the fuel and is of the order of around 3% per ppm of sulphur in the fuel. Sulphur adsorption on rhodium catalyst sites was found to be reversible. The original activity of the catalyst was quickly restored when changing to a sulphur free fuel. The effect of sulphur on the rhodium catalyst does not depend on the structure of the sulphur species. Based on this work, a 10 ppm sulphur maximum seems to be a sufficiently tight specification with respect to the stability of an appropriate reformer catalyst. By contrast, the presence of other species in fuels can cause irreversible and progressive catalyst deterioration. This work provides extra confirmation that Gas-to-Liquid fuels appear to be an excellent choice for combined use in reformers and ICEs since they are extremely pure and almost completely devoid of sulphur.