Sulfur as a catalyst promoter or selectivity modifier in heterogeneous catalysis
For most heterogeneous catalysts adsorbed sulfur and sulphur-containing molecules are generally regarded as a poison. However, a growing number of reports from academia and industry demonstrate that sulfur may act as an activity promoter or selectivity modifier in heterogeneous catalysis. Reports from a variety of areas such as Fischer–Tropsch synthesis, catalytic reforming, regio and chemoselective hydrogenation as well as CO oxidation, hydrocarbon oxidation and NOx reduction are discussed. Based on the literature cited, comments on the levels of sulfur necessary to observe a promotional effect are suggested/proposed, as well as some of the techniques which can be applied to understand such effects.