Sulfur-33 Isotope Tracing of the Hydrodesulfurization Process: Insights into the Reaction Mechanism, Catalyst Characterization and Improvement.

The novel approach based on S isotope tracing is proposed for the elucidation of hydrodesulfurization (HDS) mechanisms and characterization of molybdenum sulfide catalysts. The technique involves sulfidation of the catalyst with S-isotope-labeled dihydrogen sulfide, followed by monitoring the fate of the S isotope in the course of the hydrodesulfurization reaction by online mass spectrometry and characterization of the catalyst after the reaction by temperature-programmed oxidation with mass spectrometry (TPO-MS). The results point to different pathways of thiophene transformation over Co or Ni-promoted and unpromoted molybdenum sulfide catalysts, provide information on the role of promoter and give a key for the design of new efficient HDS catalysts.