A highly efficient process for transforming methyl mercaptan into hydrocarbons and H2S on solid acid catalysts
Résumé
The catalytic conversion of CH3SH and CH3SCH3 (DMS) on protonic zeolites H-ZSM-5, H-Y and H-ferrierite was studied in a gas flow reactor from 423 to 823 K. Below 700 K, CH3SH is converted at equilibrium into DMS and H2S. Above 700 K, light alkanes (C1-C3), benzene, toluene and xylene appear alongside H2S in the gas phase, and a carbonaceous deposit builds up on the catalyst. DMS is assumed to be the intermediate in the CH3SH transformation into H2S and hydrocarbon species. At 823 K, the CH3SH conversion is total on H-ZSM-5, and only partial on H-Y and H-ferrierite. These are selective to alkanes, and produce large quantities of coke. In contrast, much less coke builds up on H-ZSM-5, which is also more selective to aromatics. After calcination in air flow at 823 K, the spent H-ZSM-5 sample recovers the properties of the fresh catalyst. Similarities and differences with the methanol-to-hydrocarbons process are discussed.