Study on methanethiol synthesis from H2S and dimethyl sulfide over Al2O3 catalysts promoted with phosphorus

A series of P-promoted alumina catalysts with phosphorous contents varying in the range of 1–5% for the reaction of hydrogen sulfide (H2S) and dimethyl sulfide (DMS) to produce methanethiol (MT) were prepared and characterized by using XRD, SEM, BET, FT-IR and NMR techniques. The activity assay results showed that at the reaction temperature of 593 K, the P-promoted alumina catalyst exhibits as high as 100% selectivity toward MT; the DMS conversion ranges from 44.7% to 51.4% depending on the loading of phosphorus. The characterization results showed that introducing a small amount of phosphorus into γ-Al2O3 increases the specific surface area, pore volume and the amount of Lewis acid sites. The increase of the Lewis acid sites enhances the capacity of the catalyst to break the CS bond of dimethyl sulfide to methylthiolate (CH3S−) and CH3+, and H2S adsorbed on alumina to SH− and H+, both of CH3+ and H+ then interact further with lattice oxygen O2− of the catalyst to form methoxyl (CH3O−) and OH−, respectively, subsequent combination of CH3S− with OH− or CH3O− with SH− leads to the formation of methanethiol.

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► The DMS was used as a feed to synthesize MT, an important chemical intermediate.
► Phosphorus-modified alumina was applied to the synthesis of MT from H2S and DMS.
► Phosphorus-modified alumina has a longer life time at 773 K than pure alumina.
► The O2 was added in H2S feed to inhibit the deactivation at high temperature.