Probing the particle size effect of carbon disulfide deep hydrogenation over low-loading Pt/Al2O3 catalysts

To investigate the mechanism of the role of active center size on the selectivity of methyl mercaptan (CH 3 SH) and methane (CH 4 ) in the deep hydrogenation reaction of carbon disulfide (CS 2 ), it was first derived from DFT calculations that the Pt cluster geometries showed a decreasing and increasing pattern on the energy barriers of the two key hydrogenation steps: (I) HCSS* to HCSSH* and (II) deep hydrogenation of CH 2 S* to CH 3 SH. For further validation, we synthesized Pt NPs with varied average sizes (1.7–4.0 nm) using a reduction-agglomeration strategy to probe the source of size sensitivity at low Pt loading. It was found that the active centers of Pt NPs located in the 2.0–3.0 nm region have the highest proportion of medium-coordinated Pt sites, which can effectively promote hydrogen spillover and enhance the HCSS* pathway. Finally, with this modulation strategy, the catalytic activity and selectivity were significantly improved at 1 wt% Pt loading, which exceeded that of the fresh 4 wt% Pt/Al 2 O 3 catalyst, and the long-term stable production of CH 3 SH (selectivity was maintained at 80 %) was achieved at 250 ℃ in the high-concentration CS 2 environment.