CHARACTERIZATION BY TEMPERATURE-PROGRAMMED REDUCTION OF NONCONVENTIONAL CATALYSTS FOR HYDROTREATMENT

A temperature-programmed reduction (TPR) study of three series of biph asic hydrotreating (HDT) catalysts - PtS/gamma Al2O3/(PtS/gamma-Al2O3 + MoS2); Rh2S3/gamma-AlOOH/(Rh2S3/gamma-AlOOH + WS2) and PdS/gamma-Al2 O3/(PdS/gamma-Al2O3 + WS2) - is presented. In all cases, the quantity of H2S produced is larger than that which would correspond to the arit hmetic addition of the quantities produced by each of the sulfide phas es alone. This fact suggests that the noble metal sulfide dissociates the hydrogen molecule to spillover hydrogen (H-SO), the latter produci ng a deeper reduction of molybdenum sulfide or tungsten sulfide. The s imilitude of catalytic effect in hydrogenation (HYD) and hydrodesulfur ization (HDS) observed with the same mechanical mixture strongly sugge sts that H-SO also plays a role in the synergy between MoS2 or WS2 and the noble metal sulfides.