Pretreatment of new reduced ternary molybdenum sulfide catalysts

Pretreatment of a new lanthanum molybdenum sulfide (LaMoS) hydrodesulfuriza tion (HSD) catalyst in flowing H-2 has been investigated. Following pretrea tment up to 800 degrees C, the catalyst surface area decreased from 175 to 11 m(2)/g; the average pore diameter increased due to the loss of pore diam eters smaller than 100 Angstrom. TPD characterization of the as-prepared La MoS was used to monitor the evolution of solvents and adsorbed materials up to 800 degrees C. The Mo oxidation state was examined after various pretre atment procedures using X-ray photoelectron spectroscopy (XPS) and temperat ure-programmed reduction (TPR). Following temperature-programmed desorption (TPD), two types of surface oxygen were detected which could be reduced at 250 degrees C and 950 degrees C by a flow of 10% H-2 in N-2. Transformatio n of the amorphous LaMoS to the corresponding crystalline Chevrel phase [La (Mo6S8)] was detected at 1000 degrees C using TPR and x-ray diffraction (XR D). (C) 2000 Elsevier Science B.V. All rights reserved.