Catalytic Functionalities of H-β-Zeolite-Supported Molybdenum Hydrotreating Catalysts

Abstract

Catalysts containing 2−12 wt % Mo and 1−5 wt % Co or Ni were prepared using commercial H-β-zeolite as a support. The support as well as various catalysts were characterized by X-ray diffraction (XRD), BET surface area, temperature-programmed reduction (TPR), and in situ oxygen chemisorption in the sulfided state. The XRD studies indicated that the crystallinity of β-zeolite decreases rapidly at higher loadings of molybdenum, and there is no evidence for the presence of crystalline Mo phases below 10 wt % Mo loading. At higher loadings, however, MoO3/MoS2 may be present in small quantities. The BET surface area analysis indicated that molybdenum is well-dispersed up to 6 wt % Mo loading in both oxide and sulfide states. The oxygen uptakes increased up to 6 wt % Mo and then decreased at higher loadings. The crystallite sizes evaluated by oxygen chemisorption are small, indicating that MoS2 is well-dispersed on the support up to 6 wt % Mo. The TPR results indicated that a Co or Ni promoter helps decrease the temperature of the Mo reduction. TPR results indicated that two molybdenum phases with differing reduction behavior exist before and after 6% Mo loading. Catalytic activities for HDS, HYD, and HCK followed the same trend as oxygen uptake. A comparison with γ-Al2O3 indicated that the β-zeolite support imparts superior HYD activities in Mo, CoMo, and NiMo catalysts. Y-zeolite catalysts exhibit higher HDS activities but lower HYD activities than β-zeolite-supported catalysts.