Multitechnique analysis of a deactivated resid demetallation catalyst

Abstract

A spent resid demetallation catalyst has been characterized using kinetic analysis, N 2 adsorption, X-ray photoelectron spectroscopy (XPS or ESCA), elemental analysis, X-ray diffraction (XRD), electron microprobe analysis, and CO chemisorption. During the demetallation process Ni, V, Fe, S, and C deposited from the resid feed onto the catalyst surface leading to its deactivation. The catalyst accepted about 100% of the original catalyst weight as metals and coke. Surface areas dropped by 30–65% and pore volumes were reduced by 60–85%. The deposition of metals, sulfur, and coke takes place preferentially at the entrances of pores, causing pore mouth plugging. This effect can be semiquantitatively described by the constraint index which is obtained by division of the N 2 adsorption/desorption hysteresis loop area by pore volume. All elements exhibit preferential deposition on the catalyst extrudate surfaces as evidenced by XPS and by electron microprobe extrudate cross-section analyses. Vanadium and nickel sulfides are formed on the working catalyst surface. The sulfides have been identified as V 3S 4 and Ni 3S 2 or Ni 2S. Upon air exposure these sulfides oxidize slowly on the surface. Nickel and vanadium deposition through the reactor bed parallel each other with a maximum deposition at about 17% of bed depth, whereas the carbon profile is relatively uniform. The top section of the catalyst bed, containing 1.5 times the metals but 0.9 times the carbon compared to the bottom section, was 30–50% more active for both V and Ni removal.