Novel SOx removal catalysts for the FCC process: Manufacture method, characterization, and pilot-scale testing

Abstract

A novel method for preparing SO_x removing (ReSO_x) catalysts for the fluid catalytic cracking (FCC) process, based on multimetallic layered double hydroxides (LDHs), is presented. The synthesis procedure is industrially feasible and environmentally friendly. Ceria is incorporated in varying amounts as oxidation promoter, to obtain catalysts that are able to work efficiently in either partial or full combustion regenerator modes. The manufacturing process presented herein enables obtaining, by spray drying, microsphere particles with mechanical properties that are adequate for fluidization, without requiring addition of binding agents. The physicochemical properties of the catalysts are examined by several characterization techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). A uniform dispersion of the metal components is observed throughout the particles. Furthermore, the microspheroidal catalysts are tested for the reduction of SO_x emissions in a pilot-scale FCC plant, circulating together with a conventional cracking catalyst, during the conversion of a sulphur-containing industrial gas oil obtained from a Mexican refinery. ReSO_x catalyst addition to the pilot FCC unit, in only 0.2 wt% of the total catalyst inventory, results in a maximum %SO₂reduction of 74–80%. Additionally, the effect of the ReSO_x catalyst on the main cracking reactions is studied; it is shown that the disruption of the cracking catalyst's activity and selectivity is minimal, at a concentration of 1.5 wt% of the total catalyst inventory. Thus, the use of these SO_x removal catalysts appears as a viable, low investment, flexible and effective option for in situreduction of SO_x flue gas emissions.