Red Mud waste from the Bayer process as a catalyst for the desulfurization of hydrocarbon fuels

Abstract

The management of Red Mud generated as a waste by-product of bauxite processing in the aluminum industry is key to the long-term sustainability of alumina production. At the same time, the desulfurization of fuel oil to low-level sulfur is an ongoing challenge to the petroleum industry. In an attempt to address both these issue in an integrated fashion, Red Mud waste was studied as a catalyst in a desulfurization process using a simulated Diesel containing dibenzothiophene (DBT) as a model heterocyclic organic sulfur compound. The new process combines an oxidative-adsorptive desulfurization in which a combination of H₂O₂//H₃CCOOH and Red Mud was able to catalytically oxidize the sulfur compound to the corresponding sulfoxide (DBTO) and sulfone (DBTO₂) which are then reversibly adsorbed onto the Red Mud. Regenerative tests of Red Mud were performed, maintaining a high activity in recycles suggesting that the Red Mud could be reused after a simple thermal treatment releasing DBTO and DBTO₂. The approach synergistically addresses both problems: removal of sulfur compounds while at the same time offering a potential useful application of Red Mud. Red Mud was characterized by Mössbauer Spectroscopy, Infrared Spectroscopy, X-ray Diffraction (XRD), Scanning Electron Microscopy with dispersive energy (SEM-EDS), BET Surface area (BET), and release of volatile compounds from Red Mud by Gas chromatography-Mass Spectrometry (GC-MS) using a solvent-free solid injector (SFSI). The kinetics of the desulfurization reactions were monitored by GC-MS.