Effect of oxidation process of asphaltenes present in oil refining wastes followed by XANES spectroscopies

YANINA B. BAVA; MARINA PELUFFO; NATALIA A. DICLEMENTE; MARIA T. DEL PANNO; L. ANDRINI ; L.GIOVANETTI; MAURICIO F. ERBEN

Campinas

Congreso; 28th Annual Users? Meeting (RAU), Meeting LNLS/CNPEM; 2018

Asphaltenes are complex mixture of heteroatom rich aromatic hydrocarbons that are present as a solid suspension in crude oils. Sulphur is the most abundant heteroatom in the oil, present in the heavier fractions as asphaltenes and resins. Besides sulfur is a good marker of the alteration of oils because it is very sensitive to oxidation, and exhibits a range of oxidation states from -2 to +6. [1] The XANES spectroscopy is an appropriated technique for the speciation of chemical species and provide qualitative and quantitative information about the sulphur content in asphaltenes. [2] A large fraction of oil refining wastes contains hydrocarbons of high molecular weight and heteroatom rich aromatic hydrocarbons. [3] The general aim of this project is the remediation of oil bottom tanksludge and of a chronically hydrocarbon contaminated soil combining chemical oxidation followed by biological treatment. The knowledge of the Sulphur chemistry in asphaltenes extracted from oils bottom tank sludge before and after different oxidation treatments constitutes an important information for understanding such a complex system.Three samples of asphaltenes were extracted from different oils bottom tank sludge by precipitation with n-heptane, using a solvent to the bitumen ratio of 40:1 volume/weight. The resins coprecipitated were removed with a Soxhlet extraction with n-heptane. The asphaltenes were further treated with different oxidizing agents (persulfate, hydrogen peroxide and permanganate) followed by biological treatment with previously studied fungal species. The Sulphur speciation at different stays of the sample treatment were studied with XANES spectroscopy. The XANES measurements were performed in the SXS beamline at LNLS. Commercial molecules with sulfur in different oxidation states were measured as standard. The spectra of asphaltenes can be describe in terms of the contribution of four principal sulfur structures: sulfide, thiophene, sulfoxide and sulfonate. After oxidation treatments an increase in the contribution of more oxidated Sulphur form was observed, attributed to sulfate or sulfonate group (Figure 1). The completed oxidation ofSulphur observed with persulfate and the evaluation of total petroleum hydrocarbons (TPH) in the petrochemical sludge samples after biological treatments allow select the oxidation agents to optimize the remediation treatments.