Avaliação das condições de extração, cristalização e separação de sais e sedimentos de petróleo do pré-sal e posterior caracterização química

Abstract

In this work the experimental conditions of the ASTM D4807 standard which could influence the amount of solids retained on the surface of the nylon membrane were evaluated. Modifications to the ASTM D4807 standard, such as the vacuum level (-40 to 80 KPa), temperature (70, 80 and 90 °C), application of magnetic stirring and solubilization with different mixtures of solvents used during the filtration procedure were tested. Mixture of solvents with toluene, ethanol, isopropanol, xylene, 1-propanol, 1-butanol and 2-butanol were evaluated for the crude oil analysis using the ASTM D4807. Scanning electron microscopy (FEG-SEM) with a secondary electron detector (SE) and compositional analysis using an energy dispersive X-ray detector were used to evaluate the morphology of saline species crystals. Furthermore, the solubilization of the solids retained in the nylon membrane in water was performed for the determination of Ca and Na by ICP OES and Cl- and SO4 2- by ion chromatography. Membranes with porosities of 0.22 and 0.11 μm were evaluated for all solvent mixtures. Sample A presented the highest sediment content (1.33%) and high water content (5.55%) and was used for all assessments of the ASTM D4807. From the changes in the ASTM D4807 standard, it was possible to observe that there was no influence of temperature, agitation and vacuum level on the amount of solids retained on the membrane. The use of mixtures containing the alcohols produced a significant influence on the amount and shape of solids retained on the membrane surface compared to ASTM D4807 using toluene. All alcohols evaluated promoted a significant reduction in the amount of solids retained on the membrane surface. The greatest reduction in the amount of solids retained in the 0.45 μm nylon membrane was observed for the ethanol+toluene mixture (30%+70%). The alcohols also modified the morphology and size of the crystals retained on the membrane surface, with the predominance of cubes formed by Na, Cl and Ca. The use of membranes of 0.22 and 0.11 μm showed that some solvent mixtures promoted the crystallization of solids with a size smaller than 0.45 μm that were not retained on the membrane surface recommended by ASTM D4807. The elemental analysis of the solids retained on the surface of the membranes showed a selective solubilization of some salts, with emphasis on a greater solubilization of Ca salts in relation to salts containing Na.