Monitoring of calcium stearate formation by thermogravimetry

Naphthenates are produced when naphthenic acids present in crude oil are mixed with brine. They deposit at oil/water interface and are insoluble in either of the phases causing a large problem to the oil industry. Generally, naphthenates precipitate jointly with others compounds such as sulfates and carbonates. This fact makes difficult their characterization. In this study, calcium stearate formation from stearic acid was investigated, under different conditions, as a previous model to understanding of calcium naphthenate precipitation. Medium reactions distinct were studied and the results indicated that the ethanol medium was the most efficient for the formation of solids because in this only case, the stearic acid was completely converted into stearate. Monitoring of the conversion was performed by thermogravimetry in spite of this technique not be typical in salts characterization. Nevertheless, the thermogravimetric analysis showed that is possible to identify differences between an organic acid, a salt of this acid and an inorganic salt, in the same sample. Infrared spectra was used in order to confirm the results obtained by thermogravimetry. However, this technique showed less efficiency and sensibility.