No abstract

Naphthenic acids represent a subfraction of the crude oil resins that contains predominantly carboxylic acids with saturated cyclic structures and corresponds to a complex mixture of compounds. The naphthenic acids can cause deposition problems. These compounds however also play an important role in some phenomena occurring, and then separation from crude oil would improve oil quality during the production. In this contribution, some aspects of the solution behavior of naphthenic acids are presented. It was observed that these compounds form stable liquid mixtures with organic solvents in a wide range of solubility parameters. When added to partially soluble liquid mixtures, such as n-heptane/methanol, they improve the mutual solubility of these liquids, increasing the solubility domain and partition into both liquid phases. The precipitation onset for asphaltenes dissolved in toluene titrated with n-heptane was increased by the addition of naphthenic acids, indicating that these compounds contribute to the solubilization of asphaltenes representing a “good solvent” for this fraction. Applying the polymer solutions to the asphaltenes dissolved in liquid mixtures, treating the naphthenic acids as pure pseudo-components, and assuming that asphaltenes precipitation onset occurs at a particular solvent composition corresponding to a “critical solubility parameter” value from 20 to 23 MPa1/2 were obtained for the naphthenic acids that are in good agreement to those obtained by differential scanning calorimetry (DSC).