Naphthenate deposition is formed from tetraprotic naphthenic acids having aliphatic chains and high molecular weight, provided with four carboxylic terminations, sometimes called ARN acids. Obtaining these species from their matrix of origin requires the prior use of sample preparation methods aiming at an efficient extraction of naphthenic acids. Obtaining ARN acids from naphthenate deposits is advantageous in the potential for reusing waste and reducing environmental damage. The process also adds value to waste materials from the oil production and exploration process.
The present invention relates to the field of laboratory-scale sample preparation, which describes a methodology for the specific isolation of tetraprotic naphthenic acids, called ARN acids, from residual naphthenate deposits from petroleum production.
The method consists of cleaning the naphthenate deposit, converting the naphthenate salts to naphthenic acids and isolating the ARN acids from the other organic acids, using a silica-based sorbent material with aminopropyl functional groups, previously selected for an efficient elution of different functional groups and polarities.
The results of ESI(−)-FT-ICR MS showed that the methodology is promising because it provided an excellent separation by difference in polarity and as a function of different molecular weight ranges, thus reducing the complexity of the organic acid extract obtained from the naphthenate deposit. Furthermore, it allowed the separation of the different acidic species that were present in the sample. The results of ESI(−)-FT-ICR MS also indicated that one of the fractions concentrated into ARN acids, including discharged species and especially ARN acids in the form of monocharged ions. The ESI(−)-Orbitrap MS data corroborated those obtained by ES(−)-FT-ICR MS, making consistent the statement that the extract obtained from the naphthenate deposit contains a mixture of acids and that the fractionation developed provided the isolation of ARN acids from naphthenate deposits. Furthermore, the integrations of the 1H NMR spectra of acidic fractions as a function of molecular weight highlighted the expressive presence of alkyl compounds and absence of aromatic hydrogens in the fraction of interest.