Desenvolvimento de métodos eletroanalíticos em sistemas nanoemulsionados para determinação do número de acidez total (NAT) e cloretos em petróleo
Nenhuma Miniatura disponível
Data
2025-05-30
Autores
Zanelato, Luana Negris
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Federal do Espírito Santo
Resumo
The determination of total acid number (TAN) and salinity is important in the petroleum industry. This work presents an innovative approach using nanoemulsion preparation for the determination of TAN and salinity in crude oil samples. The proposed method for TAN, called nanoemulsion micellar solubilization (NMS_TAN), was based on the potentiometric titration of oil-in-water (O/W) nanoemulsions formed via the micellar solubilization of the acidic compounds of crude oil with KOH in propan-2-ol. The suitability of the method was evaluated by performance criteria selectivity, precision and accuracy. Finally, the NMS_TAN method was applied to the determination of TAN in fifteen crude oil samples (API gravity 13.2–38.3), and the results were statistically compared with the ASTM D664, ASTM D8045 and ABNT NBR 14448 methods. The method developed for determining salinity, called chloride direct determination (CDD) uses the preparation of O/W nanoemulsion to transfer and solubilize inorganic chlorides from crude oil into aqueous phase. Chloride quantification is performed directly by potentiometric titration without separating the phases. The CDD method was evaluated by performance criteria (precision and accuracy). The CDD method was applied to determine salinity in fifteen oil samples (API gravity 13.2 – 38.3), and the results were statistically compared with the ASTM D6470 method and counterion quantification (Na, Ca, and Mg) by flame atomic absorption spectrometry. Recovery of NMS_TAN method was in the range of 95.0 to 100.3%. The NMS_TAN method successfully determined the TAN of crude oil samples without interference from MgCl2 and CaCl2 salts present in the samples. The NMS_TAN method did not differ statistically of the methos ASTM D664 and ASTM D8045 methods for TAN determination in crude oil samples with CaCl2 and MgCl2 concentrations below 50 mg kg-1. The TAN of crude oil samples with high salt concentrations (>500 mg kg-1) obtained by the standard methods were 77–90 % higher than those determined by NMS_TAN. The NMS_TAN method presented results comparable to the Brazilian standard ABNT NBR 14448 for all samples, as the Brazilian method extracts the salts before the NAT analysis. For the salinity method (CDD method) the recovery was in the range of 97.1 - 109.2%. The CDD method shows no statistical difference from standard potentiometric and atomic absorption spectrometry methods (p < 0.05). However, the CDD method presented lower solvent consumption, shorter analysis time and operational cost when compared to common salinity methods. The NMS_TAN and CDD methods demonstrated comparable performance to traditional methods, offering advantages such as low cost, ease of operation, reduced solvent consumption and greater sustainability. The potential of the NMS_TAN and CDD methods to minimize environmental impact while maintaining accuracy and precision makes them valuable alternatives for the determination of NAT and salinity in oil with different characteristics.
Descrição
Palavras-chave
Número de acidez total (NAT) , Salinidade , Solubilização , Nanoemulsão óleo-água , Titulação potenciométrica