Estudo sobre a aplicação do paraformaldeido como indicador termometrico na determinação da acidez de petroleo e derivados

AUTOR(ES)

Graziella Ciaramella Moita

DATA DE PUBLICAÇÃO

1996

RESUMO

Several acidic constituents, such as carboxylic acids, phenolic compounds, inorganic acids, resins, salts and additives, are present in petroleum and petroleum products. The acidity of petroleum products depends of both, the petroleum origin and the process employed for the obtention of these products. In this case of some petroleum products, such as oils, greases and insulating mineral oils the acid number is employed to monitor the oxidation of these materials and to analyse the need of their substitution. The determination of acid number of these materials is performed by two standard methods based on visual and potentiometric titrimetry. The first method may only be applied to light-colored materials and the second method is subject to the noxious effect of organic solvents to glass electrodes. In this work an aItemative method for determination of the acidity of petroleum and petroleum products is proposed. lt is based in the titration of the acidic constituents of the materials by the technique of catalytic thermometric titrimetry by employing paraformaIdehyde as end-point indicator. The titrand solvent employed was the mixture toluene/2-propanol/water (10:10:0.1 v/v) and the titrant was a 0.1 mol/l KOH 2-propanol. The statistic analysis of the results of the application of the method shows that it is comparable to the standard methods. It may be employed in the case of colored substances, where visual indicators cannot be employed, and in the cases where potentiometric titration curves do not present adequate inflections to detect the end-point of titration. Moreover paraformaIdehyde being insoluble in the sample solvent, it does not affect the solubility of the samples. In this respect the method is advantageous in respect to other titrimetric methods based on the technique of catalytic thermometric titrimetry, by employing acetone and acrylonitrile as end-point indicators.

ASSUNTO(S)

solventes petroleo acidos

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