METHOD FOR DETERMINING THE CONTENT OF HIGH MOLECULAR NAPHTHENIC ACIDS IN OIL (EMBODIMENTS) Russian patent published in 2023 - IPC G01N33/26 

FIELD: petroleum industry.

SUBSTANCE: present invention relates to the isolation, identification and determination of high molecular weight naphthenic acids present in crude oil. A method is disclosed for quantitative determination of the content of high molecular weight naphthenic acids of crude oil (HNA), including the isolation of naphthenic acids in order to remove impurities, esterification and quantitative determination of HNA by standard methods. To implement the method, a sample of crude oil is washed with an aqueous 70 vol.% solution of alkali in ethanol, impurities are extracted from the aqueous phase with petroleum ether or hexane, the organic phase is discarded, ethanol is evaporated from the aqueous-alcoholic solution and the pH is adjusted to 1-2. Then HNA is extracted with diethyl ether or hot 50-60°C by toluene, the solvent is evaporated, the presence of HNA is confirmed by mass spectrometry. The HNA is esterified with a mixture of dry methanol and methanol saturated with HCl vapor followed by purification on a low-pressure silica gel column chromatography using hexane as eluent. The eluate is evaporated to dryness, the mass of the residue is determined gravimetrically, and the HNA content is calculated according to the equation: С(HNA)= (m(esters)/V(esters))·0.94·1000, where C(HNA) is the content of high molecular weight naphthenic acids in oil (mg/l of oil), m(esters) is the mass of HNA esters obtained by weighing (mg); 0.94 is the correction factor for conversion to free HNA; V(oil) is the volume of the oil sample taken for analysis (ml), 1000 is the conversion factor per 1 litre. In the second embodiment of the method, at low concentrations of acids in the sample, the quantitative determination of the content of HNA is carried out using high performance liquid chromatography with mass spectrometry with electrospray ionization.

EFFECT: easy-to-implement preparation of a crude oil sample by HNA extraction, which significantly saves time and labour costs for analysis. The subsequent isolation of HNA esters by low pressure chromatography used in the method according to the first embodiment makes it possible to further reduce the cost of analysis.

2 cl, 1 dwg, 3 ex