Quinoline impact on composition, structure and aggregative stability of asphaltenes from heavy oil of different chemical types

Relevance. The need to establish the true mechanisms of the formation of supramolecular structures in petroleum dispersed systems. It is important to identify the role of individual functional groups in asphaltene aggregation. This will help develop effective ways to prevent sediment formation in process equipment during production, transportation and processing of heavy oils. Aim. To study the effect of quinoline on the composition, structure and aggregative stability of asphaltenes from heavy oils of various chemical types. Objects. Heavy oils from the Zyuzeevskoe field and the Usinskoe field; model petroleum systems with a basic nitrogen content of 1,0 to 3,0 wt %; asphaltenes of the original and model petroleum systems. Methods. Liquid adsorption chromatography, gas chromatography-mass spectrometry, potentiometric titration, elemental analysis, cryoscopy in naphthalene, 1H NMR spectroscopy, structural group analysis, spectrophotometry. Results. With an increase in Nbas concentration in an petroleum system to 3 wt %, the content of asphaltenes decreases regardless of the type of petroleum system. It has been established that quinoline is actively involved in the formation of supramolecular structures of naphthenic type oil. With an increase in the Nbas content in the naphthenic petroleum system to 3 wt % the molecular weight of asphaltenes increases 1,5 times with a 2-fold increase in the proportion of basic nitrogen in their composition. This is accompanied by an increase in the proportion of naphthenoaromatic structure in the average asphaltene molecule. The structure of asphaltenes isolated from model methane-type petroleum systems, on the contrary, is enriched in alkyl fragments. It wasn established that the presence of quinoline in asphaltenes of heavy oils as a coprecipitated component significantly reduces their aggregative stability. With an increase in the molecular weight of asphaltenes in naphthenic petroleum systems to 2000 amu. and the proportion of basic nitrogen up to 2,69 wt % the rate of their aggregation before precipitation is reduced by 5–6 times. The aggregative stability of methane oil asphaltenes decreases when Nbas content in their composition is higher than 1,9 wt % and does not depend directly on their molecular weight.