Mechanism Of Interaction Between The Subfractions Of Resins And Asphaltenes

Asphaltenes are responsible for problems such as deposition on the wells and pipping during production, coking around the coils of a heater in the refinery and so on, which causes heavy losses to the oil industry every year. Asphaltenes deposition is closely related with the stability of colloidal system of petroleum. Resins which are believed to act a necessary role in the stability of petroleum colloidal system play an important role in peptizing and dispersing asphaltenes in the petroleum. Thus, the objective of this study is to investigate the mechanism of the interaction between asphaltenes and resins further. First, the average molecular structure of resins and asphaltenes was analyzed,based on which the average molecular structure was obtained. Adsorption isotherm of two resins on two different asphaltenes surfaces and variations of the asphaltenes layer structure after adsorption and was obtained to investigate the dispersion of asphaltenes in homogeneous or heterogeneous subfractions of resins. And then Differential Scanning Calorimetry was carried out to characterize and quantify the interaction between asphaltenes and homogeneous or heterogeneous subfractions of resins. The results were as following:Though there is a little difference during the processes of the homogeneous or heterogeneous subfractions of resins adsorbed on two different asphaltenes, the adsorption capacity of heavy resins was greater than that of light resins. This result may be due to the differentials of the interaction between asphaltenes and subfractions of resins and interaction between different subfractions of resins is diverse. The mechanism of absorption can be explained by microporous penetration theory. The asphaltenes layer structure was broken, the distance of asphaltenes aromatic layer dm was increased and the number of aromatic layer M was decresed, which is caused by the penetration of homogeneous or heterogeneous subfractions of resins into some microporous on the asphaltenes surfaces after those resins adsorbed on asphaltenes. The crystalline parameter of asphaltenes after adsorbed by resins was obtained by X-Ray Diffraction which demonstrated the validity of the mechanism of microporous penetration theory further.The interaction energies calculated by Differential Scanning Calorimetry are in the order of-3~-18 kJ/mol. And the scope is includes in the interaction energies of hydrogen bongdings or dipolar interaction. Hence, subfractions of resins may interact with asphaltenes by means of hydrogen bongdings or dipolar interaction in the system of residual oil researched in the paper.