Mechanisms of Asphaltene Aggregation in Toluene and Heptane Mixtures

Abstract

The nature of aggregation kinetics of colloidal asphaltene particles in mixture of toluene and heptane was investigated by utilizing a polarizing microscope with appropriate magnification. The concentration of asphaltene in toluene _ heptane mixture varied from 1 g/l to 8 g/l. There are two main mechanisms associated with the aggregation process. These mechanisms are diffusion limited aggregation (DLA) and reaction limited aggregation (RLA). Each mechanism has its own characteristics and acts on limited values of asphaltene concentration. At the asphaltene concentrations below the critical micelle concentration (CMC), the DLA mechanism is dominant, while at concentrations above the CMC, at the initial stage of aggregation process, the RLA mechanism is observed and then the mechanism tends toward DLA (crossover behavior). It should be noted that the CMC for asphaltene in the solution is around 3 g/l.

On the effect of temperature on precipitation and aggregation of asphaltenes in light live oils

“…To mitigate the problems induced by asphaltenes, a thorough understanding of the mechanisms of asphaltene destabilization (aggregation/precipitation) as well as the effective related factors is essential . Asphaltene stability and the mechanisms of its precipitation and aggregation in crude dead oils or model oils have attracted substantial experimental and modelling research attention for several decades . These works are mostly limited to the synthetic asphaltenes extracted by addition of the saturated hydrocarbon solvents (e.g.…”

“…[10,11] Asphaltene stability and the mechanisms of its precipitation and aggregation in crude dead oils or model oils have attracted substantial experimental and modelling research attention for several decades. [1,[12][13][14][15][16][17][18] These works are mostly limited to the synthetic asphaltenes extracted by addition of the saturated hydrocarbon solvents (e.g. nC 5 or nC 7 ) at standard lab conditions.…”

Modelling asphaltene precipitation titration data: A committee of machines and a group method of data handling

“…Some previously published studies did not optimize the parameters of scaling models; therefore, they reported higher error for these models. Three well‐known scaling models for asphaltene precipitation titration data including Rassamdana et al, modified Rassamdana (Hu and Guo), and Ashoori et al, were used for comparison. Modified Rassamdana et al considered the effect of temperature in addition to other thermodynamic conditions.…”

“…Hu and Guo used the modified scaling equation by Rassamdana et al for Chinese crude oils and found that the modified scaling equation could accurately match the experimental data. Ashoori et al investigated the aforementioned scaling equations for extensive experimental data of precipitated asphaltenes from Iranian crude oils at different conditions. Afterward, they developed two different scaling equations for solvent to crude oil ratios higher and lower than 7.…”

“…Herein, we briefly summarize the most important intelligent models. In 2010, Ashoori et al proposed an artificial neural network (ANN) model for estimation of asphaltene precipitation titration data. Manshad and Keshavarz used fuzzy c‐clustering for estimating the amount of asphaltene precipitation.…”