Influence of Asphaltene Polarity on Crystallization and Gelation of Waxy Oils

Abstract

We report for the first time the results from a systematic investigation of how asphaltenes of different polarity affect crystallization and gelation of waxy oils. The more polar asphaltenes were found to be more aromatic in nature and more highly self-aggregated in the solvent. The presence of less polar asphaltenes in the waxy oil reduced the wax appearance temperature and wax precipitation to a greater degree compared to more polar asphaltenes, which was mainly attributed to the difference in the aggregation state of asphaltenes of different polarity. Reducing the polarity of asphaltenes present in the oil also resulted in a lower gelation temperature, lower storage modulus, and lower yield stress, which was probably because the less polar asphaltenes were more similar to wax on the molecular level and, thus, more readily interacting with wax. Notably, a 99% reduction in the yield stress was observed upon the addition of the least polar asphaltenes examined in the present work, in contrast to the 62% yield stress reduction upon the addition of the most polar asphaltenes. This observation may be of industrial significance because it suggests that the crude oil containing less polar asphaltenes may form a softer gel or deposit that is more easily broken or removed. Microscopic analysis showed that the wax crystals precipitated in the presence of less polar asphaltenes have a smaller aspect ratio.

Synergistic effect of magnetic field and nanocomposite pour point depressant on the yield stress of waxy model oil

“…Wax components in crude oil result in complex precipitation and crystallization behavior (Bai et al 2019;Guo et al 2004;Ganeeva et al 2016;Hassanzadeh et al 2018;Li et al 2018;Lim et al 2018;Wang et al 2019;Zhang et al 2013). In lowtemperature environment (e.g., deep water, polar region), the precipitated wax crystal forms three-dimensional network and may cause serious flow assurance problem such as coagulation, blockage and even rupture during pipeline transportation (Chevallier et al 2000;Pechook et al 2016;Visintin et al 2005).…”

“…In recent years, nanoparticle is selected to develop nanocomposite pour point depressant (NPPD) (AlSabagh et al 2016;Gao et al 2017;He et al 2016;Huang et al 2018Huang et al , 2019Norrman et al 2016;Song et al 2016;Tu et al 2018;Yang et al 2017;Yao et al 2018;Zhao et al 2018). Since the surface effect generated in nanometer dimension, nanoparticle possesses unique physical-chemical properties and has aroused tremendous attention in synthesizing various Edited by Xiu-Qiu Peng function materials (Guo et al 2004;Ganeeva et al 2016;Li et al 2018;Lim et al 2018;Zhang et al 2013). Research on NPPD's synthesis and application has been conducted in the modification of wax crystallization (AlSabagh et al 2016;He et al 2016;Huang et al 2019;Tu et al 2018).…”

A Stochastic Model for the Fractal Dimension Estimation of Asphaltenes Aggregation

“…Some copolymers can also modify the flow capacity in a pipeline without compromise a viscosity modification [7] by varying the alkali chains and producing a reduction of the aggregates even if the conditions of the system favor the precipitation process [8]. In general, the morphology of the crystalized solids is attributed to the polarity of the molecules involved in such a process [9]. At the macroscopic level, there are numerical simulation methods to estimate and predict the fluid flow and its behavior concerning other processes, e.g., heat exchanges [10].…”

Asphaltene fractionation based on adsorption onto calcium carbonate: Part 3. Effect of asphaltenes on wax crystallization

“…Asphaltenes have been reported to be natural PPDs by many authors [5,6,23,[25][26][27][28][29][30][31][32][33][34]. Still, the effect of asphaltenes has been discussed contradictorily [35].…”

“…Several authors have investigated the effect of asphaltene properties on wax crystallization by using either asphaltenes originating from different crude oils [24,29] or fractionated asphaltenes [4,6,34]. In two of these cases, asphaltene fractionation has been conducted by dissolving asphaltenes in dichloromethane (DCM) and inducing stepwise precipitation with pentane [34,41]. In one case, asphaltenes were fractionated on silica gel and via reverse phase chromatography [4].…”