Effect of Premixed Asphaltenes and Demulsifier on Oil-Water Interfacial Properties

Probing the interactions between asphaltenes and a PEO-PPO demulsifier at oil-water interface: Effect of temperature

HYPOTHESIS

Asphaltenes are primary stabilizers in water-in-oil (W/O) emulsions that cause corrosion and fouling issues. In oil sands industry, oil/water separation processes are generally conducted at high temperatures. A high temperature is expected to impact the interactions between asphaltenes and emulsion breakers (EBs), consequently influencing demulsification performance.

EXPERIMENTS

The adsorption and interactions of asphaltenes and a PEO-PPO type EB (Pluronic F68) at the oil-water interface were investigated at various temperatures, using tensiometer, quartz crystal microbalance with energy dissipation (QCM-D), and atomic force microscopy (AFM). The effect of temperature on EB's demulsification performance was explored through bottle tests. Additionally, demulsification mechanisms were studied using direct force measurements with the droplet probe AFM technique.

FINDINGS

Dynamic interfacial tension and QCM-D results demonstrate that the PEO-PPO type EB exhibits higher interfacial activity than asphaltenes and can disrupt rigid asphaltene films at the oil-water interfaces. Elevated temperatures accelerate the displacement of adsorbed asphaltenes by EB molecules, leading to sparse interfacial films, rapid droplet coalescence, and improved demulsification efficiency (supported by AFM and bottle test results). This work provides valuable insights into interfacial interactions between asphaltenes and EB at different temperatures, enhancing the understanding of demulsification mechanisms and offering useful implications for the development of efficient EBs to enhance oil/water separation performance.

Adsorption of Asphaltenes at Model Oil/Brine Interface: Influence of Solvent Polarity

With the exploitation of heavy oil worldwide, the influence of asphaltene aggregation in the oil phase on the stability of crude oil emulsion has been paid more and more attention. Under this background, the effects of solvent polarity on model oil/brine water interfacial properties and emulsion stability are investigated in this study. It is demonstrated that there is a critical asphaltene concentration for the formation of a stable emulsion. This critical concentration is then found to increase from 80 to 500 ppm with the mixing ratio of methylnaphthalene to n-decane changed from 2:3 to 7:3. The dynamic light scattering experiment shows that the average aggregate size increases abruptly from 132.8 to 261.1 nm at 2:3 mixing ratio of methylnaphthalene to n-decane once the asphaltenes are added to above the critical concentration. Accordingly, the diffusion coefficient of the asphaltenes decreases sharply from 4.36 × 10-12 to 5.68 × 10-13 m2/s. Similar conclusions are also found for the other mixing ratios of 1:1, 3:2, and 7:3. Besides, the aggregation degree of asphaltenes weakens, and the diffusion coefficient enlarges at the same asphaltene concentration with the enhancement of the solvent polarity. Further, the interfacial experiments manifest that the equilibrium interfacial dilation modulus decreases from 38.42 to 23.65 mN/m with the mixing ratio of methylnaphthalene to n-decane increased from 2:3 to 7:3. It can thus be inferred that the structural strength of the interfacial film decreases with the enhancement of the solvent polarity.

Organosilicone Modified Styrene-Acrylic Latex: Preparation and Crude Oil Dehydration

When crude oil is dehydrated with conventional demulsifiers, the dehydration rate is low which cannot meet the existing treatment requirements. To solve this problem, in this paper, a non-polyether demulsifier (St-BA-AA) was synthesized with styrene (St), butyl acrylate (BA), and acrylic acid (AA) as monomers, vinyl triethoxy silane as modifier by emulsion polymerization, which was compounded with the conventional demulsifier (PAMAM). The influence of temperature, setting time, compound ratio, HLB, IFT of two different demulsifiers was investigated in detail. The HLB measurement indicated that the closer the proportion value of HLB to the crude oil, emulsifiers have a better ability of replacing natural emulsifiers. The IFT measurement showed that when the dosage of demulsifier was 100 mg/L, the oil/water interfacial tension reached its lowest point. By optimizing the operating condition, more than 99.6% (wt) water was removed from the crude oil.