Abstract
The goal of this article is to test the potential application of lignosulfonates (LSs) in crude oil production and processing. Three LS samples of varying hydrophobicity and average molecular weight were considered. First, the interfacial tension between brine and xylene and interfacial dilational rheology properties of LS samples were measured. It was found that the most surface-active LS sample has the lowest molecular weight in agreement with the results from the literature. In the presence of asphaltenes, all three LS samples were able to compete with asphaltenes, the most polar crude oil component, at the interface and form mixed LS–asphaltene interfaces. However, only the most surface-active LS sample among the three tested could fully desorb asphaltenes at the highest tested LS concentration (500 ppm). Second, three possible applications were screened. LSs were tested to prevent the formation of w/o crude oil emulsions or to break these. However, the opposite effect was observed, that is, stabilization of water-in-crude oil emulsions. The potential application of LS in produced water (PW) clarification was furthermore considered. The kinetics of PW clarification was found unaffected by the presence of LS, even at very high concentrations (1000 ppm). Finally, the potential of LS for enhanced oil recovery was assessed. The LS flood changed the surface wettability toward water wetness for one of the samples, yet LS injection did not recover additional oil beyond brine recovery. It was concluded that LS has interesting properties, such as the potential to compete with crude oil indigenous components at the oil/water interface. The stabilization action of LS was dominant over any destabilization effect, which led to the conclusion that LSs are more efficient for stabilizing emulsions rather than destabilizing.
Highlights
Lignosulfonates (LSs) are poly-branched anionic polymers, which are predominantly produced during sulphite pulping of wood
The slow kinetics is most likely related to the polydispersity in molecular weight and composition of LS samples which induces competitive adsorption between the different LS molecules
The three LS systems are compared by plotting the interfacial tension measured after 1 h of adsorption, with and without 0.5 wt % of asphaltenes (Figure 5)
Summary
Lignosulfonates (LSs) are poly-branched anionic polymers, which are predominantly produced during sulphite pulping of wood. As a result of condensation reactions during wood pulping, LS can exhibit a large range of molecular weight, that is, from 1000 to 150,000 g/mol,[1] and a high polydispersity index.[2] Alternate methods have been developed to modulate the chemical structure of LS especially in terms of degree of sulfonation, molecular weight, and functional groups.[3]. LSs have a different structure than classical surfactants They are poly-branched polyelectrolyte macromolecules with multiple hydrophilic and hydrophobic moieties. This property makes LS attractive as dispersants in various industries.[4] For example, LSs are used as plasticizers in concrete, carbon black dispersants, dyestuff dispersants, and emulsion and suspoemulsion stabilizers.[3,5,6]
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