Alkylacrylic-carboxyalkylacrylic random bipolymers as demulsifiers for heavy crude oils

Abstract

This paper explains and analyses the process where two series of acrylic random bipolymers, based on alkyl acrylate/carboxyalkyl acrylate (KC) and alkyl acrylate/acrylic acid (KA), were prepared by means of emulsion polymerization technique. In both, the bipolymers’ monomers ratio was varied, while holding the more hydrophobic monomer in majority. The KC and KA bipolymers were characterized by nuclear magnetic resonance (NMR), infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and size exclusion chromatography (SEC). Afterwards, demulsifying activity of the KC and KA bipolymers in two heavy crude oils was evaluated through bottle tests. According to the obtained results, the selection and determination of weight ratio of monomers have an important impact on the bipolymers efficiency to destabilize the water/crude oil emulsion. In both crude oils, KC bipolymer with a monomer ratio of K/C = 80/20 w/w showed the best demulsifying performance in comparison with KA bipolymer at the same weight ratio. Structure-activity parameters including partition coefficient (Log P), hydration energy (HE), molar refractivity (MR), and polarizability (α) were calculated for both bipolymers. The destabilization effectiveness of bipolymers of the water/crude oil interface was found to be related to the partition coefficient (Log P), which indicated a strong diffusion capacity of the bipolymer to traverse through the oil phase and destabilize the water/oil interface. Furthermore, higher values of molar refractivity and polarizability are preferable for higher water removal efficiency (WRE). Moreover, the structure–activity parameters, as well as the quantum parameters, specific characteristics of acrylic bipolymers and some physicochemical properties of the crude oil were deployed in the process to predict the water removal efficiency. E2 equation which accomplished the external validation acted as the resultant of the two equations, E1 and E2, that fulfilled the restriction for the internal validation of Q2 > 0.6. Predictive squared correlation coefficients (QF12,QF22, and QF32) and external validation metric parameter (rm2) were calculated based on E2. Consequently, the new alkylacrylic-carboxyalkylacrylic bipolymers, insusceptible to acid environment, showed significantly improved properties as emulsion breakers, drop coalescers, and clarifiers.