Extraction of Oil from Oil Sands Using Thermoresponsive Polymeric Surfactants

Abstract

Several thermoresponsive block copolymers constituted of a poly(ethylene glycol) (PEG) and a poly(2-(2-methoxyethoxy) ethyl methacrylate) (PMEO(2)MA) block were prepared by atom transfer radical polymerization (ATRP) and their ability to extract oil from oil sands was evaluated. The chemical composition of the PEG(113)-b-PMEO(2)MAX block copolymers was determined by H-1 NMR and gel permeation chromatography (GPC) with X-values ranging between 48 and 80. Aqueous solutions of block copolymers showed a cloud point of 34 +/- 1 degrees C as determined by turbidimetry and dynamic light scattering (DLS) measurements. DLS experiments indicated that these polymers formed stable block copolymer micelles due to association of the PMEO(2)MA blocks at temperatures greater than 45 degrees C with a unimodal distribution of hydrodynamic diameters. Since characterization of the block copolymer solutions as a function of temperature indicated the formation of hydrophobic domains in water for T > 45 degrees C, extractions of oil from oil sands with the block copolymers were conducted at T = 45 and 50 degrees C. At these temperatures, 15 mL of a 1 mg/mL PEG(113)-b-PMEO(2)MA(77) aqueous solution extracted 100% of the oil trapped in 1 g of oil sand if 60 mg of toluene was added to the mixture. When the extraction was conducted under the same experimental conditions without block copolymer, a poor oil recovery of less than 30% was achieved. Starting with a 1 mg/mL block copolymer concentration, the block copolymer aqueous solution could be recycled up to five successive extractions while maintaining satisfying oil recovery. Each extraction cycle led to a 22% mass loss of block copolymer, certainly due to association with the toluene, oil, and sand particles. Together these experiments demonstrate that thermoresponsive block copolymers can be powerful aids to enhance the oil recovery of oil sands.