Separation of Viscous Oil Emulsions Using Three-Dimensional Nanotetrapodal ZnO Membranes

Abstract

The steam-assisted gravity-drainage (SAGD) method has emerged as among the leading methods of enhanced oil recovery and is predicated on the injection of steam within the wellbore followed by extraction of emulsions of viscous oil and water. The emulsions are stabilized by endogenous surfactants, necessitating extensive processing such as addition of chemical de-emulsifiers and slow gravity-based separation methods. Here, we show that a hierarchically textured membrane exhibiting orthogonal wettability, specifically, superoleophilic but superhydrophobic behavior, allows for effective separation of the water and viscous oil fractions of SAGD emulsions. The membrane is constructed by integrating ZnO nanotetrapods onto stainless steel meshes using a conformal amorphous SiO 2 layer and is both mechanically resilient and thermally robust. The intrinsic surface energy characteristics of the ZnO tetrapods as well as their three-dimensional texture when arrayed atop the stainless steel mesh substrates contribute to the observed differential wettability between water and oil. Water content in permeated bitumen is reduced to as low as 0.69 vol % through a single-pass filtration step with the further advantage of eliminating silt particles. The permeation temperature and water content are tunable based on modulation of the mesh size and ZnO loading. The membranes allow for operation at SAGD temperatures in excess of 130 °C, thereby enabling the thermal disruption of hierarchical emulsions. The membrane-based separation of SAGD emulsions under realistic process conditions paves the way for entirely new process designs for recovering dry viscous oil.

Three-Dimensional Inverse Opal TiO2 Coatings to Enable the Gliding of Viscous Oils

“…The coating scores 5B in ASTM 3359 and can withstand scrape testing up to 20–30 g in ASTM 2197. In other formulations, we have seen significant improvement in the stability upon deposition of an amorphous SiO 2 layer (>1 kg in ASTM 2197). , The coatings are thus suitable for applications in nonabrasive environments.…”

“…For instance, liquid-impregnated coatings show promising performance but are readily damaged and difficult to scale; lithographically patterned architectures provide precise control of re-entrant curvature, but their elaboration to macroscopic scales remains challenging; polymeric coatings, such as block copolymers, enable definition of tailored chemical domains but have inadequate thermal stability and are prone to fouling. In previous work, we have demonstrated the promise of ceramic/metal coatings comprising ZnO tetrapods sprayed onto metal mesh surfaces; surface functionalization of the tetrapods yields hydrophobic/oleophobic, hydrophilic/oleophobic, or hydrophobic/oleophilic , character, enabling applications ranging from gliding of viscous oils to the separation of recalcitrant water/oil emulsions. The ZnO tetrapods serve to amplify the intrinsic wettability of the surface monolayers and yield 3D interconnected plastronic architectures that extend into the pores of the metal meshes, with the meshes additionally providing periodic micron-scale texture.…”

Superhydrophobic Stainless-Steel Mesh with Excellent Electrothermal Properties for Efficient Separation of Highly Viscous Water-in-Crude Oil Emulsions

“…Despite achieving big achievement in emulsion separation, few of them are applicable for the separation of viscous water-in-crude oil emulsions. , This is because of the high viscosity of crude oil, which always causes a slow diffusion of viscous crude oil into the membrane pores. More seriously, the high viscosity and adhesive property result in a low permeation rate, pores fouling, and inefficient separation and even lead to the invalidation of related instruments. , In addition, the fabrication process of such superhydrophobic membranes is rather complicated. , Therefore, it is urgent to develop a facile and efficient superhydrophobic separation membrane to decrease the viscosity, thus enhancing the fluidity of emulsions for achieving separation of viscous water-in-crude oil emulsions.…”

“…More seriously, the high viscosity and adhesive property result in a low permeation rate, pores fouling, and inefficient separation and even lead to the invalidation of related instruments. 23,24 In addition, the fabrication process of such superhydrophobic membranes is rather complicated. 25,26 Therefore, it is urgent to develop a facile and efficient superhydrophobic separation membrane to decrease the viscosity, thus enhancing the fluidity of emulsions for achieving separation of viscous water-in-crude oil emulsions.…”

Functionalized Tetrapodal ZnO Membranes Exhibiting Superoleophobic and Superhydrophilic Character for Water/Oil Separation Based on Differential Wettability

“…Current limitations in processing of mixed water/oil streams and remediation of oil spills include low separation efficiencies, generation of secondary pollutants from sloughing of sorbent materials, need for energy-intensive processes, high cost, and potential ecological toxicity of membrane materials. Considerable recent attention has been focused on the design of membranes for realizing water/oil separation based on differential affinity, density, flow characteristics, and wettability. ,,, In a previous work, we have demonstrated the design of superoleophilic and superhydrophobic membranes comprising ZnO nanotetrapods integrated onto stainless steel meshes. , The membranes permit the high-efficiency separation of water/oil emulsions, including challenging viscous oil emulsions stabilized by endogenous surfactants extracted from the Alberta oil sands using the steam-assisted gravity drainage (SAGD) process. Notably, such membranes are fully compatible with the high-temperature operation required to crack the emulsions .…”