Aqueous Foam Stabilized by Hydrophobic SiO2 Nanoparticles using Mixed Anionic Surfactant Systems under High-Salinity Brine Condition

A primary concern of surfactant-assisted foams in enhanced oil recovery (EOR) is the stability of the foams. In recent studies, foam stability has been successfully improved by the use of nanoparticles (NP). The adhesion energy of the NP is larger than the adsorbed surfactant molecules at the air–water interface, leading to a steric barrier to mitigate foam-film ruptures and liquid-foam coalescence. In this study, the partially hydrophobic SiO₂ nanoparticles (SiO₂-NP) were introduced to anionic mixed-surfactant systems to investigate their potential for improving the foamability and stability. An appropriate ratio of internal olefin sulfonate (C_15-18 IOS) and sodium polyethylene glycol monohexadecyl ether sulfate (C₃₂H₆₆Na₂O₅S) was selected to avoid the formation of undesirable effects such as precipitation and phase separation under high-salt conditions. The effects of the NP-stabilized foams were investigated through a static foam column experiment. The surface tension, zeta potential, bubble size, and bubble size distribution were observed. The stability of the static foam in a column test was evaluated by co-injecting the NP-surfactant mixture with air gas. The results indicate that the foam stability depends on the dispersion of NP in the bulk phase and at the water–air interface. A correlation was observed in the NP-stabilized foam that stability increased with increasing negative zeta potential values (−54.2 mv). This result also corresponds to the smallest bubble size (214 μm in diameter) and uniform size distribution pattern. The findings from this study provide insights into the viability of creating NP-surfactant interactions in surfactant-stabilized foams for oil field applications.     

Krafft Point Prediction of Anionic Surfactants Using Group Contribution Method: First-Order and Higher-Order Groups

Krafft point is one of the key properties of anionic surfactants to indicate their solubility in an aqueous phase. Below the Krafft point, the surfactant is a useless solid. We have developed a prediction model for the Krafft point based on the Marrero and Gani Group Contribution (GC) concept. Literature data were analyzed and a new third-order level was proposed to improve the model accuracy. The Krafft points of 53 anionic surfactants were collected including alkyl sulfonate, alkyl sulfate, alkyl benzene sulfonate, alkyl ethoxy sulfate, alkyl ester sulfonate, alkyl ester sulfate, alkyl disulfate, alkyldiphenylether disulfonates, alkyl diester sulfonate, alkyl naphthalene sulfonate, and fluorocarbon surfactants. The coefficients of the fractional groups in a surfactant molecule reveal the dependence of the Krafft point on the internal structure. Compared to the more complicated models such as those based on advanced statistical concept, the GC model for the Krafft point developed in this work gives a higher accuracy with a simpler calculation.     

Anode butt cores: Physical characterization and reactivity measurements

Three industrial anode butts, with and without recycled butt material, were investigated in this study. Non-destructive x-ray tomography (x-ray CT) was used to enumerate the spatial distribution of density and porosity in the sample. Apparent and absolute densities, and air/CO₂ reactivities were measured as a function of the distance from the airburn side. The results from the x-ray CT and the physical properties measurement, when compared, showed a decrease in apparent density and an increase in absolute density and porosity from the center of the core to the surfaces. This work indicated that the main factors that derived the change in air and CO₂ reactivities of the anodes along the electrolytic surface to the airburn surface were the concentration of the inorganic contents and the porosity of the carbon material. For more information, contact Uthaiporn Suriyapraphadilok, The Energy Institute, Pennsylvania State University, 401 Academic Activity Building, University Park, PA 16802; (814) 863-0761; e-mail uzs101@psu.edu.