Characterization of interfacial effects during reactive transport with MRI methods

The alkoxysilane tetramethylorthosilicate (TMOS) is soluble and chemically stable in oil. Nevertheless, when a mixture of oil and TMOS is brought into contact with water, the compound is transferred from the oil phase into the water phase where it undergoes hydrolysis and, subsequently, the products of the hydrolysis condense into a gel. The coupled mass transfer and gelation processes give rise to an intriguing motion of the interface between the oleic and the aqueous phases. This phenomenon was analyzed in detail both theoretically and experimentally. The theory was developed assuming quasi-static conditions and provides a non-linear second-order boundary value problem, which was treated numerically. The experiments were done using magnetic resonance imaging (MRI) to quantify the fluids in the oil and water phases and capture the interface profiles between the oil and the water phases at time intervals. The mass transfer is complete after several hours. An excellent fit of the theoretical interface profiles to the experimental ones at various times reveals that the interfacial tension increases gradually during the extent of the mass transfer.