Synthesis, Characterization, and Evaluation of Petroleum Demulsifiers of Multibranched Block Copolymers

A series of multibranched block copolymers was synthesized by means of anionic ring opening polymerization (AROP) techniques, using different alkoxide salts obtained from molecules that present different numbers of alcohol functions as initiators. Propylene oxide (PO) and ethylene oxide (EO) were polymerized in two steps, with the intent of obtaining multibranched block copolymers (PO/EO) with demulsifying activity in petroleum. The characterization of the polymers was done by means of size exclusion chromatography (SEC), Fourier transformed infrared spectroscopy (FTIR), carbon-13 nuclear magnetic resonance (C-13 NMR), and thermogravimetric analysis (TGA). A theoretical study by semiempirical AM1/NDDO has been carried out in order to explain the growth of multiple branches from the initiators during the early stages of the anionic polymerization. These simulations revealed complex patterns of polymer growth and increasing polydispersities when initiators with a greater number of active sites were employed to start the reactions. Afterward, the water removal efficiency, as a function of the number of copolymer branches, was evaluated through bottle tests in two crude oils: a heavy crude oil with 12.71 degrees API and an extra-heavy crude oil with 9.68 degrees API, with a water content of 47 and 39 vol %, respectively. A complex and nonlinear behavior of the water removal, as a function of the number of the block copolymer branches, was observed.