Synthesis, Characterization, and Effects of Aliphatic and Aromatic Amines on Thermal and Surface Properties of Zwitterionic Amphiphiles

Solubility and thermal stability of surfactants are the key properties to consider for their possible oilfield applications. Most commercially available surfactants experience hydrolysis under high temperatures, and prolonged heating exacerbates this process, creating significant challenges for the petroleum industry. To address these complications, a novel class of propylamine and pyridinium-based zwitterionic surfactants was prepared, and their structures were confirmed using nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) spectroscopies. Salt tolerance tests were performed in distilled water, seawater, and formation water, while thermal stability was evaluated by using thermogravimetric analysis (TGA). Additionally, surface properties such as critical micelle concentration (CMC) and surface tension at the CMC (γ_CMC) were measured for these surfactants. The surfactants exhibit remarkable solubility in all types of water without any precipitation or cloudiness. TGA data demonstrated that the thermal decomposition temperatures for all of the newly prepared zwitterionic surfactants were around 300 °C, significantly greater than real reservoir temperatures. The CMC values range from 0.07 to 0.26 mmol L^-1, where the surface tension at the CMC (γ_cmc) ranges from 31.16 to 34.54 mmol/L. Moreover, low CMC values of zwitterionic amphiphiles containing a propylamine group in their core structure signify that they can make more tightly compact micelle structures than zwitterionic amphiphiles with a pyridine ring. This research fills the critical gap concerning the solubility and thermal stability of surfactants under harsh conditions by designing and evaluating these novel zwitterionic amphiphiles. The excellent solubility, thermal stability, and surface properties of the synthesized zwitterionic amphiphiles make them ideal choices for effective applications in challenging reservoir conditions, paving the way for enhanced oil recovery approaches.