Application of In Situ ATR-FTIR Sресtrоsсору for Determination of Wax Aрреаrаnсе Tеmреrаturе at High-Prеssurе СО2 Conditions

https://doi.org/10.1134/S0965544122100176

Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy was for the first time employed to investigate in situ paraffin crystallization under CO₂ high-pressure and to evaluate a critical parameter—wax appearance temperature (WAT). To determine the WAT under pressure, conventional calculation methods based on changes in the band of rocking vibrations of CH₂ group were used. Using model 10 wt % paraffin solutions in n-dodecane, temperature effects were investigated under CO₂ pressures of 10, 20, 30, and 40 atm. It was experimentally confirmed that an increase in the CO₂ pressure reduces the WAT. Furthermore, the plot of peak intensity of the spectral band attributed to dissolved CO₂ as a function of temperature showed a maximum that can serve as an additional WAT indicator. This enhances the measurement accuracy and the reliability of WAT evaluation.