Application of In Situ ATR-FTIR Spectroscopy for Determination of Wax Appearance Temparature at High-pressure CO2 Conditions

Shalygin, A.S., Morozov, E.V. & Martyanov, O.N. Application// Petroleum Chemistry//

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.