Determination of the action type of hydrate formation inhibitors by their infrared spectra

In this paper, differences of infrared spectra of hydrate formation inhibitors of thermodynamic and kinetic action types were investigated. The method was proposed for determining the action type of a hydrate formation inhibitor by its infrared spectrum. The relevance of the proposed method is due to its expressiveness in comparison with the testing of inhibitors in laboratory tests. It is proposed to use the method of Fourier transform infrared spectrometry. The method allows us to obtain data on the molecular and intermolecular interactions of the substance under study. The spectra obtained in the mode of attenuated total reflection were analyzed by the principal component analysis and the regression method of projection on latent structures, which are related to chemometric methods of analysis and make it possible to identify the key features of the inhibitor compositions that affect the mechanism of their action. The separation of the sample of infrared spectra of the studied inhibitors into two subgroups, which represent two different types of inhibitor action, was obtained. The principal component analysis makes it possible to identify the key features of the compositions of reagents that affect the mechanism of their action. For kinetic inhibitors, a characteristic ratio of the amplitudes of vibrations of the –OH and N–H functional groups in the internal standard of the spectrum was revealed. It is shown that the decisive factor in the division of inhibitors into groups is the difference between the resonant vibration frequencies corresponding to the valence vibrations of C–O, C–N bonds and the resonant vibration frequencies of organofluorine compounds. At the same time, the similarity in the amplitude of the indicated spectral regions was noted. For the group of thermodynamic inhibitors, the most influential bands in the IR spectrum were the bands of symmetric and asymmetric stretching vibrations of the C–H bonds in the CH2 and CH3 groups. There was a significant increase in the amplitude in the spectral range of 2950–2750 cm–1 compared with the signal amplitude in the regions of 3300–3400 cm–1 and 1200–1100 cm–1, also found in the spectra of this group of inhibitors. The method of projection on latent structures was used to develop a regression model to determine the mechanism of action of the studied inhibitors. The proposed method allows for express determination of the action type of hydrate formation inhibitors. Results could be used in oilfield chemistry to determine the action type of hydrate formation inhibitors used to prevent the formation of gas hydrates during the production, preparation or transportation of hydrocarbons.