A Comparative Study of ATR-FTIR and FT-NIR Spectroscopy for In-Situ Concentration Monitoring during Batch Cooling Crystallization Processes

Crystallization is a widely used separation and purification process in the chemical industry. The final product properties such as the crystal size distribution and the morphology are largely defined during this process. In order to achieve proper control over the crystallization process, accurate in situ measurements are necessary. This paper presents the assessment of in situ infrared spectroscopic techniques for solute concentration measurements. It presents a comparative study of attenuated total reflectance (ATR), Fourier transform infrared (FTIR), and Fourier transform (FT) near infrared (NIR) spectroscopy for batch cooling crystallization of four different crystallization systems. These two techniques were compared based on the partial least square models developed by extensive calibration in the laboratory, the independent data sets generated while determining saturation concentrations in the presence of crystals and monitoring the batch cooling crystallization processes. The ATR-FTIR spectroscop...