Experience of Using the Lazerokhim Densitometer to Determine the Densities of Water–Organic Reaction Media

The dependencies of the reaction mixture density on temperature are analyzed for the following processes: (1) catalytic CO2 hydrogenation and (2) conversion of phenol and cyclohexanol in sub- and supercritical water. Density measurements were performed using a Lazerokhim fiber-optic densitometer. The state of the waveguide end face surface after measurements at elevated temperature was analyzed by scanning electron microscopy (SEM). It was found that for nonaqueous reaction mixtures, the laser-optical density monitoring method is applicable in a wide range of temperatures and pressures. In the case of water and water–organic mixtures, correct determination of densities is possible only at temperatures of 25–190°C, since an increase in the temperature above 200°C leads to irreversible etching of the silicate optical waveguide end face surface by the aqueous fluid.