Distillation Principles of Formaldehyde Solutions

Cross determination of the vapor liquid equilibrium of formaldehyde aqueous solutions by quadrupole mass spectrometry and infrared diode laser spectroscopy

Quantitative measurements of the partial vapor pressure of formaldehyde are performed above aqueous H2CO solutions of different concentrations (from 10(-5) to 0.3 molar fraction) using mass spectrometry and IR diode laser spectroscopy. Both experimental techniques allow direct probing of the gas phase concentration collected at equilibrium above the aqueous solutions. A correlation is observed between the polymerization processes occurring in the solution and the partial pressure of H2CO measured at vapor liquid equilibrium (VLE). A similar correlation is observed from total pressure measurements for which the equilibrium vapor pressure decreases as [VLE XH2CO]liq is increased. A saturation regime of the H2CO partial pressure is reached as the dissolved fraction of formaldehyde increases above approximately 0.15 mol frac. Henry's law constants are derived at 295K for the diluted solutions.