Equilibria in Furfural-Water Systems under Increased Pressure and the Influence of Added Salts upon the Mutual Solubilities of Furfuraland Water

Abstract

Liquid-vapour equilibrium data are reported for the furfural-water system at pressures of 6.17, 7.85, and 9.83 kg. per cm². Under these pressures the system forms a homoazeotropic mixture differing only slightly in composition from the heteroazeotropic mixture formed at normal pressures. The data are checked by the calculation of activity coefficients. Abnormal activity coefficients are found for water in mixtures of high furfural content.

The equation

log₁₀ P= -2209/T + 7.959

fits published data and that now reported for t'he vapour pressure of furfural over the range of pressures 100 to 6,000 mm. Hg.

Changes in the mutual solubilities of furfural and water caused by the addition of metallic sulphates are determined. All the sulphates examined raised the critical solution temperat'ure, sodium sulphate being most effective. With magnesium sulphate there was a region of discontinuity, which may possibly be attributed to a change of phase or of hydration of magnesium sulphate.

The velocities of reaction (decomposition or polymerization) of furfural in aqueous and in aqueous acidic medium at 180°C. are reported. The data are used to estimate the amount of furfural lost by such reactions in a commercial process for the production of furfural. It is considered that the use of metallic sulphat'es in the commercial prociuotion of furfural should not influence the yield appreciably.