Oxygen absorption into stirred emulsions of n-alkanes

Abstract

Absorption of pure oxygen into aqueous emulsions of n-heptane, n-dodecane, and n-hexadecane, respectively, has been studied at 0 to 100 oil volume fraction in a stirred tank at the stirring speed of 1000min-1. The volumetric mass transfer coefficient, kLa, was evaluated from the pressure decrease under isochoric and isothermal (298.2K) conditions. The O/W emulsions of both n-dodecane and n-hexadecane show a kLa maximum at 1-2 oil fraction as reported in several previous studies. Much stronger effects never reported before were observed at high oil fractions. Particularly, all n-heptane emulsions showed higher mass-transfer coefficients than both of the pure phases. The increase is by upto a factor of 38 as compared to pure water at 50 n-heptane. The effect is tentatively interpreted by oil spreading on the bubble surface enabled by a high spreading coefficient. In W/O emulsions of n-heptane and n-dodecane kLa increases with the dispersed water volume fraction; the reason for this surprising trend is not clear. Copyright © 2012 Thanh Hai Ngo and Adrian Schumpe.