GAS-LIQUID MASS TRANSFER IN CYCLOHEXANE OXIDATION PROCESS USING GAS-INDUCING AND SURFACE-AERATION AGITATED REACTORS

摘要

The equilibrium solubilities: C*, and volumetric liquid-side mass transfer coefficients (k(L)a) for gaseous nitrogen and oxygen in liquid cyclohexane were obtained in wide ranges of pressures (1-40 bar), temperatures (380-480 K) and mixing speeds (13.3-20 Hz) in gas-inducing (CIR) and surface-aeration (SAR) agitated reactors. The C* values were calculated using a modified Peng-Robinson equation of state and the transient physical gas absorption technique was employed to obtain the mass transfer coefficients. The C* values for both N-2 and O-2 were found to increase with the solute gas equilibrium partial pressure and temperature. Under the same operating conditions, O-2 appeared to be more soluble in cyclohexane than N-2. The k(L)a values for the two gases were found tp increase strongly with mixing speed and slightly increase with pressure in both reactor types. k(L)a values for both gases appeared to slightly increase with temperature in the SAR while an opposite trend was observed in the GIR. k(L)a values for both gases in the GIR were higher than those in the SAR at higher mixing speeds (16.6 and 20.0 Hz). It appeared that k(L)a values in the SAR were controlled by the mass transfer coefficient, k(L), whereas those in the GIR were controlled by the gas-liquid interfacial area, a. The effect of gas nature on k(L)a values in bath reactors was insignificant. Two empirical correlations to predict k(L)a and gas holdup values for N-2 and O-2 in liquid cyclohexane in both reactor types with +/-30% accuracy were developed. (C) 1997 Elsevier Science Ltd. [References: 41]