Supercritical Antisolvent Micronization of Natural Carotene by the SEDS Process through Prefilming Atomization

Abstract

Natural carotene is micronized by the SEDS process through prefilming atomization (SEDS−PA) with the aim of evaluating the efficiency of prefilming atomization, examining the variation of carotene purity induced by the SEDS−PA process and studying the influence of operating variables on the particle size (PS) of the carotene precipitates. The carotene/dichloromethane solution to be atomized is driven through a liquid distributor with spiral slots in the prefilming atomizer as a thin film swirling at 45°. At the exit of the atomizer, the atomizing supercritical CO2 (SC-CO2) stream impinges on the film at 45°. Through the impingement and the use of swirling, the annular solution film is disintegrated into fine drops, and the mixing of the SC-CO2 and solution is intensified. Compared to the process in which solution is driven through the inner capillary of the atomizer while SC-CO2 is driven through its annular passage, the SEDS−PA process can obtain smaller droplets and finer microparticles with a narrower particle size distribution (PSD). After micronization by the SEDS−PA process, the purity of carotene microparticles is increased for unprocessed carotene with purity ranging from 30% to 87%, but it decreased for carotene with purity higher than 87%. The CO2 flow rate, solution flow rate, solution concentration, and pressure have marked influences on the particle size (PS), and the PSD broadens with increasing PS. Mechanisms that control PS are explained in terms of liquid atomization, agglomeration of particles, volumetric expansion of solution in SC-CO2, and nucleation and growth processes of particles. The dependence of the PS on temperature is not clear from all of the experiments performed.