Extraction of solid lanoline from raw wool with near-critical ethanol-modified CO2 —A mass transfer model

Abstract

This study deals with the modelling of the extraction of solid lanoline from raw wool under near-critical conditions using 5% ethanol in CO 2 , using our previous experimental data. A mass-transfer model is developed to explain the extraction results at T = 30ºC, below the melting point of lanoline (36-42ºC). Two variables are studied, the extraction pressure and the solvent mass flowrate. Our model depends on three parameters: the solubilities of the two lanoline fractions and the lanoline mass transfer coefficient. The model is a set of first-order partial differential equations, that is solved by orthogonal collocation in combination of optimization of the parameters. The fluid-side masstransfer coefficient decreases with extraction pressure and is about 5 x 10-6 m/s for Re < 1 (at 70-150 bar) and depends on fluid velocity. The solubilities of lanoline fractions, independent of flowrate, agree very well with those previously reported. Nomenclature: See end of the manuscript. 1.Introduction Lanoline is a natural wax secreted by the sebaceous glands of sheep that finds valuable applications in pharmacy and cosmetics [1-2]. Lanoline is traditionally obtained from raw wool by washing the sheep with water and soap. For pharmaceutical and cosmetic applications, however, it cannot be used directly, as it requires a complex purification process. An interesting alternative is to use a waterless washing with high pressure carbon dioxide, either neat [3,4] or modified with co-solvents [5,6], in the liquid state or as supercritical fluid. This paper focuses on the high pressure extraction of lanoline from raw wool under near-critical conditions with ethanol-modified CO 2 , using our previously published experimental results [6, 7]. Among the first authors to study SCF applied to lanoline extraction from raw wool are King and coworkers [3], Koo at al. [5] as well as New Zealand researchers [3]. These authors used neat CO 2 in their studies. Shortly later, we filed a patent [7] based on the fractionation of lanoline lipids using compressed CO 2 , using either raw wool or technical lanoline as a starting material, with a solvent based on modified CO 2 [7]. Solvent-modified CO2 under quasi-critical conditions is faster than neat CO2 [6,7] requiring less pressure and temperature. In the present paper, we specifically focus on the two lanoline fractions obtained in the process of Bayona et al. [7] and the evidence about their existence provided in our previous work [6]. Bayona found that there are two fractions: 1) A lanoline soluble in the cosolvent, that is highly polar and has a narrow molecular weight, and 2) Another lanoline fraction insoluble in the cosolvent, that has a wide molecular weight distribution. More recently, further characterization have been made [8-10].

Hybrid nonlinear autoregressive neural network—Weibull statistical model applied to the supercritical extraction of lanolin from raw wool

“…It is a reasonable behavior since both values are close and b increases as expected because of the profile of the curve. Solubility values obtained from the regressed equation (c'') agree very well too those found experimentally by Eychenne et al [5] for most of the operating conditions; besides, the first two regressions at 3 kg/h, are probably due to the lack of extracted fraction values at higher extraction times.…”

“…c'' is the solubility value obtained from Weibull distribution, while sol. is the solubility extracted from Eychenne et al [5].…”

“…Higher extraction yields were possible. Recently, we published an article dealing with the modeling of the extraction of solid lanolin from raw wool using modified CO 2 [5]. At 30 ºC, the lanolin is a solid (mp.…”

“…38-44 ºC) and the fluid is a liquid. For these conditions, extraction kinetics could be interpreted with the shrinking-core concept [5]. In this case, the pure solid lanolin covering the wool fibers is in direct contact with the fluid and is progressively dissolved by direct contact with the flowing solvent.…”

Modelling mass transfer from a packed bed by fluid extraction

“…The basic mathematical framework for extraction or erosion consists of a mass balance for the extract within the solvent coupled to a transfer model between the solid and solvent. In the context of column extraction various forms of this framework may be found in the literature, from coupling two differential equations [13], coupled mass balances in both the solid and fluid phases [7,14,15,16,17] to accounting for a moving solid-fluid interface representing the desorption of the material into the solvent [18,19,20,21,22,23,24]. Solutions are invariably numerical, via some form of discretization [14,15,21,23,18] or a polynomial approximation [19].…”