Exploratory Pressure Impregnation Process Using Supercritical CO2, Co-Solvents, and Multi-Cycle Implementation

Abstract

Supercritical carbon dioxide (scCO2) is extensively used for extracting chemicals from materials, but the impregnation of materials with chemicals using scCO2 has received little attention in comparison. To the best of our knowledge, most technologies described in the literature operate by the principle of diffusion, where impregnation yield is limited by solubility. The objective of this exploratory study is to prove the feasibility of an scCO2 impregnation process that can extract solutes from one material and release them into another material through a single extraction/impregnation stage that can be applied in cycles to increase the yield. The feasibility of the concept was proven in the laboratory using radiata pine bark wax as the solute and radiata pine wood as the impregnated material. Extraction/impregnation tests were performed at temperatures between 40 and 60 °C, pressures between 12 and 16 MPa, and with the addition of ethanol and acetone as co-solvents. The study demonstrated the feasibility of multi-cycle scCO2 impregnation of wax into wood, where the novelty of the concept is the implementation as traditional pressure impregnation methods.