Potentials for utilizing the solubility parameters in the design of single and mixed solvents for recycling used lubricating oils
Paint industry and coatings manufactures have long been utilizing the solubility parameter to correlate and predict the cohesive and adhesive properties of material from the knowledge of component properties. In this paper we are extending this application to the design of single and composite solvents for the recycling of used lubricating oils. In a previous study, we introduced a simple and practical technique to determine suitable design parameters for the solvent extraction to recover base oil from used lubricating oil. This technique based on a new parameter that we created and defined as the Anti-Solvency Energy (ASE). The ASE represents the solubility parameter difference between the solvent(s) and typical additives blended with the base oil to either enhance or suppress certain property recommended by the engine manufacturer. Our findings showed that the ASE correlates well with the experimentally measured percentage sludge removal (PSR) from the used oils after the extraction process. More importantly, the introduction of the ASE and the concept described in the aforementioned publication can be considered as useful tool to provide preliminary knowledge in designing an effective solvent extraction process for recycling used oils prior to any extensive and/or expensive experimental investigations. Nevertheless, the PSR is not the only parameter in determining the overall effectiveness of this process since the percentage oil losses in the sludge phase (POL) is also an important parameter for the technoeconomic feasibility of this process. The current study shows a correlation between the calculated solubility parameters difference of solvent and base oil (represented in energy units by a new parameter we named as the Solvency Energy (SE)) and the POL that measured experimentally. Three organic solvents, namely 1-Butanol, 2-Propanol and Methyl Ethyl Ketone, were used in the experimental investigations, to measure the solvent extraction performance at different temperatures and solvent to oil ratios. Similar to the ASE, the new term SE is correlating well with POL over a wide range of the extraction conditions. In this paper we also describing a method to optimize the design of a single or composite solvent for recycling used lubricating oil while considering both the PSR and the POL.