Lubricant oils fractionation using liquefied gases (T219)

HEGEL, PABLO E.; RODRIGUEZ REARTES, SABRINA B.; M. S. ZABALOY

Nova Friburgo

Congreso; X Congresso Brasileiro de Termodinâmica Aplicada (CBTermo 2019); 2019

Universidade do Estado do Rio de Janeiro (UERJ)

Lubricant oils play an important role in different sectors from energy generation, metal-working and chemical production, to food/drink industry, and pharmaceutical laboratories. The elaboration of special lubricants for compressors, turbines, electronic devices, or medical purpose applications has strict composition regulations regarding the presence of residual monomers and oligomers that alter the final product quality. However, the removal of these non-desired minor compounds from the oily lubricants by classical vacuum distillation is difficult and expensive because of the high temperatures governing the process.In this work we study the fractionation of lubricant oils using liquefied CO2 + propane solvent mixtures under liquid-liquid-vapor phase equilibrium. CO2+propane solvents have shown interesting properties for extraction of viscous fluids regarding environmental aspects, high selectivity and non-flammability properties. To evaluate the technical feasibility of the technology proposed in this work, a synthetic oil mixture prepared from two commercial silicone oils (MW: 8000 and MW: 38000) is used as a model lubricant. The liquid-liquid-vapor phase behavior of the multicomponent system is studied in a high pressure view cell to set preliminary operating conditions. The effect of the different variables governing the separation process such as solvent composition (CO2/propane: 60/40 to 90/10) and temperature (T: 298 K to 323 K) are being studied to determine its effect on liquid partial miscibility. Then, a semi-batch liquid-liquid extraction process is carried out to evaluate the selectivity different CO2 + propane solvent mixtures. Results are pointing out liquefied gases with up to 30 wt.% propane exhibit partial liquid miscibility between silicone oils + solvent at 313 K turning feasible a liquid-liquid fractionation process. Preliminary extractions show liquefied gases with up to 30 wt.% propane are more suitable to fractionate silicone oils than pure CO2 or propane/CO2 liquified gases (18 wt.% propane) due to the lower operating pressures observed in the system and mainly the higher solvent power to carry out the fracitonation.