Comprehensive Volumetric Property of Eco-Friendly Pressurized Fluids by Experimental, Theoretical Modeling, and MD Simulation for Sustainable Oil Extraction from Waste Rice Bran

Abstract

A comprehensive investigation into the densities of eco-friendly pressurized fluids, including pressurized biobased ethanol, CO 2 -expanded ethanol (CXE), and supercritical CO 2 (sc-CO 2 ), is notably lacking. This research gap covers experimental, theoretical modeling, and molecular dynamics (MD) simulations. Moreover, there is limited research on the extraction of rice bran oil (RBO). We have comprehensively investigated the densities of these pressurized fluids, employing a combination of experimental, theoretical modeling, and MD simulation approaches, combined with eco-friendly fluid techniques, to extract RBO from the waste biomass of rice bran. We have first developed a novel pulse response method with curve fitting for the simultaneous determination of density and diffusivity in pressurized fluids. Initially, density measurements were conducted for pressurized CO 2 and pressurized ethanol, showing strong agreement with literature data within 298.15−323.15 K and 1.97−25.09 MPa. Applying this method to CXE resulted in minimal deviation within 6.0−10.0 MPa at 313.15 K. Moreover, this study introduces new density data for CXE at 313.15 K. The data covers CO 2 mole fraction x 1 values from 0.18 to 0.88 at 15.0 MPa and from 0.4 to 0.95 at 20.0 MPa. These findings are significant, revealing density peaks near x 1 = 0.7 and providing valuable insights for the first time. Simultaneously, the experimental densities were successfully correlated using the semiempirical equation, while PC-SAFT EoS accurately represented the density. MD simulations cover pressurized CO 2 , pressurized ethanol, CXE, and sc-CO 2 densities over varied temperatures and pressures. The densities of CO 2 were simulated by using four models: Cygan, EPM2, TraPPE, and Zhang. EPM2 proves most accurate with an average absolute relative deviation (AARD) of 5.5%, outperforming the other models. Ethanol densities were replicated using the OPLS-AA model with an AARD of 5.5%. The novel ReaxFF and CPMD models exhibited excellent agreement for CXE, with AARD of 1.90 and 1.38%, respectively. Furthermore, CPMD performed extremely well compared with classical MD simulation and ReaxFF for all pressurized fluids, particularly near the critical point of CO 2 and the critical point of ethanol. Expanding on research into pressurized fluid properties, novel eco-friendly extraction methods employing pressurized ethanol, CXE, and sc-CO 2 have been developed for RBO extraction from rice bran. Notably, the pioneering CXE technique demonstrates outstanding results with a remarkable 0.23 yield ratio achieved at 313.15 K, 20.0 MPa, and x 1 = 0.7. These insights into pressurized fluid equilibrium and transport properties hold great potential for diverse environmentally friendly industrial applications.