Experimental and molecular simulation of carbon dioxide solubility in hexadecane at varying pressures and temperatures
Xiuyan Liu, Yahao Huang, Saeed Babaei, Bodhisatwa Hazra, Mehdi Ostadhassan
Abstract
• Raman spectroscopy revealed CO 2 solubility in hexadecane under PT conditions. • CO 2 solubility in hexadecane decreases with increasing temperature. • CO 2 solubility in hexadecane increases with increasing pressure. • Validated results with hybrid GCMC/MD simulations, achieving high accuracy. • Highlighted the importance of volumetric changes in solubility calculations. CO 2 -EOR can make underground storage efforts possible, addressing both energy demands and climate issues. This study establishes an in-situ method to measure the degree of CO 2 solubility in hexadecane in a wide range of P-T conditions. CO 2 and hexadecane with known volumes were mixed in silica capillaries and examined by Raman spectroscopy after reaching an equilibrium at certain P-T condition to establish a relationship between mole fraction of CO 2 in hexadecane and ratio of Raman peak area. Results showed that solubility of CO 2 decreases with increasing temperature and increases with pressure. Complementing the experimental data, hybrid grand canonical Monte Carlo/molecular dynamics (GCMC/MD) simulations were performed to study the swelling effect of CO 2 /hexadecane system and the diffusion of CO 2 within hexadecane. Simulation results were validated against Raman spectroscopy and previously published CO 2 solubility data, as well as a genetic algorithm-based (GA) predictive model, all matching with high accuracy and conforming each other. Based on molecular simulation results, the necessity of accounting for volumetric changes in solubility calculations to enhance the accuracy of predictive models in similar systems was revealed. Additionally, in contrast to temperature, the effect of pressure on the diffusion coefficient remains relatively minimal. Ultimately, this study provides solutions for in-situ probing techniques to determine the solubility of various fluids in a wide range of P-T conditions, processes supporting CO 2 -EOR and carbon storage operations underground.