Accuracy of Several Cubic Equations of State for Predicting Vapor Pressures Using Critical Properties from Experimental Constants, PR+COSMOSAC-Based Constants, and Full PR+COSMOSAC Calculations

Sulfur-containing compounds can be emitted from multiple sources, but there is often minimal physical property data for those compounds. Using established computational methods, we calculated the physical properties of compounds and the radiative efficiency of compounds to determine if a compound could be a greenhouse gas. Using physical properties, like critical temperature and pressure, and acentric factor, the vapor pressure of a molecule can be calculated using cubic equations of state. We compared the use of equations of state with experimental and predicted (PR + COSMOSAC) physical properties, combined with direct PR + COSMOSAC calculations for vapor pressure. Equations of State (EOS) calculations based on experimental data yielded an average percent error, with ranges of 15.7%, 16.0%, and 154.3% using the Peng-Robinson (PR), Soave-Redlich-Kwong (SRK), and Redlich-Kwong (RK) EOS methods, respectively. For PR + COSMOSAC, predicted physical properties had average percent errors of 38.1%, 36.0%, and 107.9% for PR, SRK, and RK, respectively. In comparison, the PR + COSMOSAC direct prediction for vapor pressures had an average percent error of 34.5%. From our calculations, based on the EPA's definition for volatile organic compounds, all sulfur-containing species researched here are classified as volatile organic compounds (VOCs) and will become greenhouse gases. In combination with the VOC classification, sulfur-containing species were found to have higher-than-average radiative efficiency when compared to prior work on other compounds. The combination of these factors highlights sulfur-containing species as a focus for further study in terms of atmospheric lifetime, aerosol formation, and volatility validation, since these compounds may be greenhouse gases.