| 摘要: | 熱力學性質對化工製程而言是很重要的資訊，Peng-Robinson+COSMOSAC狀態方程式(本文以PR+COSMOSAC表示之)已被證明可以提供純物質之熱力學性質與混合流體相行為可靠的預測結果，且不會有缺少參數的問題，在以COSMO為基礎之模型中，分子間相互作用力由QM/COSMO計算得到之分子表面電荷決定，在先前的文獻中已經證明COSMOSAC模型在預測流體相平衡時的準確度可能會受到使用之量子化學計算方法影響。
本研究探討使用不同量子化學計算軟體(ADF、DMol3和Gaussian)和不同計算方法(GGA-BP、VWN-BP、B3LYP和PM6)以及不同基組(TZP, DNP, and 6-31G(d,p)-cosmo)得到之QM/COSMO結果作為PR+COSMOSAC預測純流體之熱力學性質，如臨界性質和蒸氣壓，以及混合流體相行為，如氣-液相平衡和固體溶質於超臨界二氧化碳之溶解度，計算所需資訊得到之準確度，並將PR+COSMOSAC中使用之參數針對每種量子化學計算方法重新優化，可以發現不管使用哪種量子化學計算方法得到之QM/COSMO結果作為PR+COSMOSAC預測純流體之熱力學性質及雙成份氣-液相平衡計算所需資訊得到之結果都很接近，以ADF(GGA-BP/TZP)為例，純物質之蒸氣壓(ALD-P = 0.194)、純物質之昇華壓(ALD-P = 0.647)、純物質之臨界壓力(AARD = 8.00%)、純物質之臨界溫度(AARD = 4.20%)、純物質之臨界體積(AARD = 17.76%)、純物質之沸點(AAD = 14.11K)、雙成份氣-液相平衡(AARD-P = 21.97%、AAD-y = 7.90%)，而在預測固體溶質於超臨界二氧化碳之溶解度時，ADF(GGA-BP/TZP) (ALD-x = 0.95)與Gaussian(B3LYP/6-31G(d,p)-cosmo) (ALD-x = 0.85)可能會得到較好之預測結果。;Thermodynamic properties are important information for the design of chemical engineering processes. The Peng-Robinson+COSMOSAC equation of state, denoted as PR+COSMOSAC, has been shown to provide reasonable prediction for thermodynamic properties of pure substances and fluid phase behavior of mixtures without the issue of missing parameters. In COSMO-based models, the molecular interactions are determined from molecular surface charges obtained from the quantum mechanical and COSMO (QM/COSMO) calculations. It has been shown that the accuracy of the COSMOSAC model in predicting fluid phase equilibrium may be affected by the use of quantum chemical computation method in previous literature.
In this work, we investigate the accuracy of the PR+COSMOSAC in predicting thermodynamic properties of pure fluids, such as critical properties and vapor pressures, and fluid phase behavior of mixtures, such as vapor–liquid equilibria and solubility of solid solute in supercritical carbon dioxide, using different QM/COSMO results from different quantum chemical packages (ADF, DMol3, and Gaussian), computational methods (GGA-BP, VWN-BP, B3LYP, and PM6) and basis sets (TZP, DNP, and 6-31G(d,p)-cosmo). The values of parameters in the PR+COSMOSAC were re-optimized for each quantum chemical computation method. It is found that the prediction results of thermodynamic properties of pure fluids and vapor-liquid equilibria are very similar using different QM/COSMO results from different quantum chemical packages. Taking ADF(GGA-BP/TZP) as the example, vapor pressures of pure fluids (ALD-P = 0.194), sublimation pressures of pure fluids (ALD-P = 0.647), critical pressures of pure fluids (AARD = 8.00%), critical temperatures of pure fluids (AARD = 4.20%), critical volumes of pure fluids (AARD = 17.76%), boiling temperatures of pure fluids (AAD = 14.11K), vapor-liquid equilibria (AARD-P = 21.97% and AAD-y = 7.90%). However, the prediction results with ADF(GGA-BP/TZP) (ALD-x = 0.95) and Gaussian(B3LYP/6-31G(d,p)-cosmo) (ALD-x = 0.85) may be more accurate than the other quantum chemical computation methods in the solubility of solid solutes in supercritical carbon dioxide. |
