| 摘要: | 乙烯-正辛烯共聚物為現今重要的塑膠，線性低密度聚乙烯( linear low density polyethylene，LLDPE )的一種，在其生產程序中，乙烯在2,2,4-三甲基戊烷及正辛烯混合溶液中的溶解度將會影響聚合出來LLDPE性質，因此我們欲探討不同操作條件下，乙烯的溶解度情形，並使用熱力學模式進行關聯，以增加對未知條件下之預測能力。 本研究主要探討不同溫度、壓力下，乙烯在2,2,4-三甲基戊烷、正辛烯混合溶液之溶解度情形。實驗溫度為323.15 K、373.15 K及423.15 K，壓力範圍5 bar至25 bar，混合溶液中正辛烯含量為0 wt%至85 wt%。實驗方法採用壓力下降法，利用平衡槽之壓力變化判斷系統是否達平衡，為靜態式平衡法。實驗結果發現乙烯在上述混合溶液中的溶解度將隨壓力上升而增加，但隨溫度上升而下降；不同溫度下，2,2,4-三甲基戊烷與正辛烯混合溶液組成比例的不同對乙烯溶解度的影響情形將有所不同。 對於熱力學模式的關聯，我們選用Peng-Robinson 狀態方程式(PR EOS)並配合凡得瓦單一流體(vdW1)混合律及Zhong-Masuoka (Z-M)混合律兩種，計算方式採用泡點壓力計算法，進行數據關聯，以求得最佳化之雙成分交互作用參數。為了進行其他溫度的預測，我們將關聯所得的交互作用參數以溫度的線性關係表示，對於乙烯與2,2,4-三甲基戊烷雙成分系統，vdW1及Z-M混合律的交互作用參數與溫度具優異的線性關係；乙烯、2,2,4-三甲基戊烷與正辛烯三成分系統，vdW1混合律的交互作用參數隨溫度變化情形較難預測，而Z-M混合律的交互作用參數則是與溫度呈線性關係。我們以PR EOS配合vdW1及Z-M混合律進行關聯，結果皆相當精確，AAD值在5%內。 Ethylene-1-octene copolymer is one of important plastics today. In the producing process, the property of LLDPE is affected by the solubility of ethylene in 2,2,4-trimethylpentane and 1-octene mixtures. So this study was measuring the solubility of ethylene at different conditions, and correlating the solubility by thermodynamic model. The correlation parameters will be used to predict the solubility of ethylene of conditions when the experimental data are not available. In this study, the solubility of ethylene at various temperatures (323.15 K~423.15 K), pressures (5 bar~25 bar), concentration of 1-octene (0~85 wt%) were measured by a pressure decaying method. The results show that the solubility of ethylene increases with increasing pressure, decreases with increasing temperature. The solubility of ethylene in mixtures is affected by the composition of mixtures. The solubility data were correlated by the Peng-Robinson equation of state (PR EOS) with the van der Waals one-fluid (vdW1) and the Zhong-Masuoka (Z-M) mixing rules using bubble pressure calculation method with the binary interaction parameters, lij or kij. For predicting the solubility of ethylene in mixtures at other temperatures, the binary interaction parameters were showed linear relationship with temperature. For ethylene and 2,2,4-trimethylpentane binary system, the binary interaction parameters of vdW1 and Z-M mixing rules curve very linearly dependent on temperature. For ethylene, 2,2,4-trimethylpentane, and 1-octene ternary system, the binary interaction parameters of Z-M mixing rule have very good linear relationship with temperature, but not vdW1 mixing rule. Finally, PR EOS with vdW1 or Z-M mixing rules was used to correlate the experimental results with good accuracy. |
