醋酸甲酯 - 甲醇 - 水三元物系液液平衡數(shù)據(jù)的測(cè)定與關(guān)聯(lián)-

1、醋酸甲酯2甲醇2水三元物系液液平衡數(shù)據(jù)的測(cè)定與關(guān)聯(lián)邱挺1,馬沛生2,王良恩1,鄭輝東1(1.福州大學(xué)化工系,福建福州350002; 2.天津大學(xué)化工學(xué)院,天津300072摘要:測(cè)定了常壓下20、30、40、50時(shí)醋酸甲酯2水二元體系及醋酸甲酯2甲醇2水三元體系的液液平衡(LLE 數(shù)據(jù),并與文獻(xiàn)中已有的醋酸甲酯2水的液液平衡數(shù)據(jù)進(jìn)行比較,證明了測(cè)定方法的可靠性。采用二元與三元液液平衡數(shù)據(jù)相結(jié)合的關(guān)聯(lián)方法,并用NRT L 和UNI QUAC 模型對(duì)所測(cè)數(shù)據(jù)進(jìn)行了熱力學(xué)關(guān)聯(lián),得出了相應(yīng)的模型參數(shù)。用該模型對(duì)三元體系進(jìn)行計(jì)算,結(jié)果令人滿意。用Visual Basic 6.0語(yǔ)言開(kāi)發(fā)了液液相平衡關(guān)聯(lián)軟件

2、,可方便地用于二元和三元液液相平衡的計(jì)算。關(guān)鍵詞:醋酸甲酯;甲醇;水;液液平衡;關(guān)聯(lián);軟件中圖分類號(hào):T Q 031.1文獻(xiàn)標(biāo)識(shí)碼:A 文章編號(hào):100529954(20040420062205Determination and correlation of liquid 2liquid equilibrium datafor the methyl acetate 2methanol 2w ater ternary systemQIU Ting 1,MA Pei 2sheng 2,WANG Liang 2en 1,ZHENG H ui 2dong 1(1.Department of Chemi

3、cal Engineering ,Fuzhou University ,Fuzhou 350002,Fujian Province ,China ;2.Institute of Chemical Engineering ,T ianjin University ,T ianjin 300072,China Abstract :LLE (liquid 2liquid equilibrium data were determined for the methyl acetate 2methanol 2water ternary system and the related methyl aceta

4、te 2water binary system at 20,30,40and 50under atm ospheric pressure.The experimen 2tally determined LLE data for the binary system were in satis factory agreement with available literature data.The experi 2mental data were correlated by the activity coefficient m odels of NRT L and UNI QUAC ,and th

5、e com paris on between cal 2culated and experimental data shows g ood agreement.The s oftware of LLE C orrelation and Calculation was developed by Visual Basic 6.0,which can correlate and calculate LLE data of the binary and ternary system conveniently.K ey w ords :methyl acetate ;methanol ;water ;l

6、iquid 2liquid equilibrium ;correlation ;s oftware在聚乙烯醇(PVA 生產(chǎn)過(guò)程中,副產(chǎn)大量的醋酸甲酯(MeOAc 。醋酸甲酯沒(méi)有很大的工業(yè)價(jià)值,一般的維尼綸廠都把MeOAc 水解生成醋酸和甲醇,但水解率只能達(dá)到23%25%。近年來(lái),催化精餾技術(shù)以其獨(dú)特的優(yōu)點(diǎn)成為MeOAc 水解的首選技術(shù),王良恩領(lǐng)導(dǎo)的課題小組已在福建紡織化纖集團(tuán)有限公司首家實(shí)現(xiàn)工業(yè)化。為了進(jìn)一步提高M(jìn)eOAc 催化精餾的水解轉(zhuǎn)化率,在完成了該體系的汽液平衡研究1的基礎(chǔ)上,對(duì)該體系進(jìn)行液液平衡系統(tǒng)性的研究是很有必要的。它不但可以為催化精餾塔的設(shè)計(jì)以及模擬計(jì)算、水解產(chǎn)物的分離提純提供

7、基礎(chǔ)數(shù)據(jù)和熱力學(xué)模型,而且有助于深入了解精餾塔內(nèi)的傳質(zhì)特性,從而改進(jìn)催化精餾技術(shù),提高水解率。但前人對(duì)該體系的液液平衡研究很少,文獻(xiàn)中僅能找到部分互溶的醋酸甲酯2水二元物系2。本文用改進(jìn)的液液平衡釜測(cè)定了常壓下醋酸甲酯(12甲醇(22水(3三元LLE 數(shù)據(jù),為與文獻(xiàn)值進(jìn)行比較,也測(cè)定了醋酸甲酯2水的二元LLE 數(shù)據(jù)。本文采用適用于LLE 的NRT L 和UNI QUAC 模型對(duì)實(shí)驗(yàn)數(shù)據(jù)進(jìn)行關(guān)聯(lián),利用可視化語(yǔ)言Visual Basic 6.0開(kāi)發(fā)出液液相平衡關(guān)聯(lián)和計(jì)算的應(yīng)用軟件。作者簡(jiǎn)介:邱挺(1974,男,博士,主要從事化工分離工程方面的研究,E 2mail :tingqiu 。第32卷第4期

8、2004年8月化學(xué)工程CHE MIC A L E NGI NEERI NG (CHI NA V ol.32N o.4Aug.20041實(shí)驗(yàn)部分1.1實(shí)驗(yàn)試劑水為福州大學(xué)國(guó)家化肥催化劑中心制備的去離子水;甲醇為AR 級(jí)試劑,摩爾分?jǐn)?shù)不低于99.5%,齊齊哈爾輕工學(xué)院試劑廠生產(chǎn);醋酸甲酯為AR 級(jí)試劑,摩爾分?jǐn)?shù)不低于98.0%,上海試劑一廠生產(chǎn)。上述試劑均經(jīng)精密精餾柱提純。醋酸甲酯提純中加入醋酐、碳酸鉀、五氧化二磷以除去雜質(zhì)醇、酸、水。提純中截取頂溫恒定部分餾分,經(jīng)色譜分析均無(wú)雜峰。1.2實(shí)驗(yàn)裝置液液平衡釜由浙江大學(xué)提供;溫度計(jì)為1/10刻度水銀溫度計(jì);501型超級(jí)恒溫水槽和K F 24型低溫浴槽

9、聯(lián)合控溫,波動(dòng)不超過(guò)±0.05;磁力攪拌器攪拌。1.3分析方法采用美國(guó)瓦里安公司VARI AN CP 23800氣相色譜儀進(jìn)行樣品定性定量分析。用相對(duì)保留時(shí)間來(lái)定性測(cè)定,醋酸乙酯作為內(nèi)標(biāo)的內(nèi)標(biāo)法進(jìn)行定量分析。氣相色譜儀的操作條件:氫焰離子檢測(cè)器(FI D ;毛細(xì)柱<0.25mm XP 21701;氫氣流量20m L/min ,空氣流量20m L/min ,氮?dú)饬髁?5m L/min ;柱溫50保持1min ,20/min 升溫3min ,110保持1min ;進(jìn)樣口溫度130,檢測(cè)器溫度200。1.4實(shí)驗(yàn)方法當(dāng)體系達(dá)到液液相平衡時(shí)沒(méi)有能夠直接觀察到的現(xiàn)象,經(jīng)過(guò)驗(yàn)證:對(duì)于該體系,

10、快速攪拌1h ,慢速攪拌0.5h ,再靜置2.5h 即可達(dá)到平衡。實(shí)驗(yàn)時(shí),往平衡釜中加入一定質(zhì)量的各個(gè)組分,并使分層位置處于取樣口中部,控制體系溫度為所需溫度,然后開(kāi)始上述操作使之達(dá)到平衡,分別取上下層溶液進(jìn)行分析。由于該三元體系的二相區(qū)較小,因此采用多次測(cè)定取平均值來(lái)減少誤差。1.5實(shí)驗(yàn)結(jié)果常壓下測(cè)定了20、30、40、50醋酸甲酯(12水(3二元物系及醋酸甲酯(12甲醇(22水(3三元物系的液液平衡數(shù)據(jù),所得結(jié)果見(jiàn)表1、表2。從表中可以看出,水相的x 1測(cè)定值與文獻(xiàn)值相對(duì)偏差較大,這是由于x 1很小,相對(duì)實(shí)驗(yàn)誤差較大。表1醋酸甲酯(12水(3二元體系液液平衡實(shí)驗(yàn)數(shù)據(jù)T ab.1LLE da

11、ta of methyl acetate (12water (3溫度/水相中x 1有機(jī)相中x 1測(cè)定值文獻(xiàn)值偏差相對(duì)偏差%測(cè)定值文獻(xiàn)值偏差相對(duì)偏差%200.07780.07290.0049 6.720.75980.7400.0198 2.68300.07070.06670.0040 6.000.72080.6940.0268 3.86400.06860.06610.0025 3.780.64170.642-0.00030.47500.06670.0688-0.00213.050.63450.6270.00751.20表2醋酸甲酯(12甲醇(22水(3體系液液平衡實(shí)驗(yàn)數(shù)據(jù)T ab.2LLE da

12、ta of methyl acetate (12methanol (22water (3溫度/編號(hào)水相有機(jī)相x 1x 2x 3x 1x 2x 32010.07710.00200.92090.75150.00620.242320.10670.03590.85740.68510.03500.279930.13150.05330.81520.63350.04410.322440.15840.06280.77880.49660.07170.431750.20630.07060.72310.37440.07240.55323010.07760.00230.92010.71320.00510.281720

13、.11690.03220.85090.59430.03940.366330.14960.04460.80580.55470.04860.396740.18830.05730.75440.41620.06870.515150.20790.06480.72730.32940.07520.599436邱挺等醋酸甲酯2甲醇2水三元物系液液平衡數(shù)據(jù)的測(cè)定與關(guān)聯(lián)續(xù)表2溫度/編號(hào)水相有機(jī)相x1x2x3x1x2x34010.08340.00490.91170.63400.00670.359320.10460.02480.87060.51180.02900.459230.11370.03230.85400.43

14、870.03680.524540.15860.04580.79560.30810.05790.634050.19510.05450.75040.27760.05690.6655 5010.08870.00280.90850.62990.00420.365920.10410.01340.88250.53640.01630.447330.14420.02980.82600.46170.03750.500840.19190.04620.76190.31830.05010.631650.21950.05080.72970.29240.05040.65722數(shù)據(jù)處理醋酸甲酯2甲醇2水三元體系屬于只含一對(duì)

15、部分互溶的體系,而且從實(shí)驗(yàn)數(shù)據(jù)可以看出這個(gè)體系的二相區(qū)是比較小的。因此僅從二元相平衡數(shù)據(jù)或三元LLE數(shù)據(jù)來(lái)關(guān)聯(lián)均會(huì)存在較大的誤差。因此本文采用二元和三元數(shù)據(jù)相結(jié)合的方法3對(duì)實(shí)驗(yàn)數(shù)據(jù)進(jìn)行關(guān)聯(lián),即用二元LLE數(shù)據(jù)關(guān)聯(lián)部分互溶對(duì)參數(shù),然后用三元LLE數(shù)據(jù)關(guān)聯(lián)完全互溶對(duì)參數(shù)。對(duì)于液液相平衡數(shù)據(jù)利用活度系數(shù)模型進(jìn)行關(guān)聯(lián),屬于非線性多變量函數(shù)的最優(yōu)化問(wèn)題。采用單純形法4求解模型的最佳參數(shù),采用的活度系數(shù)模型為NRT L方程和UNI QUAC方程。2.1二元LLE數(shù)據(jù)的關(guān)聯(lián)由相平衡原理,可得LLE方程:x ii=x iii=1,3(1式中,x為水相摩爾分率,為水相活度系數(shù),x為油相摩爾分率,為油相活度系數(shù)。

16、兩邊取對(duì)數(shù),經(jīng)整理可得lni-lni-ln(x i/x i=0(2然后根據(jù)測(cè)得的醋酸甲酯(12水(3部分互溶的實(shí)驗(yàn)數(shù)據(jù),以及相應(yīng)的活度系數(shù)模型利用非線性最小二乘法來(lái)求解模型參數(shù)。2.2三元LLE數(shù)據(jù)的關(guān)聯(lián)由于前面已經(jīng)得到了醋酸甲酯(12水(3二元系的模型參數(shù),因此對(duì)于醋酸甲酯(12甲醇(22水(3三元體系,另2對(duì)模型參數(shù)均由三元液液平衡數(shù)據(jù)關(guān)聯(lián)得到。根據(jù)文獻(xiàn)5建議,ij 均取0.2,OF為目標(biāo)函數(shù)6,利用單純形法迭代求取最佳模型參數(shù)。其優(yōu)化得到的模型參數(shù)見(jiàn)表3。OF=Nk=13 i= 1K實(shí)ik-K計(jì)ikK實(shí)ik2(3N(3式中:K計(jì)ik=ik/ik,K實(shí)ik=x ik/x ik,K為分配比,

17、 k為數(shù)據(jù)組,N為總數(shù)據(jù)組。表3醋酸甲酯(12甲醇(22水(3三元物系NRT L和UNIQUAC模型參數(shù)T ab.3NRT L and UNI QUAC m odel parameters for methyl acetate(12methanol(22water(3system 溫度/NRT L模型參數(shù)/(Jm ol-120g12=7338.7g21=-2244.8g23=-6847.1g32=18750.0g13=1271.9g31=6247.930g12=7360.6g21=-2877.1g23=-6648.2g32=16266.3g13=745.8g31=7110.140g12=864

18、7.0g21=-2650.0g23=-6607.2g32=15283.0g13=-108g31=8205.750g12=8900.3g21=-3328.1g23=-6513.9g32=14824.9g13=-220g31=8622.3UNI QUAC模型參數(shù)/(Jm ol-1U12=91.0U21=1869.7U23=6836.9U32=-234.5U13=3015.1U31=312.9U12=317.2U21=1679.6U23=6100.9U32=-468.2U13=2605.6U31=610.5U12=448.5U21=2169.6U23=6326.0U32=-745.1U13=1964

19、.4U31=1005.1U12=353.8U21=2128.9U23=-6275.5U32=-707.99U13=1937.4U31=1172.646化學(xué)工程2004年第32卷第4期2.3三元LLE數(shù)據(jù)的計(jì)算關(guān)聯(lián)出上述2種模型參數(shù)后,便可進(jìn)行三元LLE計(jì)算。對(duì)于三元體系LLE,必須滿足以下方程:x ii=x iii=1,2,3(4x1+x2+x3=1(5x1+x2+x3=1(6在一定壓力、溫度條件下,該方程組若給定其中一個(gè)未知數(shù)x2,即可求出其他5個(gè)未知數(shù)。通過(guò)單純形替換法,求解目標(biāo)函數(shù)OF式(7的最小值,即可求解。其計(jì)算結(jié)果與實(shí)驗(yàn)值的比較如表4所示。OF=3i=1(x ii-x ii3(7表

20、4醋酸甲酯(12甲醇(22水(3三元LLE計(jì)算值和實(shí)驗(yàn)值的比較T ab.4Deviation of LLE calculated results of experimental data for methyl acetate(12methanol(22water(3system溫度/編號(hào)NRT L模型UNI QUAC模型|x1|x2|x1|x2|x3|x1|x2|x1|x2|x3|2010.00350.00350.00290.00060.00350.00680.00680.00360.00210.001520.00160.00160.00890.00280.00610.00010.00010.

21、01000.01100.001030.01090.01090.00230.00040.00200.00010.00010.01000.01400.004040.00580.00580.00120.00180.00300.00020.00020.01000.01000.000050.00170.00170.00660.00500.00170.00010.00010.00990.01000.0001| x i|0.00470.00470.00440.00210.00330.00150.00150.00870.00940.0013 3010.00140.00140.00570.00030.00590

22、.00510.00510.00010.00110.000920.00180.00180.00890.00610.00280.00730.00730.00390.00650.010430.01000.01000.00010.00010.00020.00020.00020.00990.01000.000140.01010.01010.00010.00020.00030.00010.00010.01010.00000.010050.01000.01000.00200.00100.00100.00420.00420.00570.00250.0042| x i|0.00670.00670.00340.0

23、0150.00200.00340.00340.00590.00400.0051 4010.00350.00350.00290.00060.00350.01000.01000.00090.00050.000420.00320.00320.00210.00010.00200.00510.00510.01000.00330.006730.00250.00250.00170.00580.00420.00410.00410.00350.00100.002440.00000.00000.00110.00210.00320.01110.01110.01340.00260.016150.01000.01000

24、.01000.00000.01000.01950.01950.01220.00670.0056| x i|0.00380.00380.00360.00170.00460.01000.01000.00800.00280.0062 5010.00930.00930.00310.00030.00340.01490.01490.00810.00040.007620.00440.00440.00800.00270.00530.00550.00550.00750.00240.010130.00150.00150.00550.00050.00600.00920.00920.00830.00080.00754

25、0.00170.00170.00890.00470.00420.00200.00200.00660.00110.005550.00170.00170.00670.00500.00170.00820.00820.01070.00320.0075| x i|0.00370.00370.00640.00260.00410.00800.00800.00820.00160.00763用VB語(yǔ)言開(kāi)發(fā)液液相平衡關(guān)聯(lián)與計(jì)算軟件鑒于液液相平衡的關(guān)聯(lián)和預(yù)測(cè)計(jì)算復(fù)雜(活度系數(shù)模型以及算法并且涉及較多參數(shù)的輸出和輸入,選擇Visual Basic6.07作為軟件開(kāi)發(fā)工具。VB 不僅使軟件開(kāi)發(fā)過(guò)程可視化,而且利用計(jì)算機(jī)圖形技術(shù)與方法,對(duì)大量的數(shù)據(jù)進(jìn)行處理,并利用圖形、圖象的形式表現(xiàn)出來(lái)。由于液液相平衡的關(guān)聯(lián)和預(yù)測(cè)涉及大量的數(shù)據(jù)、參數(shù)的輸出和輸入,只有處理好了數(shù)據(jù)、參數(shù)的正確輸入、輸出,才能保證程序運(yùn)行的穩(wěn)定性、正確性及高效性。因此,采用F ormula One6.0控件。它支