第36卷第3期北京化工大學(xué)學(xué)報(bào)(自然科學(xué)版)Vol 36, No. 32009年Journal of Beijing University of Chemical Technology( Natural Science)2009乙酸乙酯-乙醇-離子液體等壓汽液平衡數(shù)據(jù)的測定朱久娟張繼國李群生”邢風(fēng)英(北京化工大學(xué)化學(xué)工程學(xué)院,北京100029)犢要:在101.32kPa下,用改進(jìn)的 Othmer釜測定了兩種乙酸乙酯乙醇離子液體三元物系的等壓汽液平衡數(shù)據(jù),即乙酸乙酯乙醇-1-丁基-3-甲基咪唑四氟硼酸鹽([BMIM]BF)與乙酸乙酯乙醇1-辛基3-甲基咪唑四氟硼酸鹽([OMIM]BF4)。實(shí)驗(yàn)結(jié)果表明:加入[BMIM]BF4和[OMIM]BF4,汽液平衡線偏離乙酸乙酯乙醇物系的汽液平衡線;離子液體摩爾分?jǐn)?shù)越大,偏離程度越大;[BMIM]JBF4與[OMM]BF4表現(xiàn)出明顯鹽效應(yīng),使乙酸乙酯對乙醇的相對揮發(fā)度發(fā)生改變,均消除了乙酸乙酯乙醇物系的共沸點(diǎn)。離子液體對乙酸乙酯的鹽析效應(yīng)順序?yàn)?[OMM]BF4>[BMIM]JBF4因此,[BMIM]BF4和[OMM]BF4可以作為乙酸乙酯乙醇物系萃取精餾的溶劑,汽液平衡數(shù)據(jù)的測定可為分離過程優(yōu)化設(shè)計(jì)提供依據(jù)。關(guān)鍵詞:汽液相平衡;乙酸乙酯;乙醇;1-丁基3-甲基咪唑四氟硼酸鹽;1-辛基3甲基咪唑四氟硼酸鹽中圖分類號:TQ0131引言BF4/[OMIM]BF4)三組分物系等壓汽液平衡數(shù)據(jù)并討論了離子液體對乙酸乙酯乙醇共沸物物系分乙酸乙酯是應(yīng)用廣泛的脂肪酸酯之一,因其具離的不同影響。有極好的溶解性,故被應(yīng)用于涂料、水果香精等]。目前,乙酸乙酯主要由乙酸和乙醇通過酯化反應(yīng)生1實(shí)驗(yàn)部分產(chǎn),工業(yè)上采用乙醇過量的方法提高生產(chǎn)率而乙酸1.1原料乙酯與乙醇的沸點(diǎn)只差1℃,常壓下形成共沸物,乙酸乙酯、乙醇,分析純,天津化學(xué)試劑公司;不能用一般的精餾方法分離因此國內(nèi)外在乙酸乙[BMIM]BF4、[ OMIMJBF4,質(zhì)量分?jǐn)?shù)大于98%,河酯與乙醇的分離方面做了大量的工作13北師范大學(xué)化學(xué)化工研究所。共沸體系不能通過簡單蒸餾實(shí)現(xiàn)完全分離。離1.2實(shí)驗(yàn)裝置子液體作為一種新型“綠色”溶劑因其溫度范圍寬實(shí)驗(yàn)中所采用的汽液相平衡裝置為北洋化工實(shí)蒸氣壓低熱穩(wěn)定性好、無污染等優(yōu)點(diǎn)而被廣泛應(yīng)用驗(yàn)設(shè)備公司CE2型改進(jìn)的 Othmer汽液平衡釜,如于萃取和對于共沸物或沸點(diǎn)相近物系的分離過圖1所示。程4,發(fā)展與完善含有離子液體物系的熱力學(xué)數(shù)據(jù)對更好地理解離子液體的分離規(guī)律及發(fā)展熱力學(xué)模型很重要4。目前,已有文獻(xiàn)報(bào)道了相關(guān)的研究成果612),如液液平衡、無限稀釋時(shí)的活度系數(shù)等但等壓汽液平衡數(shù)據(jù)還很缺乏,同時(shí)也沒有建立很好的理論預(yù)測模型。由文獻(xiàn)[78]可知[BMIM]BF4對共沸物的分離效果較好,但是[OMM]BF4對共沸物物系的分離數(shù)據(jù)還沒有報(bào)道,故有必要進(jìn)行測定。本文測定乙酸乙酯乙醇離子液體(BMIM]溫度計(jì);5一冷凝器收稿日期:20080828中國煤化工9氣相取樣第一作者:女,1983年生,碩士生CNMHGE通訊聯(lián)系人Fig. 1 Othmer vapor-liquid equilibrium stillE-mail:ligs@mail.buct.edu.cn北京化工大學(xué)學(xué)報(bào)(自然科學(xué)版)年13實(shí)驗(yàn)步驟表1乙酸乙酯(1)-乙醇(2)-[BMIM]BF4(3)OMIM]BF4采用稱重法配制試樣。將50mL試樣加入到平(3)三組分物系的汽液平衡數(shù)據(jù)(101.32kPa)衡釜中,加熱至沸騰。平衡室溫度恒定不變時(shí)達(dá)到 Table1 vle data for the termary systems of ethyl acetate平衡,保持約30min,然后采用微量進(jìn)樣器分別直接(1)-ethanol (2)with [BMIM]BF, (3)or [OMIM]從汽相、液相取樣口取樣分析,取樣間隔約15minBF(3)at 101.32 kPa14分析方法r([BMIMJBF/% T/K II y汽、液相中乙酸乙酯與乙醇的含量分析采用氣349.760.1120.2002.0151.0741.982相色譜法測定,液相中離子液體的含量通過稱重法346.950.3050.4121.6761.1311.597測定。氣相色譜儀為北京東西電子生產(chǎn)的345.940.5220.5731.4091.2451.229GC4000A型氣相色譜儀,操作條件: Porapak-Q填充9.976345.940.6770.6791.2861.3831.009346.350.7710.7441.2201.5290.863柱(3m×0.3mm),載氣(氫氣)流量30mL/min,柱10.024346.700.8230.7881.1971.6170.799溫383.15K,汽化室溫度413.15K,TCD溫度350.850.9630.9511.0761.5120.746423.15K,采用面積歸一化法定量。30.199353.350.1830.3032.1361.1391.9412結(jié)果與討論30.235351.950.2670.3942.0071.1641.78530.275350.350.3600.4881.9371.2021.6942.1汽液平衡數(shù)據(jù)的校證29,865349.950.4920596用本實(shí)驗(yàn)裝置所測定的乙酸乙酯乙醇二組分30.227349400.5890.6791.6981.2181物系的等壓汽液平衡數(shù)據(jù)與文獻(xiàn)值1甚本吻合(見30.109349,200.6460.7281.6691.2061.467圖2),最大偏差為0.004,說明實(shí)驗(yàn)裝置可靠。29919348.760.6700.7451.6681.2331.43929.919349440.8081.1631.413350.950.9280.9471.4261.0771.386IM]BF4)/%T/K351450.0920.1802.084349650.1860.3151.92310210.160348.450.3040.4401.7101.0131.7990.5281.5951.0311.6570204060.81.010.263347.350.5270.6251.4551.0461.496347.300.5810.6601.3941.0721.400圖2101.32kPa下乙酸乙酯(1)乙醇(2)物系x1y1曲線10.104347.540.6670.7291.3291.0641.343Fig 2 Vapor-liquid equilibrium (vle) diagram of the ethyl10.081347.840.7620.8021.2681.0731.265acetate(1)-ethanol (2)system at 101.32kPa349.060.9130.9291.1762.2汽液平衡數(shù)據(jù)10.205349,340.9630.9701.1550.9921.242在101.32kPa下,測定了乙酸乙酯乙醇離子30.740365840.0870.2012.0550.7352.64液體三元物系汽液相平衡的數(shù)據(jù)(見表1),其中液30.540363650.141029619780.7422.56130.506361.500.2270.4171.8450.7402436相組成是按脫離子液體的摩爾分?jǐn)?shù)計(jì)算的。30.455359250.3140.5241.8010.7402,405活度系數(shù)(y)的計(jì)算公式12如式(1),計(jì)算結(jié)30.276357650.4040.6181.7260.7232.387果列于表1中。356.560.5480.7411.5810.6752.360y(1)y、x為組分i在汽、液相中的摩爾分?jǐn)?shù);p為平衡中國煤化工時(shí)的總壓,即10132kPa;p是純物質(zhì)i的飽和蒸CNMHG1.3320.5922.316氣壓,由 Antoine方程計(jì)算2);;是組分i在汽相中y為活度系數(shù);an為乙酸乙酯對乙醇的相對揮發(fā)度第3期朱久娟等:乙酸乙酯乙醇離子液體等壓汽液平衡數(shù)據(jù)的測定的逸度系數(shù),P是純組分i在飽和狀態(tài)時(shí)的逸度系數(shù)。離子液體被認(rèn)為不揮發(fā)故把汽相看作為理想狀態(tài),式(1)可以簡化為(2)s16乙酸乙酯對乙醇的相對揮發(fā)度(a12)6計(jì)算結(jié)果列于表1中,定義式如式(3)a12-y2/x206081023離子液體濃度對汽液相平街的影響隨離子液體([BMM]BF4和[OMIM]BF4)的●無離子液體;vx([BMIM]BF4=10%;加入,汽相組分中的乙酸乙酯含量增加。由圖3可Ar([BMIM]BF4)=30%; Vr([OMIM]BF )=10%;▲x([OMM]BF4=30%見汽液平衡曲線偏離乙酸乙酯乙醇二組分物系的圖4離子液體對相對揮發(fā)度的影響汽液平衡曲線;且隨離子液體含量的增加汽液線偏Fig 4 Effect of ionic liquid on relative volatility離程度增大,乙酸乙酯乙醇的共沸點(diǎn)消失,故[OMM]BF,使y1的增加更大;綜上可知離子液BMIMJBF4與[OMM]BF可作為乙酸乙酯乙醇體與乙醇的結(jié)合作用強(qiáng)于乙酸乙酯故離子液體對萃取精餾的溶劑。乙酸乙酯為鹽析效應(yīng),且對于乙酸乙酯的鹽析效應(yīng)遵循如下規(guī)律:[OMM]BF4>[BMIM]BF4這是0.8因?yàn)樵谟袡C(jī)溶劑中,離子液體的“分子”特性占主導(dǎo)地位,當(dāng)陰離子相同時(shí),陽離子體積越大,離子液體“分子”與有機(jī)溶劑分子之間的色散作用力越強(qiáng)?！胺肿印斌w積較大的離子液體[OMM]BF4溶于乙酸乙酯乙醇體系中,通過化學(xué)親和力、氫鍵力以及離p=10132kPa子的靜電引力等作用與乙醇“綁定”,使得乙醇的活度系數(shù)減少,從而提高了乙酸乙酯的活度系數(shù)、對乙醇的相對揮發(fā)度無離子液體;vx(BMM]BF4=10%;圖5是乙酸乙酯(1)-乙醇(2)離子液體(3)三Ar([BMIM]BF4)=30%:Vr([OMIM]BF4)=10%;組分物系的Tx1-y1圖。由圖5可見,隨離子液體含量的增加,平衡溫度(T)均有所升高;當(dāng)[BMIM]圖3三組分物系的等壓汽液平衡曲線Fig 3 Isobaric Vle diagram of the ternary systems離子液體的加入明顯提高了乙酸乙酯乙醇物系的相對揮發(fā)度。由圖4可知離子液體的加入量越多,乙酸乙酯乙醇的相對揮發(fā)度提高幅度越大,說明離子液體對乙酸乙酯乙醇物系表現(xiàn)出明顯的鹽效應(yīng),可以提高此物系的分離效果。24離子液體種類對汽液相平衡的影響060810觀察圖3和圖4可知[OMIM]BF4的分離效果摩爾分?jǐn)?shù)強(qiáng)于[BMM]BF4從表1中y1可知離子液體的加液體:·r(BMIM|RF)=10%;入對乙酸乙酯的活度系數(shù)有增大作用,對乙醇的活中國煤化工BE,)=10%;度系數(shù)影響不大,但當(dāng)[OMIM]BF4的摩爾分?jǐn)?shù)約CNMHO圖;實(shí)心點(diǎn):T-y1圖為30%時(shí),乙醇的活度系數(shù)降低顯著(y2<1000圖5三組分物系的Tx1y1圖加入等摩爾分?jǐn)?shù)的[OMIM]BF4與[BMIM]BF4時(shí)Fig. 5 T-x1-y1 diagram of the termary system北京化工大學(xué)學(xué)報(bào)(自然科學(xué)版)2009年BF4摩爾分?jǐn)?shù)為10%時(shí),共沸點(diǎn)并未消失,但共沸the heat capacity of the ionic liquid [Emim]BFa and its物的組成改變(x1≈0.680),當(dāng)[BMIM]BF4摩爾分agueous solution [J]. Journal of Beijing University of數(shù)為30%時(shí),共沸點(diǎn)消失,均有一個(gè)最低溫度,但此Chemical Technology: Natural Science, 2008, 35 (3)最低溫度和共沸物的最低共沸點(diǎn)并不一樣,因?yàn)樵?7-30. (in Chines[5]史奇冰,鄭逢春,李春喜,等.用NRTL方程計(jì)算含此最低溫度時(shí)汽、液相的組成(x1,y1)并不相同;當(dāng)離子液體體系的汽液平衡[J.化工學(xué)報(bào),2005,56[OMIM]BF4摩爾分?jǐn)?shù)為10%時(shí),共沸點(diǎn)消失,且(5):751-756[OMIM]BF4摩爾分?jǐn)?shù)為30%時(shí),最低溫度點(diǎn)消失。Shi Q B, Zheng F C, LiCX, et al. Calculation of vapor-3結(jié)論liquid equilibrium for ionic liquid-containing systems withNrTL equation [J]. Journal of Chemical Industry and(1)在10132kPa下,測定了[BMM]BF4與Engineering, 2005, 56(5): 751-756.(in Chinese)[OMIM]BF4摩爾分?jǐn)?shù)分別為10%、30%時(shí)的乙酸6]李群生,邢風(fēng)英,雷志剛,異丙醇水1乙基3甲基乙酯乙醇離子液體的汽液平衡數(shù)據(jù),補(bǔ)充了含離氟硼酸咪唑鹽物系等壓汽液平衡數(shù)據(jù)的測定[J].石子液體體系汽液平衡熱力學(xué)數(shù)據(jù)。油化工,2008,37(1):6771(2)在乙酸乙酯乙醇物系中加入[BMIM]BF4LiQ S, Xing F Y, Lei Z G. Isobaric vapor- liquid equi.librium for isopropanol-water- 1-ethyl-3-methylimida與[OMM]BF4,均可打破物系的共沸點(diǎn),增大乙酸zolium tetrafluoroborate [J]. Petrochemical Technology,乙酯的活度系數(shù)、提高乙酸乙酯對乙醇的相對揮發(fā)2008,37(1):67-71.( (in Chinese)度且[OMM]BF摩爾分?jǐn)?shù)為30%時(shí)消除了最低[7] Zhang L Z, Deng d s,HnJz,etl. Isobaric vapor溫度liquid equilibria for water 2-propanol 1-butyl-3-(3)[BMM]BF4與[OMIM]BF4對乙酸乙酯methylimidazolium tetrafluoroborate [J]. Journal of乙醇物系表現(xiàn)出明顯的鹽效應(yīng),適宜做萃取劑,且Chemical Engineering Data, 2007, 52(1): 199-205[OMIM]BF4的分離效果優(yōu)于[BMIM]BF4[8]Zhao J, Dong CC, LiCX, et al. Isobaric vapor-liquid e參考文獻(xiàn)ionic liquids at atmospheric pressure[J]. Fluid Phase E-[1]華超,白鵬,李鑫鋼,等,N,N二甲基甲酰胺和乙quilibria,2006,242(2):147-153醇、乙酸乙酯二元物系常壓汽液平衡數(shù)據(jù)的測定[J][9] Doker M, gmehling J. Measurement and prediction of石油化工,2005,34(6):547-550vapor-liquid equilibria of temary systems containingHua C, Bai P, Li X G, et al. Atmospheric vaporliquids[J]. Fluid Phase equilibria, 2005, 227(2):255f ethanol-N, N-dimethyl formamide[10]張志剛,張衛(wèi)江,楊志才,等.萃取精餾分離乙酸乙酯ethyl acetate-N, N-dimethyl formamide systems[J]Petrochemical Technology, 2005, 34(6): 547-550.乙醇的溶劑[J].化工學(xué)報(bào),204,55(2):226-230Zhang Z G, Zhang W J, Yang Z C, et al. Solvent for[2] Yan W D, Rose C, Gmehling J. Isothermal vapor-liquidseparating ethyl acetate-ethanol by extractive distillationequilibrium data for the ethanol ethyl acetate sodi[J]. Journal of Chemical Industry and Engineering,um iodide system at five temperatures [J]. Journal of2004,55(2):226-230.( in Chinese)[11] Tu CH, Wu Y S, Ou F C. Effect of 1, 2-propanediol onChemical Engineering Data, 1997, 42(3): 603-608[3] Hu X S, LiY X, Cui N, et al. Separation of ethyl ace vapor liquid equilibria of the ethyl acetate+ ethanoletate and ethanol by room temperature ionic liquids witsystem at 101.3 kPa[J]130(1/2):243-252.the tetrafluoroborate anion[J]. Journal of Chemical engi[12] Orchille's A V, Miguel P J, Vercher E, et al. Isobaricneering Data,2008,53(2):427-433[4]田濤,鄭丹星,武向紅,等.室溫離子液體[Emm]BF4vapor-liquid equilibria for ethyl acetate ethanol及其水溶液體系的比熱容測定[J].北京化工大學(xué)學(xué)luwwomethanesulfonate at報(bào):自然科學(xué)版,2008,35(3):27-30.TH中國煤化工 Engineering daiCNMHGTian T, ZhengDx, Wu X H, et al. Determination of第3期朱久娟等:乙酸乙酯-乙醇-離子液體等壓汽液平衡數(shù)據(jù)的測定Isobaric vapor-liquid equilibria for ethyl acetate-ethanol-ionicliquid ternary systemsZHU JiuJuan ZHANG JiGuo LI Qun Sheng XING Feng YingCollege of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029,ChinaAbstract: Isobaric vapor-liquid equilibrium data for ethyl acetate-ethanol-ionic liquid ternary systems were mea-sured in a modified Othmer still at 101. 32 kPa. The ionic liquids employed were 1-butyl-3-methylimidazoliumtetrafluoroborate([BMIM]BF4)and ethyl 1-octyl-3-methylimidazolium tetrafluoroborate([OMIM]BF4).Thevapor-liquid equilibrium curves of the ethyl acetate-ethanol-ionic liquid systems deviate from that of the IL-freesystem and the deviation increases with increasing amounts of IL. The ILs show a salting-out effect which increases the volatility of ethyl acetate relative to that of ethanol, and even leads to an elimination of the azeotropicpoint. The salting-out effect on ethyl acetate decreases in the order: [OMIM]BF4>[BMIM]BF. As a result,it is concluded that [BMIM]BF4 and [OMIM]BF4 can be used as entrainers for the separation of ethyl acetateand ethanol, and the vle data obtained here can be used to optimize the processKey words: vapor-liquid equilibrium; ethyl acetate; ethanol; 1-butyl-3-methylimidazolium tetrafluoroborate; 1octyl-3-methylimidazolium tetrafluoroborate中國煤化工CNMHG