揭會(huì)民,崔現(xiàn)寶,彭艷枚,李曉兵,徐麗,林瑞榕(天津大學(xué)化工學(xué)院,化學(xué)工程聯(lián)合國(guó)家重點(diǎn)實(shí)驗(yàn)室,天津 300072)
離子液體反應(yīng)萃取精餾合成乙酸乙酯
揭會(huì)民,崔現(xiàn)寶,彭艷枚,李曉兵,徐麗,林瑞榕
(天津大學(xué)化工學(xué)院,化學(xué)工程聯(lián)合國(guó)家重點(diǎn)實(shí)驗(yàn)室,天津 300072)
摘要:采用離子液體1-磺酸丁基-3-甲基咪唑硫酸氫鹽([HSO3bmim][HSO4])和1-丁基-3-甲基咪唑雙三氟甲磺酰亞胺鹽([BMIM][Tf2N])分別作為催化劑和萃取劑,對(duì)乙酸甲酯與乙醇合成乙酸乙酯和甲醇的反應(yīng)萃取精餾(RED)過(guò)程進(jìn)行了模擬計(jì)算。在反應(yīng)動(dòng)力學(xué)和汽液相平衡分析基礎(chǔ)上建立了反應(yīng)萃取精餾流程,研究了理論板數(shù)、回流比、持液量、進(jìn)料位置、溶劑比(萃取劑進(jìn)料與原料進(jìn)料摩爾流量的比值)、催化劑進(jìn)料流量等參數(shù)對(duì)反應(yīng)萃取精餾過(guò)程的影響。在優(yōu)化的操作條件下,甲醇純度為0.9922,乙酸乙酯純度為0.9905,乙酸甲酯轉(zhuǎn)化率為0.9922。
關(guān)鍵詞:離子液體;反應(yīng)萃取精餾;乙酸甲酯;甲醇;共沸物;模擬
2015-07-31收到初稿,2015-09-06收到修改稿。
聯(lián)系人:崔現(xiàn)寶。第一作者:揭會(huì)民(1990—),男,碩士研究生。
Received date: 2015-07-31.
離子液體作為一種綠色溶劑和催化劑近年來(lái)受到了很多關(guān)注。離子液體具有獨(dú)特的性質(zhì),使其能夠運(yùn)用于很多領(lǐng)域,包括作為有機(jī)反應(yīng)的反應(yīng)介質(zhì)[1-2]、化學(xué)反應(yīng)催化劑[3-5]、電化學(xué)電解液[6-7]、萃取精餾及萃取過(guò)程的萃取劑[8-12]、分析化學(xué)試劑[13]等。離子液體幾乎可忽略的蒸氣壓和良好的熱穩(wěn)定性又使其易于與大部分有機(jī)物通過(guò)簡(jiǎn)單蒸餾分離,能夠?qū)崿F(xiàn)循環(huán)利用,可以節(jié)省分離過(guò)程的能耗,替代傳統(tǒng)工藝中的溶劑。離子液體具有可設(shè)計(jì)性,可以合成具有催化功能的酸性離子液體,作為化學(xué)反應(yīng)的催化劑[14-17]。
反應(yīng)萃取精餾(RED)是將反應(yīng)精餾和萃取精餾集成于同一設(shè)備內(nèi)同時(shí)進(jìn)行的過(guò)程。反應(yīng)萃取精餾適合反應(yīng)物和產(chǎn)物形成共沸物或近沸物而難以采用反應(yīng)精餾的反應(yīng)體系。通過(guò)在反應(yīng)體系中加入萃取劑改變待分離體系的相對(duì)揮發(fā)度,同時(shí)將反應(yīng)產(chǎn)物及時(shí)分離出去,能夠使平衡反應(yīng)獲得高轉(zhuǎn)化率和高純度產(chǎn)品。反應(yīng)萃取精餾過(guò)程結(jié)合了反應(yīng)精餾和萃取精餾各自的優(yōu)點(diǎn),降低了設(shè)備的投資和能耗,是一種很有前景的分離方法[18]。目前關(guān)于反應(yīng)萃取精餾的報(bào)道并不多[18-21]。Jiménez等[20-21]將反應(yīng)萃取精餾運(yùn)用于乙酸甲酯和正丁醇的酯交換反應(yīng)過(guò)程,該過(guò)程使用酸性離子交換樹(shù)脂作為酯交換反應(yīng)的催化劑,以鄰二甲苯作為萃取劑。Cai等[18]以離子液體作為催化劑和萃取劑,對(duì)乙酸甲酯和正丁醇合成甲醇和乙酸正丁酯的反應(yīng)萃取精餾過(guò)程進(jìn)行了模擬計(jì)算,結(jié)果表明通過(guò)反應(yīng)萃取精餾過(guò)程可以獲得高純度的甲醇和乙酸正丁酯。
乙酸乙酯(EtOAc)是一種重要的有機(jī)溶劑,廣泛用于染料、涂料、黏合劑等產(chǎn)品,還可用于生物、制藥、食品等行業(yè)。乙酸甲酯(MeOAc)作為PVA生產(chǎn)過(guò)程中的副產(chǎn)物,在工業(yè)上的應(yīng)用范圍很小。將乙酸甲酯與乙醇(EtOH)的酯交換反應(yīng)運(yùn)用于反應(yīng)萃取精餾過(guò)程,不僅能得到用途更廣泛的乙酸乙酯產(chǎn)品,還會(huì)獲得高純度甲醇(MeOH),而甲醇是PVA生產(chǎn)的原料之一。
本研究利用流程模擬軟件Aspen Plus模擬計(jì)算了乙酸甲酯與乙醇合成乙酸乙酯和甲醇的反應(yīng)萃取精餾(RED)過(guò)程,以離子液體1-磺酸丁基-3-甲基咪唑硫酸氫鹽([HSO3bmim][HSO4])為催化劑、1-丁基-3-甲基咪唑雙三氟甲磺酰亞胺鹽([BMIM][Tf2N])為萃取劑。在反應(yīng)動(dòng)力學(xué)和汽液相平衡分析基礎(chǔ)上建立了反應(yīng)萃取精餾流程,討論了理論板數(shù)、回流比、持液量、進(jìn)料位置、溶劑比、催化劑進(jìn)料流量等參數(shù)對(duì)離子液體反應(yīng)萃取精餾過(guò)程的影響。
乙酸甲酯與乙醇酯交換反應(yīng)方程式如下
乙酸甲酯與乙醇酯交換反應(yīng)的離子液體催化劑為[HSO3bmim][HSO4]。Peng等[15]研究了以該離子液體作為催化劑的乙酸甲酯與乙醇的酯交換反應(yīng)的動(dòng)力學(xué),反應(yīng)動(dòng)力學(xué)方程如下
式中,r代表反應(yīng)速率,V代表反應(yīng)體系體積,ni為反應(yīng)體系中組分i的物質(zhì)的量,vi為反應(yīng)體系中組分i的化學(xué)計(jì)量數(shù),ρ是反應(yīng)混合物密度,ccat是催化劑濃度,αMeoAc、αEtOH、αEtOAc、αMeoH分別是乙酸甲酯、乙醇、乙酸乙酯、甲醇在離子液體反應(yīng)萃取精餾體系中的活度。
式(1)中正反應(yīng)速率常數(shù)k+和逆反應(yīng)速率常數(shù)可以通過(guò)Arrhenius方程計(jì)算,表達(dá)式如下其中,k0+=4694.8 L1.5·mol?1.5·min?1;k0?=4678.5 L1.5·mol?1.5·min?1;Ea+=38.90 kJ·mol?1;Ea?=39.36 kJ·mol?1。
在后面的反應(yīng)萃取模擬計(jì)算中,反應(yīng)萃取精餾塔內(nèi)既有催化劑又有萃取劑,但是萃取劑是惰性組分,不參與反應(yīng),而且上述動(dòng)力學(xué)方程的定義是基于不含萃取劑的反應(yīng)體積,因此萃取劑的加入對(duì)于反應(yīng)速率[式(1)]沒(méi)有影響。如果反應(yīng)速率的定義是基于包括萃取劑的反應(yīng)體積,那么萃取劑會(huì)使反應(yīng)速率降低。但是,這兩種方法計(jì)算得到的單位時(shí)間的反應(yīng)量是相同的。本研究的模擬計(jì)算直接采用式(1)所描述的反應(yīng)速率,反應(yīng)體積采用扣除萃取劑的反應(yīng)體積。
乙酸甲酯與乙醇酯交換反應(yīng)體系中存在3個(gè)共沸體系:甲醇-乙酸甲酯、乙醇-乙酸乙酯和甲醇-乙酸乙酯。本研究利用COSMO-SAC模型[22-23]選出一種能同時(shí)打破這3種共沸體系的離子液體萃取劑,具體篩選過(guò)程參見(jiàn)李瑞等[24]的研究。篩選結(jié)果表明1-丁基-3-甲基咪唑雙三氟甲磺酰亞胺鹽([BMIM][Tf2N])可以作為萃取劑打破上述3個(gè)共沸體系的共沸點(diǎn)。離子液體[BMIM][Tf2N]作用下的甲醇-乙酸甲酯、乙醇-乙酸乙酯、甲醇-乙酸乙酯的汽液平衡相圖如圖1~圖3所示,圖1和圖3中x′1表示除去離子液體的甲醇的歸一化摩爾分?jǐn)?shù),圖2 中x′1表示除去離子液體的乙醇的歸一化摩爾分?jǐn)?shù)。從圖中可以看出,在這3個(gè)共沸體系中分別加入足夠量的離子液體[BMIM][Tf2N],它們的共沸點(diǎn)就會(huì)消失。汽液平衡數(shù)據(jù)采用NRTL模型進(jìn)行回歸,得到的NRTL方程參數(shù)見(jiàn)表1。
圖1 甲醇(1)-乙酸甲酯(2)-[BMIM][Tf2N](3)物系的等壓汽液平衡相圖(101.3 kPa)[25]Fig.1 Isobaric VLE diagram of methanol (1) - methyl acetate(2) - [BMIM][Tf2N] (3) ternary system at 101.3 kPa ○ x3=0; ■ x3=0.2; ▲ x3=0.4; solid lines, calculated by NRTL model
圖2 乙醇(1)-乙酸乙酯(2)-[BMIM][Tf2N](3)物系的等壓汽液平衡相圖(101.3 kPa)[26]Fig.2 Isobaric VLE diagram of ethanol (1) - ethyl acetate (2) -[BMIM][Tf2N] (3) ternary system at 101.3 kPa ○ x3=0; ■ x3=0.2; ▲ x3=0.3; solid lines, calculated by NRTL model
圖3 甲醇(1)-乙酸乙酯(2)-[BMIM][Tf2N](3)物系的等壓汽液平衡相圖(101.3 kPa)[26]Fig.3 Isobaric VLE diagram of methanol (1)-ethyl acetate (2)-[BMIM][Tf2N] (3) ternary system at 101.3 kPa ○ x3=0; ■ x3=0.2; ▲ x3=0.4; solid lines, calculated by NRTL model
表1 NRTL方程的二元交互作用參數(shù)和非隨機(jī)參數(shù)Table 1 Values of binary parameters and non-randomness parameters of NRTL equation
NRTL模型如下
式中,Bji為二元交互作用參數(shù),αji為非隨機(jī)參數(shù),T為溫度,xi為液相組分i的摩爾分?jǐn)?shù),γi為組分i的活度系數(shù)。
3.1工藝描述
圖4是該反應(yīng)萃取精餾工藝流程圖,操作壓力為101.3 kPa,其中包含一個(gè)離子液體反應(yīng)萃取精餾塔(T-1)和一個(gè)閃蒸罐(T-2)。低沸點(diǎn)反應(yīng)物乙酸甲酯從靠近塔底進(jìn)料,高沸點(diǎn)反應(yīng)物乙醇從塔中部進(jìn)料,離子液體催化劑和萃取劑混合物從靠近塔頂?shù)奈恢眠M(jìn)料。T-1塔是化學(xué)反應(yīng)和萃取精餾進(jìn)行的場(chǎng)所,是該流程的關(guān)鍵部分。T-1塔頂部獲得輕組分產(chǎn)物甲醇,塔底得到的產(chǎn)物乙酸乙酯和離子液體混合液則進(jìn)入T-2塔。T-2塔是重組分產(chǎn)物乙酸乙酯和離子液體分離的場(chǎng)所,乙酸乙酯從T-2塔頂部采出,離子液體催化劑和萃取劑混合液則從T-2塔底部采出。
圖4 離子液體反應(yīng)萃取精餾工藝流程Fig.4 Schematic diagram of RED process using ionic liquids as catalyst and entrainer
3.2參比操作條件及模擬計(jì)算結(jié)果
采用上述工藝流程進(jìn)行初步模擬計(jì)算,得到較為適宜的參比操作條件,后文所述的影響因素分析將以此條件為參照,即改變其中某一個(gè)操作條件而保持其他條件不變。參比操作條件及其模擬計(jì)算結(jié)果見(jiàn)表2。其中第1塊理論塔板為冷凝器,最后一塊理論塔板為再沸器。
4.1理論板數(shù)的影響
理論板數(shù)是反應(yīng)萃取精餾塔的一個(gè)重要參數(shù),對(duì)化學(xué)反應(yīng)過(guò)程和分離過(guò)程具有一定的影響,理論板數(shù)不足達(dá)不到分離要求,理論板數(shù)過(guò)大則會(huì)造成設(shè)備投資大。圖5表示的是理論板數(shù)從35增加到55時(shí)對(duì)產(chǎn)物純度和乙酸甲酯轉(zhuǎn)化率的影響。從圖中可以看出,當(dāng)理論板數(shù)大于50時(shí)甲醇和乙酸乙酯純度以及乙酸甲酯轉(zhuǎn)化率基本保持不變。所以,綜合考慮經(jīng)濟(jì)因素和分離效果,適宜的理論板數(shù)為50。
圖5 理論板數(shù)對(duì)產(chǎn)物純度和乙酸甲酯轉(zhuǎn)化率的影響Fig.5 Effects of theoretical stages on purities of products and conversion of methyl acetate
4.2回流比的影響
反應(yīng)萃取精餾塔內(nèi)化學(xué)反應(yīng)和分離過(guò)程是同時(shí)進(jìn)行的,所以回流比對(duì)反應(yīng)萃取精餾過(guò)程的影響比對(duì)傳統(tǒng)精餾過(guò)程更為復(fù)雜。為了研究回流比對(duì)反應(yīng)萃取精餾的影響,在其他條件與表2中參比條件相同的情況下,采用不同的回流比進(jìn)行模擬計(jì)算?;亓鞅扰c反應(yīng)產(chǎn)物純度及乙酸甲酯轉(zhuǎn)化率的關(guān)系如圖6所示。傳統(tǒng)精餾過(guò)程產(chǎn)物純度會(huì)隨回流比增大而增大,但在反應(yīng)萃取精餾過(guò)程中存在一個(gè)最佳回流比,使產(chǎn)物純度和反應(yīng)物轉(zhuǎn)化率達(dá)到最大值。這是因?yàn)樵诨亓鞅容^小時(shí)體系內(nèi)的反應(yīng)物與產(chǎn)物無(wú)法徹底分離,故產(chǎn)物純度和反應(yīng)物轉(zhuǎn)化率較低,回流比增大后產(chǎn)物純度和反應(yīng)物轉(zhuǎn)化率都提高,但回流比過(guò)大時(shí)塔的回流量大,造成萃取劑被稀釋,萃取劑的作用減弱,不利于共沸物的分離,導(dǎo)致產(chǎn)物甲醇和乙酸乙酯純度及乙酸甲酯轉(zhuǎn)化率降低。由圖6分析得出最佳回流比為6。
圖6 回流比對(duì)產(chǎn)物純度和乙酸甲酯轉(zhuǎn)化率的影響Fig.6 Effects of reflux ratio on purities of products and conversion of methyl acetate
4.3塔板持液量的影響
離子液體反應(yīng)萃取精餾過(guò)程中的酯交換反應(yīng)是在整個(gè)塔內(nèi)進(jìn)行的,塔板為化學(xué)反應(yīng)發(fā)生的場(chǎng)所。塔板持液量對(duì)產(chǎn)物純度及乙酸甲酯轉(zhuǎn)化率的影響如圖7所示。從圖中可以看出,隨著塔板持液量的增加,產(chǎn)物純度和乙酸甲酯轉(zhuǎn)化率先增加后趨于穩(wěn)定。這是因?yàn)榉磻?yīng)萃取精餾過(guò)程同時(shí)受反應(yīng)和分離控制,當(dāng)塔板持液量少時(shí)單位時(shí)間內(nèi)的反應(yīng)量少,反應(yīng)過(guò)程為整個(gè)過(guò)程的控制步驟,因此增大持液量會(huì)使產(chǎn)物純度和乙酸甲酯轉(zhuǎn)化率提高;而當(dāng)持液量足夠大時(shí),單位時(shí)間內(nèi)的反應(yīng)量增大,控制步驟逐漸向分離過(guò)程過(guò)渡,此時(shí)持液量增大對(duì)于反應(yīng)精餾過(guò)程影響很小。由圖7得出每塊塔板的適宜持液量為30 L。
圖7 持液量對(duì)產(chǎn)物純度和乙酸甲酯轉(zhuǎn)化率的影響Fig.7 Effects of liquid holdup on purities of products and conversion of methyl acetate
4.4進(jìn)料位置的影響
本研究討論兩種情況下進(jìn)料位置的影響:①同時(shí)改變乙酸甲酯和乙醇的進(jìn)料位置,從而改變兩者之間的進(jìn)料間隔塔板數(shù);②固定反應(yīng)物之間的進(jìn)料間隔,改變乙酸甲酯和乙醇的進(jìn)料位置。
針對(duì)第1種情況,研究了表3中的7種反應(yīng)物進(jìn)料位置對(duì)甲醇和乙酸乙酯純度及乙酸甲酯轉(zhuǎn)化率的影響,結(jié)果如圖8(a)所示。從圖中可以看出,隨著進(jìn)料間隔的增加,甲醇和乙酸乙酯的純度及乙酸甲酯的轉(zhuǎn)化率都隨之增加,適宜的原料進(jìn)料間隔為20塊塔板。
表3 乙醇和乙酸甲酯的進(jìn)料位置及間隔板數(shù)Table 3 Feed tray of ethanol and methyl acetate and feed tray interval
圖8 進(jìn)料間隔及乙酸甲酯進(jìn)料位置對(duì)產(chǎn)物純度和乙酸甲酯轉(zhuǎn)化率的影響Fig.8 Effects of feed tray interval and feed tray location of methyl acetate on purities of products and conversion of methyl acetate
針對(duì)第2種情況,固定乙醇與乙酸甲酯進(jìn)料間隔為20塊塔板,研究了不同的進(jìn)料位置對(duì)產(chǎn)物純度及乙酸甲酯轉(zhuǎn)化率的影響,結(jié)果見(jiàn)圖8(b),圖中橫坐標(biāo)為乙酸甲酯進(jìn)料位置,乙醇進(jìn)料位置應(yīng)在其上20塊塔板。從圖中結(jié)果可以看出,甲醇和乙酸乙酯純度及乙酸甲酯轉(zhuǎn)化率隨乙酸甲酯進(jìn)料位置下移而增大,當(dāng)乙酸甲酯在第38塊板進(jìn)料、乙醇在第18塊板進(jìn)料時(shí),甲醇和乙酸乙酯純度及乙酸甲酯轉(zhuǎn)化率達(dá)到較大值。
4.5溶劑比的影響
溶劑比即離子液體萃取劑的摩爾流量與兩個(gè)反應(yīng)物進(jìn)料的摩爾流量之和的比值。從圖9可以看出,隨著溶劑比的增加,產(chǎn)物純度及乙酸甲酯轉(zhuǎn)化率不斷增加。這是因?yàn)楫?dāng)萃取劑量很少時(shí)萃取劑對(duì)反應(yīng)體系內(nèi)共沸物的作用很弱,難以對(duì)共沸物進(jìn)行分離,故甲醇和乙酸乙酯純度低;隨著塔內(nèi)萃取劑濃度的升高,萃取劑作用加強(qiáng),共沸物之間的相對(duì)揮發(fā)度增大,甲醇和乙酸甲酯純度增加;但當(dāng)溶劑比為2.5時(shí),甲醇純度已經(jīng)達(dá)到0.9905,繼續(xù)加大萃取劑的量會(huì)增加再沸器的熱負(fù)荷。綜合考慮能耗和反應(yīng)萃取精餾效率,最佳溶劑比為2.5。
圖9 溶劑比對(duì)產(chǎn)物純度和乙酸甲酯轉(zhuǎn)化率的影響Fig.9 Effects of entrainer ratio on purities of products and conversion of methyl acetate
4.6催化劑進(jìn)料流量的影響
催化劑[HSO3bmim][HSO4]進(jìn)料流量的影響如圖10所示。從圖中可以看出,甲醇和乙酸乙酯純度及乙酸甲酯轉(zhuǎn)化率隨催化劑進(jìn)料流量增加而急劇增大,當(dāng)催化劑進(jìn)料流量達(dá)到1 kmol·h?1后趨于穩(wěn)定。這是因?yàn)楫?dāng)催化劑量較少時(shí)單位時(shí)間的反應(yīng)量少,化學(xué)反應(yīng)為控制步驟,隨著催化劑進(jìn)料流量的增加,單位時(shí)間的反應(yīng)量提高,分離過(guò)程成為反應(yīng)萃取精餾過(guò)程的控制步驟,因此適宜的催化劑進(jìn)料流量為1 kmol·h?1。
圖10 催化劑進(jìn)料流量對(duì)產(chǎn)物純度和乙酸甲酯轉(zhuǎn)化率的影響Fig.10 Effects of catalyst flow rate on purities of products and conversion of methyl acetate
4.7優(yōu)化條件及結(jié)果
綜合上述各個(gè)影響因素的分析對(duì)反應(yīng)萃取精餾過(guò)程進(jìn)行了初步優(yōu)化,得到了一個(gè)優(yōu)化的操作條件。與參比操作條件相比,甲醇純度由0.9847提高到0.9922,乙酸乙酯純度由0.9831提高到0.9905,乙酸甲酯轉(zhuǎn)化率由0.9847提高到0.9922。具體操作條件及計(jì)算結(jié)果見(jiàn)表4。
表4 優(yōu)化操作條件和模擬計(jì)算結(jié)果Table 4 Optimized operating conditions and simulation results
以離子液體作為催化劑和萃取劑對(duì)乙酸甲酯和乙醇酯交換反應(yīng)合成甲醇和乙酸乙酯的反應(yīng)萃取精餾過(guò)程進(jìn)行模擬計(jì)算,結(jié)論如下。
(1)采用離子液體[HSO3bmim][HSO4]和[BMIM][Tf2N]分別作為催化劑和萃取劑,利用反應(yīng)萃取精餾進(jìn)行乙酸甲酯和乙醇的酯交換反應(yīng),能夠得到純度為0.9922的甲醇和純度為0.9905的乙酸乙酯,乙酸甲酯轉(zhuǎn)化率為0.9922。
(2)研究了理論板數(shù)、回流比、持液量、進(jìn)料位置、溶劑比、催化劑進(jìn)料流量等參數(shù)對(duì)反應(yīng)萃取精餾過(guò)程的影響。結(jié)果表明,甲醇和乙酸乙酯純度以及乙酸甲酯轉(zhuǎn)化率隨塔板持液量、溶劑比和催化劑含量升高而升高,反應(yīng)萃取精餾過(guò)程存在最佳回流比。
符號(hào)說(shuō)明
Bij——NRTL二元交互作用參數(shù)
ccat——催化劑濃度,mol·L?1
Ea+, Ea?——分別為正、逆反應(yīng)活化能,kJ·mol?1
k+, k?——分別為正、逆反應(yīng)速率常數(shù),L1.5·mol?1.5·min?1
k0+, k0
?——分別為Arrhenius方程中正、逆反應(yīng)指前因
子,L1.5·mol?1.5·min?1
ni——反應(yīng)體系中組分i的量,mol
r ——反應(yīng)速率,mol·L?1·min?1
T ——溫度,K
t ——時(shí)間,min
V ——反應(yīng)體積,L
xi——液相組分i的摩爾分?jǐn)?shù)
α ——活度
αji——非隨機(jī)參數(shù)
γi——組分i的活度系數(shù)
v ——化學(xué)計(jì)量數(shù)
ρ ——反應(yīng)混合物密度,mol·L?1
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DOI:10.11949/j.issn.0438-1157. 20151227
中圖分類號(hào):TQ 032.4
文獻(xiàn)標(biāo)志碼:A
文章編號(hào):0438—1157(2016)02—0606—08
Corresponding author:Prof. CUI Xianbao, cxb@tju.edu.cn
Synthesis of ethyl acetate via reactive and extractive distillation column using ionic liquids as catalyst and entrainer
JIE Huimin, CUI Xianbao, PENG Yanmei, LI Xiaobing, XU Li, LIN Ruirong
(State Key Laboratory of Chemical Engineering (Tianjin University), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China)
Abstract:Transesterification of methyl acetate with ethanol to produce ethyl acetate and methanol via reactive and extractive distillation (RED) was simulated, using ionic liquids, 1-sulfobutyl-3-methyllimidazolium hydrogensulfate [HSO3bmin][HSO4] and 1-butyl-3-methylimidazolium bis[(trifluoromethyl) sulfonyl]imide ([BMIM][Tf2N], as catalyst and entrainer respectively. Based on the analysis of vapor-liquid equilibrium and reaction kinetics, a reactive and extractive distillation process was developed. The effects of number of theoretical stages, reflux ratio, liquid holdup, feed locations, entrainer ratio (the ratio of solvent mole flowrate to feed mole flowrates) and catalyst flowrate on RED process were investigated. The simulation results indicated that the purities of ethanol and ethyl acetate were 0.9922 and 0.9905 (mole fraction), respectively, and the conversion of methyl acetate was 0.9922 under the optimal operating and structural conditions.
Key words:ionic liquids; reactive and extractive distillation; methyl acetate; methanol; azeotrope; simulation