第4期黃光曉等:乙醇酸甲酯水解制備乙醇酸的反應(yīng)動力學(xué)15乙醇酸甲酯水解制備乙醇酸的反應(yīng)動力學(xué)黃光曉,徐艷,李振花,王汝賢,馬新賓(天津大學(xué)化工學(xué)院綠色合成與轉(zhuǎn)化教育部重點(diǎn)實(shí)驗室,天津300072摘要:在無外邡催化劑的條件下對乙醇酸甲酯水解制備乙醇酸的反應(yīng)動力學(xué)進(jìn)行了研究,分別考察了攪拌轉(zhuǎn)速、初始水酯的物質(zhì)的量比和溫度對反應(yīng)速率的影響?；诰嗄Ｐ?通過實(shí)驗數(shù)據(jù)的回歸得到了指前因子與活化能。研究發(fā)現(xiàn)用活度代替物質(zhì)的量分?jǐn)?shù)進(jìn)行反應(yīng)動力學(xué)擬合效果更好,其中各組分的活度系數(shù)用 UNIFAC法估算通過范特霍夫方程估算得到該反應(yīng)的標(biāo)準(zhǔn)反應(yīng)焓約為1612kJ/mol關(guān)鍵詞:乙醇酸甲酯;水解;乙醇酸;反應(yīng)動力學(xué);自催化中圖分類號?TQ0132;TQ22541文獻(xiàn)標(biāo)識碼A文章編號:1001-9219(2012)0415-04乙醇酸(CA)又稱羥基乙酸,是一種重要的有機(jī)原料合成乙二醇過程中的重要副產(chǎn)品。隨著乙二合成中間體和精細(xì)化學(xué)品,主要用于皮革、清洗劑醇的合成技術(shù)工業(yè)化進(jìn)程的不斷推進(jìn),水解原料問和化妝品等行業(yè)近年來,尤其是隨著生物醫(yī)學(xué)材題勢將會得到很好解決。料和可降解聚合材料聚乙醇酸(PGA和聚乳酸-乙鑒于自催化工藝的優(yōu)勢,本文對無外加催化劑醇酸( PLA-PGA的應(yīng)用不斷擴(kuò)大,對高純度的聚合條件下的乙醇酸甲酯水解的工藝參數(shù)進(jìn)行了考察,單體乙醇酸的需求量的增長已成必然。并在消除了傳質(zhì)阻力影響的前提下,進(jìn)行了動力學(xué)目前,國內(nèi)外采用的乙醇酸的生產(chǎn)方法主要實(shí)驗測定和動力學(xué)參數(shù)佔(zhàn)算。旨在為后續(xù)乙醇酸甲有:氯乙酸水解法、羥基乙腈的酸催化水解法和甲酯水解過程模擬提供數(shù)據(jù)支持。醛羰基化法。氯乙酸水解法和羥基乙腈水解法產(chǎn)品收率高,但原料的毒性、腐蝕性以及由此而引發(fā)的實(shí)驗部分環(huán)境問題值得重視;甲醛羰基化法雖然原料成本11實(shí)驗原料與儀器低,但操作壓力高,產(chǎn)物分離精制復(fù)雜,且催化劑難乙醇酸甲酯,分析純,≥99%;甲醇,分析純以回收利用。一直以來,人們都在積極致力于工99%;乙醇酸,分析純,≥99%;去離子水。超級恒溫藝條件的改進(jìn)如微生物催化合成法岡,目的在于能水浴,上海實(shí)驗儀器廠;數(shù)顯無極恒速攪拌器,河南夠獲得反應(yīng)條件溫和、環(huán)境友好的合成乙醇酸的綠予華儀器廠;高效液相色譜儀,美國 Agilent1100色工藝路線。型通過酯類化合物的水解制備高純度酸這一工1.2實(shí)驗方法藝路線已得到很多研究者認(rèn)同,他們運(yùn)用先酯化再實(shí)驗在帶有攪拌器、溫度計和冷凝器的250ml水解的工藝過程成功實(shí)現(xiàn)了難度較大的酸的純化團(tuán)。的四口燒瓶中進(jìn)行,反應(yīng)溫度控制精度為±05K。實(shí)因此,以乙醇酸甲酯QMC)為原料水解制備乙醇酸的驗時,先將準(zhǔn)確計量的乙醇酸甲酯加入反應(yīng)器預(yù)方法十分值得關(guān)注。事實(shí)上,受到乙醇酸甲酯生產(chǎn)熱,開啟攪拌器并將轉(zhuǎn)速調(diào)至指定轉(zhuǎn)速,當(dāng)達(dá)到指規(guī)模的限制,原料來源自然也就成為了抑制該水解定溫度時,再將準(zhǔn)確計量并已預(yù)熱到指定溫度的去工藝技術(shù)發(fā)展的瓶頸,迄今為止,尚未見乙醇酸甲離子水迅速加入到燒瓶,開始記錄反應(yīng)時間。反應(yīng)酯水解制備乙醇酸的研究文獻(xiàn)報道。乙醇酸甲酯除過程中定時取樣分析?？梢圆捎矛F(xiàn)有生產(chǎn)方法生產(chǎn)外隊,也是以合成氣為1.3分析方法采用 Agilent1100型高效液相色譜儀進(jìn)行液相收稿日期:2012-02-22;作者簡介:黃光曉(1987-),女,碩士研組成分析,流動相為乙腈和水的混合,紫外(UV)檢究生。電郵hgxvivi@163.com;*聯(lián)系人:徐艷,副教授,電話測器,柱溫為25℃,采用面積歸一法對各組分進(jìn)行02227890041,電郵xuyan4006@Ptju.edu.cno定量分析叫乙醇酸甲酯水解率按式(1)計算。16天然氣化工(C1化學(xué)與化工)2012年第37卷(1)srS=∑MC Fc(4)Aall sampl式中:X-乙醇酸甲酯水解率;c-乙醇酸甲酯水解產(chǎn)MRD=∑XGA calc \\ x100%(5)物中乙醇酸的濃度,molL;cM-乙醇酸甲酯水解液nt ausampxG中乙醇酸甲酯的濃度,molL式中:幾-實(shí)驗數(shù)據(jù)數(shù);下標(biāo)ex表示實(shí)驗值,calc表2反應(yīng)動力學(xué)示計算值。2.1模型方程3結(jié)果與討論基于 Gmehling的研究,在不加入催化劑的酯3.1攪拌轉(zhuǎn)速的影響類水解過程中,起催化作用的是反應(yīng)自身產(chǎn)生的在相同的溫度條件下考察了不同攪拌轉(zhuǎn)速對酸,且酸的含量對反應(yīng)速率的影響與酸在反應(yīng)介質(zhì)反應(yīng)的影響,如表1所示,當(dāng)攪拌轉(zhuǎn)速達(dá)到200r/min中的解離狀態(tài)有關(guān)。在提出的模型中,反應(yīng)由酸解時,加大攪拌轉(zhuǎn)速對水解的影響可以忽略不計。為離產(chǎn)生的溶劑化質(zhì)子催化時a為05,而由分子酸了消除傳質(zhì)對反應(yīng)的影響,本文的動力學(xué)實(shí)驗均在催化時a為1。 Beltran在關(guān)于乳酸酯化及其酯的攪拌轉(zhuǎn)速為300min下進(jìn)行。水解的研究論文中也采用了類似的模型形式,并取1攪拌轉(zhuǎn)速對乙醇酸甲酯水解率的影響得了較好的結(jié)果。鑒于本研究考察的實(shí)驗條件范圍內(nèi),未發(fā)現(xiàn)副轉(zhuǎn)速醇酸甲酯水解率r/min 0.5h3h6反應(yīng)發(fā)生,因此采用式(2)所示的模型形式對乙醇0.0240.0530.100.30.3910573酸甲酯水解的動力學(xué)數(shù)據(jù)進(jìn)行擬合。2000032006]0.1890.3240.4700655E300003200650195033204630.652r=n,=k expAa/K)(2)50000330.0650.1890.3300.4700656RT式中:r-乙醇酸甲酯的水解速率, mol min2;no-乙醇32水酯的物質(zhì)的量比的影響酸甲酯初始的物質(zhì)的量,mol;X-乙醇酸甲酯的水解相同溫度條件下不同水酯比對反應(yīng)的影響如率;k0-指前因子, mol min;EA1活化能, kJ mol;a-圖1所示。圖1結(jié)果顯示:相同的時間點(diǎn),水解速率酸的活度指數(shù);反應(yīng)體系中讠組分的活度(i=MG、隨著水酯比的增大而增大,且在實(shí)驗范圍內(nèi)的水酯GA、W、M,分別代表乙醇酸甲酯、乙醇酸、水和甲比條件下,平衡轉(zhuǎn)化率也隨著水酯比的增大而增醇);K反應(yīng)平衡常數(shù)。大考慮反應(yīng)介質(zhì)的非理想性的影響,模型中組分的組成以活度表示,活度系數(shù)用 UNIFAC法估算0.8平衡常數(shù)由式(3)表示。06KGAMK(3)bcxy≥0430:式中:x-物質(zhì)的量分?jǐn)?shù);y-活度系數(shù)。25:1▲-20:10222動力學(xué)參數(shù)估算y-l5:17:1將實(shí)驗獲得的不同反應(yīng)時刻的各組分的濃度00數(shù)據(jù)轉(zhuǎn)換為乙醇酸甲酯水解轉(zhuǎn)化率隨時間的變化200400600Reaction time /min關(guān)系,使用B-樣條對數(shù)據(jù)進(jìn)行擬合,再利用微分工具對各時間點(diǎn)的樣條函數(shù)求導(dǎo),獲得相應(yīng)的反應(yīng)速圖1水酯的物質(zhì)的量比對乙醇酸甲酯水解率的影響率。運(yùn)用最小二乘法使式(4)表示的目標(biāo)函數(shù)值最圖2體現(xiàn)了反應(yīng)過程中生成的乙醇酸的濃度小,對數(shù)據(jù)進(jìn)行回歸得到相應(yīng)的動力學(xué)參數(shù),用式與乙醇酸生成速率的關(guān)系,說明該反應(yīng)是可逆反(5)對模型進(jìn)行檢驗。應(yīng),并且具有自催化反應(yīng)的特點(diǎn)。第4期黃光曉等:乙醇酸甲酯水解制備乙醇酸的反應(yīng)動力學(xué)想(y=1)和非理想(y≠1)兩種狀態(tài)下進(jìn)行動力學(xué)參08數(shù)的回歸,數(shù)據(jù)處理結(jié)果如表2所示。0.6表2動力學(xué)模型參數(shù)回歸結(jié)果kI/mol.-minEAJ/JmSRSMRDYO0410.51.022×10750.92138×1033.71109015x10750.942.09×1035690.2手0.51.7T3×1049823.48101.458×104990162×1085,600000.3060.91.21.51.8Concentration of glycolic acd /mmog4結(jié)論圖2乙醇酸濃度與反應(yīng)速率的關(guān)系(1)在無外加催化劑的條件下,乙醇酸甲酯水解過程為一可逆吸熱過程,無其他副反應(yīng)發(fā)生,該33溫度的影響在32815K~3581K范圍內(nèi)考察了溫度對水過程的標(biāo)準(zhǔn)反應(yīng)焓約為161 ckJ/mol解反應(yīng)的影響結(jié)果如圖3所示,結(jié)果表明:反應(yīng)速(2)乙醇酸甲酯水解過程的本征動力學(xué)方程可表示為率隨著反應(yīng)溫度的升高而增大,然而溫度對反應(yīng)平衡轉(zhuǎn)化率的影響不顯著,說明該反應(yīng)的熱效應(yīng)較r=1.713×10′exp(49820005\ Mc Q w aGAQMIKalRT(3)使用活度代替物質(zhì)的量分?jǐn)?shù)得到的動力學(xué)模型更符合實(shí)驗數(shù)據(jù)。0.8參考文獻(xiàn)0.6[]田克勝王保偉許根慧乙醇酸的合成及應(yīng)用門天然氣化工(C1化學(xué)與化工),2006,31(6:606c0.4[2]宋芳.聚羥基乙酸的合成技術(shù)與發(fā)展石油化工技358.15K348.15K術(shù)與經(jīng)濟(jì),2008,245)23-28≥0.2338.15K一v-328.15K[3] Yamaoka T, Takahashi Y, Ohta T, et al. Synthesis andties of multiblock copolynting0.001002003004005006007008009001000lactic acid)and poly (oxypropylene-co-oxyethyleneReaction time /minprepared by direct polycondensation[J]. J Ploym Sci, Part圖3溫度對乙醇酸甲酯水解率的影響A: Ploym Chem,1999,37:1513-1521.4]陳棟梁翟美臻白宇新等.乙醇酸的合成及應(yīng)用小合將實(shí)驗測定得到的平衡組成數(shù)據(jù),按lnK對1成化學(xué),2001,93):194-198T進(jìn)行擬合,通過線性回歸可得到如下關(guān)系式:InK。[5]黃光斗,張智,胡兵,等。乙醇酸合成門化工時刊,=-2006×100+31986,R2=09854按van' t hoff2005,19(2;:5456方程,如式(6)所示計算后得到該反應(yīng)的標(biāo)準(zhǔn)反應(yīng)胡基埂α羥基乙酸合成與分析方法綜述化工進(jìn)展,焓約為1612kJ/mol。這一結(jié)果也表明,在本文考察2007,26(4):496-500的溫度范圍內(nèi),乙醇酸甲酯水解反應(yīng)是吸熱過程。[7 Sawistowski H, Pilavakis P A. Performance of esterification in a reaction-distillation column [] Chem Eng Sci,In K=l1988,43(2)355-360RTR[8]王保偉田克勝許根慧乙醇酸甲酯的合成及應(yīng)用天然氣化工C1化學(xué)與化工,2005,30(4)64-6834動力學(xué)模型9]陳棟梁,李慶,儲偉等.乙醇酸甲酯的合成研究U精在對乙醇酸甲酯水解反應(yīng)動力學(xué)模型回歸時,細(xì)石油化工,2000,3:41-44為確定反應(yīng)介質(zhì)的非理想性,分別在反應(yīng)介質(zhì)按理[10]倪良,趙琛漩,姜勇等乙醇酸甲醋結(jié)構(gòu)和性質(zhì)的理18天然氣化工(C1化學(xué)與化工)2012年第37卷論研究天然氣化工(C1化學(xué)與化工),209,34(6):35heterogeneously catalyzed acetic acid esterification withmethanol and methyl acetate hydrolysis []. Ind Eng Chem[l]黃光曉,徐艷趙玉軍等.反相高效液相色譜測定在乙Res,2000,39:2601-2611.醇酸甲酯存在下的乙醇酸的含量化學(xué)工業(yè)與工程,[13] Delgado P, Sanz m t, Beltran s. Kinetic study for2012,29(1):48-51.esterification of lactic acid with ethanol and hydrolysis of[12] Popken T, Gotze L, gmehling J. Reaction kinetics andethyl lactate using an ion-exchange resin catalyst [Jchemical equilibrium of homogeneously arChem Eng J,2007,126:11118.Kinetics for hydrolysis of methyl glycolate to glycolic acidHUANG Guang-xiao, XU Yan, LI Zhen-hua, WANG Ruxian, MA Xin-bin(Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, TianjinUniversity, Tianjin 300072, China)Abstract: The kinetics for the preparation of glycolic acid by hydrolysis of methyl glycolate without addition of catalyst wasstudied. The effects of stirrer speed, initial reactant ratio of water to methyl glycolate and temperature on the reaction wereinvestigated. The pre-exponential factor and activation energy were obtained by correlating the experimental data based on thehomogenerous model. It was found that the model fitted better when the activities were used instead of the mole fractions, in whichthe activity coefficients were predicted by UNIFAC equation. The standard reaction enthalpy was calculated by vant Hoff equationand the value was about 1612k/molKeywords: methyl glycolate; hydrolysis; glycolic acid; reaction kinetics; auto-catalysisa“…···?！啊ぁ瘛啊瘛ぁぁ啊ぁ啊ぁ?●*·……·“·,·:…···““··…·…“*魯…·●…?···(上接第14頁)Effect of surfactant dosage on the performance of Cu-Zn-Al catalyst prepared by completeliquid-phase technology for alcohol synthesisYAN Jing LI Wen-hui, HUA NG Wei(1. Key Laboratory of Coal Science and Technology of Ministry of Education and Shanxi Province, Taiyuan University of Technology,Taiyuan 030024, China;2. Lanzhou Branch of Space Changzheng Chemical Engineering Co, Ltd, Lanzhou 730000, ChinaAbstract: Cu-Zn-Al slurry catalysts were prepared by a complete liquid-phase technology and characterized by XRD, Hr-TPRand NH]-TPD. The effect of dosage of the surfactant polyvinylpyrrolidone(PvP)used for catalyst preparation on the perormance ocatalysts in synthesis of higher alcohols from syngas was investigated. The results showed that increasing PVP amount could improveselectivity of C2+* alcohols and reduce methanol formation. PVP amount affected Cu particle size of the catalysts, which was closelyrelated to selectivity of alcohols. The smaller the Cu particle size was, the higher the selectivity of methanol was. The larger the Cuarticle size was, the higher the selectivity of Co* alcohols was.Keywords: Cu-Zn-Al catalyst; complete liquid-phase technology; higher alcohols; synthesis; syngas; surfactant; PVP