TWI417283B - Process for preparing lactic esters - Google Patents
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本發明係關於將乳酸經酯化反應以生成乳酸酯之方法，尤其有關該酯化反應中所使用之觸媒。The present invention relates to a process for the esterification of lactic acid to form a lactate, and more particularly to the catalyst used in the esterification reaction.
乳酸是重要的生物化工產品，廣泛應用於醫藥、食品、化工、皮革、合成纖維和塑膠原料等領域。乳酸是可由石油化工合成或由發酵製得，未來乳酸需求增長主要來自兩方面：聚乳酸和乳酸酯溶劑。近年來由於環保議題備受矚目，隨著以乳酸為原料合成的綠色溶劑(乳酸酯)和生物可分解塑膠(聚乳酸)製品的成功開發與利用，乳酸的需求量正在逐年上升。Lactic acid is an important biochemical product widely used in the fields of medicine, food, chemical, leather, synthetic fiber and plastic raw materials. Lactic acid can be synthesized by petrochemical or by fermentation. The future demand for lactic acid will increase mainly from two aspects: polylactic acid and lactate solvent. In recent years, environmental protection issues have attracted attention. With the successful development and utilization of green solvents (lactic acid esters) and biodegradable plastics (polylactic acid) products synthesized from lactic acid, the demand for lactic acid is increasing year by year.
乳酸酯類可作為綠色溶劑，乳酸酯是一種優良而又安全的高沸点溶劑，對油脂和聚合物具有極强的溶解力及獨特的溶解性。乳酸酯當作綠色溶劑的應用，可以避免傳統有機溶劑所造成的環境污染之問題。Lactic acid esters are used as green solvents. Lactic acid esters are an excellent and safe high-boiling solvent with excellent solubility and unique solubility for greases and polymers. The use of lactate as a green solvent avoids the environmental pollution caused by traditional organic solvents.
乳酸酯化反應亦可以應用在純化乳酸的製程中。由於聚乳酸材料的合成需要高純度的乳酸單體，因此從乳酸發酵液中分離和純化乳酸的技術已成為當前乳酸生產中的關鍵。反應蒸餾法是一優良的乳酸純化方法，可用來得到高純度的乳酸。反應蒸餾法純化乳酸主要包括三個步驟：乳酸酯化、減壓蒸餾和乳酸酯水解，即先進行乳酸與醇類間的酯化反應，以生成乳酸酯，再經過減壓蒸餾分離乳酸酯及水解乳酸酯，而得到精製乳酸。因此由乳酸經酯化反應以生成乳酸酯亦可為精製乳酸的步驟之一。The lactation reaction can also be applied to the process of purifying lactic acid. Since the synthesis of polylactic acid materials requires high-purity lactic acid monomers, the technique of separating and purifying lactic acid from lactic acid fermentation broth has become the key in current lactic acid production. The reactive distillation method is an excellent method for purifying lactic acid and can be used to obtain high-purity lactic acid. The purification of lactic acid by reactive distillation mainly comprises three steps: lactation, distillation under reduced pressure and hydrolysis of lactate, that is, esterification reaction between lactic acid and alcohol is first carried out to form lactate, and then subjected to vacuum distillation. The lactic acid ester and the lactic acid ester are hydrolyzed to obtain purified lactic acid. Therefore, the esterification reaction of lactic acid to form lactate can also be one of the steps of purifying lactic acid.
美國專利第2350370號(Schopmeyer,H .H.,C.R. Arnold,“Lactic acid purification”,1944)為最早使用反應蒸餾的概念來純化乳酸，其乃以甲醇進行乳酸的酯化反應，他們使用硫酸當酯化反應的觸媒。U.S. Patent No. 2,350,370 (Schopmeyer, H.H., CR Arnold, "Lactic acid purification", 1944) is the first to use the concept of reactive distillation to purify lactic acid, which is an esterification reaction of lactic acid with methanol. Catalyst for esterification.
Choi and Hong(Choi,J.,Hong,W. H.,“Recovery of lactic acid by batch distillation with chemical reactions using ion exchange resin”,J. Chemical Eng. Japan,32(2),P. 184(1999))，Seo et al.(Seo,Y.,Hong,W. H.,and Hong,T. H.,“Effects of operation variables on the recovery of lactic acid in a batch distillation process with chemical reactions”,Korean J. of Chem. Eng.,16(5),P. 556(1999))，以及Kim et al.(Kim,J.Y.,Kim,Y. J.,Hong,W. H.,and Wozny,G.,“Recovery process of lactic acid using two distillation columns”,Biotech. & Bioprocess Eng.,5(3),P. 196(2000))等以批式反應蒸餾的方式純化乳酸，他們皆以陽離子交換樹脂作為觸媒，進行甲醇與乳酸之酯化反應，及其後續之水解反應。Ma et al.(Ma,L.,Zhang,Y.,and Yang,J.,“Purification of lactic acid by heterogeneous catalytic distillation using ion-exchange resins”,Chinese J. of Chem. Eng.,13(1),P. 24(2005))則在蒸餾塔內以陽離子交換樹脂為觸媒，使用甲醇來酯化乳酸，同時以反應蒸餾方式進行乳酸甲酯的水解反應。Kumar et al.(Kumar,R.,Nanavati,H.,Noronha,S. B.,Mahajani,S. M.,“A continuous process for the recovery of lactic acid by reactive distillation”,Journal of Chemical Technology & Biotechnology,81(11),P. 1767(2006))使用二相連續攪拌反應器反應，在其內添加甲醇來進行乳酸酯化反應，而含乳酸甲酯，水，甲醇之氣相產物，則再將其送入水解塔，可得到較純之乳酸。Kumar and Mahajani(Kumar,R. and Mahajani,S. M.,Esterification of lactic acid with n-butanol by reactive distillation,Ind. Eng. Chem. Res.,46(21),P. 6873(2007))則以丁醇與乳酸反應為基礎，以酯化反應蒸餾塔，水解反應蒸餾塔，配以氣提塔的分離程序完成乳酸的純化，Kumar等人使用之催化乳酸酯化及水解反應之觸媒亦為陽離子交換樹脂。陽離子交換樹脂之缺點為其無法在較高之溫度下使用，我們發現於攝氏150度以上使用陽離子交換樹脂催化乳酸與丁醇之酯化反應，會造成反應溶液嚴重變色的情況。Choi and Hong (Choi, J., Hong, WH, "Recovery of lactic acid by batch distillation with chemical reactions using ion exchange resin", J. Chemical Eng. Japan, 32(2), P. 184 (1999)), Seo et al. (Seo, Y., Hong, WH, and Hong, TH, "Effects of operation variables on the recovery of lactic acid in a batch distillation process with chemical reactions", Korean J. of Chem. Eng., 16 (5), P. 556 (1999)), and Kim et al. (Kim, JY, Kim, YJ, Hong, WH, and Wozny, G., "Recovery process of lactic acid using two distillation columns", Biotech. & Bioprocess Eng., 5(3), P. 196(2000)), etc. Purification of lactic acid by batch reactive distillation, which uses cation exchange resin as a catalyst to carry out the esterification reaction of methanol with lactic acid, and its subsequent Hydrolysis reaction. Ma et al. (Ma, L., Zhang, Y., and Yang, J., "Purification of lactic acid by heterogeneous catalytic distillation using ion-exchange resins", Chinese J. of Chem. Eng., 13(1) , P. 24 (2005)) In the distillation column, a cation exchange resin is used as a catalyst, methanol is used to esterify lactic acid, and a hydrolysis reaction of methyl lactate is carried out by a reactive distillation method. Kumar et al. (Kumar, R., Nanavati, H., Noronha, SB, Mahajani, SM, "A continuous process for the recovery of lactic acid by reactive distillation", Journal of Chemical Technology & Biotechnology, 81 (11), P. 1767 (2006)) using a two-phase continuous stirred reactor reaction, adding methanol to carry out lactation reaction, and a gas phase product containing methyl lactate, water and methanol, and then feeding it to hydrolysis The tower can obtain relatively pure lactic acid. Kumar and Mahajani (Kumar, R. and Mahajani, SM, Esterification of lactic acid with n-butanol by reactive distillation, Ind. Eng. Chem. Res., 46(21), P. 6873 (2007)) Based on the reaction with lactic acid, the esterification reaction distillation column, the hydrolysis reaction distillation column, and the separation process of the stripping tower complete the purification of lactic acid. The catalyst used by Kumar et al. to catalyze the esterification and hydrolysis of lactic acid is also a cation. Exchange resin. The disadvantage of cation exchange resins is that they cannot be used at higher temperatures. We have found that the use of cation exchange resins to catalyze the esterification of lactic acid with butanol at temperatures above 150 °C can cause severe discoloration of the reaction solution.
乳酸之酯化反應為一可逆反應，典型地可以下列化學反應式表示：The esterification of lactic acid is a reversible reaction and is typically represented by the following chemical reaction formula:
CH3 CH(OH)COOH+ROH=CH3 CH(OH)COOR+H2 OCH 3 CH(OH)COOH+ROH=CH 3 CH(OH)COOR+H 2 O
(乳酸+烷基醇=乳酸酯+水)(Lactic acid + alkyl alcohol = lactate + water)
基於化學動力學之理論，能夠催化乳酸之酯化反應之觸媒(即正反應)亦可同時用於催化乳酸酯之水解反應(即逆反應)。此可逆反應為一吸熱反應，因此溫度的增加有利於平衡常數之增加及乳酸酯產率的增加。由上述之文獻可知以液體酸及陽離子交換樹脂可以催化乳酸和醇的酯化反應以及催化乳酸酯之水解反應，使用液體酸為觸媒之缺點是容易腐蝕反應設備級造成環境污染問題，而使用陽離子交換樹脂為觸媒之缺點則為其不耐高溫。因此需要有一固體觸媒，能夠於高溫有效催化乳酸與醇之酯化反應及乳酸酯之水解反應，以應用於綠色溶劑(乳酸酯)之合成及應用於以反應蒸餾方式進行乳酸純化之製程中。Based on the theory of chemical kinetics, a catalyst capable of catalyzing the esterification reaction of lactic acid (ie, a positive reaction) can also be used to catalyze the hydrolysis reaction of a lactate (ie, a reverse reaction). This reversible reaction is an endothermic reaction, so an increase in temperature favors an increase in the equilibrium constant and an increase in the yield of lactic acid ester. It is known from the above literature that liquid acid and cation exchange resins can catalyze the esterification reaction of lactic acid and alcohol and catalyze the hydrolysis reaction of lactic acid ester. The disadvantage of using liquid acid as a catalyst is that it is easy to corrode the environmental pollution caused by the reaction equipment level, and The disadvantage of using a cation exchange resin as a catalyst is that it is not resistant to high temperatures. Therefore, a solid catalyst is needed, which can effectively catalyze the esterification reaction of lactic acid with alcohol and the hydrolysis reaction of lactic acid at high temperature, and is applied to the synthesis of green solvent (lactic acid ester) and to the purification of lactic acid by reactive distillation. In the process.
本發明之主要目的係在提供一種製備乳酸酯的改良方法，其包括在一含有鈦和鋯之觸媒系統存在下使乳酸和一含有烷基醇之液體進行酯化反應以生成乳酸酯。出乎意料的，在相同之反應條件下，該鈦鋯混合觸媒較單獨之鈦觸媒或單獨之鋯觸媒有較高之乳酸酯產率。SUMMARY OF THE INVENTION The primary object of the present invention is to provide an improved process for the preparation of a lactate comprising esterifying a lactic acid and a liquid containing an alkyl alcohol in the presence of a catalyst system comprising titanium and zirconium to form a lactate. . Unexpectedly, under the same reaction conditions, the titanium-zirconium mixed catalyst has a higher lactate yield than the titanium catalyst alone or the zirconium catalyst alone.
本發明之鈦鋯混合觸媒可以使用共沉澱法、含浸法或固態反應法(solid-state reaction)加以製備，較佳是共沉澱法。共沉澱法是改變溶液中之pH值或改變溶液溫度等方式使鈦化合物和鋯化合物產生共沉澱，然後經過濾、乾燥及鍛燒等步驟產生鈦鋯混合觸媒。The titanium-zirconium mixed catalyst of the present invention can be produced by a coprecipitation method, an impregnation method or a solid-state reaction, preferably a coprecipitation method. The coprecipitation method is to change the pH value in the solution or change the temperature of the solution to coprecipitate the titanium compound and the zirconium compound, and then to produce a titanium-zirconium mixed catalyst by filtration, drying and calcination.
產生共沉澱之較佳方法是使用含有鈦前驅物及鋯前驅物之混合水溶液與一鹼性水溶液接觸以產生不溶的鈦鋯氫氧化物或不溶的鈦鋯碳酸鹽，此些氫氧化物及碳酸鹽經加熱後可以形成鈦鋯混合氧化物。A preferred method of producing a coprecipitation is to use a mixed aqueous solution containing a titanium precursor and a zirconium precursor to contact an aqueous alkaline solution to produce an insoluble titanium zirconium hydroxide or an insoluble titanium zirconium carbonate, such hydroxide and carbonic acid. The salt can be heated to form a titanium-zirconium mixed oxide.
適合用於本發明之鈦前驅物包括鹵化鈦、氧化鈦、鈦酯、硫化鈦、硫酸鈦、草酸鈦、氮化鈦、氫化鈦、碳化鈦，較佳的為鹵化鈦及鈦酯，更佳的為氯化鈦。Titanium precursors suitable for use in the present invention include titanium halides, titanium oxides, titanium esters, titanium sulfide, titanium sulfate, titanium oxalate, titanium nitride, titanium hydride, titanium carbide, preferably titanium halides and titanium esters, more preferably It is titanium chloride.
適合用於本發明之鋯前驅物包括鹵化鋯、氧化鋯、鋯酯、硫化鋯、硫酸鋯、草酸鋯、氮化鋯、氫化鋯、碳化鋯，較佳的為鹵化鋯及鋯酯，更佳的為氯化鋯。Zirconium precursors suitable for use in the present invention include zirconium halides, zirconium oxides, zirconium esters, zirconium sulfides, zirconium sulfates, zirconium oxalates, zirconium nitrides, zirconium hydrides, zirconium carbides, preferably zirconium halides and zirconium esters, more preferably It is zirconium chloride.
本發明乳酸之酯化反應包括在一以上述製備之含有鈦和鋯之觸媒系統存在下使乳酸和一烷基醇進行酯化反應以生成乳酸酯。適合之烷基醇含有之碳數目為一個至七個，較佳的為甲醇、乙醇、丙醇及丁醇。The esterification reaction of lactic acid of the present invention comprises esterifying lactic acid and a monoalkyl alcohol in the presence of a catalyst system comprising titanium and zirconium prepared as described above to form a lactate. Suitable alkyl alcohols contain from one to seven carbons, preferably methanol, ethanol, propanol and butanol.
本發明之酯化反應可以在批式反應器或連續式反應器或反應蒸餾塔中進行，連續式反應器可以為連續攪拌之泥漿反應器(slurry reactor)、滴流反應器(trickle-bed reactor)或固定床反應器。環氧化反應之反應溫度係介於20至300℃之間，較佳為介於50至200℃之間。The esterification reaction of the present invention can be carried out in a batch reactor or a continuous reactor or a reactive distillation column. The continuous reactor can be a continuously stirred slurry reactor or a trickle-bed reactor. ) or a fixed bed reactor. The reaction temperature of the epoxidation reaction is between 20 and 300 ° C, preferably between 50 and 200 ° C.
以下實施例可進一步說明本發明方法，但該等實施例僅供作為說明之用而非用於限制本發明之範圍。The following examples are intended to further illustrate the method of the invention, but are not intended to limit the scope of the invention.
此實際例中使用之酯化觸媒為鈦鋯莫耳比為1：1之觸媒。The esterification catalyst used in this practical example is a catalyst having a titanium zirconium molar ratio of 1:1.
將3.8克四氯化鈦及4.7克四氯化鋯分別溶於10毫升之無水酒精中，再將此些溶液混合。然後將45毫升之28%氨水慢慢滴入於混合後之酒精溶液中，產生共沉澱反應，並加以繼續的攪拌兩小時，使共沉澱反應更完全。經過過濾、水洗、乾燥(110℃,12小時)後，再經鍛燒(以每分鐘升溫攝氏2度的方式升溫至攝氏550度，然後在攝氏550度維持四小時)，即得鈦鋯莫耳比1：1之混合觸媒。3.8 g of titanium tetrachloride and 4.7 g of zirconium tetrachloride were separately dissolved in 10 ml of absolute alcohol, and these solutions were mixed. Then, 45 ml of 28% aqueous ammonia was slowly dropped into the mixed alcohol solution to cause a coprecipitation reaction, and stirring was continued for two hours to complete the coprecipitation reaction. After filtering, washing with water, drying (110 ° C, 12 hours), and then calcining (heating to 550 ° C for 2 hours Celsius, then maintaining at 550 ° C for four hours), then get titanium zirconium Mixed catalyst with ear ratio 1:1.
於一100毫升的高壓反應器中加入1.32克的乳酸(88%純度)和14毫升的丁醇，再加入上述製備之鈦鋯觸媒0.32克，然後加熱使反應器達到所設定好之溫度，攪拌速率設定為200rpm。反應達設定之時間後，將反應器降溫至室溫，取反應過之溶液，以氣相層析儀(GC)進行成份分析，以測量剩下之乳酸的莫耳數及產生之乳酸丁酯的莫耳數。由此可以下列之方程式計算乳酸之轉化率及乳酸丁酯之產率：乳酸之轉化率=(乳酸反應掉之莫耳數)/(乳酸放入之莫耳數)×100%；乳酸丁酯產率=(乳酸丁酯之莫耳數)/(乳酸放入之莫耳數)×100%。乳酸轉化率之結果列於表一，乳酸丁酯產率之結果列於表二。Add 1.32 g of lactic acid (88% purity) and 14 ml of butanol to a 100 ml high pressure reactor, and then add 0.32 g of the titanium zirconium catalyst prepared above, and then heat to bring the reactor to the set temperature. The stirring rate was set to 200 rpm. After the reaction has reached the set time, the reactor is cooled to room temperature, the reacted solution is taken, and the component analysis is carried out by gas chromatography (GC) to measure the molar number of the remaining lactic acid and the produced butyl lactate. The number of moles. From this, the conversion of lactic acid and the yield of butyl lactate can be calculated by the following equation: conversion of lactic acid = (mole of lactic acid reaction) / (mole of lactic acid) × 100%; butyl lactate Yield = (molar number of butyl lactate) / (molar number of lactic acid added) × 100%. The results of the lactic acid conversion rate are shown in Table 1. The results of the butyl lactate yield are shown in Table 2.
此實際例中使用之酯化觸媒為鈦鋯莫耳比3：1之觸媒。觸媒的製備步驟如同實施例1，只是使用5.7克四氯化鈦及2.3克四氯化鋯。酯化反應的步驟亦如同實施例1，乳酸轉化率之結果亦列於表一，乳酸丁酯產率之結果亦列於表二。The esterification catalyst used in this practical example is a catalyst having a titanium zirconium molar ratio of 3:1. The catalyst was prepared as in Example 1, except that 5.7 grams of titanium tetrachloride and 2.3 grams of zirconium tetrachloride were used. The esterification reaction was also carried out in the same manner as in Example 1. The results of the lactic acid conversion were also shown in Table 1. The results of the butyl lactate yield are also shown in Table 2.
此比較例中使用之酯化觸媒為不含鋯之鈦觸媒，鈦觸媒的製備步驟如同實施例1，只是使用5.7克四氯化鈦及0克四氯化鋯。酯化反應的步驟亦如同實施例1，乳酸轉化率之結果亦列於表一，乳酸丁酯產率之結果亦列於表二。The esterification catalyst used in this comparative example was a zirconium-free titanium catalyst, and the titanium catalyst was prepared in the same manner as in Example 1, except that 5.7 g of titanium tetrachloride and 0 g of zirconium tetrachloride were used. The esterification reaction was also carried out in the same manner as in Example 1. The results of the lactic acid conversion were also shown in Table 1. The results of the butyl lactate yield are also shown in Table 2.
此比較例中使用之酯化觸媒為不含鈦之鋯觸媒，鋯觸媒的製備步驟如同實施例1，只是使用7克四氯化鋯及0克四氯化鈦。酯化反應的步驟亦如同實施例1，乳酸轉化率之結果亦列於表一，乳酸丁酯產率之結果亦列於表二。The esterification catalyst used in this comparative example was a zirconium catalyst containing no titanium. The zirconium catalyst was prepared in the same manner as in Example 1, except that 7 g of zirconium tetrachloride and 0 g of titanium tetrachloride were used. The esterification reaction was also carried out in the same manner as in Example 1. The results of the lactic acid conversion were also shown in Table 1. The results of the butyl lactate yield are also shown in Table 2.
由表一及表二之數據可以看出，鈦鋯混合觸媒(實施例一及實施例二)較單獨之鈦觸媒或單獨之鋯觸媒(比較例一及比較例二)有較高之乳酸轉化率及乳酸酯產率，此結果顯然是出乎意料之外。It can be seen from the data of Tables 1 and 2 that the titanium-zirconium mixed catalyst (Example 1 and Example 2) is higher than the titanium catalyst alone or the zirconium catalyst alone (Comparative Example 1 and Comparative Example 2). The lactic acid conversion rate and lactate yield were clearly unexpected.
從以上描述可以了解到本發明方法具有增進功效而確為一甚具產業上利用價值的新發明。It can be understood from the above description that the method of the present invention has an improved effect and is indeed a new invention which is of industrial value.
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| TW (1) | TWI417283B (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6841505B2 (en) * | 2002-07-26 | 2005-01-11 | E..I. Du Pont De Nemours And Company | Titanium-zirconium catalyst compositions and use thereof |
| CN100545141C (en) * | 2007-02-15 | 2009-09-30 | 南京工业大学 | A kind of preparation method of lactate |
-
2010
- 2010-04-27 TW TW99113163A patent/TWI417283B/en not_active IP Right Cessation
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6841505B2 (en) * | 2002-07-26 | 2005-01-11 | E..I. Du Pont De Nemours And Company | Titanium-zirconium catalyst compositions and use thereof |
| CN100545141C (en) * | 2007-02-15 | 2009-09-30 | 南京工业大学 | A kind of preparation method of lactate |
Also Published As
| Publication number | Publication date |
|---|---|
| TW201136890A (en) | 2011-11-01 |
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