Synthesis of Lactic Acid and Alkyl Lactate from Carbohydrate-Containing Materials
A method for synthesizing lactic acid and lactate is invented from carbohydrates, such as monosaccharides and/or polysaccharides in the presence of the catalyst that is the combinations of nitrogen-heterocycle aromatic ring cation salts and metal compounds. In the reaction, at least one alcohol and at least one solvent are used. Specifically, in the presence of [SnCl 4 -1-ethyl-3-methylimidazolium chloride ([EMIM]Cl)], SnCl 4 -1,3-dimethylimidazolium methyl sulfate ([DMIM]CH 3 SO 4 )], [SnCl 2 -1-ethyl-3-methylimidazolium chloride ([EMIM]Cl)], or SnCl 2 -1,3-dimethylimidazolium methyl sulfate ([DMIM]CH 3 SO 4 )] in methanol.
1 . A method for synthesizing lactic acid and alkyl lactate from carbohydrate-containing raw materials, comprising:
(a) preparing a mixture of at least one carbohydrate-containing raw material, at least one alcohol, at least one catalyst comprising nitrogen-heterocycle aromatic cation salts and metal compounds, and at least one solvent; and
(b) heating the mixture to obtain lactic acid and alkyl lactate.
2 . The method of claim 1 , wherein the alkyl lactate is selected from the group consisting of methyl lactate and ethyl lactate.
3 . The method of claim 1 , wherein the carbohydrate is selected from the group consisting of polysaccharides and monosaccharides.
4 . The method of claim 1 , wherein the carbohydrate is selected from the group consisting of cotton, cellulose, starch, dextran, sucrose, fructose and glucose.
5 . The method of claim 1 , wherein the alcohol is selected from the group consisting of monohydroxyl alcohols, dihydroxyl alcohols, and multihydroxyl alcohols.
6 . The method of claim 5 , wherein the monohydroxyl alcohol is selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and tert-butanol.
7 . The method of claim 5 , wherein the dihydroxyl alcohol is selected from the group consisting of ethylene glycol, 1,2-propandiol, and 1,3-propandiol.
8 . The method of claim 5 , wherein the multihydroxyl alcohol is glycerol.
9 . The method of claim 1 , wherein the anion of the nitrogen-heterocycle aromatic cation salts is selected from the group consisting of F − , Cl − , Br − , I − , SO 4 2− , CH 3 SO 4 − , CH 3 SO 3 − , C 6 H 5 SO 3 − (benzenesulfenate anion), HSO 4 − , H 2 PO 4 − , HPO 4 2− , PO 4 3− , PF 6 − , BO 2 − , BF 4 − , SiF 6 2− , and CH 3 CO 2 − .
10 . The method of claim 1 , wherein the cation of the nitrogen-heterocycle aromatic cation salts is an organic cation that contains at least one hex-member aromatic ring and/or at least one pent-member aromatic ring that bring at least one of nitrogen atoms on the ring.
11 . The method of claim 10 , wherein the organic cation is selected from the group consisting of
(wherein the two nitrogen atoms are respectively located on the two hex-member rings, each N atom is located at any position among 1, 2, 3, and 4 for each ring),
(wherein the three nitrogen atoms are respectively located on the three hex-member rings, each N atom is located at any position among 1, 2, 3 and 4 for each ring),
(wherein the two nitrogen atoms are respectively located on the two hex-member rings, each N atom is located at any position among 1, 2, 3 and 4 for each ring),
(wherein the two nitrogen atoms are respectively located on the two hex-member rings, each N atom is locate at any position among 1, 2, 3 and 4 for each ring; n and m are positive integers), and derivatives thereof, wherein the substituting group R n on carbon atoms is selected from the group consisting of H—, C n H 2n+1 — (n≧1), C n H 2n−1 —, C n H 2n−3 —, C n H m — (m≧3), C n H 2n−7 — (n≧6), Cl—, Br—, I—, and —OSO 3 − .
12 . The method of claim 11 , wherein the substituting group R n on nitrogen atoms is selected from the group consisting of C n H 2n+1 — (n≧1), C n H 2n−1 —, C n H 2n−3 —, C n H m — (m≧3), and C n H 2n−7 — (n≧6).
13 . The method of claim 10 , wherein the organic cation is selected from the group consisting of 1,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium ([EMIM] + ), and 1,3-dimethylimidazolium ([DMIM] + ).
14 . The method of claim 1 , wherein the metal compound is a tin-containing compound.
15 . The method of claim 14 , wherein the tin-containing compound comprises Sn 4+ , Sn 2+ , or mixtures thereof.
16 . The method of claim 14 , wherein the anion of the tin-containing compound is selected from the group consisting of F − , Cl − , Br − , I − , SO 4 2− , HSO 4 − , CH 3 SO 3 − , C 6 H 5 SO 3 − , H 2 PO 4 − , HPO 4 2− , PO 4 3− , PF 6 − , BO 2 − , BF 4 − , SiF 6 2− , and CH 3 CO 2 − .
17 . The method of claim 1 , wherein the catalyst is a combination of 1,3-dimethylimidazolium methyl sulfate and SnCl 4 .5H 2 O.
18 . The method of claim 1 , wherein the catalyst is a combination of 1,3-dimethylimidazolium methyl sulfate and SnCl 2 .
19 . The method of claim 1 , wherein the catalyst is a combination of 1-ethyl-3-methylimidazolium chloride and SnCl 4 .5H 2 O.
20 . The method of claim 1 , wherein the catalyst is a combination of 1-ethyl-3-methylimidazolium chloride and Sn(C 6 H 5 SO 3 ) 2 .
21 . The method of claim 1 , wherein the catalyst is a combination of 1-ethyl-3-methylimidazolium chloride and Sn(CH 3 SO 3 ) 2 .
22 . The method of claim 1 , wherein the solvent is capable of dissolving the catalyst.
23 . The method of claim 1 , wherein the solvent comprises a polar solvent selected from the group consisting of water and alcohol.
24 . The method of claim 1 , wherein the alcohol is selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, ethylene glycol, 1,2-propandiol, 1,3-propandiol, and glycerol.
25 . The method of claim 1 , wherein the heating is carried out in a one-pot reactor.
26 . The method of claim 1 , wherein the mixture is heated up to a temperature between 25 and 200° C.
27 . The method of claim 26 , wherein the temperature is between 80 and 180° C.
28 . The method of claim 26 , wherein the temperature is between 100 and 160° C.