Lactate Production Process
A process for producing alkyl R-lactate from an initial compound comprising substructure (I) is provided. The process involves producing an intermediate comprising R,R- and S,S-lactide from the initial compound, wherein the initial compound is subjected to stereoisomerisation conditions; and reacting at least a portion of the intermediate with an alkyl alcohol to produce a product comprising alkyl R-lactate, wherein alkyl R-lactate is produced in the presence of an enzyme. Also provided are processes for the production of R-lactic acid, oligomeric R-lactic acid, R,R-lactide, poly-R-lactic acid and stereocomplex lactic acid.
1 . A process for producing alkyl R-lactate comprising: producing an intermediate comprising R,R- and S,S-lactide from an initial compound comprising substructure (I)
wherein the initial compound is subjected to stereoisomerisation conditions; and
reacting at least a portion of the intermediate with an alkyl alcohol to produce a product comprising alkyl R-lactate, wherein alkyl R-lactate is produced in the presence of an enzyme.
2 . The process as claimed in claim 1 , wherein the initial compound is contacted with a tertiary amine stereoisomerisation catalyst.
3 . The process as claimed in claim 1 , wherein the initial compound comprises oligomeric S-lactic acid, S-lactic acid or a salt thereof, alkyl S,S-lactyllactate and/or alkyl S-lactate, and wherein the intermediate is produced by:
(i) subjecting the initial compound to stereoisomerisation conditions; and
(ii) converting at least a portion of the product of step (i) into the intermediate.
4 . The process as claimed in claim 3 , wherein the initial compound comprises oligomeric-S-lactic acid, wherein the oligomeric S-lactic acid is produced from S-lactic acid, and wherein step (i) comprises contacting the oligomeric S-lactic acid with a tertiary amine stereoisomerisation catalyst at a temperature of from about 100° C. to about 200° C. to produce oligomeric lactic acid.
5 . The process as claimed in claim 4 , wherein step (ii) comprises converting at least a portion of the oligomeric lactic acid into R,R- and S,S-lactide by heating at a temperature of from about 160° C. to about 240° C. in the presence of a Lewis acid catalyst comprising an oxide, alkoxide or carboxylate salt of a metal.
6 . The process as claimed in claim 2 , wherein tertiary amine is recovered and recycled to the process.
7 . The process as claimed in claim 1 , wherein R,R- and S,S-lactide are separated from R,S-lactide, and R,S-lactide is recycled to the process.
8 . The process according to claim 1 , wherein the alkyl alcohol is a C 2 to C 8 alkyl alcohol.
9 . The process according to claim 1 , wherein the enzyme is a lipase.
10 . The process as claimed in claim 9 , wherein the enzyme is a Candida antarctica lipase B.
11 . The process according to claim 1 , wherein alkyl R-lactate is separated from alkyl S,S-lactyllactate by distillation.
12 . The process as claimed in claim 11 , wherein alkyl S,S-lactyllactate is recovered and optionally recycled to the process.
13 . The process according to claim 1 , wherein alkyl alcohol is recovered and recycled to the process.
14 . The process for producing R-lactic acid comprising producing R-alkyl lactate according to claim 1 , and converting the R-alkyl lactate into R-lactic acid.
15 . The process for producing oligomeric R-lactic acid comprising producing R-alkyl lactate according to claim 1 , or producing R-lactic acid according to claim 14 , and converting the R-alkyl lactate or R-lactic acid into oligomeric R-lactic acid.
16 . The process for producing R,R-lactide comprising producing R-alkyl lactate according to claim 1 , or producing R-lactic acid according to claim 14 , or producing oligomeric R-lactic acid according to claim 15 , and converting the R-alkyl lactate, R-lactic acid or oligomeric R-lactic acid into R,R-lactide.
17 . The process for producing poly-R-lactic acid comprising producing R,R-lactide according to claim 16 , and converting the R,R-lactide into poly-R-lactic acid.
18 . The process for producing stereocomplex lactic acid, comprising producing poly-R-lactic acid according to claim 17 , and combining the poly-R-lactic acid with poly-S-lactic acid to produce stereocomplex lactic acid.
19 . A process for producing alkyl S,S-lactyllactate comprising: producing an intermediate comprising R,R- and S,S-lactide from an initial compound comprising substructure (IP)
wherein the initial compound is subjected to stereoisomerisation conditions; and reacting at least a portion of the intermediate with an alkyl alcohol to produce alkyl S,S-lactyllactate and alkyl R,R-lactyllactate, wherein the alkyl R,R-lactyllactate is reacted with alkyl alcohol in the presence of an enzyme to produce alkyl R-lactate.
20 . The process as claimed in claim 19 , wherein alkyl R-lactate is recovered and optionally recycled to the process.