Process for producing fatty-acid lower-alkyl mono-esters

DETAILED DESCRIPTION We claim: 1.
In a process for producing fatty-acid lower-alkyl mono-esters which comprises a first esterification-step (1) wherein one or more fatty-acid glycerolesters and a monohydric lower-alkylalcohol are reacted in the presence of an alcoholysis catalyst to produce a mixture comprising fatty-acid lower-alkyl mono-esters, fatty-acid glycerolesters and glycerol, a separation step (2) wherein said mixture produced in step (1) is separated into a glycerol-rich fraction (a) and a fraction (b) rich in fatty-acid lower-alkyl mono-ester, and a recovery step (4) wherein said fatty-acid lower-alkyl mono-esters are recovered from said fraction (b), the improvement comprising a second esterification step (3) in which before said recovery step (4) substantially all glycerol and fatty-acid glycerolesters of said fraction (b) are esterified to the corresponding fatty-acid glycerol tri-esters.
2.
The process of claim 1 in which the monohydric lower-alkylalcohol is selected from the from the group of the C.
sub.
1 -C.
sub.
5 mono-alcohols.
3.
The process of claim 2 in which the monohydric lower-alkylalcohol is methanol.
4.
The process of claim 1 in which during the second esterification step (3) lower-alkylalcohol is removed by distillation.
5.
The process of claim 1 in which the second esterification step (3) is carried out at a temperature within the range of from 70.
degree.
to 120.
degree.
C.
6.
The process of claim 1 in which in the second esterification step (3) a top-up amount of catalyst is introduced into fraction (b).
7.
The process of claim 6 in which the top-up amount of catalyst is within the range of from 0.
01 to 0.
1 mol per kg of fraction (b).
8.
The process of claim 1 in which the second esterification step (3) is continued to a level of partial glycerolesters in fraction (b) of 0.
5% by weight or less.
9.
The process of claim 4 in which the lower-alkyl alcohol removed by distillation in the second esterification step (3) is recirculated to the reaction mixture of the first esterification step (1)