Continuous method for the heterogenically catalyzed esterification of fatty acids
View Patent ↗Continuous method for the esterification of free fatty acids in plant and animal fats with alcohols using a heterogenic acid catalyst.
1. Continuous process for esterifying free fatty acids present in starting materials, comprising the steps of:
1) removing the free fatty acids from the remaining starting material by distillation or rectification,
2) reacting the deacidified starting material remaining after step 1) in a transesterification to obtain fatty acid alkyl esters,
3) reacting the free fatty acids with alcohols using at least one acidic catalyst in a fixed bed, in an esterification reaction,
4) removing the water formed as a by-product in step 3), optionally together with at least a portion of the alcohol unconverted in step 3),
5) converting the dewatered product obtained from step 4), with addition of further alcohol, using at least one acidic catalyst in a fixed bed, in an esterification reaction,
6) mixing the reaction product obtained from step 3) and/or the reaction product obtained from step 5) with the remaining starting material obtained from step 1) and/or the fatty acid alkyl esters obtained from step 2).
2. Process according to claim 1 , wherein the at least one acidic catalyst comprises a strongly acidic ion exchange resin.
3. Process according to claim 1 , wherein the at least one acidic catalyst comprises a polymeric, macroporous resin with free sulphonic acid groups.
4. Process according to claim 1 , wherein step 5) is performed more than once, and the sequence of step 4) and step 5) is optionally performed more than once.
5. Process according to claim 1 , wherein the alcohol is added in step 3) in a molar ratio between 5 and 40.
6. Process according to claim 1 , wherein reaction (step 3) and/or further conversion (step 5) are carried out at temperatures between 70 and 120° C.
7. Process according to claim 1 , wherein a catalyst hourly space velocity of 0.5 to 10 kg of free fatty acid per kg of catalyst an hour exists in step 3) and/or step 5).
8. Process according to claim 1 , wherein the pressure in step 3) and/or step 5) is selected to correspond to at least the vapor pressure of the alcohol used.
9. Process according to claim 1 , wherein further alcohol is added in step 5).
10. Process according to claim 1 , wherein the removal in step 4) is effected by membrane processes or evaporation.
11. Process according to claim 1 , wherein a superficial velocity of a fluid phase of the free fatty acids with alcohols in the fixed catalyst bed is 1 to 5 mm/s and the fixed catalyst bed has a length of 1 to 10 m, so as to result in a residence time of less than 30 minutes.
12. A process for producing biodiesel which includes the process of claim 1 .
13. Process of claim 5 wherein said molar ratio is between 10 and 25.
14. Process of claim 13 , wherein said molar ratio is between 10 and 20.
15. Process of claim 6 wherein said temperatures are between 80 and 95° C.
16. Process of claim 7 wherein said hourly space velocity is between
1
and
5
kg
kg
·
h
.
17. Process of claim 16 wherein said hourly space velocity is between
1.5
and
4
kg
kg
·
h
.