Process for the preparation of 3,3-dimethylbutanal
3,3-Dimethylbutanal is prepared from 3,3-dimethylbutanol. Intermediate 3,3-dimethylbutanol is obtained by reacting ethylene, isopropylene and a mineral acid to produce a 3,3-dimethylbutyl ester which is hydrolyzed to the alcohol. The hydrolysis step is effectively carried out by reactive distillation. Alternatively, 3,3-dimethylbutanal is prepared from 3,3-dimethylbutanol obtained by reduction of the corresponding carboxylic acid or 1,2-epoxy-3,3-dimethylbutane, or by hydrolysis of 1-halo-3,3-dimethylbutane. Fixed bed gas phase and stirred tank liquid phase processes are provided for converting 3,3-dimethylbutanol to 3,3-dimethylbutanal by catalytic dehydrogenation.
1. A process for the preparation of 3,3-dimethylbutanol comprising:
heating a hydrolysis feed mixture comprising a 3,3-dimethylbutyl ester and a mineral acid in the presence of water, thereby hydrolyzing the ester and producing a hydrolysis reaction mixture comprising 3,3-dimethylbutanol; and
distilling 3,3-dimethylbutanol formed in the hydrolysis from the hydrolysis reaction mixture.
2. A process for the preparation of 3,3-dimethylbutanol comprising:
heating a hydrolysis feed mixture comprising a 3,3-dimethylbutyl ester and a mineral acid in the presence of water, thereby hydrolyzing the ester and producing a hydrolysis reaction mixture comprising 3,3-dimethylbutanol; and
distilling 3,3-dimethylbutanol formed in the hydrolysis from the hydrolysis reaction mixture as the hydrolysis reaction proceeds.
3. A process as set forth in claim 2 wherein said hydrolysis feed mixture comprises between about 10% and about 75% by weight H 2 S 4 , between about 25% and about 95% water, and between about 1% and about 50% by weight 3,3-dimethylbutyl hydrogen sulfate.
4. A process as set forth in claim 3 wherein said hydrolysis feed mixture further comprises between about 0.5% and about 50% by weight di(3,3-dimethylbutyl) sulfate, both said 3,3-dimethylbutyl hydrogen sulfate and said di(3,3-dimethylbutyl) sulfate being hydrolyzed to 3,3-dimethylbutanol.
5. A process as set forth in claim 3 wherein said distillation is conducted at a head pressure of between about 0.1 atm and about 2 atm and a bottoms temperature of between about 35° and about 175° C.
6. A process as set forth in claim 5 wherein the distillation is conducted at atmospheric head pressure and an overhead condensate fraction rich in 3,3-dimethylbutanol is collected at a temperature of between about 90° and about 99° C.
7. A process as set forth in claim 6 wherein said overhead condensate comprises an azeotrope of 3,3-dimethylbutanol and water.
8. A process as set forth in claim 6 wherein said rich fraction contains at least about 50% by weight 3,3-dimethylbutanol.
9. A process as set forth in claim 8 wherein said rich fraction contains between about 75% and about 95% by weight 3,3-dimethylbutanol.
10. A process as set forth in claim 9 wherein said rich fraction condensate comprises an organic phase containing at least 75% by weight 3,3-dimethylbutanol and an aqueous phase comprising no more than about 2% by weight 3,3-dimethylbutanol.
11. A process as set forth in claim 10 wherein 3,3-dimethylbutanol obtained in said organic phase of said rich fraction is converted to 3,3-dimethylbutanal.
12. A process as set forth in claim 11 wherein 3,3-dimethylbutanol is converted to 3,3-dimethylbutanal by catalytic dehydrogenation.
13. A process as set forth in claim 12 wherein 3,3-dimethylbutanal produced in said catalytic dehydrogenation is reacted with L-α-aspartyl-L-phenylalanine 1-methyl ester in the presence of a reducing agent to produce N-[N-(3,3-dimethybutyl)-L-α-aspartyl]-L-phenylalanine 1-methyl ester.
14. A process as set forth in claim 12 wherein the t-butylacetic acid content of the 3,3-dimethylbutanol product is not greater than about 1% by weight.
15. A process as set forth in claim 2 wherein said 3,3-dimethylbutyl ester is prepared by reacting isobutylene, ethylene, and a mineral acid.
16. A process as set forth in claim 15 wherein isobutylene and ethylene are substantially simultaneously brought into contact with said mineral acid.
17. A process as set forth in claim 15 wherein said mineral acid is sulfuric acid.
18. A process as set forth in claim 15 wherein isobutylene, ethylene, and said mineral acid are reacted in the presence of an organic solvent in an alkylation/esterification reaction zone, thereby producing an alkylation/esterification reaction mixture comprising an organic phase and a pregnant liquor phase, said organic phase comprising said solvent, and said pregnant liquor phase containing said ester and said mineral acid.
19. A process as set forth in claim 18 wherein the volumetric ratio of organic solvent to mineral acid in said alkylation/esterification reaction zone during the alkylation/esterification reaction is less than 4 to 1.
20. A process as set forth in claim 19 wherein the volumetric ratio of organic solvent to mineral acid is less than about 3 to 1.
21. A process as set forth in claim 19 wherein the volumetric ratio of organic solvent to mineral acid is between about 0.1 to 1 and about 2.5 to 1.
22. A process for the preparation of 3,3-dimethylbutanol comprising:
reacting isobutylene, ethylene, and a mineral acid in the presence of an organic solvent in an alkylation/esterification reaction zone, thereby producing an alkylation/esterification reaction mixture comprising an organic phase and a pregnant liquor phase, said organic phase comprising said solvent, and said pregnant liquor phase containing a 3,3-dimethylbutyl ester and said mineral acid;
separating said pregnant liquor phase from said organic phase;
heating a hydrolysis feed mixture comprising said pregnant liquor phase in the presence of water, thereby hydrolyzing the ester contained in said pregnant liquor phase and producing a hydrolysis reaction mixture comprising 3,3-dimethylbutanol; and
distilling 3,3-dimethylbutanol formed in the hydrolysis from the hydrolysis reaction mixture as the hydrolysis reaction proceeds.
23. A process as set forth in claim 22 comprising diluting said pregnant liquor phase prior to hydrolysis of said ester.