Production of para-propylbenzaldehyde
The present invention is a process for preparing a 4-alkylbenzaldehyde (para-alkylbenzaldehyde). An alkylbenzene, solvated in a solvent comprising at least one aliphatic solvent having in the range of 3 to 15 carbons, is reacted with carbon monoxide, in the presence of an aluminum halide and a hydrogen halide acid. Disproportionation is reduced and proportion of para-alkyl-benzaldehyde is increased with respect to other methods.
1. A process comprising:
A) adding to a reactor an alkylbenzene, aluminum halide, and at least one aliphatic hydrocarbon solvent having in a range of 3 to 15 carbons;
B) cooling contents of the reactor to one or more temperatures in a range of 0 to −50° C.;
C) adding to the reactor an amount of hydrogen halide acid sufficient to charge the reactor to a pressure in a range of about 25 psig to about 200 psig;
D) adding to the reactor an amount of carbon monoxide sufficient to charge the reactor to a pressure in a range of about 200 psig to about 2000 psig; and
E) maintaining a reaction temperature at one or more temperatures in a range of about −50° C. to about 20° C.;
thereby synthesizing a 4-alkylbenzaldehyde.
2. A process as in claim 1 wherein a molar ratio of the hydrogen halide acid to the alkylbenzene is in a range of 1:1 to 20:1.
3. A process as in claim 1 wherein Gas Chromatography analysis of reaction mixture after, and optionally, prior to reaction completion indicate that the 4-alkylbenzaldehyde is formed in greater than 85 area % GC based on an amount of alkylbenzene consumed.
4. A process as in claim 1 wherein step E) proceeds until the aluminum chloride is used up and an ortho:meta:para isomer ratio is such that the para-isomer is at least 90 percent by quantitative NMR with respect to combined ortho- and meta- and para-isomers.
5. The process of claim 1 , wherein the aliphatic hydrocarbon solvent comprises greater than 90 wt % n-isomers.
6. The process as in claim 5 wherein the aliphatic hydrocarbon solvent comprises one or more of the following: propane, n-butane, n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane.
7. The process of claim 1 wherein the aliphatic hydrocarbon solvent comprises greater than 10 wt % branched isomers.
8. The process of claim 7 wherein the branched isomers comprise one or more of the following: butanes, isobutane, pentanes, isopentane, neopentane, hexanes, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, heptanes, 2-methylhexane, 3-methylhexane, 2,2-dimethylpentane, 2,3-dimethylpentane, 2,4-dimethylpentane, octanes, isooctane, 2,2-dimethylhexane, 2,2,3,3-tetramethylbutane, nonanes, decanes, and petroleum distillates and mixtures thereof.
9. The process of claim 1 wherein the aliphatic hydrocarbon solvent comprises greater than 5 wt % cyclic aliphatic isomers.
10. The process of claim 9 wherein the cyclic aliphatic isomers comprise one or more of the following: alkyl-substituted cyclopentane, alkyl-substituted cyclohexane, alkyl-substituted cycloheptane, alkyl-substituted cyclooctane, decalin, cyclopentane, cyclohexane, cycloheptane, cyclooctane, methylcyclopentane, methylcyclohexane, dimethylcyclopentane, and dimethylcyclohexane.
11. The process of claim 1 , wherein, in step (C), an amount of hydrogen halide acid is the amount sufficient to charge the reactor to one or more pressures in a range of about 40 psi to about 130 psi.
12. The process of claim 11 , wherein the pressure is from about 80 psig to about 120 psig.
13. The process of claim 1 , wherein, in step (D), an amount of carbon monoxide is the amount sufficient to charge the reactor to a total pressure in a range of about 300 psig to about 1000 psig.
14. The process of claim 1 , wherein, in step (E), a time sufficient to reach completion is about 4 hours or less.
15. The process of claim 1 , wherein a formylated product comprises at least 85% yield by quantitative NMR of 4-propylbenzaldehyde.
16. The process of claim 15 , wherein the formylated product comprises at least 90% yield by quantitative NMR of 4-propylbenzaldehyde.
17. The process of claim 1 , wherein the reaction temperature is from about −35° C. to about 20° C.
18. The process of claim 17 , wherein the reaction temperature is from about −35° C. to about 5° C.
19. The process of claim 1 , further comprising a disproportionation product comprising an amount of di-n-propylbenzene (DNPB) of about 1.5% or less.
20. The process of claim 1 , further comprising a disproportionation product comprising an amount of dipropylbenzaldehyde (DPBA) of about 1.0% or less.
21. The process of claim 1 , wherein a para-isomer is 4-propylbenzaldehyde.
22. The process of claim 1 , wherein, in step (E), a para-isomer comprises at least 90 percent of combined ortho, meta, and para isomers.
23. The process of claim 22 , wherein, in step (E), the para-isomer comprises at least 97 percent of combined ortho, meta, and para isomers.
24. The process of claim 1 , further comprising separating the 4-alkylbenzaldehyde product.
25. The process of claim 24 , wherein the separating comprises extraction, distillation, chromatograph, or combinations thereof.
26. The process of claim 1 , wherein the hydrogen halide acid is hydrogen chloride or hydrogen bromide.
27. The process of claim 1 , wherein the aluminum halide acid is aluminum chloride or aluminum bromide.