Process for preparing phthaloyl chloride

1. A process for preparing phthaloyl chloride of the formula (I)

in which phthalic anhydride of the formula (II)

is reacted with phosgene in the presence of a catalyst, wherein the catalyst used is an N,N-disubstituted formamide of the general formula (III)

in which

R 1 and R 2 are each independently

C 3 –C 8 -cycloalkyl,

C 6 –C 10 -aryl or

C 7 –C 12 -arylalkyl.

2. A process for preparing phthaloyl chloride of the formula (I)

comprising:

reacting a phthalic anhydride of the formula (II)

with phosgene in the presence of a catalyst;

wherein the catalyst used is an N,N-disubstituted formamide of the general formula (III)

in which:

R 1 and R 2 are each, independently, a straight-chain or branched C 8 –C 22 -alkyl- or -alkenyl radical, wherein the total molecular weight of the N,N-disubstituted formamide is at least 269 g/mol.

3. The process according to claim 1 , wherein the N,N-disubstituted formamide of the formula (III) used has an R 1 and R 2 which are each independently a C 3 –C 8 -cycloalkyl radical.

4. A process for preparing phthaloyl chloride of the formula (I)

comprising:

reacting a phthalic anhydride of the formula (II)

with phosgene in the presence of a catalyst:

wherein the catalyst used is an N,N-disubstituted formamide of the general formula (III)

in which R 1 and R 2 are each independently a benzyl, phenyl, phenylpropyl, naphthyl, naphthylmethyl or naphthylethyl radicals.

5. The process according to claim 2 , wherein the N,N-disubstituted formamide of the general formula (III) used is

N,N-dioctylformamide,

N,N-dinonylformamide,

N,N-didecylformamide,

N,N-diundecylformamide,

N,N-didodecylformamide,

N,N-ditridecylformamide,

N,N-ditetradecylformamide,

N,N-dipentadecylformamide,

N,N-dihexadecylformamide,

N,N-dioctadecylformamide,

N,N-dicyclopentylformamide,

N,N-dicyclohexylformamide,

N,N-dibenzylformamide,

N-methyl-N-benzylformamide or

N-methyl-N-naphthylmethylformamide.

6. The process according to claim 1 , wherein the N,N-disubstituted formamides of the formula (III) are prepared by reacting the corresponding amine of the formula HNR 1 R 2 where R 1 and R 2 may each be as defined for the formula (III) with formic acid.

7. The process according to claim 1 , wherein 1.0 mol to 3.0 mol of phosgene are used for 1 mol of phthalic anhydride of the formula (II).

8. The process according to claim 1 , wherein, based on 1 mol of phthalic anhydride of the formula (II), a total of 0.01–0.20 mol of N,N-disubstituted formamide of the formula (III) is used.

9. The process according to claim 1 , wherein phthalic anhydride is initially charged in an inert diluent, and the phosgene and the N,N-disubstituted formamide of the formula (III) are subsequently each independently metered in continuously or “semi-continuously”.

10. The process according to claim 9 , wherein the N,N-disubstituted formamide of the formula (III) metered in is dissolved in an inert solvent which is selected from the inert solvent of the phthalic anhydride and a different inert solvent.

11. The process according to claim 1 , wherein the phthalic anhydride is initially charged in an inert solvent together with the entire amount or a portion of the N,N-disubstituted formamide of the formula (III), the mixture is then heated to the reaction temperature and the phosgene and any remaining N,N-disubstituted formamide of the formula (III) are metered in continuously or “semi-continuously”.

12. The process according to claim 1 , wherein the N,N-disubstituted formamide of the formula (III) used has an R 1 and R 2 which are each the same C 3 –C 8 -cycloalkyl radical.

13. The process according to claim 1 , wherein the N,N-disubstituted formamide of the formula (III) used has an R 1 and R 2 which are each a cyclopentyl or a cyclohexyl radical.

14. The process according to claim 2 , wherein 1.0 mol to 3.0 mol of phosgene are used for 1 mol of phthalic anhydride of the formula (II).

15. The process according to claim 12 , wherein 1.0 mol to 3.0 mol of phosgene are used for 1 mol of phthalic anhydride of the formula (II).

16. The process according to claim 2 , wherein, based on 1 mol of phthalic anhydride of the formula (II), a total of 0.01–0.20 mol of N,N-disubstituted formamide of the formula(III) is used.

17. The process according to claim 12 , wherein, based on 1 mol of phthalic anhydride of the formula (II), a total of 0.01–0.20 mol of N,N-disubstituted formamide of the formula (III) is used.

18. The process according to claim 9 , wherein the N,N-disubstituted formamide of the formula (III) metered in is initially melted and then metered in as a melt.