Process for preparing C
A process for preparing C 5 aldehydes involves hydroformylation of butenes with synthesis gas in the presence of a homogeneous catalyst system and a solvent. It is a feature of the process that the aldehyde concentration in the reaction mixture is limited.
1. A process for preparing C 5 aldehydes by hydroformylation of butenes, the process comprising:
reacting the butenes with synthesis gas in at least one reaction zone of a reactor, in the presence of a homogeneous catalyst system and of a solvent, wherein a cycle gas containing at least a portion of product aldehydes, unconverted butenes, and butanes is removed from the at least one reaction zone, and
wherein an aldehyde concentration in a liquid reaction mixture in the reactor is kept below 15% by mass by the cycle gas.
2. The process according to claim 1 , wherein the cycle gas removed from the at least one reaction zone is first directed to an aerosol separator.
3. The process according to claim 2 , wherein the cycle gas downstream of the aerosol separator is directed to a condenser, wherein the product aldehydes present in the cycle gas, the unconverted butenes, and the solvent are condensed out.
4. The process according to claim 3 , wherein a condensed liquid phase and a gas phase are separated from one another in a phase separator.
5. The process according to claim 4 , wherein the gas phase is recycled to the at least one reaction zone via a cycle gas compressor.
6. The process according to claim 4 , wherein the condensed liquid phase is directed to a C 4 /C 5 separation consisting of one or more distillation columns.
7. The process according to claim 6 , wherein previously removed product aldehydes and the solvent are separated from one another in a solvent removal, and the solvent is recycled to the reactor.
8. The process according to claim 1 , wherein the solvent has a higher boiling point than the product aldehydes.
9. The process according to claim 1 , wherein the solvent is isononyl benzoate (INB) or diisononyl cyclohexane-1,2-dicarboxylate (DINCH).
10. The process according to claim 1 , wherein the hydroformylation in the at least one reaction zone additionally takes place in the presence of a stabilizer.
11. The process according to claim 10 , wherein the stabilizer is an organic amine compound containing at least one 2,2,8,8-tetramethylpiperidine unit of formula (I):
12. The process according to claim 1 , wherein the homogeneous catalyst system comprises a metal from group 8 or 9 of the Periodic Table of the Elements, and at least one organic phosphorus-containing ligand.
13. The process according to claim 12 , wherein the metal is iron, ruthenium, iridium, cobalt, or rhodium.
14. The process according to claim 1 , wherein the homogeneous catalyst system comprises rhodium and a ligand having the structure of formula (1):
15. A liquid mixture, comprising:
an aldehyde,
cobalt or rhodium,
an organic phosphorus-containing ligand, and
a solvent,
wherein an aldehyde concentration in the liquid mixture is below 15% by mass.
16. The process according to claim 12 , wherein the at least one organic phosphorus-containing ligand is a mono- or biphosphate ligand.
17. The process according to claim 13 , wherein the metal is cobalt or rhodium.