Process for hydroxylating phenolic substrate
View Patent ↗The invention relates to a process for hydroxylating phenolic substrates such as phenols or phenol ethers. The process comprises reacting the phenolic substrate and hydrogen peroxide in the presence of a catalyst in a reaction mixture; and simultaneously removing water from the reaction mixture. The process improves the reaction rate, yield, and product selectivities.
1. A process for hydroxylating a phenolic substrate, comprising: reacting the phenolic substrate and hydrogen peroxide in the presence of a catalyst selected from the group consisting of a strong acid, a ketone, and mixtures thereof, in a reaction mixture; and simultaneously removing water from the reaction mixture.
2. The process of claim 1 , wherein water is removed from the reaction mixture by distillation.
3. The process of claim 2 , wherein the distillation is performed with a distillation column.
4. The process of claim 3 , wherein the distillation column has from 2 to 30 theoretical plates.
5. The process of claim 2 , wherein the distillation is performed under sub-atmospheric pressure.
6. The process of claim 1 , wherein the reaction mixture has a water content of less than 1.0 wt. %.
7. The process of claim 1 , wherein the reaction mixture has a water content of less than 0.50 wt. %.
8. The process of claim 1 , wherein the strong acid has a pKa in water of less than −0.1.
9. The process of claim 1 , wherein the strong acid has a pKa in water of less than −5.0.
10. The process of claim 1 , wherein the catalyst is a ketone.
11. The process of claim 10 , performed in the presence of a sulfur-containing promoter.
12. The process of claim 1 , performed at a temperature of from 30 to 180° C.
13. The process of claim 1 , wherein the phenolic substrate is phenol.
14. The process of claim 1 , performed in the presence of a complexing agent.
15. The process of claim 14 , wherein the complexing agent is pyrophosphoric acid.