| 摘要 |
The present invention concerns a process for the preparation of a 4-hydroxybenzaldehyde and its derivatives. More particularly, the invention concerns the preparation of 3-methoxy-4-hydroxybenzaldehyde and 3-ethoxy-4-hydroxybenzaldehyde, respectively known as vanillin and ethylvanillin. The process for the preparation of a 4-hydroxybenzaldehyde and its derivatives is characterized in that it consists of selectively oxidising, to a carboxy group, the group in the 2 position with respect to the hydroxyl group, present in the phenolic compounds in a mixture comprising at least a phenolic compound (A) carrying formyl and/or hydroxymethyl groups in the 2 and 4 position, a phenolic compound (B) carrying a formyl or hydroxymethyl group in the 4 position, a phenolic compound (C) carrying a formyl or hydroxymethyl group in the 2 position, resulting in a mixture comprising a 3-carboxy-4-hydroxybenzaldehyde, a 4-hydroxybenzaldehyde and a 2-hydroxybenzoic acid, which then undergoes a decarboxylation operation to produce the 4-hydroxybenzaldehyde and a phenol which can optionally be recycled. |
