Method for producing alkoxyhydroxybenzaldehyde

1. A process for producing at least one alkoxyhydroxybenzaldehyde compound from at least one hydroxyphenol compound, wherein said process comprises the steps of:

(i) synthetizing at least one alkoxyphenol from said at least one hydroxyphenol in the presence of at least one O-alkylating agent;

(ii) recovering said at least one alkoxyphenol and impurities, wherein said impurities includes a dialkoxybenzene compound;

(iii) separing said dialkoxybenzene from the alkoxyphenol;

(iv) condensing the alkoxyphenol with glyoxylic acid and obtaining the corresponding mandelic compound;

(v) oxidizing said mandelic compound to give the corresponding alkoxyhydroxy-benzaldehyde; and

(vi) recovering said alkoxyhydroxybenzaldehyde, optionally in solid form.

2. The process according to claim 1 , wherein the hydroxyphenol is pyrocatechol and the alkoxyhydroxybenzaldehyde is selected from the group consisting of vanillin, ethylvanillin, and mixtures thereof.

3. The process according to claim 1 , wherein the hydroxyphenol is pyrocatechol, the O-alkylating agent is a methylating agent, the alkoxyphenol is guaiacol, the dialkoxybenzene is veratrole, and the step (iii) consists in separating the pyrocatechol from the guaiacol and veratrole mixture.

4. The process according to claim 1 , wherein the hydroxyphenol is pyrocatechol, the O-alkylating agent is an ethylating agent, the alkoxyphenol is the guaethol, the dialkoxybenzene is 1,2-diethoxybenzene, and the step (iii) consists in separating the pyrocatechol from the guaethol and 1,2-diethoxybenzene mixture.

5. The process according to claim 1 , wherein step (i) is carried out in a three-phase medium.

6. The process according to claim 1 , wherein step (i) is a vapour-phase synthesis.

7. The process according to claim 1 , wherein step (iii) of separation of the dialkoxybenzene from the alkoxyphenol comprises the preparation of an aqueous solution of alkoxyphenol in salified form, and the separation of the residual dialkoxybenzene from the aqueous mixture comprising the alkoxyphenoate.

8. The process according to claim 1 , wherein the separation of the dialkoxybenzene from the alkoxyphenol is carried out by distillation and/or settling out.

9. The process according to claim 8 , wherein a part of the alkoxyphenol is bypassed to a distillation column and the dialkoxybenzene is distilled at the top in the form of a dialkoxybenzene-water heteroazeotrope.

10. The process according to claim 9 , wherein the temperature at the bottom of the distillation column is of between 90 and 120° C.

11. The process according to claim 9 , wherein the dialkoxybenzene-water heteroazeotrope is then separated by settling out or another means of separation.

12. The process according to claim 1 , wherein in step (iv), the concentration of dialkoxybenzene in the alkoxyphenol is between 0.01% and 25%.

13. A process for producing at least one mandelic compound from at least one alkoxyphenol compound, wherein said process comprises the following steps:

preparation of a solution of alkoxyphenol, said solution of alkoxyphenol comprising an impurity which is a dialkoxybenzene;

preparation of a solution of alkoxyphenolate by adding water and at least one base to the solution of alkoxyphenol;

separation of the dialkoxybenzene from the alkoxyphenolate;

optional valorization of the dialkoxybenzene;

condensation of the alkoxyphenolate with glyoxylic acid and obtaining of the corresponding mandelic compound.

14. The process according to claim 13 , further comprising a step of neutralization of the mandelic compound to give the mandelic compound in acid form.