Method for separating salified phenolic compounds
A method for separating a salified phenolic compound from a reaction medium including same is described. Also described, is a method for separating salified phenolic compounds from an aqueous reaction medium resulting from the reaction of a phenolic compound and glyoxylic acid in the presence of a base, which leads to a reaction medium including at least the excess of the starting salified phenolic compound and the various salified mandelic compounds resulting from the reaction, wherein the reaction medium including the starting salified phenolic compound is contacted with an adsorbent substrate. This leads to the selective adsorption of the phenolic compound onto said substrate and to the recovery of an aqueous flow containing the salified mandelic compounds from the reaction, and in that the phenolic compound attached onto the adsorbent is desorbed by means of a regenerating treatment of the adsorbent.
1. A method of separating phenolic compounds, the method comprising separating the phenolic compounds in salified form from an aqueous reaction mixture resulting from a reaction of a phenolic compound and glyoxylic acid in the presence of a base, leading to a reaction mixture comprising at least an excess of phenolic starting compound in salified form and various mandelic compounds in salified form, resulting from the reaction, wherein the reaction mixture comprising the phenolic starting compound in salified form is contacted with an adsorbent support, wherein the adsorbent support is an activated carbon, leading to selective adsorption of said phenolic compound on said support, and to recovery of an aqueous stream comprising the mandelic compounds in salified form obtained from the reaction, and in that the phenolic compound fixed on the adsorbent is desorbed by a regenerative treatment of said adsorbent.
2. The method as defined by claim 1 , wherein the reaction mixture comprises a phenolic compound in salified form corresponding to the following formula:
in which formula:
R is an alkyl or alkoxy group having from 1 to 4 carbon atoms, or a halogen atom,
x is a number from 0 to 3, and
M is a cation of a metallic element from group (IA) of the periodic table.
3. The method as defined by claim 1 , wherein the phenolic compound in salified form of formula (I) is sodium guaiacolate or sodium guaetholate.
4. The method as defined by claim 1 , wherein the reaction mixture comprises the phenolic compound in salified form at a concentration of from 1% to 20% by weight.
5. The method as defined by claim 1 , wherein the reaction mixture comprises reaction products which are mandelic acids in salified form at a concentration of from 3% to 30% by weight.
6. The method as defined by claim 1 , wherein the reaction mixture is an aqueous mixture comprising sodium guaiacolate and mandelic compounds: 4-hydroxy-3-methoxymandelic acid, 2-hydroxy-3-methoxymandelic acid, 4-hydroxy-5-methoxy-1,3-dimandelic acid.
7. The method as defined by claim 1 , wherein the adsorbent is an activated carbon based on coal, peat, lignite, or petroleum distillation residues, or on the basis of any carbon-rich organic vegetable matter from the group consisting of wood, barks, twigs, wood pulp, shells of fruits.
8. The method as defined by claim 1 , wherein the adsorbent is a carbon-containing adsorbent resulting from the pyrolysis of a polymeric resin.
9. The method as defined by claim 1 , wherein the amount of adsorbent support employed represents at least from 2 to 10 times the weight of the phenolic compound in salified form that is to be adsorbed.
10. The method as defined by claim 1 , wherein the phenolic compound in salified form is recovered by regeneration of the adsorbent by a basic treatment.
11. The method as defined by claim 2 , wherein x is 1.
12. The method as defined by claim 2 , wherein the cation of the metallic element from group (IA) if the periodic table is selected from the group consisting of lithium, sodium, potassium, rubidium, cesium or an ammonium cation.
13. The method as defined by claim 4 , wherein the concentration of salified phenolic compound is at a concentration of from 5% to 10% by weight.
14. The method as defined by claim 5 , wherein the mandelic acids are present in a concentration of from 5% to 20% by weight.
15. The method as defined by claim 10 , wherein the phenolic compound is recovered by means of an aqueous sodium hydroxide solution.