Method for synthesising glycolic acid
The invention relates to a method for synthesizing glycolic acid or one of the salts thereof, including the following step: placing glycerol and an oxidizing agent in contact with one another in a reaction medium in the presence of a silver-based catalyst on a substrate, said substrate including a material selected from the group consisting of CeO 2 , basic Al 2 O 3 optionally doped with a calcium or cerium oxide, an amphoteric resin, ZrO 2 , and a mixture of said materials. The invention also relates to the use of a silver-based catalyst on a substrate that can be used in said method.
1. A process for the synthesis of glycolic acid or one of its salts comprising the following step:
bringing glycerol and an oxidizing agent into contact in a reaction medium in the presence of a catalyst based on silver on a support, said support comprising a material chosen from the group consisting of CeO 2 , basic Al 2 O 3 , optionally doped with a calcium or cerium oxide, an amphoteric resin, ZrO 2 and a mixture of these materials;
wherein a base which produces hydroxide ions is present in the reaction medium; and
wherein the molar ratio of hydroxide ions to glycerol [OH]/[gly] brought together is from 0.5 to 1.2.
2. The process as claimed in claim 1 , wherein said catalyst is a catalyst on a support of formula Ag/CeO 2 , basic Ag/Al 2 O 3 , optionally doped with calcium oxide or with cerium oxide, or Ag/IR45.
3. The process as claimed in claim 1 , wherein the catalyst comprises, as metal entity, only silver.
4. The process as claimed in claim 1 , wherein the pH of the reaction medium is greater than or equal to 8.
5. The process as claimed in claim 1 , wherein which said oxidizing agent is oxygen.
6. The process as claimed in claim 1 , wherein which the temperature of the reaction medium is chosen within a range extending from 50 to 150° C.
7. The process as claimed in claim 1 , wherein the catalyst based on silver on a support is a catalyst, the proportion by weight of silver with respect to the support of which varies from 10 to 0.2%.
8. The process as claimed in claim 1 , wherein the glycerol/catalyst ratio by weight in the reaction medium is chosen within a range extending from 2 to 100.
9. The process as claimed in claim 1 , wherein the glycerol is of vegetable origin.
10. The process as claimed in claim 1 , wherein the amounts of calcium or cerium oxides optionally used are less than 3 mmol of the atom used with respect to 1 g of support.