Use of hypophosphorous acid for the esterification of free fatty acids

1. A corrosion inhibiter capable of esterifying free fatty acids and comprising hypophosphorous acid and an organosulfonic acid, wherein the organosulfonic acid is of formula R—SO 3 H, wherein R is a saturated linear or branched hydrocarbon chain containing 1 to 4 carbon atoms.

2. The corrosion inhibitor according to claim 1 , wherein the organosulfonic acid is methanesulfonic acid.

3. A composition comprising

hypophosphorous acid, and

an organosulfonic acid, wherein the organosulfonic acid is of formula R—SO 3 H, wherein R a saturated linear or branched hydrocarbon chain containing 1 to 4 carbon atoms,

the hypophosphorous and organosulfonic acids being in a ratio by mass of hypophosphorous acid to organosulfonic acid ranging from 0.01 to 0.4, and

optionally an aqueous, organic or hydroorganic diluent, and

optionally one or more additives.

4. The composition according to claim 3 , comprising:

from 1% to 20% by weight of the hypophosphorous acid with respect to the total weight of hypophosphorous acid and organosulfonic acid, and

from 80% to 99% by weight of the organosulfonic acid and derivatives thereof with respect to the total weight of hypophosphorous acid and organosulfonic acid.

5. A method for the esterification of fatty acids, comprising the following successive steps:

(a) providing a fatty substance comprising from 1% to 95% by weight of at least one free fatty acid;

(b) adding at least one alcohol;

(c) adding a composition comprising

hypophosphorous acid, and

organosulfonic acid,

the hypophosphorous and organosulfonic acids being in a ratio by mass of hypophosphorous acid to organosulfonic acid ranging from 0.01 to 0.4, and

optionally an aqueous, organic or hydroorganic diluent, and

optionally one or more additives;

(d) conducting the esterification reaction at a temperature between ambient temperature and 150° C. and at atmospheric pressure or under a vacuum ranging up to 1 kPa.

6. The method according to claim 5 , including after step (d), the following step:

(e) recovering the organic phase comprising fatty acid esters.

7. The method according to claim 5 , wherein the fatty substance is an oil or a fat of vegetable or animal origin, or a used frying oil, or a mixture of the aforementioned oils or fats, optionally a mixture with one or more oils or fats of vegetable or animal origin.

8. The method according to claim 5 , wherein the fatty substance is chosen from oils of sunflower, walnut, maize, soya, peanuts, colza, linseed, hemp, safflower, milk thistle, purslane, raspberry, blackcurrant, hazelnut, almond, wheat germ, borage, evening primrose (rose mallow) and poppy, stones, pips and seeds, of argan, palm, copra, sesame, olive, castor oil, coconut, Brazil nut, jatropha, babassu, karanja, neem, mahua, saijar, jojoba, tung, tall or tall oil, algae, used frying oils, fish fat oils, oils and fats of bovines, pigs, goats, equidae and poultry, as well as mixtures of two or more thereof.

9. The method according to claim 5 , wherein the fatty substance comprises from 3% to 95% by weight of at least one free fatty acid.

10. The method according to claim 5 , wherein the free fatty acids are chosen from saturated or unsaturated, linear or branched carboxylic acids having from 3 to 32 carbon atoms, optionally including one or more rings.

11. The method according to claim 5 , wherein the alcohol is chosen from linear, branched or cyclic monoalcohols, diols or alkyl triols, comprising from 1 to 6 carbon atoms, and mixtures of two or more thereof, in any proportions.

12. The method according to claim 11 , wherein the alcohol is chosen from methanol, ethanol, propanol, ethylene glycol, and glycerol and mixtures thereof.

13. A method for preparing biodiesel, comprising the steps as defined in claim 5 .