Hydroxide → Malic Acid

A preferred procedure to be followed when using calcium carbonate as a calcium source, i.e., as a calcium starting-material, in the instant process is as follows; preformed malic acid, sodium hydroxide, a maleate reactant selected from maleic anhydride, maleic acid and mixtures thereof, and a calcium reactant selected from calcium carbonate and mixtures thereof with calcium hydroxide are reacted according to the immediately consecutive steps: (i) mixing calcium carbonate, water, malic acid and a proportion of said maleate reactant, allowing complete evolution of carbon dioxide and forming an acidic mixture; (ii) adding sodium hydroxide or a mixture thereof with calcium hydroxide, to the acidic mixture of step (i), forming a sodium cation-containing alkaline mixture; (iii) in a period of duration about 1 hour or less, adding the remainder of said maleate reactant to the stirred sodium cation-containing alkaline mixture of step (ii), at temperatures in the range from about 75° C. to about 110° C., having at the end of the step (iii) addition a net hydroxide excess MOH ; (iv) in a period of duration about 1 hour or less, cooling the mixture formed in step (iii) to a temperature in the range from about 35° C. to about 45° C.; (v) at said temperature in the range from about 35° C. to about 45° C., continuing to react the mixture of step (iv); the duration of step (v) being from about 48 hours to about 240 hours, whereby a crude product having a HPLC yield of at least 80% 2,2'-oxodisuccinate is secured; and (vi) diluting the product of step (v) with water and precipitating calcium carbonate therefrom; thereby arresting the step (iv) reaction and depleting the level of calcium; provided that in step (iii) and (iv) together; the total time at any temperature above about 100° C. does not exceed about 15 minutes; the total time at any temperature above about 90° C. does not exceed about 30 minutes; the total time at any temperature above about 80° C. does not exceed about 2 hours; the total time at any temperature above about 70° C. does not exceed about 6 hours; and the total time at any temperature above about 65° C. does not exceed about 12 hours; and provided that for each mole of preformed malic acid reacted, the total molar amount of maleate reactant is about 1.1 to about 1.6 moles; the total molar amount of calcium reactant, is from about 0.9 to about 1.65 moles; the total molar amount of sodium hydroxide, is from about 0.92 to about 3.7 moles; the net hydroxide excess in step (iii), MOH, is from about 0.02 to about 0.3 moles; and further provided that for each mole of preformed malic acid reacted (i.e., charged in the reactor), the total net amount of water added in steps (i), (ii) and (iii) together, allowing for evaporation losses, is no less than about 189 grams and no more than about 282 grams.

1. customreacted

ORD record

ord-4376f02d631f4a56886033d6829fbbd2

Source dataset

uspto-grants-1989_01

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US04798907