Process for making acrylic acid from dextrose

1. A process for making acrylic acid from dextrose, comprising:

a. fermenting dextrose in the presence of a biological catalyst to produce a fermentation broth containing lactic acid;

b. removing solids from the fermentation broth to produce a clarified fermentation broth;

c. removing lactic acid from the clarified fermentation broth by extraction into an organic solvent;

d. separating the lactic acid-loaded organic solvent from the fermentation broth remainder after lactic acid has been removed therefrom;

e. recycling at least a portion of the fermentation broth remainder to the fermentation step;

f. reacting lactic acid in the lactic acid-loaded solvent with ammonia to provide a crude dehydration feed comprising ammonium lactate;

g. separating ammonium lactate from organic solvent in the crude dehydration feed to provide a dehydration feed;

h. carrying out a vapor phase dehydration of ammonium lactate in the dehydration feed to produce a crude acrylic acid product;

i. purifying the crude acrylic acid product to provide a purified acrylic acid product, by a process including

a first distillation to remove acetaldehyde and ammonia overhead and provide a bottoms stream comprised predominantly of acrylic acid and propionic acid, and

a second distillation of the bottoms stream from the first distillation to provide a second distillation overhead stream enriched in acrylic acid and a second distillation bottoms stream enriched in propionic acid; and,

j. further purifying the acrylic acid in the second distillation overhead stream by contacting with an the amphoteric ion exchange resin to separate and elute propionic acid into a raffinate or both melt crystallization and by contacting with an the amphoteric ion exchange resin to separate and elute propionic acid into a raffinate.

2. A process according to claim 1 , wherein the purified acrylic acid product of step j) contains less than 3000 ppm by weight of propionic acid.

3. A process according to claim 2 , wherein the purified acrylic acid product of step j) contains less than 1000 ppm by weight of propionic acid.

4. A process according to claim 1 , wherein the separation of lactic acid from the clarified fermentation broth comprises the use of one or more hydrophilic nanofiltration membranes.

5. A process according to claim 1 , wherein the fermentation of dextrose comprises the use of an acid-resistant transformant of Schizosaccharomyces pombe , a recombinant strain of Schizosaccharomyces pombe or an acid-tolerant yeast strain comprising a genome that includes an exogenous lactate dehydrogenase gene.

6. A process according to claim 5 , wherein the further purification involves both melt crystallization and adsorption onto an amphoteric ion exchange resin.

7. A process according to claim 1 , wherein the contacting is accomplished in a series of columns and the eluent passes through the columns as a simulated moving bed.

8. A process according to claim 1 wherein the amphoteric ion exchange resin has a quaternary ammonium group and a carboxy group incorporated on a cross-linked polystyrene frame.

9. A process according to either of claim 1 wherein an eluent of water or of water in combination with an organic solvent is used in step j).

10. A process according to claim 9 , wherein the organic solvent is methanol or acetone.