Method for producing bioresourced acrylic acid from glycerol
An aim of the present invention is to produce, from glycerol, a bioresourced acrylic acid, that is to say an acrylic acid essentially based on a carbon source of natural origin, meeting all the quality criteria of monomers customarily used as starting material in processes for polymerization of acrylic acid and of its esters, via an economical process. The process according to the invention comprises a final stage of extraction of acrylic acid by fractional crystallization applied to one of the effluents resulting from the acrylic acid purification chain, the location of this final stage possibly depending on the initial feedstock treated, the nature and the source of the glycerol used in the process, purity specifications to be achieved for the final acrylic acid, or finally economic criteria.
1. A process for the manufacture of bioresourced acrylic acid from glycerol, comprising the following stages:
gas-phase catalytic dehydration of glycerol to give acrolein, (1)
partial condensation by cooling and extraction of water and heavy impurities present in the reaction medium of (1), (1′)
gas-phase catalytic oxidation of a gas stream from (1′) comprising water and acrolein in a molar ratio water/acrolein of 1.5/1 to 7/1 to give acrylic acid, (2)
extraction of the acrylic acid present in the effluent stream from the oxidation by water absorption with cooling, (3)
drying of a solution of the acrylic acid by distillation in the presence of a solvent that is immiscible with water, (4)
distillation of a solution thus obtained in order to remove light compounds, (5)
distillation of a heavy fraction resulting from (5) in order to remove heavy compounds, (6) a final extraction of the bioresourced acrylic acid by fractional crystallization applied to one of the following effluent streams: a heavy fraction from (4), the heavy fraction from (5) or a light fraction from (6).
2. The process as claimed in claim 1 , wherein a liquid fraction resulting from (3) is subjected to a separation (3′) from the residual acrolein by distillation or stripping with a gas.
3. The process as claimed in claim 1 , wherein a heavy fraction from (4) is subjected to the final extraction of bioresourced acrylic acid by fractional crystallization.
4. The process as claimed in claim 1 , wherein a heavy fraction from (5) is subjected to the final extraction of bioresourced acrylic acid by fractional crystallization.
5. The process as claimed in claim 1 , wherein a light fraction from (6) is subjected to the final extraction of bioresourced acrylic acid by fractional crystallization.
6. The process as claimed in claim 1 , wherein the final extraction of bioresourced acrylic acid is a fractional crystallization by a falling film fractional crystallization technique.
7. The process as claimed in claim 6 , wherein the fractional crystallization comprises between 1 and 4 purifications and between 1 and 4 concentrations of impurities.
8. The process as claimed in claim 6 , wherein the fractional crystallization is supplemented by concentration by static crystallization.