METHOD FOR MANUFACTURING POLYMER-GRADE BIO-BASED
ACRYLIC ACID FROM GLYCEROL
The studies leading to the present invention benefited from financial support
5 from the Seventh Framework Program of [The European Union] [The European
*
= .,
Atomic Energy Community] ([FP7/2007-20131 [FP7/2007-2011]) under grant
agreement No. 228867.
The present invention is targeted at a process for the manufacture of a
lo bioresourced acrylic acid of polymer grade from glycerol as starting material. The tern
bioresourced indicates that the acrylic acid is essentially based on a carbon source of
natural origin. I
Acrylic acid is a compound which is used as polymerization monomer or
comonorner for the manufacture of a very broad range of final products. The polymers
15 or copolymers are manufactured by polymerization of the acid or of the derivatives of
this acid, in the ester (polyacrylates) or arnide (polyacrylarnides) form. These polymers
are used as is or as copolymers in fields as varied as hygiene, detergents, paints,
varnishes, adhesives, paper, textiles, leather, and the like. A very important outlet for
acrylic acid is the manufacture of superabsorbents,' in which a partially neutralized
20 (mixture of acrylic acid and sodium acrylate or acrylates of other cations) acrylic acid is
polymerized or else acrylic acid is polymerized and the polyacrylic compound obtained
is partially neutralized.
~an;fact&ers'-have been developing prokesses for the synthesis of acrylic acid
for decades.
25 The first generation used, as starting material, compounds comprising a triple
bond of acetylenic type which were reacted with a mixture of carbon monoxide and
water in the presence of a nickel-based catalyst.
The second generation of processes, which- is today the most widely employed
industrially, makes use of a reaction for the catalytic oxidation of propylene and/or
30 propane using oxygen or an oxygen-comprising mixture.
This reaction is generally carried out in the gas phase and generally in two
stages: the first stage carries out the substantially quantitative oxidation of the propylene

CLAIMS
1. A process for the manufacture of bioresourced acrylic acid of polymer grade
having a content by weight of acrylic acid > 99% and the following contents of
impurities: protoanemonin < 5 ppm, total aldehydes < 10 ppm, maleic anhydride <
5 30 ppm, nonphenolic polymerization inhibitors < 10 ppm, and a content by weight of
^^"^C such that the '"^C/^^C ratio > 0.8 x 10'^^, from glycerol, characterized in that it
comprises the following stages:
i) dehydration of the glycerol to give acrolein,
ii) oxidation of the acrolein formed to give acrylic acid,
10 iii) extraction of the acrylic acid present in the effluent from the oxidation stage ii) by
absorption in a column operating countercurrentwise by means of a hydrophobic heavy
solvent, •;
iv) separation by topping by the distillation of the liquid phase resulting from stage (iii)
of a light fraction comprising water and residual light compounds, in particular acetic
15 acid and formic acid, and of a heavy fraction comprising the acrylic acid in solution in
the hydrophobic heavy solvent,
v) distillation of the heavy fraction resulting from (iv) comprising the acrylic acid in
solution iwith separation, at the bottom, of the hydrophobic heavy solvent and, at the
top, of the acrylic acid fraction comprising the intermediate impurities and possibly
20 traces of solvent, the heavy fraction resulting from this stage (v), essentially composed
of the solvent, being recycled in stage (iii), optionally after a purification treatment,
vi) distillation of the acrylic acid solution from the top fraction resulting from the
preceding stage (v) ill order to extract, at the bottom, the heaviest "intermediate"
compounds and the traces of solvent possibly entrained and, at the top, the technical
25 acrylic acid,
vii) purification by distillation of the technical acrylic acid, in order to obtain an acrylic
acid of "polymer" grade, after addition to the acrylic acid of an amino compound which
reacts with the aldehydes still present. - - -
30 2. The process as claimed in claim 1, characterized in that stage iii) employs at
least one water-immiscible absorption solvent having a boiling point of greater than
170°C and preferably of between 270 and 320°C.