Process for manufacturing acrolein and/or acrylic acid from glycerol
The present invention relates to the manufacture of bioresourced acrolein and bioresourced acrylic acid from glycerol as starting material and more particularly comes within the scope of a process for the manufacture of acrolein and acrylic acid according to which the reaction for the dehydration of glycerol to give acrolein is carried out and a stage of oxidizing a water-rich phase separated from the reaction mixture coming from this dehydration reaction is carried out, before it is recycled to the glycerol dehydration stage. This oxidation treatment prevents organic impurities from accumulating during the process, while minimizing the consumption of water and the discharge of polluted aqueous streams.
1. Process for the manufacture of acrolein from glycerol comprising at least the stages of:
a) subjecting glycerol to a dehydration reaction to obtain an aqueous stream comprising acrolein;
b) separating the stream resulting from stage a) into an acrolein-rich phase and an acrolein-depleted aqueous phase; and
c) recycling all or part of the acrolein-depleted aqueous phase to stage a), characterized in that said acrolein-depleted aqueous phase is subjected to oxidation, in the presence of oxygen, oxygen-containing gas, hydrogen peroxide or ozone, before being recycled to stage a).
2. Process according to claim 1 , comprising the step of purifying said acrolein-rich phase by absorption and/or distillation.
3. Process for the manufacture of acrylic acid from glycerol comprising at least the stages of:
a) subjecting glycerol to a dehydration reaction to obtain an aqueous stream comprising acrolein;
b) separating the stream resulting from stage a) into an acrolein-rich phase and an acrolein-depleted aqueous phase;
c) recycling all or part of the acrolein-depleted aqueous phase to stage a);
d) subjecting the acrolein-rich phase to a catalytic oxidation reaction to obtain a stream comprising acrylic acid;
e) subjecting the stream resulting from stage d) to one or more purification treatments and recovering purified acrylic acid, characterized in that said acrolein-depleted aqueous phase is subjected to an oxidation stage, in the presence of oxygen, oxygen-containing gas, hydrogen peroxide or ozone, before being recycled to stage a).
4. Process according to claim 1 , characterized in that the oxidation is a thermal oxidation in the gas phase in the presence of oxygen at a temperature above 700° C.
5. Process according to claim 1 , characterized in that the oxidation is a catalytic oxidation in the gas phase in the presence of oxygen, an oxidation catalyst, and at a temperature ranging from 200° C. to 500° C.
6. Process according to claim 1 , characterized in that the oxidation is a wet oxidation or supercritical oxidation at a temperature above 150° C. and a pressure above 5 bar, in the presence of oxygen or air.
7. Process according to claim 1 , characterized in that the oxidation is an oxidation in the liquid phase in the presence of hydrogen peroxide or ozone, or a combination thereof, optionally activated by UV radiation or iron(II) salt catalysts.
8. Process according to claim 1 , characterized in that the energy contained in the stream leaving the stage for oxidizing the acrolein-depleted aqueous phase is used to preheat the stream entering this stage.
9. Process according to claim 3 , characterized in that the aqueous phase recycled to the dehydration stage a) is in the form of the gas stream that vaporizes a glycerol stream before said dehydration reaction.
10. Process according to claim 9 , characterized in that the glycerol stream is injected into a mixing chamber with spray or atomization nozzles optionally including a gas stream comprising CO 2 coming from the stage for oxidizing the acrolein-depleted aqueous phase.
11. Process according to claim 1 , characterized in that stage a) is carried out in the gas phase and a heat pump is used to condense the gaseous reaction stream coming from stage a) and to vaporize the acrolein-depleted aqueous phase separated from the acrolein-enriched phase during stage b).
12. Process according to claim 1 , characterized in that stage a) and the stage for oxidizing the acrolein-depleted aqueous phase are carried out in the gas phase, and a heat pump is used to condense the acrolein-depleted phase during stage b) and to vaporize said acrolein-depleted aqueous phase on leaving stage b).
13. Process according to claim 1 , characterized in that stage a) and the stage for oxidizing the acrolein-depleted aqueous phase are carried out in the gas phase, and the acrolein-depleted aqueous phase coming from stage b) is vaporized at least partly by a heat exchanger (or exchangers), providing cooling on leaving stage a) and in stage b).
14. Process according to claim 13 , characterized in that the cooling of the streams on leaving stage a) and in stage b) is operated at a pressure at. least 0.5 bar above that for the vaporization of the acrolein-depleted aqueous phase coming from stage b).