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EP-4126801-B1 - RECOVERING MONO-PROPYLENE GLYCOL

EP4126801B1EP 4126801 B1EP4126801 B1EP 4126801B1EP-4126801-B1

Inventors

  • KAJANTO, ISKO

Dates

Publication Date
20260506
Application Date
20210330

Claims (16)

  1. A method for recovering mono-propylene glycol from a mixture comprising bio-derived diols and an organic impurity, wherein the mixture comprises mono-propylene glycol in an amount of at least 50 weight-% of the total weight of the mixture, wherein the organic impurity is characterized by a retention time of 6.5 - 6.7 minutes when determined by gas-chromatography-flame ionization detector (GC-FID) and by the tallest peak value at 59 m/z when determined by gas-chromatography-mass-spectrometer (GC-MS), and wherein the method comprises: (ia) separating the organic impurity from mono-propylene glycol in a first distillation process, wherein the first distillation process is carried out at a temperature within the range of 140 - 200 °C and a pressure within the range of 0.3 - 1.0 bar; and (ib) separating diols that have a boiling point lower than the boiling point of mono-propylene glycol, from mono-propylene glycol in a second distillation process, wherein the second distillation process is carried out at a temperature within the range of 90 - 150 °C and a pressure within the range of 0.05 - 0.2 bar; (ii) recovering mono-propylene glycol, and wherein the method comprises: - removing the organic impurity in a first bottom stream from the first distillation process (ia); and - removing mono-propylene glycol in a first top stream from the first distillation process (ia).
  2. The method of claim 1, wherein (ia) is carried out before (ib) or (ia) is carried out after (ib) .
  3. The method of any one of claims 1 - 2, wherein the method comprises: - removing diols that have a boiling point lower than the boiling point of mono-propylene glycol in a second top stream from the second distillation process (ib); and - removing mono-propylene glycol in a second bottom stream from the second distillation process (ib) .
  4. The method of any one of claims 1 - 3, wherein the first distillation process (ia) is carried out before the second distillation process (ib).
  5. The method of claim 4, wherein the first top stream comprises, in addition to mono-propylene glycol, diols that have a boiling point lower than the boiling point of mono-propylene glycol.
  6. The method of any one of claims 4 - 5, wherein the method comprises feeding the first top stream into the second distillation process.
  7. The method of any one of claims 1 - 3, wherein the first distillation process (ia) is carried out after the second distillation process (ib).
  8. The method of claim 7, wherein the second bottom stream comprises, in addition to mono-propylene glycol, the organic impurity.
  9. The method of any one of claims 7 - 8, wherein the method comprises feeding the second bottom stream into the first distillation process.
  10. The method of any one of the preceding claims, wherein the mixture comprises mono-ethylene glycol, mono-propylene glycol, butylene glycol, and an organic impurity in an amount of at least 80 weight-%, or at least 85 weight-%, or at least 90 weight-%, or at least 92 weight-%, of the total weight of the mixture.
  11. The method of any one of the preceding claims, wherein the mixture comprises mono-propylene glycol in an amount of at least 60 weight-%, or at least 70 weight-%, or at least 80 weight-%, or at least 90 weight-%, of the total weight of the mixture.
  12. The method of any one of the preceding claims, wherein the first distillation process is carried out at a temperature within the range of 150 - 190 °C, or 160 - 180 °C.
  13. The method of any one of the preceding claims, wherein the first distillation process is carried out at a pressure within the range of 0.5 - 0.9 bar, or 0.7 - 0.8 bar.
  14. The method of any one of the preceding claims, wherein the second distillation process is carried out at a temperature within the range of 100 - 140 °C, or 110 - 130 °C.
  15. The method of any one of the preceding claims, wherein the second distillation process is carried out at a pressure within the range of 0.1 - 0.15 bar.
  16. The method of any one of the preceding claims, wherein the method comprises recovering mono-propylene glycol at a concentration of at least 99 weight-%, or at least 99.5 weight-%, or at least 99.7 weight-%, or at least 99.9 weight-%, or at least 99.99 weight-%.

Description

TECHNICAL FIELD The present disclosure relates to a method for recovering mono-propylene glycol from a mixture comprising bio-derived diols. The present disclosure further relates to mono-propylene glycol. The invention is defined in the claims. BACKGROUND Mono-propylene glycol (MPG, also called 1,2-propanediol), is an important raw material finding use e.g. in the manufacturing of polymers. Mono-propylene glycol is a compound which is generally recognized as safe and can be further used for e.g. food applications as well as a vehicle for topical, oral and some intravenous pharmaceutical preparations. Mono-propylene glycol can be produced from propylene oxide e.g. by a non-catalytic high-temperature process at 200 °C - 220 °C, or by a catalytic process, which proceeds at 150 °C - 180 °C in the presence of ion exchange resin or a small amount of sulfuric acid or alkali. Mono-propylene glycol can also be obtained from glycerol, a byproduct from the production of bio-diesel. In addition, mono-propylene glycol may be produced from sugars together with mono-ethylene glycol. However, when producing such polyols as mono-ethylene glycol and mono-propylene glycol from sugars also other diols, alcohols and other substances are formed as side-products. Typically, when mono-ethylene glycol is distilled from such a composition, mono-propylene glycol may be obtained as a side-product together with other lighter impurities and needs further purification. The purification of the mono-propylene glycol has however been challenging. The inventor has thus recognized the need to provide a manner for recovering purified mono-propylene glycol e.g. from the side-product when producing mono-ethylene glycol. WO 2017/202727 A1 discloses a process for the production of a high purity first diol from a product stream comprising two or more C2 to C7 diols. SUMMARY A method for recovering mono-propylene glycol from a mixture comprising bio-derived diols is disclosed. The mixture may comprise an organic impurity. The method may comprise: (ia) separating the organic impurity from mono-propylene glycol in a first distillation process. The first distillation process may be carried out at a temperature within the range of 140 - 200 °C and a pressure within the range of 0.3 - 1.0 bar. The method may further comprise (ii) recovering mono-propylene glycol. Further is disclosed a method for recovering mono-propylene glycol from a mixture comprising bio-derived diols and an organic impurity, wherein the mixture comprises mono-propylene glycol in an amount of at least 50 weight-% of the total weight of the mixture. The method may comprises: (ia) separating the organic impurity from mono-propylene glycol in a first distillation process, wherein the first distillation process is carried out at a temperature within the range of 140 - 200 °C and a pressure within the range of 0.3 - 1.0 bar; and(ib) separating diols that have a boiling point lower than the boiling point of mono-propylene glycol, from mono-propylene glycol in a second distillation process, wherein the second distillation process is carried out at a temperature within the range of 90 - 150 °C and a pressure within the range of 0.05 - 0.2 bar. The method may further comprise (ii) recovering mono-propylene glycol. Further it is disclosed mono-propylene glycol obtainable by the method as disclosed in the current specification. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the embodiments and constitute a part of this specification, illustrate various embodiments. In the drawings: Fig. 1a discloses one embodiment of the arrangement disclosed in the current specification;Fig. 2a discloses one embodiment of the arrangement disclosed in the current specification; andFig. 2b discloses another embodiment of the arrangement disclosed in the current specification. DETAILED DESCRIPTION A method for recovering mono-propylene glycol from a mixture comprising bio-derived diols is disclosed. The mixture may comprise an organic impurity. The method may comprise: (ia) separating the organic impurity from mono-propylene glycol in a first distillation process. The first distillation process may be carried out at a temperature within the range of 140 - 200 °C and a pressure within the range of 0.3 - 1.0 bar. The method may further comprise (ii) recovering mono-propylene glycol. Further is disclosed a method for recovering mono-propylene glycol from a mixture comprising bio-derived diols and an organic impurity, wherein the mixture comprises mono-propylene glycol in an amount of at least 50 weight-% of the total weight of the mixture. The method may comprises: (ia) separating the organic impurity from mono-propylene glycol in a first distillation process, wherein the first distillation process is carried out at a temperature within the range of 140 - 200 °C and a pressure within the range of 0.3 - 1.0 bar; and(ib) separating diols that have