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EP-4735531-A1 - METHOD FOR PRODUCING A LIGNIN PRODUCT

EP4735531A1EP 4735531 A1EP4735531 A1EP 4735531A1EP-4735531-A1

Abstract

It is disclosed a method for producing a precipitated lignin product comprising the steps of: providing a soluble lignin-containing organic solution; providing an aqueous precipitant solution comprising about 5% to about 40% of acid(s); adding the aqueous precipitant solution to the soluble lignin-containing organic solution to provide a mixture having a temperature in the range of about 40°C to about 90°C; cooling the mixture containing a precipitated lignin product for about 2 sec to about 2 hours; separating and recovering the precipitated lignin product from the mixture.

Inventors

  • Rousu, Päivi
  • ROUHIAINEN, MAIJA
  • ANTTILA, JUHA RAINER
  • Kupiainen, Laura

Assignees

  • Chempolis Oy

Dates

Publication Date
20260506
Application Date
20240628

Claims (20)

  1. 1. A method for producing a precipitated lignin product comprising the steps of: - providing a soluble lignin-containing organic solution, - providing an aqueous precipitant solution comprising about 5% to about 40% of acid(s), - adding the aqueous precipitant solution to the soluble lignin -containing organic solution to provide a mixture having a temperature in the range of about 40°C to about 90°C, - cooling the mixture containing a precipitated lignin product for about 2 sec to about 2 hours, - separating and recovering the precipitated lignin product from the mixture.
  2. 2. The method of claim 1, wherein the soluble lignin-containing organic solution is a spent cooking liquor from an organosolv pulping process of a lignocellulosic material.
  3. 3. The method of claim 2, wherein the organosolv pulping process of a lignocellulosic material is performed using an aqueous organic solvent as a cooking liquor.
  4. 4. The method of claim 3, wherein the aqueous organic solvent comprises at least one of formic acid and acetic acid.
  5. 5. The method of claim 4, wherein the aqueous organic solvent comprises furfural.
  6. 6. The method of any one of the preceding claims, wherein the soluble lignin-containing organic solution comprises formic acid, acetic acid, and water.
  7. 7. The method of claim 6, wherein the soluble lignin-containing organic solution further comprises furfural.
  8. 8. The method of any one of the preceding claims, wherein the soluble lignin-containing organic solution comprises about 65 wt.% to about 90 wt.% of formic acid and acetic acid in total based on the liquid part of the soluble lignincontaining organic solution.
  9. 9. The method of any one of the preceding claims, wherein the soluble lignin-containing organic solution contains at most 8 wt.% alcohol(s), such as methanol and ethanol.
  10. 10. The method of any one of the preceding claims, wherein the dry matter of the soluble lignin-containing organic solution is in the range of about 50% to about 90%, specifically about 60% to about 85%, more specifically about 70% to about 80%.
  11. 11. The method of any one of the preceding claims, wherein the aqueous precipitant solution comprises about 20% to about 30% of acid(s).
  12. 12. The method of claim 11, wherein the acid(s) in the aqueous precipitant solution are organic acid(s).
  13. 13. The method of claim 11 or 12, wherein the organic acid(s) comprise^) at least one of formic acid and acetic acid.
  14. 14. The method of any one of the preceding claims, wherein the aqueous precipitant solution comprises an acidic process side stream from organosolv pulping process of the lignocellulosic material.
  15. 15. The method of any one of the preceding claims, wherein the aqueous precipitant solution is added to the soluble lignin-containing organic solution in a weight ratio of about 0.7:1 to about 2.5:1, specifically about 1:1 to about 2:1.
  16. 16. The method of any one of the preceding claims, wherein the mixture has a temperature of about 50°C to about 90°C, specifically 60°C to about 85°C, more specifically about 65°C to about 80°C.
  17. 17. The method of any one of the preceding claims, wherein the content of organic acids in total based on the liquid part of the mixture is at most 60 wt.%, specifically in the range of about 5 wt.% to about 60 wt.%.
  18. 18. The method of any one of the preceding claims, wherein the mixture is cooled to about 20°C to about 50°C, specifically about 25°C to about 40°C.
  19. 19. The method of any one of the preceding claims, wherein the cooling of the mixture is performed within 60 minutes, specifically about 10 minutes to about 60 minutes.
  20. 20. The method of any one of the preceding claims, wherein the separation is carried out by solid-liquid separation method, such as filtration and centrifugal means.

Description

METHOD FOR PRODUCING A LIGNIN PRODUCT FIELD OF THE INVENTION The present invention relates to a method for producing a lignin product. More particularly, the invention relates to an improved method for producing a precipitated lignin product with high purity in an efficient and controlled way. BACKGROUND OF THE INVENTION Precipitation of lignin from a lignocellulosic material with water is known. WO 2011/154293 Al discloses a process for separation of lignins and sugars from an extraction liquor involving concentrating the extraction liquor, mixing the concentrated liquor with water in equal parts, stirring the resultant mixture to obtain a stable suspending of the lignins in the solution, filtering the solution comprising the suspended lignins. WO 2021/198555 Al discloses a method for the separation of lignin from an organic solvent, comprising multiple two-step cycles involving a first step of adding an aqueous solution to a lignin-containing organic solvent to precipitate lignin, and a second step of subjecting the resultant lignin-reduced solution to the first step of addition of an aqueous solution. Precipitated lignin is separated and recovered in each step. The multi-step addition of an aqueous solution to a lignincontaining solution provides lignin precipitates with a different molecular weight distribution. WO 2019/162277 Al discloses a method of production of lignin and hemicellulose from a plant lignocellulosic material comprising contacting a plant lignocellulosic material with an extraction solution comprising acetic acid, formic acid and water to obtain a solid fraction and a liquid fraction. The liquid fraction is separated, concentrated and mixed with equal part by weight of water to provide a suspension comprising solid particle in suspension. Use of water in precipitation of lignin from an organic spent cooking liquor from organosolv pulping of a lignocellulosic material generates high amount of waste water or a diluted hemicellulose solution. High losses of organic acids and/or high processing costs to purify hemicellulose solution and further treatment of waste water cannot be avoided to recover water and organic acids. There has also been challenges in recovering of a precipitated lignin product by filtration, e.g., due to the wide range of particle sizes and shapes. BRIEF DESCRIPTION OF THE INVENTION We have now found an improved method for efficient and controlled production of a precipitated lignin product having targeted properties. The method is based on an organosolv pulping of a lignocellulosic material in which cellulose, lignin and hemicellulose present in the lignocellulosic material are separated in two main streams, i.e., cellulosic pulp and a solution of soluble lignin and hemicellulosic sugars, by using an aqueous organic solvent as a cooking liquor. The cooking liquor is acidic and includes formic acid and acetic acid, water and furfural. During cooking, hemicellulosic sugars and a portion of lignin are dissolved in the cooking liquor. In the context or the present invention, the term "organosolv pulping" means that delignification of the lignocellulosic material is performed with organic acids in an aqueous solution constituting a cooking liquor. The organic acids include formic acid and acetic acid. In the invention, the organosolv pulping of a lignocellulosic material is thus performed in acidic conditions wherein the total content of organic acids in the cooking liquor is about 65% wt.% to about 90% wt.%. In the present invention, the cooking liquor used in the organosolv pulping may contain a low amount alcohol (s), such as methanol and ethanol, of at most 8 wt.%. Due to the low content of alcohol in the cooking liquor, organosolv pulping in the present invention does not correspond to organosolv delignification with alcohols. In context of the invention, a soluble lignin-containing organic solution obtained from cooking of a lignocellulosic material with an aqueous organic solvent is described here as "a spent cooking liquor". The spent cooking liquor thus contains, e.g.., soluble lignin, hemicellulosic sugars, inorganics, proteins and extractives, and also components of original cooking liquor. As used herein, the terms "soluble lignin-containing organic solution" and "spent cooking liquor" are interchangeable. In the method of the invention, soluble lignin is precipitated from the spent cooking liquor using an aqueous solution which comprises organic acids. It was surprisingly found, firstly, that a lignin precipitate of high purity was obtained using specific precipitation conditions involving employing an aqueous organic solution comprising acids as a precipitant solution, and secondly, using a dynamic mixer in mixing the spent cooking liquor and an aqueous organic solution in a continuous manner affected the precipitated lignin product yield and properties, and thirdly, quick cooling of the lignin precipitate provided beneficial filterability of the lignin