Method for activating and precipitating lignin

• US 10,894,866 B2
• Filed: 06/23/2016
• Issued: 01/19/2021
• Est. Priority Date: 06/26/2015
• Status: Active Grant

• Current Assignee: Teknologian tutkimuskeskus VTT Oy
• Original Assignee: Teknologian tutkimuskeskus VTT Oy
• Inventors: Wikberg, Hanne, Ohra-Aho, Taina, Leppavuori, Juha, Liitia, Tiina
• Primary Examiner(s): Hill, Nicholas E
• Application Number:
  US15/736,308
• Publication Number:
  US 20180179339A1
• Time in Patent Office: 1,671 Days
• CPC Class Codes: C07G 1/00 Lignin; Lignin derivatives
• CPC Class Codes: C08G 8/24 with mixtures of two or more phenols which are not covered by only one of the groups C08G8/10 - C08G8/20
• CPC Class Codes: C08G 8/38 Block or graft polymers prepared by polycondensation of aldehydes or ketones onto macromolecular compounds
• CPC Class Codes: C08H 6/00 Macromolecular compounds derived from lignin, e.g. tannins, humic acids
• CPC Class Codes: C08L 61/12 with polyhydric phenols
• CPC Class Codes: C08L 97/005 Lignin
• CPC Class Codes: D21C 11/00 Regeneration of pulp liquors or effluent waste waters
• CPC Class Codes: D21C 11/0007 Recovery of by-products, i.e. compounds other than those necessary for pulping, for multiple uses or not otherwise provided for volatile compounds obtained by decomposition of spent liquors in order to regenerate them D21C11/125; compounds obtained by fractionating the liquors in order to regenerate them D21C11/0042

Abstract

According to an example aspect of the present invention, there is provided a method of producing reactive lignin from an alkaline lignin containing stream, such as black liquor, e.g. kraft lignin, by using thermal treatment with temperatures between 200 and 250° C. for simultaneous activation (for example by demethylation and/or demethoxylation) and precipitation of the lignin.

Claims

1. A method for activating and recovering lignin from an alkaline lignin-containing feedstock by a thermal treatment, the method comprising:

simultaneously activating and precipitating the lignin in the feedstock by a thermal treatment being carried out on the feedstock having a dry matter content of between 10 and 40 wt-% and a pH of 10-12, without added demethylation and demethoxylation enhancing agents, and at a self-generated pressure, by applying temperature between 200 and 220°

C. and a retention time between 1 and 7 hours to the feedstock, wherein the pH, temperature, and retention time are selected along with the self-generated pressure to provide simultaneous demethylation and demethoxylation of the lignin.

2. The method of claim 1, wherein the alkaline lignin-containing feedstock is from an alkaline pulping process.

3. The method of claim 1, wherein the dry content of the alkaline lignin-containing feedstock during the activation and precipitation step is between 20 and 40 wt-%.

4. The method of claim 1, comprising operating at a self-generated pressure between 15 and 40 bars.

5. The method of claim 1, comprising operating the thermal treatment step using a retention time of 1 to 4 hours.

6. The method of claim 1, wherein, after the activation and precipitation, the lignin is purified by acidic washing.

7. The method of claim 1, further comprising removing excess filtrate, whereby the lignin is obtained.

8. The method of claim 1, wherein a number of reactive sites of the activated lignin for curing reactions with aldehydes is increased at least 1.5 fold compared to a number of reactive sites of a lignin in untreated feedstock, and wherein the method further comprises substituting the recovered lignin for phenol in a curing reaction with an aldehyde.

9. The method of claim 1, wherein the activated lignin comprises a methoxyl percentage of from 0.5-7 mmol/g.

10. The method of claim 1, wherein the activated lignin comprises at least 1 mmol/g of non-methoxylated catechol-type lignin units and at least 0.5 mmol/g of p-hydroxyphenyl-type lignin units.

11. The method of claim 10, wherein the activated lignin comprises 1.5-1.9 mmol/g of non-methoxylated catechol-type lignin units and 1.0-1.5 mmol/g of p-hydroxyphenyl-type lignin units.

12. The method of claim 1, wherein the activated lignin comprises 0.7-1.0 mmol/g methoxylated guaiacyl units.

13. The method of claim 1, wherein a number of reactive sites of the activated lignin for a reaction with formaldehyde for formation of a phenol formaldehyde resin is increased compared to a number of reactive sites of a lignin in feedstock untreated by the process of claim 1, and wherein the method further comprises reacting the activated lignin with formaldehyde to form the phenol formaldehyde resin.