Process for depolymerization of lignin

Patent metadata

Field	Value
Publication number	US-9550710-B2
Application number	US-201414890020-A
Country	US
Kind code	B2
Filing date	May 9, 2014
Priority date	May 9, 2013
Publication date	Jan 24, 2017
Grant date	Jan 24, 2017

Abstract

The present invention discloses a process for depolymerization of lignin to yield substituted phenolic monomers using Brönsted ionic liquid as catalyst under mild reaction conditions to obtain an overall yield of monomers up to 97%.

First claim

We claim:

1. A process for the depolymerization of lignin to obtain aromatic products comprising the steps of:
a. adding dealkaline lignin and Brönsted ionic liquid having —SO 3 H group in the range of 1:0.25 to 1:1 to a mixture of water and methanol wherein the ratio of methanol to water is in the range of 0:1 to 5:1 to obtain a reaction mixture;
b. stirring the reaction mixture obtained in step (a) at a temperature range of 100 to 170° C. for a period of 0.5 to 6 hrs to afford the aromatic products with 95-97% yield and a mass balance of >90%.

2. The process according to claim 1 , wherein the Brönsted ionic liquid having —SO 3 H group used in step (a) is selected from the group consisting of (1-methyl-3-(3-sulfopropyl)-1H-imidazol-3-ium 4-methylbenzenesulfonate), (1-methyl-3-(3-sulfopropyl)-1H-imidazol-3-ium hydrogensulfate), and (1-methyl-3-(3-sulfopropyl)-1H-imidazol-3-ium chloride).

3. The process according to claim 2 , wherein the Brönsted ionic liquid having —SO 3 H group used is (1-methyl-3-(3-sulfopropyl)-1H-imidazol-3-ium hydrogensulfate).

4. The process according to claim 1 , wherein the aromatic products are phenolic monomers obtained with m/z in the range of 100 to 300.

5. The process according to claim 4 , wherein the phenolic monomers are THF soluble.

6. The process according to claim 4 , wherein the phenolic monomers are selected from the group consisting of 3,5 di ter-butyl,4-methylphenol, 2-ter-butyl, 4-methylphenol, 4-acetyl benzoic acid, butyl 2-(acetyloxy) benzoate, 4-methoxy,2-(prop-2-en-yl) phenol, 3,6 dimethylbenzene-1,2,4 triyl triacetate, and (4-ter butylphenyl)methanol.

7. The process according to claim 1 , wherein the process comprises a step of isolation of aromatic products and recovery of the Brönsted ionic liquid.

8. The process according to claim 7 , wherein recovery of the Brönsted ionic liquid comprises isolating the aromatic products; treating the aromatic products with THF to isolate THF soluble aromatic products subsequently treating the insoluble part of THF with water to selectively dissolve ionic liquids from other insoluble products followed by addition of HCl to obtain a mass and finally treating the mass with ethanol or methanol to isolate ionic liquid followed by evaporating ethanol to recover ionic liquid.

9. The process according to claim 8 , wherein the recovery of ionic liquid is carried out at ambient reaction conditions.

Assignees

• Council Scient Ind Res

Inventors

• Dhepe Paresh Laxmikant
• Kelkar Ashutosh Anant
• Matsagar Babasaheb Mansub
• Singh Sandip Kumar

Classifications

• C07G1/00 Primary

  Low-molecular-weight derivatives of lignin (high-molecular-weight derivatives of lignin {C08H6/00}) · CPC title

• B01J31/0282

  of an aliphatic ring, e.g. morpholinium · CPC title

• C07C29/94

  Use of additives, e.g. for stabilisation · CPC title

• C07C27/00

  Processes involving the simultaneous production of more than one class of oxygen-containing compounds · CPC title

• C07C41/38

  by liquid-liquid treatment · CPC title