US 4,966,650 AGranted

Method for fractionation of lignins from steam exploded lignocellulosics to provide fractions with different properties

OwnerEdward A. DeLong, George S. Ritchieinventors

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Abstract

The chemical components of lignocellulosic material which have been dissociated by a steam explosion process can be extracted from the mixture of components using a solvent extraction process. The solvents are water, alcohol and a mild caustic in that order, or the alcohol step can be by-passed and only water and caustic are used. The caustic is a stronger solvent and it will extract the alcohol solubles along with the caustic only solubles. The eluant from the these extractions contains a range of lignin derived substances, which have different applications, such as thermoplastic and thermosetting characteristics. This invention describes a method for partitioning these lignin components into reproducible fractions having definable characteristics for particular applications. For instance, many copolymer applications require a thermosetting only fraction of the lignin. Other applications require a thermoplastic only lignin. The patent also describes a process for converting the thermoplastic lignin fraction to thermosetting lignin.

Claims15

Dependent claims

A method for preparing a lignin solution by extraction of steam-exploded, dissociated lignocellulosic material and providing thermosetting and thermoplastic lignins from the lignin solution, which comprises:

(a) extracting the steam-exploded dissociated lignocellulosic material with water at a temperature no greater than 40.degree. C., to provide a water solution of water solubles and residual lignocellulosic material;
(b) extracting the residual lignocellulosic material from step (a) with an extractant selected from the group consisting of an alcohol and a caustic solution to provide a solution of extracted lignins;
(c) recovering lignins from the solution of extracted lignins;
(d) treating lignins recovered in step (c) with a halocarbon solvent to provide a halocarbon solution of thermoplastic lignins and undissolved thermosetting lignins;
(e) recovering thermoplastic lignins from the halocarbon solution of thermoplastic lignins of step (d);
wherein the undissolved thermosetting lignins have a purity greater than 90 percent as measured by methoxyl content, are substantially free of carbohydrate, vegetable oil, water soluble lignin constituents and thermoplastic lignins, have a number average molecular weight in the range of 1,500-2,000 daltons and a melting point in the range of about 170.degree. C. to 180.degree. C.;
and wherein the thermoplastic lignins recovered in step (e) have a purity greater than 90 percent as measured by methoxyl content, are substantially free of carbohydrate, vegetable oil, water soluble lignin constituents and thermosetting lignins, have a number average molecular weight in the range of 800-1,000 daltons and a melting point in the range of about 125.degree. C. to 135.degree. C.

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Dependencies are inferred from the claim text.