Organic biomass fractionation process

Abstract

A method for fractionating fibrous biomass comprising cellulose, hemicellulose and lignin components to separate said lignin, cellulose and hemicellulose from one another comprises: (a) shredding said fibrous biomass; (b) concurrently with or subsequent to said shredding, contacting said biomass with an aqueous solution of a nitrate ion source at a concentration of about 0.1-0.3% at a temperature in the range of about 60° to about 80° C. to initiate nitration of the lignin component of said biomass; (c) submerging said partially nitrated biomass in an aqueous solution of a nitrate ion source in the presence of an aluminum compound at a temperature within the range of about 75-100° C. for a time sufficient to complete the nitration of said lignin component; (d) contacting the nitrated biomass produced in step (c) with an alkaline extraction liquor comprising NH4OH at an initial concentration sufficient to solubilize said nitrated lignin component and said hemicellulose component from said cellulose component of said biomass; e) recovering said cellulose from said extraction liquor containing said solubilized nitrated lignin and hemicellulose components, wherein said cellulose comprises at least about 88% alpha cellulose; (f) treating said extraction liquor with an acid to precipitate lignin contained therein, and (g) separating said lignin from soluble hemicellulose in said extraction liquor. The recovered cellulose component comprises at least 88% alpha cellulose and is useful as a starting material for the production of ethanol.

Description

[0001] The present invention is directed to an economic method for fractionating renewable biomass safely to cleanly separate the cellulosic, hemicellulosic and lignin components of fibrous plant materials in a process without the concomitant production of by-products which could pollute water, land or air. The separated components are useful for the production of fossil fuel derivatives, biodegradable plastics, edible protein, and a variety of other products.[0002] The world today is facing growing burdens caused by overpopulation, depletion of fossil fuels, increasing demands for fuels, pollution of air, water and land, global warming and climate changes, forest cover destruction, and agricultural land loss. Although to some extent some of these concerns can be met through the improved use of solar energy and windpower and increased nuclear power, more conservation of resources and more efficient use of resources are always being sought.[0003] Fibrous cellulosic material, such as ...

AI Technical Summary

Benefits of technology

[0006] Accordingly, it is an object of this invention to provide an economical and efficient method of fractionating a wide variety of renewable fibrous organic biomass to its cellulose, hemicellulose and lignin components which then can be used as base materials for the production of sugars for energy, plastics, chemicals, and protein.

[0007] It is a further object of this invention to help reduce global warming through a reduction in air pollution. Providing a clean and cost efficient process for the production of cellulose makes possible the production of bioethanol in large quantities at an economical cost. Having a means for the efficient production of ethanol using local materials that otherwise would be burned as waste will allow, for the first time, the substitution of ethanol for a significant portion of the enormous amount of gasoline that is used annually. This will reduce air pollution caused by vehicle exhaust, as well as that caused by the emission of nitrogen gases derived from the burning of what conventionally has been considered waste biomass.

[0008] It is a further object of this invention to provide a method of fractionating biomass that is environmentally clean, with no toxic by-products and no toxic air or water waste stream, with a closed liquid and chemical system.

Problems solved by technology

The world today is facing growing burdens caused by overpopulation, depletion of fossil fuels, increasing demands for fuels, pollution of air, water and land, global warming and climate changes, forest cover destruction, and agricultural land loss.

To date, however, there has not been an economical method for cleanly separating the basic components of fibrous, ligno-cellulosic materials and the fermentable sugars they represent from one another.

In particular, it has proved difficult to economically separate the mixed hexose and pentose structured hemicellulose from the lignin and other, minor, components, such as lipids and silica, present in biomass.

All use high levels of technology, fossil energy and investment and, accordingly, are expensive and, often, highly polluting.

For example, conventional pulping processes, which use high temperatures (e.g., 175.degree. C.) and pressure (e.g., 175 psi) and sulfite, kraft or alkali to obtain purified cellulose, known as alpha pulp, are well recognized as involving high investment, energy and operating costs, including recovery of chemicals, which are accompanied by severe problems of air and water pollution and the production of toxic materials.