Sustainable Carbon Nano-Fibers

Introduction

In an era where sustainability meets cutting-edge material science, the ability to produce high-performance carbonaceous nano-fibrous materials from renewable sources is a game-changing innovation. Our patented process for producing carbon nano-fibers from Kraft lignin offers a solution that combines environmental responsibility with exceptional material performance. With ultra-high specific surface areas, these carbon nano-fibers open up possibilities across multiple industries, including energy storage, filtration, and advanced manufacturing.

Current Barriers in Carbon Material Production

Carbon nano-fibers are known for their impressive mechanical, thermal, and electrical properties, making them highly desirable for use in a wide range of applications, from electronics to energy storage. However, the production of these materials often relies on non-renewable resources like petroleum, leading to environmental concerns and higher costs. Additionally, conventional processes for producing nano-fibers are often complex, expensive, and inefficient, limiting their scalability and commercial viability.

The growing demand for sustainable materials, coupled with the need for more efficient, cost-effective manufacturing processes, presents a significant challenge for industries that depend on high-performance carbon materials.

Why Choose Sustainable Carbon Nano-Fibers?

Our patented method offers a transformative approach to producing carbon nano-fibers using alkali (Kraft) lignin, a renewable byproduct from the paper industry. This process not only provides a sustainable alternative to traditional carbon sources but also yields materials with ultra-high specific surface areas, making them ideal for high-performance applications like energy storage, filtration, and advanced composites.

The use of lignin in the production of carbon nano-fibers significantly reduces the reliance on non-renewable resources and lowers production costs, making it an eco-friendly and commercially viable solution. The resulting nano-fibrous materials exhibit superior mechanical strength, electrical conductivity, and thermal stability, positioning them as a superior choice for a variety of industrial uses.

Key Benefits

Sustainable Production: Utilizes renewable lignin, reducing the environmental footprint of carbon material production.
Ultra-High Surface Area: Offers exceptional performance in energy storage devices, filters, and other applications.
Cost-Effective: Lowers production costs compared to traditional carbon nano-fiber manufacturing methods.
Versatile Applications: Suitable for use in batteries, capacitors, filtration systems, and advanced composites.

Drive Innovation with Sustainable Carbon Nano-Fibers

Licensing this sustainable carbon nano-fiber technology provides companies in energy storage, advanced materials, and environmental engineering with a powerful tool for creating high-performance, eco-friendly products. With its superior material properties and sustainable production process, this innovation offers a clear path forward for industries committed to both performance and sustainability.

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Abstract
Claims

The present application discloses carbonaceous nano-fibrous materials developed by electrospinning mixtures of alkali lignin with a polymer at varied mass ratios. The present application also discloses processing of the lignin/polymer fibers via progressive heat treatments for stabilization, pre-carbonization and carbonization. The resulting carbon nanofibers maintain a uniform shape and have high specific surface area.

What is claimed is:

1. A method for the manufacture of carbon nanofibers comprising:

(a) providing intermediate nanofibers stabilized by heating in an oxygen-containing atmosphere; and

(b) pre-carbonization heating comprising providing stabilized intermediate nanofibers in an inert atmosphere, wherein said pre-carbonization heating comprises heating said inert atmosphere from at least about 150° C. to between about 400° C. and about 600° C. at a heating rate of up to about 2° C. per minute and holding at a pre-carbonization temperature between about 400° C. and about 600° C. for a sufficient time to increase the crosslinking of the nanofibers and/or to begin to remove non-carbon elements from the nanofibers.

2. The method of claim 1, further comprising carbonization heating between about 700° C. and about 2200° C., for a sufficient time to yield carbon nanofibers.

3. The method of claim 2, wherein said sufficient time for carbonization heating is at least about 30 minutes.

4. The method of claim 1, wherein said pre-carbonization temperature is between about 450° C. and about 550° C.

5. The method of claim 1, wherein said heating rate is up to about 0.5° C./min.

6. The method of claim 5, wherein said heating rate is up to about 0.1° C./min.

7. The method of claim 6, wherein said heating rate is up to 0.05° C./min.

8. The method of claim 1, wherein said sufficient time to increase the crosslinking of said nanofibers and/or to begin to remove non-carbon elements from said nanofibers is at least about 30 minutes.

9. The method of claim 1, wherein said intermediate nanofibers are prepared by electrospinning a mixture comprising alkali lignin and a polymer.

10. The method of claim 9, wherein said electrospinning is solution electrospinning.

11. The method claim 10, wherein said mixture further comprises water and said polymer is soluble in said mixture.

12. The method of claim 11, wherein said polymer is poly(vinyl alcohol).

13. A method for preparing carbon nanofibers comprising:

(a) electrospinning a mixture comprising alkali lignin and a polymer to provide electrospun alkali lignin/polymer nanofibers;

(b) providing said electrospun alkali lignin/polymer nanofibers in an oxygen-containing atmosphere and heating the oxygen-containing atmosphere to a first stabilization temperature of at least about 100° C. at a heating rate of no more than 2.0° C. per minute;

(c) heating from said first stabilization temperature to a second stabilization temperature of at least about 160° C. at a heating rate of no more than about 1.0° C. per minute;

(d) heating from said second stabilization temperature to a third stabilization temperature of at least about 180° C. at a heating rate of no more than about 1.0° C. per minute; and

(e) heating from said third stabilization temperature to a fourth stabilization temperature of at least about 200° C. at a heating rate of no more than about 1.0° C. per minute;

wherein said stabilization heating yields stabilized nanofibers.

14. The method of claim 13, wherein said mixture further comprises water and said polymer is soluble in said mixture.

15. The method of claim 14, wherein said polymer is poly(vinyl alcohol).

16. The method of claim 13, further comprising providing said stabilized nanofibers in an inert atmosphere and heating the inert atmosphere to a pre-carbonization temperature of at least about 400° C. at a heating rate of no more than about 0.5° C. per minute to yield pre-carbonized nanofibers.

17. The method of claim 16, wherein said nanofibers

in (c) are held at said second stabilization temperature for at least about 8 hours;

in (d) are held at said third stabilization temperature for at least about 12 hours; and

in (e) are held at said fourth stabilization temperature for at least about 2 hours.

18. A method for preparing carbon nanofibers comprising

(a) electrospinning a mixture of alkali lignin and a polymer;

(b) heat treating said electrospun alkali lignin/polymer nanofibers wherein said heat treating comprises providing said nanofibers in an oxygen-containing atmosphere and progressive stabilization heating of said oxygen-containing atmosphere from a first stabilization temperature of at least about 100° C. to an final stabilization temperature of at least about 200° C. at a heating rate of no more than 1° C. per minute to yield stabilized nanofibers;

(c) providing said stabilized nanofibers in an inert atmosphere and heating the inert atmosphere up to a pre-carbonization temperature of at least about 400° C. at a heating rate of no more than about 0.2° C. per minute and holding at said pre-carbonization temperature for a sufficient time to increase crosslinking in said nanofibers to yield pre-carbonized nanofibers; and

(d) providing said pre-carbonized nanofibers in an inert atmosphere and heating the inert atmosphere up to a carbonization temperature of at least about 700° C. at a heating rate of no more than about 10° C. per minute and holding at said carbonization temperature for a sufficient time to remove most of the non-carbon impurities in said nanofibers.

19. The method of claim 18, wherein said rate of heating in (b) is between about 0.05° C./min and about 1° C./min; said rate of heating in (c) is no more than about 0.1° C./min and said pre-carbonization temperature is held for at least about 30 minutes; and said carbonization temperature is held for at least about 30 minutes.

20. The method claim 19, wherein said polymer is soluble in an aqueous solvent.

21. The method of claim 20, wherein said mixture comprises water and said polymer is poly(vinyl alcohol).

22. The method of claim 21, wherein said mixture of poly(vinyl alcohol) and alkali lignin contains at least about 50 wt % alkali lignin.

23. The method of claim 22, wherein said mixture of poly(vinyl alcohol) and said alkali lignin contains at least about 70 wt % alkali lignin.

24. Carbon nanofibers having a surface area of from about 250 m²/g to about 750 m²/g and a peak pore volume greater than about 0.04 cm³/nm/g for pores having a diameter of less than about 5 nm and an average pore size of no more than about 4 nm.

25. A electric double layer capacitor comprising the carbon nanofiber of claim 24.

Title

Production of carbonaceous nano-fibrous materials with ultra-high specific surface area from alkali (Kraft) lignin

Inventor(s)

Lifeng Zhang, Ajit Kelkar, Hao Fong, Chuilin Lai

Assignee(s)

North Carolina A&T State University, South Dakota School of Mines and Technology

Patent #

9190222

Patent Date

November 17, 2015