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EP-4739627-A2 - SUSTAINABLE MANUFACTURE OF SYNTHETIC GRAPHITE FROM REMEDIATED CARBONACEOUS FEEDSTOCKS

EP4739627A2EP 4739627 A2EP4739627 A2EP 4739627A2EP-4739627-A2

Abstract

A synthetic graphite having a purity level of at least 99.5%, wherein the graphite is obtainable from a purified carbonaceous product (PCP) or a solvent extract thereof, wherein the PCP is in particulate form with at least about 80% by volume (%v) of the particles being no greater than about 15 µm in diameter; and wherein the PCP has an ash content of less than about 8 wt%. The PCP may be derived from processing of a coal waste material comprised of coal ultrafines and/or coal microfines.

Inventors

  • UNSWORTH, JOHN FRANCIS
  • PATTABHIRAMAN, Pranetr
  • AYERS, Clayton
  • BRITNELL, Liam
  • KEVERNE, Benjamin
  • Blackburn, Timothy

Assignees

  • ARQ IP LIMITED

Dates

Publication Date
20260513
Application Date
20240703

Claims (20)

  1. 1. A synthetic graphite having a purity level of at least 99.5%, wherein the graphite is obtainable from a coal, wherein the coal is comprised within a purified carbonaceous product (PCP), wherein the PCP is in particulate form with at least about 80% by volume (%v) of the particles being no greater than about 15 pm in diameter; and wherein the PCP has an ash content of less than about 8 wt%.
  2. 2. The synthetic graphite of claim 1 , wherein at least about 90%v (d90) of the PCP particles are no greater than about 25 pm in diameter, optionally no greater than about 20 pm in diameter.
  3. 3. The synthetic graphite of claim 1 or claim 2, wherein at least about 90%v (d90) of the PCP particles are no greater than about 15 pm in diameter, optionally no greater than about 10 pm in diameter.
  4. 4. The synthetic graphite of claim 1 or claim 2, wherein at least about 95%v (d95) of the PCP particles are no greater than about 25 pm in diameter.
  5. 5. The synthetic graphite of claim 4, wherein at least about 99%v of the PCP particles are no greater than about 20 pm in diameter, suitably no greater than about 15 pm in diameter.
  6. 6. The synthetic graphite of claim 1 , wherein at least about 80%v (d80) of the PCP particles are no greater than about 12 pm in diameter, preferably no greater than about 10 pm in diameter, suitably no greater than about 8 pm in diameter, optionally no greater than about 5 pm in diameter.
  7. 7. The synthetic graphite of any preceding claim, wherein the average particle size of the PCP is no more than 10 pm, wherein the average particle size of the PCP is determined by laser diffraction.
  8. 8. The synthetic graphite of claim 7, wherein the at least about 99%v of the PCP particles have an average particle size of the PCP that is not more than 10 pm.
  9. 9. The synthetic graphite of any preceding claim, wherein the PCP has an ash content of less than about 5 wt%, or less than about 3 wt%, or less than about 1 .5 wt%, or less than about 1 .0 wt%, or less than about 0.8 wt%, or optionally less than 0.5 wt%.
  10. 10. The synthetic graphite of any preceding claim, wherein the PCP has a water content of less than about 5 wt%, optionally less than about 3 wt%, suitably less than about 1 wt%.
  11. 11. The synthetic graphite of any preceding claim, wherein the synthetic graphite is obtained by a process selected from one of: (i) graphitising the PCP at a temperature of around 2500 to around 3000°C in an inert atmosphere; (ii) calcining the PCP at a temperature of between around 1000 and around 1200 °C in an inert atmosphere, followed by graphitisation at a temperature of around 2500 to around 3000°C in an inert atmosphere; (iii) pyrolyzing the PCP at a temperature of between around 400 and around 1000°C in the absence of air, followed by graphitisation at a temperature of around 2500 to around 3000°C in an inert atmosphere; or (iv) pyrolyzing the PCP at a temperature of between around 400 and around 1000°C in the absence of air, calcining at a temperature of between around 1000 and around 1200 °C in an inert atmosphere, followed by graphitisation at a temperature of around 2500 to around 3000°C in an inert atmosphere.
  12. 12. The synthetic graphite of claim 11 , wherein: the graphitising occurs over a time period of at least 1 minute, at least 1 hour, at least 12 hours or at least 24 hours; and/or the calcining occurs over a time period of at least 1 hour, at least 6 hours, at least 12 hours, or least 24 hours; and/or the pyrolysis occurs over a time period of at least 1 hour, at least 3 hours, at least 6 hours, or least 12 hours.
  13. 13. The synthetic graphite of any preceding claim, wherein the PCP is obtained from a carbonaceous feedstock material selected from: (a) a coal waste material comprised of coal ultrafines and/or coal microfines, and wherein the coal waste material is comprised of one or more of the group consisting of: hard coal, such as anthracite; bituminous coal; sub-bituminous coal; and brown coal, including lignite (as defined in ASTM D388-23); (b) a microfine natural graphite; and/or (c) a biochar, and/or (d) a PCP solvent extract.
  14. 14. The synthetic graphite of claim 13, wherein the carbonaceous feedstock material is subjected to one or more floatation steps to remove entrained ash in order to produce the PCP.
  15. 15. The synthetic graphite of claims 13 or 14, wherein the carbonaceous feedstock material is not pre-treated with a strong acid to reduce ash content.
  16. 16. A method of using a coal waste material in a process for the manufacture of a synthetic graphite, wherein the coal waste material comprises coal ultrafines and/or coal microfines, and wherein the coal waste material is comprised of one or more of the group consisting of: hard coal, such as anthracite; bituminous coal; sub-bituminous coal; and brown coal, including lignite (as defined in ISO 11760:2005), and wherein the coal waste material is comprised within a purified carbonaceous product (POP) that is derived from the coal waste material, wherein the POP is in particulate form with at least about 80% by volume (%v) of the particles being no greater than about 15 pm in diameter; and wherein the POP has an ash content of less than about 8 wt%.
  17. 17. The method of claim 16, wherein the POP is in particulate form with at least about 90% by volume (%v) of the particles being no greater than about 25 pm in diameter; and wherein the PCP has an ash content of less than about 5 wt%, typically less than about 3 wt%, suitably less than about 2 wt%.
  18. 18. A method of using a PCP solvent extract in a process for the manufacture of a synthetic graphite, wherein the PCP solvent extract is derived by solvent extraction of a purified carbonaceous product (PCP) where the PCP is in particulate form with at least about 80% by volume (%v) of the particles being no greater than about 15 pm in diameter; and wherein the PCP has an ash content of less than about 8 wt%.
  19. 19. The method of claim 18, wherein the PCP is in particulate form with at least about 90% by volume (%v) of the particles being no greater than about 25 pm in diameter; and wherein the PCP has an ash content of less than about 5 wt%, and typically less than 3 wt%, suitably less than about 2 wt%.
  20. 20. The method of any one of claims 16 to 19, wherein the PCP has an ash content of less than about 1.5 wt%, 1.0 wt%, 0.8 wt%, optionally less than 0.5 wt%.

Description

SUSTAINABLE MANUFACTURE OF SYNTHETIC GRAPHITE FROM REMEDIATED CARBONACEOUS FEEDSTOCKS FIELD OF THE INVENTION [0001] The invention relates to compositions and methods for the manufacture of synthetic graphite. BACKGROUND OF THE INVENTION [0002] Graphite is a naturally occurring crystalline form of the element carbon. It consists of stacked layers of graphene and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on large scale with demand currently standing at 700,000 to 800,000 metric tons (MT) annually, with the lithium-ion battery sector accounting for 200,000 MT. It is estimated that by 2030, total global demand is expected to rise substantially to 4 million MT a year, with the lithium- ion battery market consuming nearly 3 million MT. Many approaches focusing on the need to reduce fossil fuel dependence require graphite as a key component within their energy generation and storage technology solutions. [0003] Naturally mined graphite is a finite resource, and its extraction comes with trade-offs in terms of environmental degradation as well as generation of waste and toxic by-products. The principal export sources of mined graphite are in order of tonnage: China, Mexico, Canada, Brazil, and Madagascar. Indeed, China accounts for nearly three quarters of global output of the natural mineral supply. Hence, to meet the growing demand for high purity graphite interest has shifted to manufacture of synthetic graphite from other sources of carbon. [0004] Synthetic graphite is a unique material often used in metal fabrication and as a primary component of lithium batteries. It is composed of high-purity carbon and is known for its ability to withstand high temperatures and corrosion. Synthetic graphite is purer in terms of carbon content and tends to behave more predictably than naturally sourced graphite, which in turn contributes to its perceived value in specialty applications such as solar energy generation, electrical storage and in electric arc furnaces. However, synthetic graphite can be significantly more expensive to produce than natural graphite, as the process is energy intensive particularly if high purity graphite is needed. It is estimated that the production cost of synthetic graphite can be double or triple that for naturally mined graphite. In addition current processes for manufacturing synthetic graphite generate nearly 5 kg of carbon dioxide per kg of graphite which is more than three times higher than mining the natural mineral (Dai et al. Batteries 2019, 5(2), 48). [0005] High purity graphite may be obtained from natural or synthetic sources using a variety of processes that vary depending on the specific source material and desired purity level. Natural sources include graphite ore or flake graphite, while synthetic carbon sources involve carbonaceous materials like petroleum coke or coal tar pitch. Whatever the carbon source typically the raw material will undergo purification steps to remove impurities and increase the carbon content. This process typically involves crushing the material and subjecting it to various physical, chemical and/or thermal treatments. The purified material is then ground into fine particles, using ball mills for example, to achieve the desired particle size distribution. The graphite particles can mixed with a binder material, such as pitch or a synthetic resin, to form a paste. This paste is then shaped and moulded into the desired product form using techniques like extrusion, isostatic pressing, or vibration moulding. The shaped graphite products are suitably subjected to a baking process, also known as carbonization, where they are heated to high temperatures in an inert atmosphere or under vacuum conditions. This step drives off volatile components and converts the binder material into a carbon matrix. The baked graphite products are further processed through a graphitization step, which involves exposing them to extremely high temperatures (over 2,000°C) often in the presence of a catalyst or by using electric resistance furnaces. This process rearranges the carbon atoms into a more ordered graphite crystal structure, resulting in improved electrical and thermal conductivity. For applications requiring ultra-high purity graphite, an additional purification step may be included. This can involve chemical or thermal treatment methods to further remove any remaining impurities and, thus, increase the purity level. [0006] US-20230017556 (Azenkeng) describes a process that utilises chemical cleaning of coal feedstock using a cesium chloride bath to purify the carbon content. As a result of this step the ash content is actually increased so that there is a need to introduce additional chemical de-ashing steps to remove the cesium from the cleaned coal. This is followed by multiple stages of heating in order to achieve sufficient graphitization and to drive off ash components introduced via the chemical cl