Improved thermoplastic carbon precursor materials for use in coating, bonding, and impregnation processes for steel and aluminum production and for the manufacture of electrodes for batteries

Abstract

The present invention is directed to a carbon precursor material comprising a petroleum-derived pitch product derived from a petroleum-based feedstock characterized by a flash point above 290°C and a Mettler softening point of 110-300°C and having a concentration of asphaltenes less than 40 wt% as measured by SARA analysis. The present invention is further directed to the use of such carbon precursor material in a binding / coating / impregnation process in the production of graphite electrodes for electric arc furnaces used in steel / ferroalloy / silicon production, or carbon electrodes for aluminum production, and / or in the production of graphite particles for the manufacture of battery electrodes. The present invention is further directed to a carbon or graphite electrode, in particular a battery electrode, comprising said pitch binder in a converted state. The present invention also provides a method for producing coated and / or bonded and / or impregnated carbon precursor materials comprising a petroleum-derived pitch product, the method comprising the steps of providing a petroleum-based feedstock having a concentration of asphaltenes less than 40 wt.% as measured by SARA analysis, heat treating said petroleum-based feedstock at greater than 300° C. and atmospheric pressure, followed by distilling the heat treated material, thereby obtaining a distillation residue that is said petroleum-derived pitch product.

Description

[Technical field]

[0001] Technical Field The present invention relates generally to carbon precursor materials.

[0002] Additionally, the present invention relates to methods for producing such carbon precursor materials.

[0003] More specifically, the invention generally relates to the use of such carbon precursor materials in bonding and / or impregnation processes for the manufacture of graphitized electrodes for electric arc furnaces, (semi-)graphitized carbon anodes / cathodes for aluminum production and Soderberg pastes, or as coating materials for carbon coated particles or for the agglomeration of fine particle grains into larger electrically conductive agglomerates or carbon-containing particle composites, or for the production of carbon matrices used to produce battery electrode material powders.

[0004] Furthermore, the present invention relates to electrodes, and more particularly to battery electrodes, comprising electrode materials having particle coatings made of such carbon precursor materials, or composites of particles embedded in a carbon matrix made of such carbon precursor materials, forming a particle composite for use as a battery electrode material. [Background technology]

[0005] background Traditionally, the hydrocarbon pitch material in the bonding or impregnation process for coatings, graphite electrodes for electric arc furnaces, carbon anodes / cathodes and Soderberg pastes for aluminum production, and for the manufacture of battery electrodes, particularly Li-ion batteries, is coal tar pitch, and the hydrocarbon impregnation pitches used for impregnation of graphite electrodes after the initial carbonization of the electrodes are typically based on coal tar distillation products.

[0006] Coal tar has always been available in abundance as a by-product of the production of metallurgical coke used in steel production. Recently, however, due to a decline in demand for virgin iron, less metallurgical coke is being produced and therefore less coal tar is available. Greater recycling of iron or steel scrap using electric arc furnaces has contributed to this trend. Furthermore, steel production produces high CO 2 The move away from exhaust manufacturing processes, e.g., blast furnaces using metallurgical coal as the reducing medium, towards the direct reduction of iron ore with hydrogen, is another reason for the expected decline in coal tar availability.

[0007] Another drawback of coal tar pitch binders is the high amount (about 10,000 ppm in typical viscosity ranges) of benzo(a)pyrene (B[a]P), which is classified as rather carcinogenic. In addition to the B[a]P content, several other polycyclic aromatic constituents are also considered to be hazardous to health and the environment. In general, the 16 EPA-PAH can be used to calculate toxicity index values ​​for these materials.

[0008] In an attempt to produce an alternative pitch that contains less benzo[a]pyrene than coal tar pitch and ensures future security of supply, petroleum-derived pitches have been considered.

[0009] However, normal petroleum-derived pitch, when used pure in the electrode production process, does not achieve the same quality parameters of the carbon artifacts produced as coal tar pitch. The first disadvantage is that it has a lower coke yield than coal tar pitch.

[0010] Additionally, existing industrial petroleum-based pitches can have flash points starting at 200° C., which is well below the typical flash point of coal tar pitch, and therefore can raise potential safety concerns in electrode fabrication processes that can involve thermal mixing processes at temperatures up to 200° C. This also limits the extent to which petroleum pitch can be blended with coal tar pitch.

[0011] Another drawback of existing industrial petroleum-based pitches is that these pitch types generate significantly more volatile matter than coal tar pitches upon heating to 400° C., potentially interfering with the carbonization process applied in the manufacture of carbon anodes or cathodes.

[0012] In summary, none of the prior art attempts have provided an alternative carbon precursor material to coal tar pitch that can be used in substantial volume / blend ratios to reliably serve the aluminum and steel industries with high product volumes. Summary of the Invention [Problem to be solved by the invention]

[0013] It is therefore a general object of the present invention to provide alternative carbon precursors that allow for an enhanced security of supply and that meet the requirements for use in bonding, coating and impregnation processes as precursors for conductive carbon in the manufacture of (semi-)graphitic carbon electrodes and likewise battery electrodes.

[0014] Another object of the present invention is to provide alternative carbon precursors for bonding, coating and impregnation processes that result in similar coke values, as well as similar processing and performance of graphite electrodes, pre-calcined anodes and Soderberg pastes, aluminum production, carbon anodes, and battery electrodes.

[0015] It is a further object of the present invention to provide an alternative carbon precursor for bonding, coating and impregnation processes having lower B[a]P and 16EPA-PAH total content. [Means for solving the problem]

[0016] overview In a first aspect according to the present invention, there is provided a carbon precursor material comprising a petroleum-derived pitch product derived from a petroleum-based feedstock having a concentration of asphaltenes of less than 40 wt.% as measured by SARA analysis, the petroleum-derived pitch product being characterized by a flash point greater than 290°C and a Mettler softening point of 110-300°C.

[0017] In a second aspect of the invention, the use of such a carbon precursor material is provided as a binder and / or impregnation material in the production of graphite electrodes for electric arc furnaces used in steel production, or (semi-)graphitized electrodes for aluminium production, and / or as a coating and / or binding material for graphite particles for the manufacture of battery electrodes.

[0018] In a third aspect, the present invention provides a carbon or graphite electrode, in particular a battery electrode, comprising the pitch binder in a converted state.

[0019] In a fourth aspect according to the present invention there is provided a method for producing a coated and / or bonded and / or impregnated carbon precursor material, the petroleum derived pitch product being described throughout the text, the method comprising: - providing a petroleum-based feedstock having a concentration of asphaltenes of less than 40 wt.% by SARA analysis; - heat treating said petroleum-based feedstock at above 300°C and atmospheric pressure; - subsequently distilling the heat treated material, thereby obtaining a distillation residue which is said petroleum derived pitch product; Includes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Detailed Description In a first aspect according to the present invention, there is provided a carbon precursor material comprising a pitch product derived from a petroleum-based feedstock characterized by a flash point above 290° C. and a Mettler softening point of 90-300° C., and having a concentration of asphaltenes of less than 40 wt.% as measured by SARA analysis (clay gel adsorption chromatography according to ASTM D2007).

[0021] As is well known, asphaltenes are solids that are insoluble in paraffinic solvents due to their highly aromatic ring structure and high molecular weight, have high melting points and tend to easily form isotropic coke. For example, asphaltenes can be pentane or heptane insoluble (cfr eg. EP 0072243 B1).

[0022] SARA analysis is a commonly used method for measuring saturates, asphaltenes, resins, and aromatics in heavy crude oils, distillates, and feedstocks. SARA analysis is typically performed by clay gel adsorption chromatography (ASTM D2007) and is readily available through analytical services laboratories.

[0023] Additionally, the amount of asphaltene as described throughout this text includes losses as defined in ASTM D-2007.

[0024] The petroleum-based feedstocks having less than 40 wt.% asphaltenes may be further characterized by having a saturates concentration of >10 wt.% and / or a resin concentration of >35 wt.% as measured by SARA analysis.

[0025] In certain embodiments, the petroleum-based feedstock may have less than 35, less than 30, or even less than 25% (by weight) of asphaltenes as measured by SARA analysis. Furthermore, the amount of asphaltenes as described above may include losses as defined in ASTM D2007.

[0026] The carbon precursor material according to the invention may combine the more advantageous properties of conventional coal tar based pitches with the more advantageous properties of petroleum based pitches, namely: - coking values ​​at the level of coal tar pitches at comparable softening points, and therefore higher than existing petroleum pitches; and / or - a viscosity at the level of coal tar pitches at a comparable softening point, and therefore lower than existing petroleum pitches; and / or a flash point superior to both coal tar pitch and petroleum pitch at comparable softening points, and / or - a lower benzo[a]pyrene content than both coal tar pitch and conventional petroleum pitch at comparable softening points, and / or Very little evolution of volatile matter below -400°C, better than ordinary coal tar and petroleum pitches at comparable softening points. - The isotropic nature of the coke formed by carbonizing the precursor material making it particularly suitable for electrode applications.

[0027] The carbon precursor material of the present invention may exhibit high carbon yield combined with high flash point, and low viscosity in the molten state combined with low B[a]P content. In addition, it may exhibit low quinoline insolubles and toluene insolubles content that are ideal for particle coating processes, as well as good grinding properties for dry particle coating processes. It may also exhibit high flash point and low viscosity for safe and efficient mixing with powders in bonding and coating processes, while being environmentally friendly with low B[a]P concentration and / or improved toxicity index.

[0028] The high flash point and low viscosity in the molten state may also make the carbon precursor material suitable for direct coating in the liquid state. In this case, the freshly produced carbon precursor material may be sprayed directly into the particles to be coated, which have been fluidized by an intensive mixer or a fluidized bed. The freshly produced liquid carbon precursor may also be used directly for particle bonding and agglomeration. In this case, the hot liquid precursor is sprayed directly onto the agglomerated particles, which have been treated by high shear forces in a heated mixer.

[0029] Furthermore, while neither pure petroleum-derived pitches nor blends of petroleum pitch and coal tar pitch with significant amounts of petroleum pitch above 25% have been able to meet the requirements for producing graphite electrodes so far due to their low coking values ​​and high viscosities, the carbon precursor material according to the invention may make it possible to meet the requirements of the present application while having a lower B[a]P content.

[0030] Furthermore, while pure petroleum-derived pitches as well as blends of petroleum pitch and coal tar pitch with a significant amount of petroleum pitch of more than 25% have been able to meet the requirements for producing semi-graphitic carbon anodes and graphitic carbon cathodes and Soderberg pastes for the aluminum industry so far due to their low coking values, low flash points and high evolution of volatiles below 400° C., the carbon precursor material according to the invention may make it possible to meet the requirements of the present application with a lower B[a]P content.

[0031] While conventional petroleum-derived pitches have drawbacks for the manufacture of battery electrodes with respect to coking value, viscosity and benzo[a]pyrene content, another advantage of the carbon precursor material according to the present invention is that it may realize substantial advantages with respect to these parameters.

[0032] Furthermore, the carbon precursor material according to the present invention can be applied in significantly higher blend ratios with coal tar pitches than with conventional petroleum derived pitches, thereby meeting the objective of having an enhanced assurance of supply of high quality carbon precursor to downstream users.

[0033] In one embodiment of the present invention, the petroleum derived pitch product may have a softening point of 90-300° C. Mettler, preferably 110° C.-250° C., more preferably 120° C.-220° C. Mettler. In view of particle coating applications, a softening point above 120° C. may allow the carbon precursor to be ground into fine particles for use in the dry particle coating process.

[0034] Additionally, the petroleum derived pitch product may have a coke value of at least 50% ALCAN, or at least 55% ALCAN, preferably greater than 60% ALCAN, resulting in less porosity carbon artifacts after carbonization / graphitization, leading to better properties in aluminum production and subsequent use as electrodes in battery cells.

[0035] In one embodiment of the present invention, the petroleum derived pitch product may have a coke value of at least 50% ALCAN, a B[a]P content of less than 500 mg / kg, and a softening point of greater than 110° C. Mettler.

[0036] In one embodiment of the present invention, the petroleum derived pitch product may have a flash point greater than 290° C., a coke value of at least 55% ALCAN, a B[a]P content of less than 500 mg / kg, and a softening point greater than 110° C. Mettler.

[0037] In another embodiment, the petroleum derived pitch product may have a coke value of at least 70% ALCAN, a B[a]P content of less than 100 mg / kg, and a softening point of greater than 200° C. Mettler.

[0038] When the carbon precursor material is converted to carbon during the carbonization process, which is a heat treatment in an inert gas atmosphere or vacuum, a sufficiently high coke yield makes it possible to avoid high porosity in the graphite particles thus obtained due to the less volatile substances formed during the carbonization process. A dense carbon layer may form in a morphology that is favorable for the formation of an efficient solid electrolyte interface at the electrode particle surface, i.e., with a passivation layer formed from electrolyte decomposition products at the electrochemically active electrode surface area in contact with the electrolyte. In the case of a liquid electrolyte, this passivation layer is formed at the electrochemically active electrode surface area wetted by the liquid electrolyte. The nature and quality of the carbon film formed at the particle surface positively influences the solid electrolyte interface and therefore some battery cell parameters, such as the specific charge loss of the battery cell, the current discharge and charge performance, the charge / discharge cycling stability, and the safety performance.

[0039] In one embodiment of the present invention, the petroleum-derived pitch product may have a Mettler softening point of 110-130°C while having a viscosity of less than 600 mPa·s at 180°C and / or a viscosity of less than 200 mPa·s at 200°C.

[0040] In another embodiment, the viscosity may be less than 2000 mPa·s at 300° C. while having a 230° C. Mettler softening point.

[0041] The low melt viscosity enhances the wetting and impregnation of the particle surface such that a thin film of carbon is achieved that is uniformly distributed on the particle surface. The enhanced surface wetting and impregnation results in good coverage of the geometric particle surface, as well as the micro- and mesopores, and roughness that can typically be found on the particle surface.

[0042] The carbon precursor material of the present invention may comprise 25-90% by weight, preferably 50-90% by weight, of said petroleum-derived pitch products and coal tar-based pitches.

[0043] In an even more preferred embodiment of the present invention, the carbon precursor material may consist exclusively of said petroleum-derived pitch product, i.e., contain 100% by weight of the petroleum-derived pitch product.

[0044] The benzo[a]pyrene content may be less than 500 ppm for carbon precursor materials containing 100 wt.% petroleum-derived pitch products, less than 2000 ppm for 85 wt.% petroleum-derived pitch products and coal tar-based pitches, less than 6000 ppm for 50 wt.% petroleum-derived pitch products, or less than 8500 ppm for 25 wt.% petroleum-derived pitch products.

[0045] In one embodiment of the present invention, the carbon precursor material may have a concentration of asphaltenes of at least 80% by weight, or at least 90% by weight, as measured by the SARA method. This may ensure a dense (low porosity) and uniform carbon coating on the electrode material surface, reducing the surface reactivity towards the electrolyte and the surface area of ​​the electrode material in direct contact with the battery electrolyte. Furthermore, the morphology of the carbon layer formed on the particle surface upon subsequent carbonization of the carbon precursor ensures good electrical conductivity and particle contact of the electrode material in the battery cell electrode.

[0046] In one aspect of the invention, the carbon precursor material may be used in the production of graphite electrodes for electric arc furnaces or semi-graphitized carbon anodes and graphitized carbon cathodes for the aluminum industry and Soderberg pastes, and / or in the bonding / impregnation / coating process for particles of electrode material for the manufacture of battery electrodes. The particles to be coated may be of graphite, silicon, silicon oxide, or carbonaceous composites thereof with a carbon surface layer, thereby obtaining a carbonaceous powdered material or powder composite. Particles of the same nature may also be agglomerated using the same carbon precursor material.

[0047] According to the present invention, there is provided a method for producing carbon precursor materials as described throughout this text, including petroleum derived pitch products, the method comprising: - providing a petroleum-based feedstock having a concentration of asphaltenes of less than 40 wt.% by SARA analysis; - heat treating said petroleum-based feedstock at above 300°C and atmospheric pressure; followed by distilling the heat-treated material; wherein the distillation is adapted to obtain a distillation residue that is a pitch product derived from the petroleum.

[0048] The inventors have found that the typically low pitch yields of such petroleum-based feedstocks can be significantly improved by thermal treatment at atmospheric pressure above 300° C., preferably up to 400° C. This treatment can optionally be carried out in the presence of a catalyst or reactivity inducer, such as an organic peroxide, a superacid, a strong Lewis acid, oxygen or a selected petroleum stream suitable for promoting the polymerization of aromatic constituents and the formation of condensed polycyclic aromatic hydrocarbons.

[0049] Distillation of the thermally treated feedstock may include, for example, vacuum distillation with a vacuum distillation column to obtain a distillation residue that is the petroleum-derived pitch product. Such subsequent distillation may be performed to remove volatile constituents and result in a petroleum-derived pitch product and thus a carbon precursor material with a wide range of softening points with a reasonable pitch yield of more than 30%. Typically, the final boiling point of the distillation may be between 450 and 650°C ambient equivalent temperature (AET).

[0050] In a preferred embodiment of the process, the petroleum-based feedstock is heat treated at 380° C. for up to 8 hours, followed by distillation under vacuum to a degree that the resulting petroleum-derived pitch product exhibits a targeted softening point at an economical pitch yield.

[0051] In the process of the present invention, the petroleum-based feedstock having less than 40 wt.% asphaltenes may be further characterized by having a concentration of >10 wt.% saturates and / or a concentration of >35 wt.% resins as measured by SARA analysis.

[0052] In certain embodiments of the process of the present invention, the petroleum-based feedstock may have less than 35 wt%, less than 30 wt%, or even less than 25 wt% asphaltenes as measured by SARA analysis.

[0053] Further, such methods may include blending the petroleum-derived pitch product with a coal tar-based pitch to obtain a carbon precursor material having the petroleum-derived pitch product in an amount of 25-90% by weight in a mix.

[0054] The carbon precursor manufacturing process may be part of a process for manufacturing a graphite or carbon electrode, which may include providing a number of particles to be coated, coating and / or bonding the particles using a carbon precursor material, and further shaping and graphitizing or carbonizing to form a graphite or carbon electrode. EXAMPLES

[0055] The following tables illustrate examples of carbon precursor material formulations according to one embodiment of the present invention, namely, Table 1 provides carbon precursor material Examples 1-5 that contain only a petroleum-derived pitch product, while Table 2 provides Examples 6-8 that contain a petroleum-derived pitch product mixed with a coal tar-based pitch.

[0056] [Table 1]

[0057] [Table 2]

[0058] [Table 3]

[0059] [Table 4]

[0060] Example 9: Natural graphite (spherical shape, average particle size of 17 mm and 6.0 mm) using the carbon precursor materials of Examples 5 and 2 2 g -1 Reduction in BET specific surface area (BET SSA) of: Natural graphite was suspended in tetrahydrofuran (THF, 100 mL) together with an appropriate amount of carbon precursor according to the invention (total mass equal to 50 g). The mixture thus obtained was sonicated at room temperature for 1 hour, after which the tetrahydrofuran was gently evaporated at a temperature of 40° C. with a sustained vacuum of 300 mbar (a) or more. Once a solid cake was formed, another 100 mL of THF was added and the evaporation step was repeated until a free-flowing powder was obtained. The material thus obtained was dried at 80° C. for 24 hours, after which the dried mass was heat-treated at 1050° C. under an inert gas atmosphere for 2 hours. The carbonized material thus obtained was then sieved through a 200 μm sieve.

[0061] [Table 5]

[0062] [Table 6]

[0063] Example 10: Pilot anode production procedure using CTP for carbon precursor materials of Examples 6, 7 and 8: Dry agglomerates based on standard calcined petroleum coke were preheated to mixing temperature and transferred to a preheated 10L intensive mixer and homogenized for 1 minute. Liquid carbon precursor was preheated on the SPM to a temperature of 100°C and added after 1 minute of dry mixing. The anode paste was mixed at 180°C for 10 minutes. After mixing, the paste was cooled to 20°C on the SPM and transferred into a preheated pilot anode press followed by pressing at 42MPa for 1 minute. The green anodes were removed, cooled to ambient temperature and the green apparent density was calculated. The anode batches were fired to an equivalent temperature of 1210°C using a heating rate of 20°C / h. After firing, the anode weight and physical dimensions were measured and the shrinkage and firing losses were calculated. Three 50mmφ cores per anode were drilled and cut to the required size and further analyzed by the respective methods. See the results in the table below:

[0064] [Table 7]

[0065] The table below provides an overview of the analytical procedures for product parameters as used in this text.

[0066] [Table 8]

[0067] [Table 9]

Claims

1. 1. A carbon precursor material comprising at least 25% of a petroleum-derived pitch product that is a distillation residue from a petroleum-based feedstock having a concentration of asphaltenes (SARA as measured by clay gel adsorption chromatography per ASTM D2007) of less than 40 wt. %; wherein the petroleum-derived pitch product is further characterized by a flash point greater than 290°C as measured in accordance with ISO 3679 and a Mettler softening point between 90 and 300°C as measured in accordance with ASTM D3104.

2. 10. The carbon precursor material of claim 1, wherein the petroleum-derived pitch product has a Mettler softening point of from 110°C to 250°C.

3. 10. The carbon precursor material of claim 1, wherein the petroleum-derived pitch product has an Alcan coke value of at least 50% measured according to ASTM D4715.

4. 2. The carbon precursor material of claim 1, wherein the petroleum-derived pitch product has an Alcan coke value of at least 50%, a B[a]P content of less than 500 mg / kg, and a Mettler softening point of greater than 110°C, or has an Alcan coke value of at least 70%, a B[a]P content of less than 100 mg / kg measured according to ISO 18287, and a Mettler softening point of greater than 200°C.

5. 2. The carbon precursor material of claim 1, wherein the petroleum-derived pitch product has a Mettler softening point of 110°C to 130°C, while having a viscosity of less than 600 mPa s at 180°C.

6. 10. The carbon precursor material of claim 1, wherein the petroleum-based feedstock is further characterized as having a concentration of >10 wt% saturates and / or >35 wt% resins as measured by SARA analysis.

7. 7. The carbon precursor material of any one of claims 1 to 6, consisting essentially of said petroleum-derived pitch product.

8. 7. The carbon precursor material of any of claims 1 to 6, comprising 25 to 90 wt% of the petroleum-derived pitch product and coal tar-based pitch.

9. 10. Use of the carbon precursor material according to claim 1 in a bonding, impregnation or coating process in the production of graphite electrodes for electric arc furnaces used in steel and / or ferroalloy and / or silicon production or (semi-)graphitized electrodes for aluminium production.

10. 10. Use of the carbon precursor material of claim 1 in coating and bonding processes for the production of carbon coated particles and carbon particle composites used as electrode materials for the production of battery electrodes.

11. 10. A graphite or carbon electrode comprising the carbon precursor material of claim 1 in a converted state.

12. A battery electrode comprising the carbon precursor material of claim 1 in a converted state.

13. 10. A method of producing the carbon precursor material of claim 1, comprising: - providing a petroleum-based feedstock having a concentration of asphaltenes of less than 40 wt.% by SARA analysis (SARA measured by clay gel adsorption chromatography according to ASTM D2007); - heat treating said petroleum-based feedstock at above 300°C and atmospheric pressure; - subsequently distilling said heat-treated material, said distillation step being adapted to obtain a distillation residue, said petroleum-derived pitch product; A method comprising:

14. 14. The method of claim 13, wherein the distillation step is adapted to obtain a distillation residue having a Mettler softening point, measured according to ASTM D3104, of between 90°C and 300°C.

15. 14. The method of claim 13, wherein the distillation step is adapted to obtain a distillation residue having an Alcan coke value of at least 50%, measured according to ASTM D4715.

16. 14. The method of claim 13, wherein the petroleum-based feedstock has a concentration of >10 wt. % saturates and / or >35 wt. % resin as measured by SARA analysis.

17. The method of claim 13, wherein the heat treatment is carried out at 300 to 400°C.

18. 14. The method of claim 13, wherein the distillation of the heat-treated material comprises vacuum distillation.

19. 19. The method of any of claims 13 to 18, comprising mixing the petroleum-derived pitch product with a coal tar-based pitch to obtain an amount of the petroleum-derived pitch product in a mix of 25 to 90 wt.%.

20. 1. A method for producing a graphite or carbon electrode, comprising: - providing some particles to be coated; - coating and / or bonding said particles using a carbon precursor material according to claim 1; - further shaping and graphitizing or carbonizing to form graphite or carbon electrodes; A method comprising: