Graphite-like carbon material from melanoidins and preparation thereof

Abstract

The present disclosure pertains to a process for the preparation of graphite-like carbon material from melanoidins comprising: a. extracting melanoidins from food products waste material, isolating the melanoidin and b. Pyrolyze the extracted and isolated melanoidin at a temperature of 500 to 1200°C, at inert atmosphere. The resulting material is used as hard carbon material and as a precursor for graphite, graphene, graphene carbon quantum dot material, carbon nanotubes, graphitic carbon nitride quantum dots, graphene oxide or combinations thereof.

Description

[0001]

[0002] GRAPHITE-LIKE CARBON MATERIAL FROM MELANOIDINS AND PREPARATION

[0003] THEREOF

[0004] Field

[0005] The present disclosure is directed to graphite-like carbon material from melanoidins and the preparation thereof . More particularly, it is directed to a method for producing high-quality ni- trogen-dOoped graphite-Like Carbon Materials from extracted melanoidins of spent coffee grounds via Microwave-Assisted Pyrolysis under vacuum conditions .

[0006] Background

[0007] Graphite-like carbon materials encompass a range of carbon materials that share structural similarities with graphite , specifically the layered arrangement of sp2-hybridized carbon atoms . Graphitelike materials include hard carbon, graphite , graphene , graphene oxide , carbon nanotubes , graphene quantum dots , and graphitic carbon nitride quantum dots , all of which feature layered or graphitic structures . Materials with layered structures often exhibit anisotropic electronic properties , which can be advantageous in various applications . Layered materials can possess high tensile strength along the plane of the layers , useful in composite materials . These properties make graphite-like carbon material suitable for use in electrical devices such as energy storage devices and batteries , but also as catalyst and in composite materials .

[0008] Graphite-like carbon materials , such as hard carbon and graphite , are essential components in energy storage devices , electronics , and composite materials due to their excellent electrical conductivity, mechanical strength, and chemical stability

[0009] Hard carbons are complex structures made up of graphite-like layers, orientated randomly, forming a mixture of stacks, sheets, pores and nanopores. The sheets comprise turbotratic graphene layers, leading to a complex structure with micropores and nanopores. This structure provides a high surface area and high electrical conductivity. Hard carbon is often used as electrode material for batteries, as catalysts or in polymer coatings, and is suitable for supercapacitor electrodes.

[0010] Graphite consists of sheets of trigonal planar carbon. The individual layers are called graphene. In each layer, each carbon atom is bonded to three other atoms forming a continuous layer of sp2 bonded carbon hexagons, like a honeycomb lattice with a bond length of 0.142 nm, and the distance between planes is 0.335 nm. Graphite consists of many stacked layers of graphene, typically in the excess of hundreds of layers . Bonding between layers is relatively weak van der Waals bonds, which allows the graphene-like layers to be easily separated and to glide past each other. Electrical conductivity perpendicular to the layers is consequently about 1000 times lower. Synthetic and natural graphite are consumed on a large scale (1.3 million metric tons per year in 2022) for uses in many critical industries including refractories (50%) , lithium-ion batteries (18%) , foundries (10%) , lubricants (5%) , among others (17%)

[0011] In very basic terms graphene could be described as a single, one atom thick layer of the commonly found mineral graphite. Graphenelike materials are also used as electrode materials in electrical devices, for instance in lithium batteries. Materials with a sheetlike structure such as graphene are in high demand, but its production normally requires high energy consuming processes . 40717

[0012] Graphene Oxide is derived from graphite and retains a layered structure with oxygen-containing functional groups .

[0013] Carbon Nanotubes are essentially rolled-up graphene sheets and share the sp2-hybridized carbon structure , of graphite-like materials .

[0014] Graphene carbon quantum dots are carbon particles with graphene structure in nano-size . Graphene carbon quantum dots are small fragments of graphene and possess layered structures The graphene quantum dots are usually surface-functionalized and have a tunable fluorescence , are highly sensitive to environment and have photochemical properties . Graphene carbon quantum dots may be applied in bioimaging, solar energy harvesting , nano-sensing , light-emitting devices and photocatalysts .

[0015] Graphitic Carbon Nitride Quantum Dots contain nitrogen in a layered, graphitic-like structure .

[0016] In literature described methods for producing graphite-like carbon materials from biomass involve the direct pyrolysis or carbonization of whole biomass materials , including Spent Coffee Grounds ( SCG ) . These methods present several challenges :

[0017] 1 . Spent coffee ground are heterogeneous in composition . Whole SCG contains lipids , cellulose , hemicellulose , lignin, and other impurities that interfere with efficient carbonization and graphitization .

[0018] 2 . High processing temperatures and reaction times are needed to convert spent coffee grounds to useable graphite-like materials . Due to the complex matrix of SCG, higher temperatures ( often exceeding 2500 ° C ) and longer processing times are required, leading to increased energy consumption .

[0019] 3. The presence of various and varying impurities often result in carbon materials with variable and inferior properties .

[0020] Whole biomass materials carbonization is for instance conducted in WANG CHEN-HAO ET AL: "High-capacitance KOH-activated nitrogen-containing porous carbon material from waste coffee grounds in supercapacitor", ADVANCED POWDER TECHNOLOGY, ELSEVIER BV, NL, part 27, nr. 4, 6 May 2016, pages 1387-1395, XP029667157. This document discloses the preparation of an activated carbon material by drying waste coffee grounds at 40°C for 48 h and then immerse them 1 M KOH solution with stirring for six hours to remove contamination and oil. Then, the grounds were washed in deionized water and dried at 50°C for 24 h. They were then mixed with an equal weight of KOH, and the mixture was then introduced to a furnace for pyrolizationat particular temperature of 600, 700, and 800°C in an atmosphere of nitrogen for two hours (DI, p.1388, left-hand column last par. , fig.4) . Wang prepares the activated carbon material from whole spent coffee ground.

[0021] So far numerous attempts have been made to create graphite-like carbon materials from biomass. For instance several publications describe the use of spent coffee grounds for the preparation of hard carbon materials:

[0022] For instance CN111204731 describes sodium ion batteries, and a preparation method of a hard carbon negative electrode material of a sodium ion battery. The pure hard carbon negative electrode material is prepared through an ash removal process and a carbonization process .

[0023] CN115140725 relates to a preparation method of a coffee-ground- based Fe3+and Fe2+ion doped biochar material for hydrogen production. The preparation method comprises activating coffee grounds, pyrolysis of the coffee grounds and a hydrothermal treatment.

[0024] CN106784832 discloses a preparation method for porous carbon materials from coffee grounds. The porous carbon material is used as anode material of lithium-ion batteries.

[0025] CN105217629 discloses a preparation method for the activation of carbon from coffee ground . The preparation method comprises degreasing the coffee grounds by vacuum pyrolysis and subsequent ac- tivization using phosphoric acid . The degreasing is said to avoid clogging of the activated carbon pores .

[0026] KR20180038802 relates to a method for preparing heteroatom-doped carbon materials using spent coffee grounds , which can be used as an electrode material of a fuel cell , a super capacitor or a redox flow battery by preparing nitrogen-doped carbon materials by activating spent coffee grounds . Optionally the material is also doped with boron by addition of a boron precursor .

[0027] CN109970058 discloses a preparation method of coffee ground substrate active carbon by soaking the coffee grounds , drying and subsequently treating the coffee grounds with 8-12 % phosphoric acid solution assisted with ultrasonic treatment . Subsequently the coffee grounds are heated in a furnace at 580- 620 ° C .

[0028] The active carbon is used for treating waste water with Cr (VI ) , adsorbing Cr and preventing and treating heavy metal pollution .

[0029] WO2021154332 concerns biomass-derived activated carbon for use in fabricating energy storage devices , such as supercapacitors . Processes for preparing activated carbon from biomass using a potassium hydroxide treatment using nitrogen-doping . The biomass may be spent coffee grounds . The biomass is pre-carbonized by heat treatment under nitrogen atmosphere and chemically activating and calcining the pre-carbonized biomass with KOH and heating at a temperature between 600-1200 ° C under nitrogen or argon atmosphere . Then washing the carbonized biomass with hydrochloric acid .

[0030] CN 111892048 describes a palm-based artificial graphite and a preparation method thereof by : 40717

[0031] 1. screening palm shells, drying and crushing the qualified palm shells to obtain palm-based driving body powder; mixing asphalt and tire oil in proportion to obtain a mixture of asphalt and tire oil;

[0032] 2. mixing the palm-based driving body powder and the asphalt tire oil mixed liquid to obtain a mixture;

[0033] 3. fermenting the mixed material with the catalyst to obtain the fermentation mixed material; and

[0034] 4. sequentially subjecting the fermentation mixture to thermal cracking and graphitization to obtain palm-based artificial graphite .

[0035] CN 117 985 692 A discloses the preparation of graphite-like carbon materials by crushing and sieving bagasse (food waste of sugar cane) and heating to 300°C under nitrogen protection for 10 h to obtain a pre-car- bonized product. Then the pre-carbonized precursor is mixed with phosphoric acid solution, ultrasonicated for 3h, and filtered and rinsed until neutral. The obtained filter residue is put into 1 M phosphoric acid solution and stirred at 30°C and urea is added. The mix is filtered and rinsed until neutral, and put in a drying oven for drying. Then, under nitrogen protection, the resulting product is heated to 1000°C at a heating rate of 1 °C / min and carbonized for 10 h and cooled to obtain a nitrogen-phosphorus co-doped porous hard carbon material. In this document the melanoidins are not isolated from the bagasse.

[0036] KR 2020 0131059 discloses a process for the preparation of a synthetic precursor (glucose, ammonium chloride to form a melanoidin intermediate, pre-heated at 200-300 °C to create a foamed structure and then carbonized at 800-1500 °C to graphene. References to melanoidin-like intermediates are in situ artifacts of the synthetic mixture and do not point to isolating natural melanoidins as the starting point.

[0037] An overview of Carbon nanodots is given in J. of Carbon Research, 2018, 4, 67, pp. 1-35 and in Materials Today 2021, Vol 51, pp .1382-7.

[0038] With the process according to the present disclosure we provide high quality graphite-like carbon material by a process that is both environmentally and economically sustainable , has optimal energy consumption and provides graphite-like carbon materials with high nitrogen content and can doped with additionally other heteroatoms .

[0039] Further, with the present disclosure we provide high quality and consistently reproducible graphite-like carbon materials such as hard carbon, graphite and graphene at much lower temperatures and better structure / properties from biomass by using melanoidins and in particular coffee melanoidins as precursors .

[0040] Summary

[0041] The present disclosure is directed to a process for the preparation of graphite-like carbon material from melanoidins comprising : a . extracting melanoidins from food products waste material , and isolate the melanoidins b . Pyrolyze the extracted and isolated melanoidin at a temperature of 500 to 1200 ° C , at inert atmosphere .

[0042] The melanoidin subj ected to the pyrolization step b may be melanoidin or a salt thereof , preferably a sodium or potassium salt of melanoidin .

[0043] The resulting material may suitably be used as hard carbon material or as a precursor for graphite , graphene or other graphitelike carbon material with higher ordered structures than hard carbon material such as graphene carbon quantum dot material , carbon nanotubes and graphitic carbon nitride graphene-like material or combinations thereof

[0044] In one embodiment the melanoidin is contacted with dopant precursor prior to the pyrolization of step b . Preferably the dopant precursor is a nitrogen precursor such as urea or melamine

[0045] It is advantageous to contact the melanoidin with a metal catalyst prior to the pyrolization of step b . Suitable metal catalysts are iron or nickel salts .

[0046] In said process after the pyrolization step b a post-pyrolization step may be conducted wherein the pyrolyzed extracted melanoidin is heat treated at a temperature of between 1000 and 3000 ° C , preferably at a temperature of between 1000 and 2000 ° C, most preferably at a temperature between 1000 and 1600 ° C , in inert atmosphere . Said post-pyrolized melanoidin comprises graphite .

[0047] The extraction of the melanoidin may be conducted by alkaline treatment of the food products waste material .

[0048] Optionally a pre-treatment is conducted on the food products waste material . Said pre-treatment is conducted either simultaneous or prior to the extraction of the melanoidins .

[0049] Examples of pre-treatment comprises ultrasonic treatment , subcrit- ical water hydrolysis ( SCWH ) , microwave treatment and / or chemical treatment with either acid or alkaline , preferably ultrasonic treatment .

[0050] The graphite-like carbon material obtained after post-pyrolization of melanoidin may be used as such ( as graphite ) , but the material may also be used as precursor for the preparation of graphene , graphene carbon quantum dot material , carbon nanotubes , graphitic carbon nitride quantum dots , graphene oxide or combinations thereof . 40717

[0051] To this end the post-pyrolyzed melanoidin is further treated to form graphene or graphene-like material or combinations thereof . The graphene-like material comprises graphene carbon quantum dot material , carbon nanotubes , graphitic carbon nitride quantum dots , graphene oxide or combinations thereof

[0052] These further treatments comprise chemical vapor deposition (CVD ) , pyrolysis , exfoliation techniques or combinations thereof may be used . Also hydrothermal treatment , solvothermal , or microwave-assisted methods , or combinations thereof

[0053] The process according to the disclosure provides novel graphitelike carbon material . The present disclosure is also directed to this novel graphite-like carbon material obtainable by the methods according to the disclosure . Said graphite-like carbon material comprises pyrolyzed melanoidin which is formed into hard carbon material . The present disclosure also provides novel graphite-like material that has been further processed into graphite , graphene and other graphene-like material such as graphene carbon quantum dot material , carbon nanotubes , graphitic carbon nitride quantum dots , graphene oxide or combinations thereof .

[0054] 40717

[0055] Detailed Description

[0056] As described above , the present disclosure is directed to a process for the preparation of graphite-like carbon material from melanoidins comprising : a . extracting melanoidins from food products waste material , isolate the melanoidin, and b . pyrolyze the extracted and isolated melanoidin at a temperature of 500 to 1000 ° C, at inert atmosphere .

[0057] The preparation of graphite-like carbon materials from isolated melanoidins has not been described in the prior art .

[0058] With inert atmosphere is meant both an atmosphere of inert gas , but also vacuum atmosphere is suitable . Said vacuum pyrolysis treatment may be conducted in conventional heating devices such as furnaces but also in a microwave . The pressure used varies from 0 . 1-0 . 01 MPa . The reaction time after reaching the targeted temperature ranges from 0 . 5-1 hour .

[0059] Melanoidins are a class of brown, hydrophilic nitrogen-containing polymers which are formed during the thermal processing of foods - such as coffee , cocoa, bread, malt , barley, Brewers Spent Grain ( BSG ) , soy, meat , and honey . Although the melanoidins can be obtained from various food products waste material , the use of Spent Coffee Grounds and the Brewers Spent Grain is preferred since it has a very high melanoidin content , with Spent Coffee Grounds having the highest preference . Thus , melanoidins are complex, nitro- gen-rich polymers formed during the Maillard reaction during for instance coffee roasting .

[0060] During thermal processing of food products as described above , amino acids and reducing sugars , such as aldose and d-xylose , react to form what are termed initial Maillard reaction products . 40717

[0061] Under continued heating, melanoidins are formed by cyclizations , dehydrations , retro-aldolizations , rearrangements , isomerizations and condensations of those initial Maillard reaction products . The complexity of the Maillard reaction pathways results in a range of final reaction products , with inter alia the time of heating , type of heating , temperature , initial chemical composition of the system, moisture content , water activity and pH value being determinative of the final composition .

[0062] Utilizing melanoidins specifically exploits their high nitrogen content and aromatic structure , which enhances the properties of the resulting carbon materials compared to those derived from whole spent coffee grounds or other biomass . These specific structural properties of melanoidin increase the electrical and thermal conductivity of the resulting graphite-like carbon material .

[0063] In general , the use of extracted and isolated melanoidins as precursor for graphite-like carbon materials maximizes the value derived from SCG, supporting circular economy principles . By separating valuable components , less residual waste remains , reducing environmental impact .

[0064] By isolating melanoidins from for instance spent coffee grounds ( SCG ) , impurities such as lipids , cellulose , hemicellulose , and lignin are removed . This results in a purer precursor that leads to more reproducible and high-quality carbon materials . Furthermore , whole spent coffee grounds contain various compounds that may interfere with the carbonization and graphitization processes that take place during pyrolization, such as residual oils and carbohydrates . Extracting melanoidins minimizes these interferences , allowing for more controlled synthesis . It was found that conversion of the extracted, isolated melanoidins to graphite-like carbon material takes place within a very short reaction time 40717

[0065] ( 0 . 5 -lhour ) compared to the reaction times reported in the literature to convert whole spent coffee grounds ( up to 10 hours at

[0066] 1000 ° C have been r

[0067] Since melanoidins have a three-dimensional network of aromatic and aliphatic chains , with frequent cross-linking through C-C , C-O, and C-N bonds , it provides the ideal foundation for carbonization, as it creates a structurally robust precursor . It has a relatively high carbon content and a lower oxygen content compared to other biomass materials and other compounds present in spent coffee grounds beside the melanoidins . Furthermore , its sp2-hybridized carbon structure of the aromatic moieties , provides an excellent precursor for the formation of graphite-like structures . This results in graphite-like carbon material with a high surface area and a higher electrical and thermal conductivity than material prepared by pyrolyzing whole spent coffee grounds .

[0068] The resulting material may suitably be used as hard carbon material or as a precursor for graphite , graphene or other graphitelike carbon material with higher ordered structures than hard carbon material such as graphene carbon quantum dot material , carbon nanotubes and graphitic carbon nitride graphene-like material or combinations thereof .

[0069] Melanoidins have a higher nitrogen content compared to whole spent coffee grounds . Nitrogen atoms become incorporated into the carbon lattice during pyrolization, resulting in nitrogen-doped carbon materials . The inherent nitrogen content of melanoidins enables in-situ doping during pyrolysis , improving electrical conductivity and eliminating the need for external doping agents .

[0070] Since the original structure of melanoidins allows for the presence of heteroatoms such as nitrogen, oxygen and sulfur, it is also possible to incorporate additional heteroatoms into the 40717 graphite-like carbon material by doping . The melanoidin may for instance be contacted with dopant precursor prior to the pyroliza- tion of step b . Preferably the dopant precursor is a nitrogen precursor such as urea or melamine . The use of a dopant precursor ensures the incorporation of the nitrogen into the carbon structure . In addition to nitrogen also sulfur or phosphorus precursors may be used .

[0071] The melanoidin used in the process according to the disclosure may be melanoidin or a salt thereof , preferably a sodium of potassium salt of melanoidin . These salts were found to act as activating agents creating more porous structures beneficial for applications like energy storage and adsorption . In addition, potassium and sodium ions were found to facilitate the formation of graphitic structures , enhancing the degree of graphitization .

[0072] Prior to the the pyrolization of step b the melanoidin may also be contacted with metal catalysts such as iron and nickel salts . These metal catalyst were found to catalyze the graphitation process .

[0073] The reactive functional groups and heterocyclic structures in melanoidins lower the activation energy needed for pyrolization to graphite-like carbon material . This allows for synthesis at lower temperatures and shorter reaction times compared to using whole SCG . Lower processing temperatures translate to reduced energy consumption, making the production process more cost-effective and environmentally friendly . Furthermore the aromatic rings in melanoidins contain carbon atoms with sp2hybridization, which is critical for forming graphitic and graphitic-like materials . The abundance of functional groups in melanoidins also allows for easier functionalization of the carbon materials , enabling customization for specific applications . 40717

[0074] In short the key advantages of the process according to the description are :

[0075] Enhanced material properties compared to material prepared from whole spent coffee grounds : It produces nitrogen-doped carbon materials with superior electrical conductivity, structural integrity, and consistency compared to process wherein food waste material are fully pryrolized to form graphite-like materials .

[0076] Process is more efficient with respect to reaction temperature and time : The process according to the present description achieves carbonization and graphitization at lower temperatures and shorter times compared to traditional methods . The prosess is more sustainable : It utilizes waste materials effectively, reduces energy consumption, and contributes to environmental sustainability .

[0077] In said process optionally after the pyrolization step b a post- pyrolization step may be conducted wherein the pyrolyzed extracted melanoidin by a heat treatment at a temperature of between 900 and 3000 ° C preferably at a temperature of between 1000 and 2000 ° C, most preferably at a temperature between 1000 and 1600 ° C, in inert atmosphere . Said post-pyrolized melanoidin comprises graphite .

[0078] The post-pyrolysis heat treatment is conducted for 1-4 hours after reaching the target temperature under vacuum or inert atmosphere to enhance graphitic ordering . This is very short in comparison with the reaction time needed for conversion of while spent Coffee grounds , which is up to 12 hours .

[0079] It was found that the post-pyrolization step to form graphite can be conducted at lower temperatures than with conventional graphite production processes . Without wishing to be bound to a theory we 40717 believe that the presence of the aromatic-ring structures of melanoidin facilitates graphitization . Also the presence of metal catalyst reduces the required graphitization temperature . Also the presence of potassium and sodium ions originating from melanoidin salts were found to facilitate the formation of graphitic structures , enhancing the degree of graphitization .

[0080] Thus , it was found that the post-pyrolysation can be conducted at temperatures as low as between 1000 and 1600 ° C .

[0081] It is also possible to dope the pyrolyzed melanoidin with dopant or metal catalyst prior to the post-pyrolization, but it is preferred to do so prior to the pyrolization step b , because it avoids unwanted evaporation and / or decomposition .

[0082] It goes without saying that the pyrolization of step b and the post pyrolization step can be combined so as to perform a direct graphitization and form graphite-like carbon material directly from the extracted melanoidin .

[0083] The graphite-like carbon material obtained after post-pyrolization of melanoidin may be used as such ( as graphite ) , but the material may also be used as precursor for the preparation of graphene , graphene carbon quantum dot material , carbon nanotubes , graphitic carbon nitride quantum dots , graphene oxide or combinations thereof .

[0084] To this end the post-pyrolyzed melanoidin is further treated to form graphene or graphene-like material or combinations thereof . The graphene-like material comprises graphene carbon quantum dot material , carbon nanotubes , graphitic carbon nitride quantum dots , graphene oxide or combinations thereof

[0085] These further treatments comprise chemical vapor deposition (CVD ) , pyrolysis , exfoliation techniques or combinations thereof may be 40717 used . Also hydrothermal treatment , solvothermal , or microwave-assisted methods , or combinations thereof .

[0086] Optionally, the extraction of the melanoidin is conducted by alkaline treatment of the food products waste material . Said alkaline treatment may involve treatment with potassium hydroxide or sodium hydroxide . This will open-up the food product waste structure , making the extraction of the melanoidins more effective , but also melanoidin salts will be formed . As mentioned above , these melanoidin salts create the formation of a more porous structure , and catalyse graphitic formation

[0087] Optionally a pre-treatment is conducted on the food products waste material . Said pre-treatment is conducted either simultaneous or prior to the extraction of the melanoidins . These treatments help the extraction of the melanoidins from the food products waste material .

[0088] Examples of pre-treatment comprises ultrasonic treatment , subcrit- ical water hydrolysis ( SCWH ) , microwave treatment and / or chemical treatment with either acid or alkaline , preferably ultrasonic treatment .

[0089] Ultrasonic treatment has the following advantages :

[0090] Ultrasonication disperses melanoidin particles uniformly in the reaction medium, ensuring consistent heat transfer and reaction conditions during carbonization .

[0091] The mechanical effects of ultrasound reduce the particle size of melanoidins , increasing the surface area and exposing more reactive sites . This enhances the efficiency of the carbonization process .

[0092] Ultrasound promotes mass transfer by creating micro j ets and shockwaves , facilitating the removal of volatile compounds and promoting the formation of a more ordered carbon structure .

[0093] Ultrasonication prevents the aggregation of particles , leading to more uniform and higher-quality carbon nanomaterials .

[0094] The process according to the disclosure provides novel graphitelike carbon material . The present disclosure is also directed to this novel graphite-like carbon material obtainable by the methods according to the disclosure . Said graphite-like carbon material comprises pyrolyzed melanoidin which is formed into hard carbon material . The present disclosure also provides novel graphite-like material that has been further processed to graphite , graphene and other graphene-like material such as graphene carbon quantum dot material , carbon nanotubes , graphitic carbon nitride quantum dots , graphene oxide or combinations thereof .

[0095] Hard carbon is often used as electrode material for batteries , as catalysts or in polymer coatings and supercapacitor electrodes . This means that generally a high surface area and high electrical conductivity is desired . The process according to the present disclosure allows for the production of hard carbon material with a homogeneous pore structure and very high surface area . The use of melanoidins as a precursor for this material offers a more uniform precursor compared to the heterogeneous mixture present in whole SCG . This uniformity leads to better control over the size , morphology, and structural properties of the synthesized carbon materials . In addition to that , the abundance of functional groups in melanoidins allows for easier functionalization of the carbon materials , enabling customization for specific absorption or catalyst applications . As explained above , the electrical conductivity of the hard carbon material is higher than material obtained from whole spent coffee grains , because of its high nitrogen-content and optionally other heteroatoms . The hard carbon material obtained with the process according to the disclosure , is also suitable for use as electrode material for sodium ion batteries . This is important because of the increased demand of lithium due to global environmental issues and rising oil prices . The abundant and widely distributed sodium resources make sodium-ion batteries ( STBs ) low-cost and are considered to be one of the most promising large-scale energy storage technologies .

[0096] At present , the conventional negative electrode material of lithium ion battery is graphite , but the radius of sodium ion is larger than that of lithium ion ( 0 . 072 nm for Li+ and 0 . 102 nm for Na+ ) , so it cannot be embedded in graphite , so the negative electrode of sodium ion battery can only choose materials with larger interlayer spacing . Hard carbon prepared with the process according to the present disclosure was found a suitable candidate for carbonaceous materials for STBs because of the following advantages : low cost , low operating voltage ( ~0 V vs . Na+ / Na ) , and high capacity . Since with the process according to the present disclosure a material can be made wherein the pore structure and interlayer space can be set , hard carbon material according to the present disclosure is highly suitable for use as electrode for STBs .

[0097] As mentioned above , the graphite prepared with the processes according to the invention can suitably used for all known applications for advanced graphite owing to its high quality, high electrical conductivity, high surface area and mechanical strength .

[0098] Graphene and other graphene-like material such as graphene carbon quantum dot material , carbon nanotubes , graphitic carbon nitride quantum dots , graphene oxide or combinations thereof can be made using the graphite according to the present disclosure as a precursor . 40717

[0099] Graphene may be prepared from the graphite-like carbon material of the present disclosure by methods such as chemical vapor deposition ( CVD) , pyrolysis , or exfoliation techniques . Also combinations of these methods may be used .

[0100] For instance in the Pyrolysis and Exfoliation method generally carbonization by pyrolization of the precursor is followed by mechanical or chemical exfoliation to produce graphene sheets .

[0101] In the Ultrasound Exfoliation method ultrasonication of carbonized materials ( i . e . pyrolyzed material ) to produce few-layer graphene .

[0102] The graphene produced may be formed into carbon nanotubes and graphene oxide or combinations thereof .

[0103] The graphene carbon quantum dots CQDs may be synthesized using the graphite or graphene prepared according to the present processes by using hydrothermal , solvothermal , or microwave-assisted methods , where controlled reaction conditions allow for precise size and surface property tuning . The Hydrothermal / Solvothermal synthesis offers precise control over particle size and functionalization . This preparation method is suitable for producing CQDs with specific properties .

[0104] Microwave-Assisted synthesis provides rapid heating and uniform energy distribution, leading to shorter reaction times and high- quality CQDs . The CQDs according to the present disclosure may suitably be used in electrooptical devices , sensors , energy storage devices , and quantum computing and communication :

[0105] • Optoelectronic Devices : the CQDs have unique optical and electronic properties , such as size-tunable photoluminescence and quantum confinement effects , making them suitable for optoelectronic applications like LEDs , photodetectors , and solar cells .

[0106] • Sensors : the CQDs may be used in sensitive and selective sensors for detecting gases , chemicals , or biological 40717 agents , which are crucial in edge devices that require realtime monitoring and data processing .

[0107] • Energy Storage : The CQDs may enhance the performance of supercapacitors and batteries by improving electrode materials , contributing to efficient energy management in edge devices .

[0108] • Quantum Computing and Communication : The CQDs have potential applications in quantum dots-based qubits for quantum computing , which may be relevant for advanced edge computing technologies .

[0109] Below the disclosure is illustrated by the following nonlimiting examples .

[0110] EXAMPLES

[0111] Example 1 : GENERAL PRE-TREATMENT OF SCG

[0112] Spent coffee grounds were collected and dried to reduce moisture content . Optionally, the dried SCG is subj ected to ultrasonic treatment by immersing the SCG in water or an alkaline solution and applying ultrasonic waves at a frequency of 20-40 kHz for 30- 60 minutes . This disrupts the biomass structure and enhances extraction efficiency .

[0113] Example 2 : ALKALINE EXTRACTION

[0114] An alkaline solution using sodium hydroxide (NaOH ) at a concentration of 0 . 1-1 M was provided . The pre-treated SCG was mixed with the alkaline solution at a solid-to-liquid ratio of 1 : 10-1 : 20 (w / v) . The mixture was stirred at 50-80 ° C for 1-3 hours to extract melanoidins . The solution was filtered to separate the liquid extract containing melanoidins from the residual biomass . The 40717 extract was neutralize with hydrochloric acid (HC1) and the melanoidins were precipitated.

[0115] Example 3: MICROWAVE -ASS IS TED PYROLYSIS UNDER VACUUM

[0116] The extracted and isolated melanoidins were dried to obtain a solid precursor. The dried melanoidins were placed into a vacuum chamber suitable for microwave processing. The chamber was evacuated to achieve a vacuum of 0.1-0.01 MPa. Microwave irradiation was applied at appropriate power levels:

[0117] For industrial-scale batches (1-3 tons) , use approximately 450 kW of microwave power.

[0118] For small-scale batches (e.g., 1 kg) , use 1.5-3 kW of microwave power.

[0119] Subsequently the melanoidins were heated to a temperature of 500- 1200 °C within 10-60 minutes, depending on the batch size. The target temperature was maintained for 0.5-1 hour to ensure complete pyrolysis. The resulting graphite-like carbon material was analyzed .

[0120] Comparative example 4: PRE-TREATEMENT MICROWAVE -ASSISTED PYROLYSIS UNDER VACUUM OF WHOLE SPENT COFFEE GRAIN

[0121] Spent coffee grounds were dried and alkaline treated as in Examples 1 and 2 except that the resulting mixture was not filtered but dried as a whole. The dried mixture was pyrolyzed in a microwave under the same conditions as described in Example 3. The resulting graphite-like carbon material was analyzed for . ( Surface area, electrical conductivity, presence of SP2structures...etcetera) . It was found that the product obtained by pyrolization of extracted and isolated melanoidin was more reproducible and had a higher quality. 40717

[0122] Example 5 : Post-pyrolysis heat treatment

[0123] The pyrolyzed melanoidin material was transferred to a high-tem- perature furnace and heated under vacuum or inert gas atmosphere to temperatures between 1000-1600 ° C . The temperature was maintained for 1-4 hours to promote graphitic ordering . The resulting product was found to have a higher electrical conductivity and mechanical strength . It was further found that high-quality graph- ite-like structures could be achieved at lower temperatures compared to conventional methods .

Claims

CLAIMS1 . Process for the preparation of graphite-like carbon material from melanoidins comprising : a . extracting melanoidin from food products waste material , isolate the melanoidin and b . Pyrolyze the extracted and isolated melanoidin at a temperature of 500 to 1200 ° C, at inert atmosphere .2 . Process according to claim 1 wherein the melanoidin subj ected to the pyrolization step b is a salt of melanoidin, preferably a sodium or potassium salt of melanoidin .3 . Process according to claim 1 or 2 , wherein the food waste product is spent coffee ground or brewers spent grain, preferably spent coffee ground .4 . Process according to claim 1 , 2 or 3 wherein the resulting material is used as hard carbon material .5 . Process according to any one of preceding claims 1-4 wherein the resulting material is used as precursor for the preparation of graphite , graphene , graphene carbon quantum dot material , carbon nanotubes , graphitic carbon nitride quantum dots , graphene oxide or combinations thereof .6 . Process according to any one of preceding claims 1-5 wherein the melanoidin is contacted with dopant precursor prior to the pyrolization of step b .7 . Process according to claim 6 wherein the dopant precursor is a nitrogen precursor such as urea or melamine .8 . Process according to any one of preceding claims 1-7 wherein the melanoidin is contacted with a metal catalyst prior to the pyrolization of step b .9 . Process according to claim 8 wherein the metal catalyst is an iron or nickel salt .10 . Process according to any one of preceding claims 1- 9 wherein after the pyrolization step b a post-pyrolization step is conducted wherein the pyrolyzed melanoidin of step b is subj ected to a heat treatment at a temperature of between 1000 and 3000 ° C, preferably at a temperature of between 1000 and 2000 ° C, most preferably at a temperature between 1000 and 1600 ° C, in inert atmosphere .11 . Process according to claim 10 wherein the resulting post- pyrolized melanoidin comprises graphite .12 . Process according to any one of the preceding claims wherein the extraction of the melanoidin is conducted by alkaline treatment of the food products waste material .13 . Process according to any one of the preceding claims wherein a pre-treatment is conducted on the food products waste material either simultaneous or prior to the extraction of the melanoidins14 . Process according to claim 12 wherein the pre-treatment comprises ultrasonic treatment , subcritical water hydrolysis ( SCWH ) , microwave treatment and / or chemical treatment with either acid or alkaline , preferably ultrasonic treatment .4071715 . Process according to any one of preceding claims wherein the post-pyrolyzed melanoidin is further treated to form graphene or graphene-like material or combinations thereof .16 . Process according to claim 15 wherein the graphene-like material comprises graphene carbon quantum dot material , carbon nanotubes , graphitic carbon nitride quantum dots , graphene oxide or combinations thereof17 . Process according to claim 15 or 16 , wherein the post-pyro- lyzed melanoidin is further treated by hydrothermal , solvothermal , or microwave-assisted methods , or combinations thereof .18 . Process according to claim 11 , wherein the pyrolyzed or post-pyrolyzed melanoidin is further treated to form gra- phene-like material by chemical vapor deposition (CVD ) , pyrolysis , exfoliation techniques or combinations thereof .19 . Graphite-like carbon material obtainable by the method according to any of preceding claims 1-18 .20 . Graphite-like carbon material comprising extracted and isolated melanoidin that has been pyrolized .21 . Graphite-like carbon material according to claim 19 or 20 comprising extracted and isolated melanoidin that has been pyrolized to form hard carbon material ,22 . Graphite-like carbon material comprising extracted and isolated melanoidin that has been subj ected to pyrolization and post-pyrolization .23 . Graphite-like carbon material according to claim 22 comprising graphite .24 . Graphite-like carbon material according to claim 22 or 23 that has been subj ected to further treatment to form graphene or graphene-like material such as graphene carbon quantum dot material , carbon nanotubes , graphitic carbon nitride quantum dots , graphene oxide or combinations thereof .

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