Microcrystalline Carbon Research Articles

Eco-friendly sustainable fluorescent coal-based carbon dots as a highly selective probe for Cu2+detection

Carbon dots as fluorescent probes exhibit brilliant sensitivity and selectivity in copper ion detection, which greatly depends on their microstructure. Herein, a mild oxidation method was adopted to tailor the organic macromolecules of coal and its derivatives for preparing coal-based carbon dots. Such coal-based carbon dots comprise a carbonaceous center dominated by sp2 microcrystalline carbon, surface defects formed by sp3 amorphous carbon, and oxygen/nitrogen-containing functional groups. The coal-based humic acid-based carbon dots (HA-CDs) exhibit high dispersity (∼7.6 nm), high sp2 microcrystalline carbon (61.73 %), abundant carboxyl groups (2.09 %), hydroxy groups (8.93 %), and pyridinic nitrogen (1.06 %). Due to their unique microstructure, the HA-CDs in aqueous solutions exhibit prominent fluorescence stability under different pH conditions and show superior selectivity and sensitivity to Cu2+ even in the existence of other metal ions. Within the concentration range of 0–40 µmol/L, the fluorescence intensity of HA-CDs linearly correlates with the concentration of Cu2+. The limit of detection is 0.014 µmol/L, allowing for tracing the Cu2+ concentration in flowing water. This work affords a novel idea for the microstructure design of high-sensitivity carbon dots for Cu2+ detection in the water environment.

Comparative study of the composition and microstructural properties of semi-coke from microwave and conventional pyrolysis of low rank coal

Microwave pyrolysis technology can effectively realize the clean and quality improvement of coal. In order to study the changes of each component of coal in the process of microwave pyrolysis, the d002, La, Lc, combustion reactivity and conductivity of semi-coke after pyrolysis were analyzed by using XRD, TG, conductivity meter and other testing instruments, and the infrared spectra of semi-coke after pyrolysis were finely resolved by using Origin peak-splitting technique, and the composition of the coal gas in the process of pyrolysis and its percentage content were analyzed. The composition and percentage content of gas in the pyrolysis process were analyzed and compared with conventional pyrolysis. The results showed that compared with conventional pyrolysis, microwave pyrolysis can be completed at a lower temperature and microwave pyrolysis is more favorable to the release of volatile components, in which the content of CO and H2 in the gas fraction increased significantly compared with conventional pyrolysis. At the same pyrolysis temperature, the microwave semi-coke has a higher maximum combustion rate temperature than the conventional semi-coke, which is conducive to improving the thermal stability of semi-coke. The orderliness of the semi-coke increased with the increase of pyrolysis final temperature, resulting in the phenomenon of "similar graphitization". The increase in the number of carbon microcrystalline structures generates off-domain electrons, leading to a significant increase in conductivity. Meanwhile, FT-IR peak fitting analysis revealed that the R value inflection point temperature of microwave semi-coke was much lower than that of conventional semi-coke, which further proved that microwave pyrolysis could be accomplished at lower temperatures, and the C value showed a decreasing tendency with the increase of the final temperature of pyrolysis, which indicated that pyrolysis was an effective method to improve the quality of coal. The above analysis shows that compared with conventional pyrolysis, microwave can prepare high stability and high conductivity semi-coke at lower temperature.

A facile electrospinning strategy to prepare cost-effective carbon fibers as a self-supporting anode for lithium-ion batteries

Carbon materials with fibrous morphology and enhanced mechanical properties have shown to be promising materials as self-supporting anode materials for lithium-ion batteries (LIBs). In this study, coal-based carbon fibers (CFs) with favorable flexibility and superior tensile strength were prepared from lignite and coal derivatives such as coal-based humic acid and coal tar pitch via electrospinning in the assistance of polyacrylonitrile. All these coal-based CFs have an 1D dense fibrous microstructure with controllable diameter and appreciable specific surface area with enriched in O/N-containing groups by rationally choosing the precursor type. The organic macromolecules enriched aromatic ring in lignite and coal derivatives cross-link with linear polyacrylonitrile molecular chains to form a more solid three-dimensional (3D) network framework under the conditions of electrospinning and carbonization. Such 3D microstructure not only can significantly improve the flexibility and tensile strength of coal-based CFs, but also can increase the content of graphite-like microcrystalline carbon (sp2 carbon) in carbon fibers, thereby improving the electrical conductivity. Due to the smaller molecular structure, coal tar pitch can be more easily combined with polyacrylonitrile by electrostatic force. The CFs derived from coal tar pitch (CTP-CFs) exhibited the largest average diameter (156.2 nm), a higher microporous surface area (2.6 m2·g−1), higher pyrrole nitrogen and contained reasonable proportions of amorphous carbon (sp3 carbon) and sp2 carbon. As a consequence, among the various derived coal-based CFs applied as self-supporting anode materials for LIBs, CTP-CFs showed the highest first reversible capacity (770.8 mAh·g−1 at 20 mA·g−1) and excellent cycling performance with capacity retention rate of 89.1 % after 200 cycles. This work paves a new strategy to prepare CFs as flexible self-supporting anodes for LIBs from low-cost carbon precursors that can be rationally chosen to further tune the property of the CFs.

Graphitization transformation of aluminum electrolytic spent carbon cathode

Aluminum electrolysis spent cathode carbon (SCC), as typical solid hazardous waste, poses significant environmental risks. Harmless treatment of SCC and recycling of its carbon component are important research areas. In this study, SCC was subjected to microwave hydrothermal acid leaching to remove harmful components, followed by the production of high-quality graphite via iron-catalyzed graphitization. The effects of reaction temperature, heating time, and catalyst loading on the graphitization conversion of SCC were investigated. The catalytic graphitization process of SCC was optimized using the response surface method. The results show that when the reaction temperature is 1520 °C, the heating time is 85.24 min, and the catalyst loading is 46.15 wt%, the graphitization degree of the sample is 97.61 %. The samples prepared under the optimal conditions were characterized using XRD, Raman, SEM, and TEM. The results reveal that the catalytic graphitization process significantly influences the conversion of microcrystalline structures in SCC into graphite structures. The iron-catalyzed transformation of microcrystalline carbon was analyzed to elucidate the graphitization transformation mechanism. This study offers an effective pathway for the high-value utilization of SCC. It also serves as a technical reference for the catalytic graphitization conversion of carbon materials.

Effects of activated fuel and staged secondary air distributions on purification, combustion and NOx emission characteristics of pulverized coal with purification-combustion technology

Under the strategic objectives of carbon peaking and carbon neutrality, clean and efficient coal combustion was important in China. As a novel combustion technology, purification-combustion technology had good research prospects, and high-temperature reduction unit (HTRU) played a crucial role in fuel activation, subsequent combustion and NOx emissions based on the design of this technology. Despite previous research had proved the pivotal role of fuel and combustion air distributions in combustor in influencing the entire thermochemical process, there was the lack of research on their effects in HTRU employing purification-combustion technology. To realize deep NOx emission reduction, this study focused on influences of activated fuel and staged secondary air distributions in HTRU on purification, combustion and NOx emission characteristics in a 30 kW purification-combustion test rig. With the exception of carbon microcrystalline structure, the majority of reductive char properties exhibited superior performance when activated fuel was introduced tangentially, as opposed to axially. Nevertheless, the relationship of carbon microcrystalline structure was regulated by staged secondary air ratio (c12). Properly increasing c12 improved reductive char properties. Additionally, axial introduction of activated fuel more consistently yielded ultra-low levels of NOx emissions; however, this often occurred at the expense of combustion efficiency (η). Properly increasing c12 reduced NOx emissions while increasing η; nevertheless, the benefits derived from c12 were limited. By adjusting introduction direction and c12 (axial, 0.33), minimum NOx emissions decreased to 39.10 mg/m3 (@6 % O2) while maintaining high η of 99.39 %.

Influence mechanism of original components on mechanical properties and transformation behaviors of natural bitumen

Natural bitumen is an important component with high-purity organic matter in fossil energy and energy engineering scenarios. However, the production and application of natural bitumen could be severely hindered by the lacking of understanding the effects and influencing mechanisms of original components on physical properties of natural bitumen. Therefore, the main purpose of this work is to illustrate the influence mechanisms of original components (saturated hydrocarbon, aromatic hydrocarbon, resin and asphaltene) on mechanical properties of natural bitumen by the combination of nanoindentation technology and molecular structure analysis. The effects of each original component on the mechanical properties were carried out for Wuerhe natural bitumen which collected from Junggar Basin of China, and the influencing mechanisms were further revealed based on nanoindentation and X-ray diffraction (XRD) results. The occurrence units of each component in the chemical structural stacking of bitumen were established for the first time. It was found that hydrocarbons and resins can disintegrate the chemical structural stacking, thereby reducing the mechanical strength of natural bitumen. According to our micro-scale analysis results, the plastic and elastic deformation of natural bitumen were controlled by the structural units of amorphous carbon and aromatic carbon microcrystalline, as determined by saturated and aromatic hydrocarbons, respectively. And the schematic diagram of occurrence of each component in solid bitumen for the first time. Hence, the mechanical strength of natural bitumen can be effectively reduced by retaining or increasing the content of alkanes during exploitation, transportation and processing of natural bitumen. This research provided a new understanding for the stacking structure and physical property change mechanism of natural bitumen.

Unraveling the Microcrystalline Carbon Evolution Mechanism of Biomass-Derived Hard Carbon for Sodium-Ion Batteries

Unraveling the Microcrystalline Carbon Evolution Mechanism of Biomass-Derived Hard Carbon for Sodium-Ion Batteries

Study on the characterization and thermal conversion behavior of sequential extraction products from medium temperature coal pitch

To achieve the high value-added clean utilization of medium temperature coal pitch (MTP), five fractions were separated from MTP by the sequential extraction method using n-heptane, n-butanol, toluene, tetrahydrofuran and quinoline as solvents. Briefly, the extracts were analysed using proximate analysis, elemental analysis, fourier infrared spectrum (FTIR), ultraviolet visible spectrum (UV–vis), fluorescence spectrum, and thermogravimetric analysis (TGA) to investigate their structural parameters, aromatic condensation degree and pyrolysis properties. Meanwhile, Raman spectrum, X-ray diffraction (XRD), and polarizing microscope were used to quantitatively analyze the microstructures of thermal conversion products of the extracts. This allowed for investigation of the thermal conversion mechanism and determination of the thermal conversion behavior. In fact, the chain index (CH3/CH2), aromatic index (Iar), aromatic condensation degree and thermal stability of the extracts increase gradually with deeper extraction. Extracts with high aromatic condensation degree are more favorable for the formation of mesocarbon microbeads (MCMBs). However, overly aromatic condensation degree will lead to excessive coalescence of MCMBs. The ideal carbon microcrystalline content increases with higher temperatures during the thermal conversion of the same fraction. But the change of amorphous carbon content has no obvious regularity. The results of this work will provide theoretical and experimental support for the selection of precursors for carbon/graphite materials.

Research on purification, combustion and NOx emission characteristics of pulverized coal preheated by a novel self-sustained purifying burner

To more quickly achieve the breakthrough of minimum NOx emission, this study focused on purification, combustion and NOx emission characteristics of pulverized coal preheated by a novel self-sustained purifying burner, and deeply explored the effect of purifying temperature (Tp) in a 30 kW purification-combustion system. In the purifying burner, the main combustible gases in the reductive coal gas were CO and H2, and their concentrations ranked as CO > H2. Increasing Tp rose their yields. By contrast, the CH4 concentration was always extremely low. This burner effectively improved the particle properties of pulverized coal (including particle size, macrostructure, carbon microcrystalline structure and fuel conversion rate), and was superior over the previous self-preheating burner. Properly increasing Tp optimized the particle properties of reductive coal char except pore diameter, and there might be an optimal Tp. The pore diameter always decreased as Tp increased. Increasing Tp reduced the relative content of N-X in the reductive coal char, and its content was extremely low when Tp was above 1083 °C. Moreover, N-Q was the main form of nitrogen functional groups in the reductive coal char at an extremely high Tp. In the subsequent combustion, NO2 and NO were the main forms of nitrogen oxides in the reduction and burnout regions respectively, while N2O was not. In the whole purification-combustion system, the burning efficiency was always about 99.50 %, and its change was extremely small as Tp increased, while the NOx emission decreased first and then increased. Moreover, the adverse effect of higher Tp on the emission was more significant compared to lower Tp.

Optimizing the Preparation Process of Refined Asphalt Based on the Response Surface and Preparation of Needle Coke.

Refined asphalt was prepared by solvent extraction sedimentation based on the response surface design, using washing oil and kerosene as solvents and the coal tar pitch as raw materials. The mathematical models of the refined asphalt yield, quinoline insoluble (QI) content, ash content, solvent-to-oil ratio, aromatic-to-aliphatic hydrocarbon ratio, extraction temperature, and sedimentation time were proposed, analyzing the influence of each factor and their interactions on the response values. Therefore, the optimal combination of preparation process parameters and better operation window was obtained by optimizing the experiment. Meanwhile, refined asphalt with high QI content and low QI content was selected as raw material, and the needle coke was prepared through the process of carbonization and calcination. The influence of QI content on the composition and the structure of green coke and needle coke was investigated by X-ray diffraction (XRD), Raman spectra, and polarizing microscopy characterizations. The results showed that the solvent-to-oil ratio is 1.2, aromatic-to-aliphatic hydrocarbon ratio is 1.1, sedimentation time is 2 h, and extraction temperature is 110 °C, resulting in the yield of refined asphalt being 76%, QI content being less than 0.1%, and ash content being less than 0.05%, which meets the requirement of the high-quality needle coke. Otherwise, refined asphalt with lower QI content easily generates a mesophase with more fibers and a large structure in the thermal conversion process, and the corresponding green coke and needle coke have a relatively regular carbon microcrystalline structure.

Evolution of carbon nanostructures during coal graphitization: Insights from X-ray diffraction and high-resolution transmission electron microscopy

The evolution of carbon nanostructures during coal graphitization was investigated. The X-ray diffraction (XRD) results showed that amorphous and microcrystalline carbon coexist in anthracite and meta-anthracite, and the latter has a higher proportion of microcrystalline carbon; additionally, semi-graphite and coal-based graphite are mostly composed of crystalline carbon. Coal graphitization starts in anthracite, accompanied by an increase in crystallite size and a decrease in interplanar spacing nonlinearly, especially in semi-graphite, and a large ordered structure is formed in coal-based graphite. The high-resolution transmission electron microscopy (HRTEM) results intuitively reveal the graphitization process by false-colored microphotography, and both the XRD and HRTEM results indicate similar evolution paths. Four types of carbon nanostructures, namely, amorphous, turbostratic, concentric and graphitic-like structures, are identified according to their morphology. Aromatic fringes are arranged randomly in the amorphous structure and are composed of amorphous carbon; local ordering occurs in the turbostratic structure and is commonly observed in anthracite and meta-anthracite. In addition, a concentric structure with hollow pores and parallel annular aromatic fringes was observed, indicating multiple preferred orientations, and the graphitic-like structure was composed of parallel aromatic fringes. Micropores provide the necessary adjustment space for the ordered conversion of carbon nanostructures, and the flattening and merging of micropores may contribute to the enhancement of graphitization.

Experimental study on municipal sludge/coal co-combustion preheated by self-preheating burner: Self-preheating two-stage combustion and NOx emission characteristics

To achieve efficient and low-pollution sludge treatment, this study explored the first-time application of self-preheating combustion technology in sludge/coal co-combustion, and subsequently investigated the influences of sludge blending ratio (BR) and tertiary air types on self-preheating two-stage combustion and NOx emission characteristics in a 30 kW self-preheating combustion system with a novel two-stage down-fired combustor (DFC). This system was well adaptable for fuels, and still ran steadily even if BR was as high as 50 %. During preheating, properly increasing BR improved carbon microcrystalline structure of preheated carbon-based fuel and increased its specific surface area, but its carbon microcrystalline structure was gradually deteriorated at BR>20 %. Fuel properties of preheated coal gas were deteriorated with increasing BR. During combustion, combustion efficiency (η) increased first and then decreased with increasing BR, while NOx emission increased. For tertiary air nozzle located at top of burnout region, the structures of center symmetry and ring hedge had less effect on η and NOx emission, both of which remained at high levels, exceeding 98.5 % and 160 mg/m3. Notably, properly shifting injection position down reduced NOx emission significantly, albeit at the expense of reduction in η. Excessively low injection position had less effect on further NOx emissdddction.

A Universal Method for Regulating Carbon Microcrystalline Structure for High-Capacity Sodium Storage: Binding Energy As Descriptor.

Sodium-ion batteries (SIBs) are attracting worldwide attention due to their multiple merits including abundant reserve and safety. However, industrialization is challenged by the scarcity of high-performance carbon anodes with high specific capacities. Here, we report the metal-assisted microcrystalline structure regulation of carbon materials to achieve high-capacity sodium storage. Systematic investigations of in situ thermal-treatment X-ray diffraction and multiple spectroscopies uncover the regulation mechanism of constructing steric hindrance (C-O-C bonds) to restrain the aromatic polycondensation reaction. The carbon precursor of polycyclic aromatic hydrocarbon-type pitch contributes to a high carbon yield rate (40%) compared with those of resin and biomass precursors. The as-synthesized carbon materials deliver high capacities of up to 390 mAh g-1, surpassing many reported carbon anodes for SIBs. Through correlating specific capacity with ID/IG values in Raman spectra and theoretical calculation of carbon materials regulated by different metal elements (Mn, Nb, Ce, Cr, and V), we identify and propose the binding energy as the descriptor for characterizing the capability of regulating the carbon microcrystalline structure to promote sodium storage. This work provides a universal method for regulating the carbon structure, which may lead to the controlled design and fabrication of carbon materials for energy storage and conversion and beyond.

Effect of demineralization on waste tire pyrolysis char physical, chemical characteristics and combustion characteristics

Waste tire carbon black particles (CBp) are the main pyrolysis products of waste tires (WT), and CBp is difficult to use directly. This work mainly focuses on the physicochemical and combustion characteristics of demineralized CBp (DCBp) to explore the resourceful utilization of CBp resources in large quantities. This work also provides a comprehensive comparison with CBp and other carbon-based solid fuels. The results show that most of the minerals in CBp can be removed by chemical demineralization treatment (Ash content of DCBp <0.11 %). DCBp has a more developed pore structure than CBp. The deashing process affects the degree of loosening and stacking of the graphitic carbon microcrystalline structure, and the relative content of oxygen-containing functional groups in CBp to a minor extent. The deashing process leads to a decrease in the relative strength of the cross-linked stable structure and an increase in the disordered structure of carbon in CBp. The volatile fraction to fixed carbon ratio of DCBp is only 0.0467, and a large number of catalytic alkali metal elements and alkaline earth metal elements are removed in the demineralization process, which makes the early combustion of DCBp more difficult. As the combustion reaction proceeds, the internal pores of the particles are opened, and the micropores and mesopores in DCBp provide a larger surface area for the reaction. In addition, the decrease in the relative strength of the cross-linked stable structure and increases in the disordered structure of carbon can increase the intermolecular collision frequency during the combustion process, thus improving the burnout characteristics of DCBp. The above results indicate that DCBp has the potential to be used as fuel for large-scale resource utilization.

Heteroatom screening and microcrystal regulation of coal-derived hard carbon promises high-performance sodium-ion batteries

Coal is a cost-effective and high-yield precursor for the carbon anode of sodium-ion batteries (SIBs). To enhance Na+ storage behavior, it is crucial to prevent long-range graphitization of microcrystals within the coal structure during high-temperature carbonization. Herein, we present a strategy to inhibit graphitized microcrystals of anthracite-derived carbon, which reveals the correlations between the initial Coulombic efficiency (CE) and heteroatom/defects. By introducing NH3 during the carbonization process of anthracite, it is possible to effectively remove the heteroatoms (O, S, etc.) in anthracite, while also expanding the spacing of carbon layers derived from anthracite. This results in obtaining high capacity and high initial CE. Using Nitrogen-doped anthracite hard carbon (N-AC-1200) as an anode material for SIBs, a high reversible capacity of 220 mA h g−1 at 0.1 A g−1 is achieved. Furthermore, a full cell assembled by Na2/3Ni1/3Mn2/3O2 (NNMO) cathode and N-AC-1200 anode delivers a high capacity of 76 mA h g−1 at 5C. The insights provided by this work will help guide the design of heteroatom-controlled hard carbon microcrystalline environment and provide new ideas for practical hard carbon electrode design principles.

The effect of n-heptane soluble content on the composition and structure of coal tar pitch and the preparation of needle coke

To explore the effect of n-heptane soluble (HS) content in refined coal tar pitch (RCTP) on the preparation of needle coke (NC), a series of RCTP with different HS content were prepared by the solvent method. The RCTPs were reacted at 490 °C and 0.2 MPa for 6 h to obtain green cokes (GCs), and the GCs were calcined at 1400 °C to obtain NCs. The properties of RCTPs were studied by Fourier transform infrared (FTIR) spectroscopy, 1H nuclear magnetic resonance spectrum (1H NMR), and thermogravimetric (TG) analyses. The appearance and polarized microstructure of the GCs, and the Scanning electron microscope (SEM) image, X-ray diffraction (XRD) spectroscopy, Raman spectroscopy, linear expansion coefficient, and true density of the NCs were obtained and analyzed. The results show that with the decrease of HS content, the aromaticity of RCTPs increases, and the amount and length of branched chains decrease. Mesophase structures in GCs formed by these RCTPs have different types and orientations, which leads to obvious quality differences in NCs. The NC prepared from RCTP with HS content of 15.9% (RCTP-4) has the lowest linear expansion coefficient of 0.991 × 10−6 /°C, the highest true density of 2.1195 g/cm3, better fiber structure and carbon microcrystalline structure. Therefore, the HS content should be controlled not less than 15.9%, and the TI content should not be higher than 12.6% when RCTP was prepared by solvent method.

Trash to treasure: Sulfonation-assisted transformation of waste masks into high-performance carbon anode for sodium-ion batteries

The global pandemic of COVID-19 poses significant challenge to the recycling of disposable polypropylene (PP)-based waste masks. Herein, a simple but effective sulfonation route has been proposed to transform PP-based waste masks into value-added hard carbon (CM) anode materials for advanced sodium-ion batteries. The sulfonation treatment improves the thermal stability of the PP molecule, preventing their complete decomposition and the release of massive gas molecules during the carbonization process. Meanwhile, the oxygen functional groups introduced during sulfonation effectively facilitates the cross-linking between the PP chains, hindering the rearrangement of carbon microcrystalline structures and enhancing its structural disorder. As a result, the prepared hard carbon anode (CM-180) with a high disorder degree and minimal surface defects realizes a high sodium storage capacity of 327.4 mAh g−1 with excellent cycle and rate capability. In addition, when coupled with O3–NaNi1/3Fe1/3Mn1/3O2 cathode, the fabricated sodium-ion full cell delivers a high energy density of 238 Wh kg−1 and achieves an outstanding rate capability with a retained capacity of 75 mAh g−1 even at an ultrahigh current rate of 50 C. This work offers a novel insight into transforming the waste masks to value-added hard carbons with promising prospects for sodium-ion batteries.

Sputtering of micro-carbon-silver film (μC-Ag) for endotracheal tubes to mitigate respiratory infections

Polyurethane (PU) substrates are biocompatible materials widely used to manufacture endotracheal tubes. However, in common with other biomedical materials, they are liable to the formation of microbial films. The occurrence of pneumonia in intubated patients treated at intensive care units often takes the form of ventilator-associated pneumonia (VAP). The issue relates to the translocation of pathogenic microorganisms that colonize the oropharyngeal mucosa, dental plaque, stomach, and sinuses. New protective materials can provide a more effective therapeutic approach to mitigating bacterial films. This work concerns microcrystalline carbon film containing dispersed silver nanoparticles (μC-Ag) deposited on PU substrates using a physical vapor deposition sputtering process. For the first time, carbon paper was used to produce a carbon target with holes exposing a silver disk positioned under the carbon paper, forming a single target for use in the sputtering system. The silver nanoparticles were well distributed in the carbon film. The adherence characteristics of the μC-Ag film were evaluated using a tape test technique, and electron dispersive x-ray mapping was performed to analyze the residual particles after the tape test. The microbicidal effect of the thin film was also investigated using species S. aureus, a pathogenic microorganism responsible for most infections of the lower respiratory tract involving VAP and ventilator-associated tracheobronchitis (VAT). The results demonstrated that μC-Ag films on PU substrates are promising materials for mitigating pathogenic microorganisms on endotracheal tubes.

Conversion of Coal into Graphitized Microcrystalline Carbon with a Hierarchical Porous Structure for Electrochemical Hydrogen Storage

Conversion of Coal into Graphitized Microcrystalline Carbon with a Hierarchical Porous Structure for Electrochemical Hydrogen Storage

Investigation on the influence of inherent AAEMs on gasification reactivity of solid digestate char

Char reactivity usually determines the overall efficiency of the entire gasification process, while the presence of the alkali and alkaline earth metals (AAEMs) has a catalytic effect on char gasification. In this study, the influence of inherent AAEMs in the gasification behaviour of char was investigated. The char sample was prepared through the pyrolysis of solid digestate derived from anaerobic co-digestion of silage and dairy cattle slurry. The raw char and HCl-washed char were characterized by elemental analyzer, ICP-OES, SEM and XRD to explore their structural changes. HCl-char loses weight in the temperature range of 440–620 °C, and the weight loss percentage is significantly higher than that of char. Ash content of char is reduced by half after a pickling process. AAEMs are largely removed after char acid pickling, resulting in an increase in activation energy of the gasification reaction and a decrease in gasification reactivity, resulting in the gasification reaction time of HCl-char longer than char. Water-soluble AAEM and ion-exchange AAEM affect the evolution of carbon structure, which directly lead to char reactivity during the gasification reaction. As the carbon is consumed, the carbon microcrystalline structure of the residual carbon tends to be ordered, resulting in fewer active free carbon sites for the gasification reaction. Kinetic analysis showed that the loss and deactivation of AAEMs after char acid washing increased the average activation energy Ea by 115.76 KJ/mol compared with the original char.