Coke Surface Research Articles

Characterization of Fresh, Deactivated, and Regenerated TS‐1 for Propylene Epoxidation: Investigating Surface Deactivation Species

AbstractTitanium silicalite‐1 (TS‐1) serves as an effective catalyst for propylene epoxidation in the hydrogen peroxide propylene oxide (HPPO) process, attracting wide attention from researchers and industry. Nonetheless, the TS‐1 catalyst experienced inevitable deactivation during industrial applications, which adversely impacts its lifespan. To enhance reaction stability of catalyst, the present work conducted a systematic investigation into the deactivation reason of the TS‐1 catalyst. The fresh, deactivated, and regenerated catalysts were characterized by using various analytical techniques to compare their physicochemical properties. The surface coke species of the deactivated catalysts were extracted by the Soxhlet extraction method and subsequently analyzed using GC–MS. Additionally, the pathways for by‐product formation were simulated through Gauss software. The results indicated that the so‐called coking deposits formed during the reaction predominantly consist of propylene glycol, ethers, and oligomers. These coke species covered the partial active sites on the catalyst surface, blocked the pores of the catalyst, and accordingly led to the deactivation of the catalyst, although the crystalline structure of the catalyst hardly changed after deactivation. These results provide a theoretical basis and novel insights for the rational design and development of efficient catalysts for the HPPO process.

Reaction mechanism of catalytic gasification by calcium-based catalysts and oxidized coal residues in coalfield fire zones

Fires originating from coal spontaneous combustion within coalfields result not only in substantial coal resource depletion but also producing residual low-activity pyrolysis coal chars exhibiting varying degrees of oxidation. These chars develop progressively through successive heat penetration at the fire front and post-fire extinguishment phases. This paper focuses on the alkaline earth metal-activated catalytic gasification of residual oxidized coal in fire zones, constructs a carbon-based model of oxidized coal in fire zones. The results show that the reaction active sites of the oxidized coal carbon matrix model are mainly concentrated on the carbon atoms at the end of the aromatic ring. During catalytic gasification, the calcium-based catalyst engages with these active sites, forming a preliminary catalyst. The transformation of oxidized coal into CO primarily occurs through two distinct routes. Calcium attaches to the surface of the oxidized coal’s carbon-based structure, establishing active sites. Acting as a facilitator, it aids the movement of CO2 to the carbon-based surface, leading to its further breakdown into CO. The catalytic species containing calcium persistently amalgamates with active sites on coal coke surface, fostering the release of additional CO. Moreover, these catalytic species with calcium also bind CO2 and unite with active coal coke sites, generating carbon–oxygen complexes on the surface. These complexes are thermally unstable and decompose, yielding CO and initiating the formation of fresh active sites on the coal coke surface. Consequently, they interact further with calcium-based catalytic species, culminating in the creation of catalyst precursors, which drive a recurrent catalytic reaction process.

Usage of coke dry quenching dust to improve coke mean size

ABSTRACT Improving the mean size of surface coke is an important subject in coke-making process. Focusing on usage of crushed inertinite, we investigated on addition of coke dry quenching (CDQ) dust in coal blend in different compositions. The effect of addition of CDQ dust on coke quality including coke mean size, changes in size fractions and coke CSR was studied. CDQ dust acts as crushed inertinite and helps in minimizing the decrease in coke strength occurred because of small cracks generated during carbonization. These cracks are generated because of different contraction ratio of vitrinite and inertinite. After taking plant trials with varied CDQ dust composition from 1% to 3% in coal blend, 1% CDQ dust usage in coal blend revealed as the optimized percentage for achieving higher mean size.

Transient simulation of conjugate heat transfer of kerosene with thermal oxidative and surface coking reactions at a supercritical pressure

The regenerative cooling technology in aerospace applications often involves supercritical-pressure heat transfer of a hydrocarbon fuel, in which thermal oxidative reactions of the fuel would lead to surface coke accumulation on the cooling channel wall. In this paper, the long-term transient conjugate heat transfer of kerosene has been numerically investigated in a circular mini tube at a supercritical pressure of 3 MPa. The modified chemical mechanism and kinetics of thermal oxidative and surface coking reactions of kerosene are proposed, which, with an additional surface reaction, are capable of treating large coke deposition in regions with sharp temperature gradients. Transient surface coke accumulation and its effect on heat transfer are handled by a dynamic mesh technique. A series of numerical studies are conducted to elucidate the influences of surface heat flux, dissolved oxygen mass fraction, inlet fuel mass flow rate, and coke layer thermal conductivity on the supercritical-pressure heat transfer and thermal oxidative reactions. The effects of different reaction pathways on surface coke accumulation are analyzed comprehensively, and it is revealed that the oxygen-consuming surface coke deposition is initiated only at the high fuel temperature at around 590 K. The present numerical results would enhance fundamental understanding of the long-term transient heat transfer process of a hydrocarbon fuel at supercritical pressures in the regenerative cooling applications.

Hydrophobically modified bulk coke as a novel carbonaceous sorbent for removal of organic solvents

Designing a concise hydrophobic modification strategy for carbonaceous materials still faces challenge. In this work, the bottom-up method of growing polysiloxane nanofilaments is used for hydrophobic modification of bulk coke. Polysiloxane nanofilaments formed on the bulk coke surface not only reduce the surface energy, but also increase the surface roughness, thus achieving the synchronization of roughening and energy reduction. The water contact angle of modified coke can be up to 144°, showing an outstanding water repellency. Depending on the imparted hydrophobicity, the modified coke can be used as a novel carbonaceous sorbent to selectively remove hydrophobic organic solvents from water. A diverse of different organic solvents can be absorbed by the modified coke. After 20 consecutive cycles, the value of absorption capacity of the modified coke still remains stable, holding an exceptional recyclability. The utilization method of coke and the hydrophobic modification strategy proposed in this work provide a new idea for the functionalization of other carbonaceous materials.

Bio-aromatics synthesis via catalytic pyrolysis of cellulose with lithium-ion battery cathodes and modified HZSM-5 coupled in-situ plasma mode

This work proposed a novel method based on in-situ plasma mode to synthetize bio-aromatics from cellulose co-pyrolyzed with lithium-ion battery cathodes and tandem catalyzed by modified HZSM-5. Ni and Ti modified HZSM-5 were compared in the catalytic pyrolysis of cellulose without cathode conditions, and then cellulose was co-pyrolyzed with cathodes (LCO, LMO and LNCM). The results showed that modified-zeolites improved the upgrading of pyrolysis products, producing more refined bio-oils, and Ti-modified version was superior, while cellulose co-pyrolyzed with cathodes decreased the residual char and catalyst deposits to increase refined bio-oil. When using LNCM, the refined bio-oil yield reached 38.80%, attributing to the catalytic effect of cathodes, enhanced thermal conductivity, and micro lithium-ion battery effect. The application of cathodes and modified zeolites enhanced the conversion of furans, greatly elevating the MAHs selectivity; herein, Ni-modified version increased PAHs. After using LNCM, the selectivity of MAHs reached 77.67% (mainly C8 hydrocarbons), C10 and above hydrocarbons were suppressed, which was possibly attributed to enhanced gas-phase reactions. Abundant free radical reactions and higher cracking capability enabled coking to initially occur inside, and using LNCM decreased the catalyst coke content by approximately 80%. Co-pyrolysis with cathodes caused the surface coke to transform from filament-like to amorphous.

Enhanced electrochemical performance of N, F co-doped and etched needle coke-based lithium-ion battery anode materials by NF3 plasma treatment

NF3 plasma treatments were used to improve the electrochemical properties of needle coke-based lithium-ion battery (LIB) anode materials. The effects of the NF3 plasma treatments on the chemical, structural, and morphological properties of the needle cokes were evaluated with various analyses, and simultaneous heteroatom doping coupled with surface etching was identified. With these effects, N and F functional groups and micropores were generated on the surfaces of the needle cokes. The NF3 plasma-modified needle cokes were analyzed with LIB performance tests, and considerable enhancements were observed in the discharge capacities, rate capabilities and cycling stabilities. The resulting nitrogen functional groups and micropores improved the lithium storage capacities and rates by providing lithium-ion adsorption sites. The fluorine functional groups enhanced the cycling stability by forming LiF-based SEI layers. These effects of the NF3 plasma treatment on the electrochemical properties were proven with analytical techniques, and mechanisms for the overall process were suggested based on the results. The NF3 plasma-treated needle cokes are promising materials for fast charging LIB anodes with high stabilities and competitive discharge capacities.

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.

OXIDATIVE REGENERATION OF METAL COMPLEX CATALYTIC SYSTEM

When carrying out thermocatalytic destruction of hydrocarbon feedstock, catalysts are deactivated due to the formation of surface coke, which blocks active centers. In order to restore their previous activity and selectivity, as well as extend their service life, a process of catalyst regeneration is carried out. One of the effective methods for restoring the original activity of deactivated catalysts is oxidative regeneration, which is based on the oxidation of coke deposits on the surface of the catalyst. The article examines the dependences of the formation of surface coke when varying the temperature regime of the process from 450 °C to 550 °C during the thermocatalytic destruction of heavy petroleum feedstock – West Siberian oil fuel oil in the presence of a new metal complex catalytic system, where the active component is a chloroferrate complex (NaFeCl4 or TCFN) in an amount 10 %, deposited on a carrier, which is a deeply decationized Ymmm zeolite of the acidic form (H-form). The patterns of oxidative regeneration of a metal-complex catalytic system were studied by distilling off highly volatile products in a flow of inert gas (helium) and oxygen-containing gas. During the experiments, it was found that with an increase in the temperature of the thermocatalytic destruction process from 450 °C to 550 °C, a slight increase in coarse deposits on the surface of the catalyst was observed from 2,6 % wt. up to 3,5 % wt. respectively. When carrying out the process of oxidative regeneration of a carbonized catalyst with air oxygen (in a flow of helium) at a temperature of 500 °C for 60 min only volatile components are initially removed, and further calcination takes up to 180 min allows for complete burning of surface coke.

Performance of nitrogen-containing functional groups on SO2 adsorption by active coke

The main aim of this study is to investigate the mechanism of the effect of the nitrogen-containing functional group of activated coke on SO2 adsorption through experiments and simulations. In this work, active coke with rich pyrrole and pyridine groups was prepared by ammonia modification. It has been found that the presence of pyrrole and pyridine groups, which can increase the surface polarity of active coke and the strength of non-covalent interactions, favors SO2 adsorption. Simulations show that the adsorption energy and non-covalent interaction strength of SO2, H2O and O2 on the surface and edge of active coke models with pyrrole group are greater than those with pyridine group, except for the adsorption of H2O on the edge of active coke. The presence of H2O reduces the adsorption capacity of SO2, mainly due to the competitive adsorption between H2O and SO2. Experimental research shows that the presence of H2O increases the content of S element on the active coke surface after adsorption. So, H2O not only promotes the adsorption of SO2, but also competes with it. Compared to O2, H2O forms stronger hydrogen bonds and dipole–dipole interactions with SO2, which can promote the adsorption of SO2.

Effect of Microstructural Change under Pressure during Isostatic Pressing on Mechanical and Electrical Properties of Isotropic Carbon Blocks.

In this study, carbon blocks were fabricated using isotropic coke and coal tar pitch as raw materials, with a variation in pressure during cold isostatic pressing (CIP). The CIP pressure was set to 50, 100, 150, and 200 MPa, and the effect of the CIP pressure on the mechanical and electrical properties of the resulting carbon blocks was analyzed. Microstructural observations confirmed that, after the kneading, the surface of isotropic coke was covered with the pitch components. Subsequently, after the CIP, granules, which were larger than isotropic coke and the kneaded particles, were observed. The formation of these granules was attributed to the coalescence of kneaded particles under the applied pressing pressure. This granule formation was accompanied by the development of pores, some remaining within the granules, while others were extruded, thereby existing externally. The increase in the applied pressing pressure facilitated the formation of granules, and this microstructural development contributed to enhanced mechanical and electrical properties. At a pressing pressure of 100 MPa, the maximum flexural strength was achieved at 33.3 MPa, and the minimum electrical resistivity was reached at 60.1 μΩm. The higher the pressing pressure, the larger the size of the granules. Pores around the granules tended to connect and grow larger, forming crack-like structures. This microstructural change led to degraded mechanical and electrical properties. The isotropic ratio of the carbon blocks obtained in this study was estimated based on the coefficient of thermal expansion (CTE). The results confirmed that all carbon blocks obtained proved to be isotropic. In this study, a specimen type named CIP-100 exhibited the best performance in every aspect as an isotropic carbon block.

Evolution and process analysis of the hearth activity in hydrogen-rich blast furnace

Blast furnace (BF) hydrogen-rich smelting is an important way for the green and low-carbon development of iron and steel industry. The injection volume of hydrogen-rich gas is limited due to the need for hearth activity, which is related to the stable and smooth operation of BF. In this study, the change of coke properties after hydrogen-rich smelting was summarized, the detailed evolution process of hearth activity after hydrogen-rich smelting was analyzed. The results show that: the pores on the surface of coke are enlarged after hydrogen-rich smelting. The gasification rate of coke with H2O is significantly higher than that of CO2 due to the lower activation energy and smaller molecular diameters of H2O and H2. The interlayer spacing of coke decreases and the stacking height further increases rapidly, the degree of coke graphitization is the highest after hydrogen-rich smelting. The weakening of carbon anisotropy is the fundamental reason for the increase in the degree of graphitization of coke. The strong gasification reaction causes the coke to lose a lot of carbon, and its matrix becomes loose and incomplete, so the strength after reaction decreases sharply. The wetting model is established to analyze changes in wettability. The rough surface of coke improves the wettability between slag iron and coke at high temperature. The good wettability makes it easier for slag iron to adhere to the surface of coke. The smoothness of slag iron passing through coke is reduced, the retention amount of liquid slag iron in coke layer increases. It leads to a decrease in hearth activity, the stable and smooth operation of BF is difficult to guarantee. This is the main issue limiting the injection volume of hydrogen-rich gas in BF.

Synergistically catalytic regulation of surface chemistry on coal based needle coke by bimetallic interface for enhanced Li/Na storage

The oxygen functional groups (OFGs) on carbon surface are electrochemically active for rapid Li/Na storage, and always are introduced with environment-hazardous and time-consuming ways. Herein, the bimetallic synergistic effect between Fe and Ni metal nanoparticles is proved experimentally to promote the conversion from useless C–O groups to useful CO groups on the surface of needle coke (NC) greatly. In addition, the DFT calculations show that introducing second metals increase the active electrons of single metals, and the activity of transforming C–O bond to CO bond thus makes a difference in bimetallic systems. Among the modified samples, Fe/Ni-NC contains abundant CO groups, stripe like graphite domains, excellent electronic conductivity and large interlayer spacing. Therefore, Fe/Ni-NC anode shows the excellent capacities in half batteries (212/305.2 mA h g−1 after 1000/2000 cycles at 2.0/5.0 A g−1 in SIB/LIB) and full batteries (86/145 mA h g−1 in SIB/LIB at 0.05 A g−1 after 100 cycles), significantly better than other carbon materials. The work provides a practical and significant reference to regulate precisely the surface energy storage active sites of coal based carbon material, aiming at advanced SIB and LIB.

Coke filled bed electrode coupled with vibration regeneration for efficient electrochemical water softening

The industrial application of electrochemical water softening technology is constrained by cathode surface area and regeneration issues. In this work, a three-dimensional filled-bed electrode is built by coupling stainless steel mesh with coke. The electrochemical water softening and regeneration performances are extensively investigated. The results demonstrate that coke disperses the electrode potential, enabling more rapid precipitation of calcium carbonate in circulating water where calcium and magnesium ions are present in common. The energy consumption is 8.66 KWh/KgCaCO3 and the precipitation rate is 32.74 g/m2·h at 36 A/m2. Additionally, because the coke surface is not easy to deposit scale layer, it can maintain activity when the outer stainless steel mesh is covered with scale layer. Even if the electrode is deactivated, vibration can swiftly restore it, allowing it to keep up effective water softening performance. After several regenerations, the precipitation rate is still above 30 g/m2·h.

Influence of elevated temperature and gas atmosphere on coke abrasion resistance. Part one: Pilot oven cokes

A novel approach was developed to examine coke abrasion resistance in-situ at temperatures of up to 950 °C and in a controlled gas atmosphere using rotational tribological testing. The originality of this approach lay in the ability to apply tribological testing to the porous coke surface at elevated temperatures under a controlled inert or CO2 reactive atmosphere. Coke wear characteristics were quantified via (i) the application of advanced microscopy and image analysis techniques, and (ii) analysis of the coefficient of friction (COF) during tribological testing.Two pilot oven cokes were examined in this study, which were generated from single coking coals of similar rank but different petrographic composition. The cokes tested showed a deterioration in abrasion resistance even at 400 °C, and this was accentuated at 950 °C.The COF and the severity of the wear as a function of temperature and gas atmosphere were markedly different between the two cokes. Coke C396 from a mid-to-low vol, medium vitrinite coal showed no statistically significant differences between the wear severity results recorded following room temperature testing and high temperature testing in a CO2 environment. Conversely, the more reactive coke C426 with a higher parent coal inertinite content showed clear differences in the extent of abrasive wear at room temperature and at high temperature in both inert and reactive gas atmospheres.This suggests that the reduction in abrasion resistance at elevated temperatures is accentuated in the coke with the highest coke reactivity index (CRI) and the highest content of inertinite maceral derived components (IMDC). Our research has shown that at room temperature, the IMDC show greater resistance to abrasion than the reactive maceral derived components (RMDC). This has implications for understanding the relevance of room temperature testing to the abrasion resistance of coke under practical blast furnace operation conditions. For example, a coke from a coal or blend with a comparatively high inertinite content may show lower resistance to abrasion in the blast furnace than would be expected from tumble drum indices. Larger sample numbers and cokes from a variety of single coals need to be tested in further work to verify these assertions.Finally, a novel method using micro-CT image analysis was developed to examine the wear path generated at the coke surface during tribological testing. The purpose of this was to assess the extent of the abrasive wear by comparing the rendered micro-CT images before and after tribological testing. A colour gradient scale was used to facilitate the quantitative assessment, whereby the colour of each voxel was based on the distance from the nearest voxel that is associated with solid phase.As expected, the specific surface area (SSA) calculated for the upper 1 mm of each sample decreased following tribological testing due to the generation of a wear track which is smoother than the initially rough, porous coke surface. In the C426 coke type examined, the SSA decreased the most for the sample tested in an argon atmosphere at 950 °C, matching the COF and quantified wear severity results, which showed there was a notable increase in abrasive wear to this coke as the temperature was raised from room to elevated temperature.Coupling this method of analysis with 3D visualisation techniques in further work would provide a powerful approach to examine and quantify mechanisms of coke surface breakage and the microstructural and/or microtextural features responsible for the breakage.

Falling Angle of Fe‐C‐Based Alloy Droplet on Coke and Graphite

The hold‐up of molten pig iron and slag melt in the coke packed bed of blast furnace (BF) causes a decrease of void between coke lumps and inhibits gas permeability. Smooth dripping of those liquids in the coke bed is desirable to keep the productivity of BF. Herein, the conditions for smooth flowing of molten iron on coke surface are calrified, and the falling angles of Fe‐C and actual pig iron droplets on coke and graphite are measured at high temperature. It is found that Fe‐C droplet easily slids down on coke because of small falling angle, and the falling angle of actual pig iron is even smaller, while those droplets adhere to a graphite substrate. The carbon in iron has only a small effect on the static contact angle with coke, but has a great influence on the falling angle. From the viewpoint of the roughness of coke surface, the variation of static contact angle and falling angle is discussed.

Multi-scale relationship between coke gasification kinetics and its microstructure evolution in the blast furnace

There is a precise theoretical correspondence between the microscopic chemistry and physical structure of coke and its apparent rate constantkreaand pore diffusion coefficientDeffof carbon loss process, and a certain precise mathematical relationship betweenkrea/Deffand the degradation gradient or degradation behavior of coke in blast furnace should exist. This is the key basis for predicting and evaluating coke degradation behavior in blast furnace through coke microstructure. In this work, the evolution relationship between the chemical and physical structure of coke and the macroscopic kinetic parameterskrea,Deffwas studied by gasification experiment of coke with different particle sizes. The results show that with the deepening of coke solution loss, minerals gradually precipitate on the surface of coke, and play a catalytic role in the process of solution loss, resulting in a decrease in activation energy and an increase inkrea. At this point, the micropores in coke expand and merge into mesopores and macropores, the diffusion path of CO2molecule decreases, the diffusion activation energy decreases, andDeffincreases gradually. In the middle and late period of solution loss, the active components in coke are consumed and the ash in coke is precipitated, which increases the activation energy and decreases thekrea. Moreover, the number of macropores in coke is further increased, and the tortuous degree of porous structure is greatly reduced, which leads to the decrease of diffusion activation energy and the increase ofDeff.krea/Deffrepresents the gradient reaction ability of coke on the macro level. The higher thekrea/Deffvalue, the greater the reaction gradient of coke under the same conditions, which further affects the degradation gradient and degradation behavior of coke in the blast furnace.

Determining the Specific Surface of Special Coke Produced from Long-Flame Shubarkol Coal

Determining the Specific Surface of Special Coke Produced from Long-Flame Shubarkol Coal

Dissolution losses of metallurgical cokes in CO2-H2O mixtures

ABSTRACT Influences of the gas mixtures of carbon dioxide and water vapor with different water vapor content on the thermal properties of cokes were studied at 1,373 k using a high-temperature gas-solid reaction device to clarify the action mechanism of water vapor in the dissolution loss of metallurgical coke in the blast furnace. Furthermore, the reaction depth and the microstructure of coke samples with different water vapor content were studied. The results showed that the reactivity of cokes was significantly improved by steam, and coke strength after the reaction was significantly weakened. Cokes with strong reactivity were more affected by water vapor. When H2O content was 0 and 11.1%, the reactivity indices of cokes with strong reactivity were 2.03 and 1.67 times that of cokes with poor reactivity, respectively. The influence of H2O on the strength ratio of two kinds of cokes after the reaction was ignored when H2O content exceeded 50.1%. The analysis of coke reaction depth after the reaction under different H2O content showed that the solution loss reaction between H2O and coke is mainly concentrated on the coke surface, while CO2 can penetrate into the coke to react. In addition, by comparing two kinds of coke with different reactivity, it is found that coke with higher reactivity is more sensitive to water vapor. The micromorphologies of cokes after reactions showed that water vapor significantly affected the pore and pore sizes of cokes. When water vapor content increased, the pore sizes of cokes increased, with the thinner pore wall and the increased number of new pores.

Advances on Understanding Coke Gasification Process with CO2: A Report from Density Functional Theory

AbstractCO2 gasification process on different active edges of a particular coke model surface has been explored computationally. It is observed that the adsorption through carbon and oxygen end of CO2 (CO‐mode) through formation of four‐ and five‐membered ring on the active sites is the favoured one. Our calculation also reveals that the strength of adsorption depends on nature and position of the active sites. The exergonic adsorption energy of CO‐mode drives the first CO release process and also makes it favoured compared to the adsorption mode where CO2 has been absorbed through its two‐oxygen end (OO‐mode). Among all the intermediates, intermediate having oxygen attached to the middle‐carbon of the coke (middle‐oxygenated coke) is found to be the most stable intermediate. The energy barrier for the second CO release also depends on the attachment sites of the oxygen on the coke surface. It is noteworthy that first principles investigations of coke gasification reactions with CO2 reported to date are found to consider different coke active sites separately on different coke model surfaces. In this context, our work is believed to be the first of its kind where complete characterization of CO2 gasification reactions has been performed considering all the active sites in a single coke model, thus providing a more coherent picture of it.