Thermogravimetry Mass Spectrometry Research Articles

Formation of ZrC-SiC Composites from the Molecular Scale through the Synthesis of Multielement Polymers.

In the field of non-oxide ceramic composites, and by using the polymer-derived ceramic route, understanding the relationship between the thermal behaviour of the preceramic polymers and their structure, leading to the mechanisms involved, is crucial. To investigate the role of Zr on the fabrication of ZrC–SiC composites, linear or hyperbranched polycarbosilanes and polyzirconocarbosilanes were synthesised through either “click-chemistry” or hydrosilylation reactions. Then, the thermal behaviours of these polymeric structures were considered, notably to understand the impact of Zr on the thermal path going to the composites. The inorganic materials were characterised by thermogravimetry-mass spectrometry (TG-MS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). To link the macromolecular structure to the organisation involved during the ceramisation process, eight temperature domains were highlighted on the TG analyses, and a four-step mechanism was proposed for the polymers synthesised by a hydrosilylation reaction, as they displayed better ceramic yields. Globally, the introduction of Zr in the polymer had several effects on the temperature fragmentation mechanisms of the organometallic polymeric structures: (i) instead of stepwise mass losses, continuous fragment release prevailed; (ii) the stability of preceramic polymers was impacted, with relatively good ceramic yields; (iii) it modulated the chemical composition of the generated composites as it led, inter alia, to the consumption of free carbon.

Thermo-catalytic studies on a mixture of plastic waste and biomass

AbstractThe effects of various catalysts on the composition of volatile pyrolysis products of a plastic waste and biomass mixture (1:1) were studied, by pyrolyzing the mixture sample using slow and fast heating rate. Various zeolite catalysts (β-and Y-zeolites, ZSM-5 and FCC) and nickel-molybdenum catalyst on alumina support were applied to find suitable catalysts for upgrading the quality of the thermal decomposition products of the waste mixture. A sample to catalyst ratio of 2:1 was used in the experiments. The rate of evolution of the decomposition products under slow pyrolysis was measured by thermogravimetry/mass spectrometry (TG/MS). The composition of the pyrolyzates was analyzed in detail by pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS) method. The influence of all applied catalysts was more pronounced on the plastic content of the sample than on biomass. The pyrolysis experiments revealed that the catalysts promoted the cracking reactions of the evolved hydrocarbons; furthermore, the formation of aromatic products was enhanced remarkably in the presence of all zeolite catalysts. Beta-zeolite and ZSM-5 catalysts were found the most effective in cracking hydrocarbons to gaseous products and in aromatization, while the highest CO2 formation was obtained by FCC from the biomass part of the studied waste mixture. NiMo catalyst promoted the H2 production from the plastic part; furthermore, slight aromatization and cracking effects were also observed.

In-situ evolution process understanding from a salan-ligated manganese cluster to supercapacitive application

The goal of material chemistry is to study the relationship among hierarchical structure, chemical reaction and precision preparation for materials, yet tracking pyrolysis process on multi-dimensional scale is still at primary stage. Here we propose packing mode analysis to understand evolution process in high temperature reaction. As a proof of concept, we first design a salan-ligated Mn3 (Mn3(3-MeOsalophen)2(Cl)2) cluster and pyrolyze it under an inert atmosphere directly to a mixed valence MnOx embedded in a porous N-doped carbon skeleton (MnOx/C). Meanwhile, combining thermogravimetry-mass spectrometry (TG-MS) with other characterization techniques, its pyrolysis process is precisely tracked real-time and Mn2+/Mn3+ ratios in the resulting materials are deduced, ensuring excellent electrochemical advantages. As a result, the as-preferred MnOx/C-900 sample reaches 943 F/g at 1 A/g, maintaining good durability under 5,000 cycles with 90% retention. The highlight of packing mode analysis strategy in this work would provide a favorable approach to explore the potential relationship between structure and performance in the future.

Effect of torrefaction pretreatment on biomass chemical looping gasification (BCLG) characteristics: Gaseous products distribution and kinetic analysis

The biomass chemical looping gasification (BCLG) of torrefied spruce-pine-fir (SPF) sawdust with Fe2O3 was studied using thermogravimetry-mass spectrometry (TG-MS). The effects of torrefaction temperature and OC ratio on the BCLG were investigated. The thermal characteristics of torrefied SPF with Fe2O3 and the distribution of gaseous products were discussed. Thermogravimetric kinetics and gas release kinetics were implemented to understand the mechanism. The results showed the volatiles release intensity of the SPF reached the maximum when the torrefaction temperature was 270 °C. The solid–solid reaction performance between OC and biochar reached the highest as the OC fraction was 50 wt%. The thermogravimetric kinetics revealed the activation energy of the BCLG gained the minimum when the OC ratio was 50 wt%. Moreover, the increase of OC ratio and torrefaction temperature could improve the reactivity of biochar. The torrefaction affected the gaseous products distribution of the BCLG, which consequently promoted the H2/CO ratio of the syngas from 1.06 to 1.30. Meanwhile, the gas release kinetic analysis demonstrated the E(H2) made the minimum (88.66 kJ·mol−1) when the torrefaction temperature was 270 °C. All these indicate the torrefaction has a positive effect on the BCLG process.

Solid-state polymerization of diaminomaleonitrile: Toward a new generation of conjugated functional materials

The solid-state polymerization (SSP) of organic molecules to form two-dimensional (2D) materials remains a challenge, especially when these reactions are performed in one pot using a single reagent. As will be shown, the SSP of the HCN tetramer diaminomaleonitrile (DAMN) may be an excellent example of these reactions. Dynamic experiments by differential scanning calorimetry (DSC) allow the analysis of the thermally initiated bulk polymerization of DAMN. Under nonisothermal measurements at low heating rates, a multiple-step polymerization reaction takes place. The SSP of DAMN is highly efficient, possibly due to the autocatalytic nature of its kinetics, which are consistent with the two-parameter Šesták-Berggren (SB) model and describe the three stages found in its complicated mechanism, confirmed also from an analysis of the variation in the apparent activation energy with the conversion degree. Relevant mechanistic aspects, such as the dehydrocyanation and deamination processes during SSP, are extracted by thermogravimetry-mass spectrometry (TG-MS). Moreover, some structural and morphological properties of these materials are characterized by Fourier-transform infrared (FTIR) spectroscopy and microscopy. All this information allows us to propose hypothetical pathways for the production of a complex conjugated system, predominantly constituted by a 2D macrostructure based on imidazole rings. This work opens up new possibilities for the synthesis of functional poly(heterocycle) systems, expanding our view of a plausible prebiotic chemical reaction space and providing the foundation for systematic studies of the structure-property relationships of novel HCN-derived polymers, which are currently of great interest in the fields of materials and surface science.

Thermal decomposition of biomass wastes derived from palm oil production

The palm oil industry produces large amounts of biomass by-products, such as palm empty fruit bunch (EFB), mesocarp fiber (MF), and kernel shell (KS). The thermal behavior and decomposition of the oil palm biomass wastes have been studied by thermogravimetry/mass spectrometry (TG/MS) and pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS). The determination of biopolymer and inorganic composition facilitated the interpretation of the thermal decomposition results. It was established that the chemical compositions of KS and MF were similar, while EFB contained significantly higher amount of cellulose and potassium, and decomposed in a narrower temperature range. In addition to the thermogravimetric curves (TG and DTG), the product distribution of pyrolyzates also reflected the compositional differences. Py-GC/MS and TG/MS experiments showed that the increasing potassium content of the samples reduced the intensity of 4-hydroxy-5,6-dihydro-2H-pyran-2-one, which is formed via depolymerization and dehydration of xylan units. Consequently, these experiments proved that beside cellulose, the depolymerization of hemicellulose was also hindered, while the dehydration, fragmentation, and charring reactions were catalyzed by potassium. Additionally, the evolution of the characteristic cellulose and lignin products shifted to lower temperatures. The most dominant aromatic pyrolysis product was phenol from each sample, which formed to a large extent from the abundant 4-hydroxybenzoate (4Hb) lignin subunits by scission and decarboxylation. KS also produced 4-hydroxybenzoic acid in significant amounts during pyrolysis at 450 °C confirming the presence of 4Hb subunits in lignin. The evolution of phenol started at 220 °C from the 4Hb moieties, and ended at about 600 °C from the residual phenolic units, while the release of guaiacol, vinylguaiacol, and syringol occurred between 300 and 450 °C as monitored by TG/MS. Some characteristic carbohydrate products were attributed to either hemicellulose or cellulose degradation based on the evolution profiles of KS and MF with separated carbohydrate decomposition steps. The comparison of the oil palm biomass wastes showed that EFB is supposed to be treated separately from KS and MF during the utilization process due to the different thermal behavior and composition.

Cellulose Gasification with Ca-Fe Oxygen Carrier in Chemical-Looping Process

Biomass-derived chemical looping gasification (BCLG) is a novel technology for lignocellulose energy applications. Ca-Fe oxygen carriers have been proven to be a potential material for efficient lignocellulose conversion and hydrogen-enriched syngas production in process studies. In this study, Thermogravimetry-mass spectrometry (TG-MS), pyrolysis chromatography-mass spectrometry (Py-GC-MS) and fixed-bed experiments were conducted, and the cellulose BCLG product was analyzed to explore the mechanism of reaction between Ca-Fe OCs and biomass char or volatiles. The mechanism of the synergistic effect of Ca-Fe was analyzed to explain the characteristics of the OCs. The results showed the Ca-based materials act as catalysts to promote the decomposition of cellulose monomers at primary reaction and char at secondary reaction. And also promote the reforming and oxidation of volatiles by chemisorption. Ca participates in the construction of inert substances, such as Ca 2 Fe 2 O 5 , to avoid the deep oxidation of CO and H 2 . Fe-based material supplies oxygen and promotes the reforming of volatile. Compared with Fe 2 O 3 and CaO/Fe 2 O 3 , CaFe 2 O 4 showed a better performance on carbon conversion and H 2 production below 850 °C.

Fabrication of Expanded Layered Double Hydroxide for Toxic Anion Elimination

Layered double hydroxide (LDH), known as a toxic ion absorber, is layered structured material composed by metal hydroxide cation layer and anion layer. As followed process, LDH can selectively absorb cations or anions such as As5+, Cl-, NO3 - , and so on. This absorption materials have been highlighted as a critical factor to treat of wastewater.In this research, we suggest new structure of LDH which is called expanded LDH for enhancing anion absorption efficiency. The expanded LDH is synthesized by heat treatment at relatively low temperature than calcined LDH. At heat treatment temperature, water of crystallization and part of anions are eliminated as gases. The cation layer of expanded LDH is partially anchored by remained anions. Because of anchored region, cationic layer is not able to move away freely from another cationic layer. The unique structure of expanded LDH cause recovery to initial LDH structure through anion absorption as refolding process.Fabricated expanded LDH is characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffractometer, thermogravimetry-mass spectroscopy and Fourier transmission infrared analysis. Figure 1

High-temperature pyrolysis of petroleum coke and its correlation to in-situ char-CO2 gasification reactivity

The understanding of the pyrolysis behavior of petroleum coke (PC), a by-product of oil refining, is very critical to its energy utilization. Different from most previous work, this investigation particularly focused on PC pyrolysis at high temperatures > 1273 K. The CO2 gasification reactivity of in-situ char, rather than quenched char, was evaluated and correlated to PC pyrolysis behavior at different temperatures. A Chinese PC with sizes below 100 μm was tested on a high-temperature thermogravimetric analyser (TGA). Three sets of tests were carried out for different purposes. The first set was to simultaneously obtain sample mass loss and gas evolution data during pyrolysis through thermogravimetry-mass spectrometry (TG-MS). The second set aimed to collect char samples for subsequent analyses by scanning electron microscopy (SEM) and Raman spectrometry. The third set was to evaluate in-situ char-CO2 gasification reactivity through the TGA. The results showed that, in addition to the commonly-observed primary pyrolysis stage at low temperatures, there was a secondary PC pyrolysis stage at high temperatures > 1300 K. In this process, the gases such as HCN, CO2 and SO2 were significantly released. The observed changes of char morphology suggested a four-staged thermoplastic transformation of the PC during pyrolysis, which has little been discussed previously. At different stages, i.e. softening, plasticizing, resolidification and graphitization, the rate of carbon ordering was different. The in-situ char-CO2 gasification reactivity was found to first increase, then decrease and finally increase again with increasing temperature. Such changes coincided with the thermoplastic state of the pyrolyzed char, but not with the changes of char surface area or carbon ordering. The obtained knowledge is new and highlights the potentially important roles of char thermoplastic state in determining its reactivity towards CO2.

Synthesis and combustion inhibition efficiency of iron short-chain perfluorocarboxylates

This study reports an experimental exploration of the combustion inhibition efficiency of iron short-chain perfluorocarboxylates, namely, iron trifluoroacetate (FeTFA) and iron pentafluoropropionate (FePFP). The aim is to develop a new phosphor-free fire-extinguishing agent. The synthesized FeTFA and FePFP were characterized by ultraviolet–visible spectroscopy, Fourier-transform infrared spectroscopy, X-ray fluorescence measurements, and fast-atom bombardment mass spectrometry. The FeTFA and FePFP ligands (i) coordinate with the iron ions in bridging form via carboxylate oxygens, (ii) contain no Cl−, and (iii) are hexanuclear complexes with chemical formulas of C18F27O22Fe6 and C27F45O22Fe6, respectively. Suppression trials and thermogravimetric measurements revealed that (i) both FeTFA and FePFP have higher combustion inhibition ability at lower suppressant concentrations than ammonium dihydrogen phosphate (an active component in conventional fire-extinguishing agents), (ii) FePFP is remarkably more inhibition-efficient than FeTFA, and (iii) neither FeTFA nor FePFP hinder cellulose pyrolysis and char combustion in the condensed phase. Thermogravimetry–mass spectrometry measurements confirmed that (i) the main gas-phase decomposition product of FeTFA and FePFP is CF3, and (ii) FePFP is a better CF3 generator than FeTFA. The different inhibition abilities of the two complexes were attributed to their different CF3 generation abilities and eases of decomposing the complex.

Characterization of a New Solvatomorph of Drospirenone by Thermogravimetry-Mass Spectrometry Combined with Other Solid-State Analysis Methods.

Drospirenone (DE) is a fourth-generation progesterone that has been widely used in oral contraceptives for women because of its safety and few side effects in terms of pharmacological activity. A new solvatomorph (crystal form C) of DE with dimethyl sulfoxide was identified and characterized for the first time through a thermogravimetry–mass spectrometry (TG–MS) coupling system. The thermodynamic property of the new solvatomorph of DE was different from those of most pharmaceutical solvatomorphs, and it was revealed via the skimmer-type interfaced TG–MS system and differential scanning calorimetry. This new solvatomorph and a polymorph of DE obtained without solvent (crystal form A) were well characterized by X-ray crystallography and vibrational spectroscopic analysis. Computational studies based on their single-crystal structures, such as Hirshfeld surface analyses, were used to determine the intermolecular interactions in the crystal network. The single-crystal structure of crystal form C of DE was determined and reported for the first time.

The Effect Mechanism of Fe on Coal Pyrolysis to NO x Precursors: Quantum Chemical Calculations and Mass Spectrometry Experiments.

Density functional theory is adopted to thoroughly analyze the influence mechanism of Fe on the formation of NH3 and HCN. The structure of Fe adsorbed on the surface of seven-membered zigzag coal containing pyridine nitrogen is selected as the Fe-containing coal model. The effect of Fe on the nitrogen distribution during Zhundong coal pyrolysis is further studied by thermogravimetry–mass spectrometry. The theoretical calculations show that Fe increases the Mulliken charge density on the N5 surface, which increases the rate-determining step energy barrier value of NH3 generated from coal pyrolysis and inhibits the NH3 formation. On the other hand, Fe significantly enhances the bonding energy between σ N5–C6 and π N5–C6, increases the activation energy required for N stripping from the pyridine ring (about 69.14 kJ/mol higher than that without Fe), and inhibits HCN formation. The experimental results show that Fe catalyzes the precipitation peaks of NH3 and CH3CN about 20 K ahead of time and has no obvious catalytic effect on HCN and HNCO. In terms of the nitrogen distribution, Fe significantly promotes the CH3CN formation and shows a significant inhibitory effect on NH3, HCN, and HNCO. Kinetic results show that Fe reduces the precipitation rates of NH3 and HCN, and the inhibitory effect on HCN is more significant.

Status and relative content of water in shale determined by thermogravimetry-mass spectrometry analysis

Understanding the status and the relative content of water in shale is of great significance for shale gas and oil reserve estimations and production predictions. In this work, a facile and efficient method to quantitatively determine the status and relative content of water in shale is proposed. As shale composition significantly influences the distribution and status of water, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis were conducted; the results showed that shale composition is very complex, thus suggesting that is rather difficult to efficiently analyze the water in shale. Because the weight loss during a TG experiment not only contains water but also complicated organic hydrocarbons, it is impossible to obtain the status and relative content of water in shale by TG. In the present investigation, thermogravimetry-mass spectrometry (TG-MS) technology was employed to solve this problem, and the water ion currents of MS were utilized to record the removal behavior of water in shale. The integral area of the water ion current curves within different temperature ranges corresponds to the status (free, bound and structural water) and relative content of water. The TG-MS results indicate that the structural water content in the six typical shale samples is all greater than 50% of the total water. Among the six shale samples, the structural water content varies from 71.24% to 57.37%. At the same time, free water is the least abundant, and most of the free water contents of the shale samples contribute less than 10% of the bound water contents. A retort method was utilized to verify the effectiveness of the TG-MS method, and the results indicate this method is efficient and reliable. The results show that TG-MS technology can efficiently determine the removal behavior of water in shale, and the different statuses of water can be qualitatively described by using this method. This work provides a simple and effective method to explore the status of water and its relative content in shale.

Combustion mechanism and model free kinetics of different origin coal samples: Thermal analysis approach

Five coal samples from different origins are characterized for their pyrolysis and combustion features using coupled thermogravimetry - mass spectrometry (TG-MS). The samples are heated at temperatures ranging from 25 to 900 °C in air atmosphere under heating rates of 10, 20, and 30 °C/min. The characteristic temperatures (initial, peak, burn out), reaction intervals, mass loss rate, ash residues, ignition and combustion performances, an ignition-combustion index and the reactivities of the coal samples are calculated and the associated heating rate effects are estimated. The less reactive coal exhibits higher peak temperature in conversion and low value of ignition index and reactivity. The reactivity of the coal samples varied in between 2.31 and 7.84 x102 (1/min). The main volatile and combustion products (H2, CH4, H2O, CO, CO2, C6H6, COS, SO2) release for the corresponding TG and temperatures are estimated using online 3D measurements of MS based on their relative intensities and relevancy. Ozawa-Flynn-Wall (OFW) and Kissinger-Akahira-Sunose (KAS) type model free kinetic methods are applied to determine the activation energies of the coals which are exhibited in-between 44.6 - 75.1 kJ/mol and 50.5–96.6 kJ/mol using OFW and KAS methods respectively. The estimated kinetic constants are compared and found consistent with combustion performance parameters.

Three-dimensional nickel foam templated MgCo2O4 nanowires as an efficient catalyst for the thermal decomposition of ammonium perchlorate

Spinel–type oxides MgCo2O4 and Co3O4 nanowires (NWs) were successfully prepared using nickel foam (NF) as a template. The catalytic performance of MgCo2O4 NWs on the thermal decomposition of ammonium perchlorate (AP) was investigated by differential scanning calorimetry (DSC) and simultaneous thermogravimetry–mass spectrometry (TG/MS) techniques. In the presence of MgCo2O4 NWs, the process of the high temperature decomposition (HTD) and the low temperature decomposition (LTD) of AP was combined to one with a peak temperature of 277.35 ​°C. Meanwhile, the apparent activation energy decreased from 139.05 to 123.61 ​kJ·mol−1 on the basis of thermal analysis kinetics. This was attributed to the synergistic effect between the metals of this ternary metal oxide and the larger specific surface area of MgCo2O4 NWs. Therefore, MgCo2O4 with nanowires morphology holds a promise to catalyze energetic components.

Co-combustion behavior of dyeing sludge and rice husk by using TG-MS: Thermal conversion, gas evolution, and kinetic analyses

Co-combustion of dyeing sludge (DS) and rice husk (RH) is a promising energy-from-waste method. The aim of this work was to investigate and quantify the effect of RH additive on combustion performance, gas evolution (especially gaseous pollutants) and kinetics during DS combustion by thermogravimetry-mass spectrometry method. Results revealed that the introduction of RH improved the combustibility, burnout performance and combustion stability of DS. Optimal RH addition (10% RH) reduced the emission of gaseous pollutants (NH3, NO2, COS, SO2 and CS2). The interaction between DS and RH inhibited the devolatilization reaction and emission of gaseous sulfur substances, and it also restrained NO2 emission under optimal RH additive amount. A four-interval kinetic model (D1 → F3 → D1 → F3) was established to describe the co-combustion process (R2 greater than 0.9999). RH addition, especially at high doses, led to an increase in activation energy relative to DS.

Investigation into the co-pyrolysis behaviors of cow manure and coal blending by TG–MS

In this study, the co-pyrolysis characteristics of cow manure (CM) and Meihuajing bituminous coal (MHJ) blends were investigated in detail. The mass loss behavior and gas evolution characteristics of the blends were analyzed online by thermogravimetry–mass spectrometry (TG–MS), and kinetic analysis was performed. The results demonstrate that the addition of CM to the MHJ increases the reactivity of blends, indicating that interaction between the CM and MHJ occurred during co-pyrolysis. For conventional gases, the release order of gases during CM and MHJ blend pyrolysis is H2O, CO2, CO, CH4, H2. For sulfur-containing gases, with increasing proportion of CM, the emissions of H2S, COS, and C4H4S increase and that of SO2 decrease, and the release temperature interval shifts to lower directions. The Coats & Redfern model was used, an increase of activation energy with CM addition was observed. The optimum blending ratio based on the lowest activation energy is CM:MHJ = 1:3 and the activation energy is 41.9 kJ/mol.

Concentration-composition-isotherm for the ammonia absorption process of zirconium phosphate.

The ammonia absorption process of zirconium phosphate has been studied using the concentration-composition-isotherm (CCI), X-ray diffraction and thermogravimetry-mass spectrometry (TG-MS). It was clarified that the equilibrium plateau concentration appeared due to two phase coexistence.

The pyrolysis of vitrinite and inertinite by a combination of quantum chemistry calculation and thermogravimetry-mass spectrometry

In this study, pyrolysis behaviour of vitrinite and inertinite from Heidaigou long-flame coal was studied via quantum chemical calculation and TG-MS. Quantum chemical calculation showed that vitrinite contains bonds with long bond length and small bond order, whereas inertinite revealed the opposite. And vitrinite and inertinite presented the same order of breaking bonds, but the numbers of breaking bonds showed differences. Before CO2 release, bond breakages and initial breakdown of macromolecular structure were observed. TG-MS analysis showed that the emissions with the same number of carbon, whether from vitrinite pyrolysis or inertinite pyrolysis, showed the same variation trend. Emissions from both vitrinite and inertinite can be divided into following four types. The first includes CO2, which was detected at 300 °C. The second consists of C1, C2, C3 and C4 compounds, which were observed at 420 °C and showed a fast release rate. The third comprises C6 and C7 compounds and CO, which were also detected at 420 °C with a slow release rate, and the fourth includes H2, which was identified at 500 °C. The escapes of the same substances during pyrolysis of vitrinite and inertinite were compared. Almost all emissions from vitrinite were higher than those from inertinite, but the temperature of maximum CO2 release from vitrinite was lower than that of inertinite.

The effect of metal calcium on nitrogen migration and transformation during coal pyrolysis: Mass spectrometry experiments and quantum chemical calculations

The effect of CaCl2 on the precipitation characteristics of NH3, HCN, CH3CN, and HNCO during Zhundong Coal pyrolysis are investigated by thermogravimetry-mass spectrometry (TG-MS). Density functional theory is used to study the formation mechanism of NH3 and HCN in the presence of Ca. Seven-membered ring containing pyridine is selected as carbonaceous surface, and the stucture of Ca adsorption on coal surface is used as coal model containing Ca. The experimental results show that the addition of CaCl2 shifts the NOx precursors formation, including NH3, HCN, CH3CN and HNCO, toward a lower temperature. CaCl2 promotes the formation of NH3 and CH3CN while it inhibits the formation of HCN and HNCO, and the release laws of HCN and HNCO are basically consistent. The theoretical calculation results reveal that Ca can increase coal surface activity, so that the energy barrier value of the rate-determining step during NH3 formation in the presence of Ca is 274.74 kJ/mol lower than that in the absence of Ca, and obviously promotes NH3 formation. The presence of Ca significantly increases the interatomic bonding force between N5 and C6 in the pyridine ring, so that the N atom stripping from benzene ring in the rate-determining step of HCN formation requires a higher activation energy, and inhibits HCN formation. Ca obviously increases NH3 formation rate and is more conducive to NH3 formation.