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In order to study the role of metal sodium in the spray pyrolysis of biomass tar, this paper designs a sodium-containing naphthalene pyrolysis system (NSS) and a pure naphthalene pyrolysis system (PNS) using naphthalene as the carbon source and sodium chloride as the sodium metal donor for comparison. This enables an exploration of the effect of sodium on the initial nucleation of carbon fumes formed by naphthalene pyrolysis using reaction molecular dynamics (ReaxFF MD). The simulation results show that NSS undergoes pyrolysis reactions earlier and faster than PNS at the same temperature. Simulated at 3250 K temperature for 2 ns, the naphthalene pyrolysis consumption rate of the NSS was faster than that of the PNS, and the addition of sodium atoms during the condensation process provided more active sites and accelerated the condensation of macromolecular products. Moreover, Na+ and carbon rings form a Na+-π structure to promote the bending of graphite lamellae to facilitate the formation of carbon nuclei. Molecular dynamics simulations were used to simulate the formation of carbon nuclei during the initial stage of naphthalene pyrolysis, revealing that the mechanism of sodium salt catalyzed the acceleration of organic matter pyrolysis from a microscopic visualization perspective. [ABSTRACT FROM AUTHOR]

The soot produced in the process of coal pyrolysis seriously affect the atmosphere environment and health of human beings. This study used naphthalene-the most abundant precursor species in coal tar-was used as a raw material to conduct pyrolysis experiments in a self-designed drop tube furnace, combined with density functional theory, to explore the influence mechanism of Na in the formation of coal-derived soot. The microstructure and functional group information of soot derived from the pyrolysis of naphthalene are obtained through transmission electron microscopy, infrared spectroscopy, Raman spectroscopy and XPS analysis. The experimental result shows that Na can inhibit the aggregation of polycyclic aromatic hydrocarbons, resulting in a shorter average length of graphite-like crystallites in the soot particles, and promoting the oxidation of the soot surface. The simulation result shows that Na inhibits the polymerization of aromatic rings. These experiments and simulation results show that the ions formed by gaseous Na form a Na+-π structure with naphthalene, which increases the energy barrier of the reaction between naphthalene molecules and naphthalene radicals and inhibits the polymerization of aromatic rings. • In the pyrolysis experiment, naphthalene-the most abundant precursor species in coal tar, was selected as the raw material. • The effect of Na on the formation mechanism of coal-derived soot was studied from two aspects of experiment and simulation. • Na has an inhibitory effect on aromatic ring polymerization. [ABSTRACT FROM AUTHOR]

Coal-derived carbon black is the main composition of PM 2.5 , used in the rubber industry and energy storage fields. The formation and structure control of carbon black have attracted significant attention. Alkali metals have influence on the dynamic formation of coal-derived carbon black. To analyze the mechanism of Na in the formation of carbon black, a high-temperature drop tube furnace was used to analysis of carbon black from the pyrolysis of acid-washed coal and Na-containing coal at 1250 °C. DFT was applied to simulate the stepwise inhibitory effect of Na on the polymerization of PAHs into carbon black. The results show that Na promotes the oxidative cracking of large PAHs into small PAHs during the formation of coal-derived carbon black (reaction energy barrier is reduced by 17.7%), and inhibits the condensation of small PAHs molecules to form carbon black molecules (reaction energy barrier is increased by 74.7%), which causes the length of carbon black is shortened by 14.3%, and its curvature is increased by 1.7%. Na could change the spatial structure of formed carbon black-graphite crystallites, which increases the spacing of carbon black by approximately 6.2% to 16.3%. Na enhances the electrochemical performance of carbon black by 2 to 3 times. [Display omitted] • Experimental and DFT study of the catalytic effect of Na on carbon black. • Na promotes oxidation of PAHs and fracture of carbon black crystallites. • Na inhibits the polymerization of PAHs into carbon black particles. • Na changes carbon black structure, increasing the spacing by 6.2% ~ 16.3%. • The electrochemical performance of carbon black is enhanced 2–3 times by Na. [ABSTRACT FROM AUTHOR]

• Iron inhibits the formation of soot significantly in the process of coal pyrolysis. • After addition of iron, microstructure defects in soot derived from coal pyrolysis increase and the size of the graphite layers become smaller. • Iron may inhibit carbonyl formation and promote C–O formation during the process of soot formation. The addition of metal to fuel can effectively control the soot emission. However, there are few studies on the effect of metallic additive to coal on soot emissions. In this study, the effect of iron on the characteristics of coal-derived soot was analyzed. Soot particles were obtained at different temperatures from coal pyrolysis in a drop tube furnace without and with the addition of iron nitrate (Fe(NO 3) 3) into the coal, respectively. The microstructure and functional group information of soot derived from coal were obtained through Raman spectroscopy, infrared spectroscopy and XPS. The results showed that the yield of soot derived from coal pyrolysis with iron addition was reduced by 48–68% than that derived from coal pyrolysis without iron addition at different temperature. With the iron addition, the number of holes in the graphite layers in soot produced by coal pyrolysis was increased, while the valued of sp2/sp3 and the length of graphite layer were decreased. At the same time, the C–O and COO-functional groups in the soot increased, and the carbonyl content decreased. These phenomena indicated that the addition of iron can significantly inhibit the soot formation in the coal pyrolysis process, increase the defects of graphite layers in soot, inhibit the carbonyl formation, and promote the formation of C–O during the process of soot formation. [ABSTRACT FROM AUTHOR]

Soot formation is one major challenge in developing clean and efficient utilizes based on hydrocarbon fuels. We report the physical and chemical characteristics of a set of soot samples obtained from coal and coal mixed with iron nitrate pyrolysis on a drop tube furnace at different reaction times. Yimin lignite was chosen for the experiments, using acid washing to remove its metals and adding iron by impregnation. The pyrolysis processes of the two coal samples were analyzed by TG-DTG, DSC and MS. Characterization was carried out with transmission electron microscopy(TEM), Raman spectrometer, X-ray photoelectron spectroscopy(XPS), and infrared spectroscopy (FTIR). The results show that the iron nitrate significantly reduces the yield of soot and decreases the sizes of the primary soot particles. This inhibition effect on soot production increase with reaction time. With the addition of iron nitrate, the carbon lamellae in soot are more graphitized, but the primary particle surface roughness increases. In addition, the addition of iron results in more aliphatic functional groups and C–O on the surface of the soot. • Iron inhibited soot formation and positively correlated with pyrolysis time. • Iron affects extra-core lamellae accumulation and reduces particle size. • Iron promotes soot oxidation, and divot-like structures appear on the surface. • Iron promotes C–O and aliphatic C–H formation during soot formation. [ABSTRACT FROM AUTHOR]

• Cracking experiments were performed with pyrene instead of coal tar. The reactants are simple and the process can be controlled. • The effect of Na on the soot formation process was analyzed by a combination of experiments and simulations. • Na promoted the oxidation of soot, promoted the formation of five-membered rings in the microchip layer, and increased the curvature of the microchip layer. This work aims to investigate the effects of Na on the characteristics of coal-derived soot. Soot, which has long been regarded as an unwelcome source of air pollution, has been classified as a pollutant. However, with the proposed clean and efficient utilization of coal, soot has been found to be effectively inhibited by adding metal catalysts and changing the reaction environment, and it can even realize the transformation of pollutants to functional materials. To understand the effect on physiochemical properties, pyrene was used as a coal tar substitute, and the structural transformation of soot was thoroughly investigated by DFT calculation method in combination with elemental analysis, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The presence of Na changed the π electron distribution of benzene ring, promoted the dehydrogenation condensation and oxidation exfoliation of the surface microchip layer, and accelerated the condensation of PAHs and the formation of five-membered ring in the microchip layer. Na participates in the oxidation and growth process of soot, which can regulate the micromorphology of soot. With the participation of Na, the diameter of soot particles decreases, the microcrystal length and curvature become larger, and the internal holes increase. [ABSTRACT FROM AUTHOR]