Direct coal liquefaction (DCL) relies on the dynamic transformation of catalyst active phases, yet the transformation pathway of Fe-based catalysts and their regulation of products distribution remain insufficiently understood. In this work, alpha-Fe2O3 precursor was employed to decouple catalyst phase transformation via quenching at different temperatures and their catalysis characteristics during liquefaction process, and Density Functional Theory (DFT) calculations were integrated to explicitly resolve the correlation between sulfidation mechanisms and liquefaction properties. Experimental results reveal that the transformation pathway for active phase during heating (150-450 degrees C) followed Fe2O3-* Fe3O4-* high S/Fe sulfides (FeS2/Fe3S4)-* pyrrhotite (FeS/Fe1-xS), along with a progressively decreasing S/Fe ratio and different liquefaction performances at corresponding quenched temperature. At low temperature, the removal of surface lattice oxygen from Fe2O3 generates oxygen vacancies that promote surface-dominated sulfidation under high hydrogen pressure, whereas increasing temperature favors sulfur redistribution and bulk phase evolution in catalyst. Nevertheless, these intermediates will form final active phase Fe1-xS at liquefaction temperature of 450 degrees C. When the quenched intermediates were used as the precursor, the pre-formed pyrrhotite as dominant active phase significantly enhanced liquefaction behaviors, resulting in coal conversion increase from 76.42 wt% to 80.10 wt% and the maximum oil yield of 54.44 wt%. DFT calculations reveal that catalyst sulfurization favors the pathway involving H2-induced deoxygenation and vacancy-mediated sulfur incorporation, whereas the reductive deoxygenation path via H2S needs high energy barrier (2.419 eV). Lower sulfurized catalysts preferentially adsorb H2S to promote gaseous hydrogen supply. The fully sulfurized catalysts more effectively utilize the gaseous hydrogen. The transformation from Fe2O3 to iron sulfides drives coal conversion into heavy intermediates through solvent hydrogen and gas hydrogen from catalytic decomposition of H2S, while the subsequent evolution into pyrrhotite enables deep hydrocracking and improves hydrogen utilization. This study provides mechanistic understanding of the surface-dominated sulfidation, hydrogen activation and phase-dependent hydrogen utilization during DCL.

Understanding the influence of metaplast (fragments of coal macromolecular network in char) on polycondensation during coal pyrolysis is beneficial for studying the mechanism of coal conversion and realizing the regulation of coal pyrolysis products. The solvent extraction and swelling treatment of rapid pyrolysis char was carried out to reduce the content of metaplast. The metaplast extracted with tetrahydrofuran (THF) solvent contained abundant aromatic compounds with a low degree of polycondensation, and its orientation distribution in char was disordered. After solvent extraction and swelling, the reactivity of the residues was enhanced, making more residues convert into liquid and gas products during the re-pyrolysis. Solvent extraction and swelling only increased the specific surface area of the char from 4 m(2)/g to 5 m(2)/g and 7 m(2)/g, respectively, and at P/P-0 < 0.05, the N-2 adsorption isotherms of 500HLL, R500HLL, and S500HLL essentially overlap, indicating that metaplast cannot directly influence pyrolysis by occupying pores. In re-pyrolysis, the relative growth rates of 4 & times; 4 and larger aromatic sheets in the extraction and swelling residues were decreased from 66.35% (char without solvent treatment) to 52.21% (char after extraction treatment) and 36.4% (char after swelling treatment), respectively. It indicates that metaplast can promote the polycondensation. After solvent treatment, the orientational concentration of aromatic cores in the char increased during re-pyrolysis, whereas that in the untreated char did not. It indicates that the metaplast was more likely to being trapped by the char's skeletal framework through cross-linking reactions or pore adsorption and was further polycondensed with the volatiles to form amorphous aromatic cores within the char matrix.

The synergistic thermal conversion of waste tire and coal is an effective approach to achieve the resource recovery of waste tire and the reduction and substitution of coal. However, the complexity of co-pyrolysis system, especially different rubbers in waste tire, hinders the understanding of pyrolysis mechanism. Therefore, this work employed an infrared-heated fixed-bed reactor to investigate the interaction behaviors of different rubbers with coal, and synergistic effects during co-pyrolysis were revealed through analysis of product yields, tar compositions and char properties. Results showed that more tar and less char and water were produced in co-pyrolysis between coal and different rubbers than individual coal pyrolysis. Besides, tar formation was easily affected by softening and melting of rubber during co-pyrolysis. More light tar was generated and its formation was promoted. The distribution of tar components presented lower content of phenols and long-chain aliphatic hydrocarbons, but the contents of alicyclic hydrocarbon and mono-ring aromatic hydrocarbon were boosted during co-pyrolysis in comparison with individual coal pyrolysis. In addition, obvious coating phenomenon over co-pyrolysis char varied with the reactivity of rubber, and the interactions between volatiles released from coal and waste tire pyrolysis were affected by coating phenomenon, and the inorganic components contained in coal or waste tire contributed to the enhancement of interaction of waste tire with coal. The possible reaction route between coal and waste tire was proposed, which will provide a basis for resource utilization of waste tire and coal.

Co-pyrolysis of waste tire and low-rank coal provides an environmentally friendly and efficient solution to recycle the solid waste and obtain high value-added products. Herein, the co-pyrolysis mechanism of Naomaohu coal (NMH) and waste truck tire (WT) was explored through in-situ pyrolysis time-of-flight mass spectrometry (in-situ Py-TOF-MS). Results demonstrate that the release of NMH volatiles occurs at a higher temperature range (270 - 600 degrees C) than that of WT (150 - 550 degrees C), the key distinction lies in the sorts of their primary volatiles. NMH coal mainly produces alkenes, benzenes, phenols, and naphthalenes, with benzenes exhibiting the highest relative content (7.65 %). In contrast, WT primarily releases the alkenes, benzenes, and cycloolefins, and cycloolefins show the highest relative content (4.35 %). Moreover, WT pyrolysis generates abundant H-rich free radicals at low temperature, which can effectively suppress condensation reactions during co-pyrolysis, contributing to the generation of more high value-added compounds. During co-pyrolysis, the total phenols content declined to 3.11 %, especially for the diphenols. Nevertheless, the experimentally relative content of phenol (1.30 %) exceeded the theoretically calculated value (0.53 %), indicating that hydrogen free radicals facilitate the conversion of diphenols to phenol. Moreover, hydrogen radicals also inhibit the generation of char, resulting in a lower total radicals concentration in the co-pyrolysis char (5.17 x1018 spins/g) than its theoretical value (7.86 x1018 spins/g). The study explores the relationship between primary volatiles evolution behaviors and the radicals reactions during co-pyrolysis, which will provide a guidance to the regulation of co-pyrolysis products.

To elucidate the conversion mechanism of Naomaohu coal-derived asphaltenes (NMH-ASP) in the high-temperature stage during the two-stage liquefaction (TSL) process, various catalysts, including Fe2O3, alpha-FeOOH, iron stearate (FeSA) and NiMo/gamma-Al2O3, were presulfurized at low-temperature to reveal the effect of their active phase on liquefaction performance and products selectivity. The results showed that NMH-ASP conversion and oil yield dropped in the following order at 430 degrees C for 60 min: NiMo/gamma-Al2O3 (85.32 wt%; 71.20 wt%) > FeSA (70.97 wt%; 63.71 wt%) > alpha-FeOOH (68.79 wt%; 61.50 wt%) > Fe2O3 (63.46 wt%; 54.76 wt%). The NiMoS phase from NiMo/gamma-Al2O3 sulfurization exhibited superior H-2 activation ability, facilitating aromatic-ring hydrogenation and the cleavage of C-al-O and C-ar-O bonds, resulting in deep deoxygenation. Consequently, the liquefied oil showed the highest cycloalkane content (10.39 %) and the lowest oxygen-containing compounds (1.89 %), along with higher CO2 content (1.50 wt%) in the gas. The Fe1-xS phase of FeSA showed smaller, more uniform crystallite sizes, promoting the cleavage of aliphatic side chains and C-al-C-al bonds, leading to increased formation of chain alkanes (20.82 %) and C-1-C-4 gases (2.34 wt%). alpha-FeOOH-derived Fe1-xS enhanced solvent hydrogen transfer to free radical fragments and promoted C-al-C-ar dealkylation, resulting in a higher benzene series content (29.62 %). However, the Fe1-xS phase of Fe2O3 exhibited lower efficiency in C-ar-O bond cleavage, leading to the accumulation of phenols (8.21 %) and a higher content of the naphthalene series (43.49 %) due to insufficient aromatic-ring hydrogenation. This work provides theoretical guidance for catalyst design and process optimization in TSL.

The direct conversion of carbon dioxide and diols into polycarbonate is a promising approach in the field of carbon utilization. However, simultaneous enhancement of the activity and stability of catalytic systems remains challenging. In this study, a series of lanthanide-substituted CeO2 solid solutions were synthesized and evaluated in the copolymerization of CO2 with 1,6-hexanediol (1,6-HDO). X-ray photoelectron spectroscopy and O2 temperature-programmed desorption indicate that the surface oxygen vacancy density initially increases and then decreases with the increase in Gd or Pr content; 1%Gd-CeO2 and 1%Pr-CeO2 exhibit the highest diol conversion and oligomer selectivity. CO2 temperature-programmed desorption, in-situ infrared spectroscopy, and Density Functional Theory calculations demonstrate that 1%Pr-CeO2 possesses a higher surface vacancy concentration, stronger CO2 chemisorption, and superior resistance to catalyst poisoning compared with pristine CeO2. Collectively, these characteristics endow the catalyst with enhanced competitive activity and stability compared to pristine CeO2. A plausible deactivation pathway and atomistic reaction mechanism are proposed based on combined spectroscopic and theoretical evidence.

Amine-based solution absorption as the most promising and commercialized CO2 capture method, attracted the increasing attention. However, its key lies in improving the CO2 desorption performance while reducing the energy consumption in desorption. In this paper, HZSM-5 was dealuminated by sulfuric acid, further loaded by Fe2O3, Co3O4, NiO and ZnO via impregnation method and used in catalytic desorption of the blended amine solution of N-methyl-diethanolamine and piperazine. Results indicated that sulfuric acid leaching increased the number of acid sites and mesoporous surface area. When sulfuric acid reached 0.8 mol/L, the resultant catalyst (0.8H(2)SO(4)-HZ) improved the amount of the desorbed CO2 by 10.26% and decreased the heat duty to 2128 kJ/mol CO2, with a reduction of 17.01% compared to non-catalytic system. The loading of metal oxides on 0.8H(2)SO(4)-HZ decreased surface area and changed acidity of catalysts. CO2 desorption amount under catalysis of metal oxide modified M/0.8H(2)SO(4)-HZ followed the order of Fe/0.8H(2)SO(4)-HZ > Zn/0.8H(2)SO(4)-HZ > Ni/0.8H(2)SO(4)-HZ > Co/0.8H(2)SO(4)-HZ, whereas the relative heat duty was in order of Zn/0.8H(2)SO(4)-HZ > Co/0.8H(2)SO(4)-HZ > Ni/0.8H(2)SO(4)-HZ > Fe/0.8H(2)SO(4)-HZ. Fe/0.8H(2)SO(4)-HZ exhibited excellent catalytic performance, along with 12.82% increase in amount of CO2 desorbed and reduction in heat duty to 2039 kJ/mol CO2, with a 20.49% decrease. Meanwhile, Fe/0.8H(2)SO(4)-HZ showed good stability after ten cycles and the addition of Fe/0.8H(2)SO(4)-HZ promoted CO2 absorption. Suitable pore structure and abundant acid sites of the modified catalyst contributed to proton transfer and decomposition of carbamate. A possible mechanism for catalytic desorption over modified HZSM-5 was proposed. The work indicates that catalytic desorption by modified HZSM-5 catalyst is a promising way to decrease the energy consumption of amine solution regeneration.

Catalytic pyrolysis of low-rank coal was performed in a decoupled triple bed reactor (DTBR) using natural magnetite as a catalytic solid heat carrier. The DTBR consists of a pyrolysis reactor, a catalytic reactor, and a combustion reactor. The coal is fast pyrolyszed in the pyrolysis reactor with the help of the hot heat carrier. The generated volatiles then pass through the catalytic reactor, where tar upgrading and particulate interception occur simultaneously. The spent heat carrier and char are subsequently transported to the combustion reactor for regeneration. The effects of particle size of coal, catalytic temperature and heat carrier to coal mass ratio (HC/C) on product distribution, tar composition, gas formation, attrition behavior, and dust removal were systematically investigated. The results showed that coal particle size negligibly affects product distribution in the 0.18-0.85 mm range. The magnetite significantly improved tar quality compared with quartz sand by increasing the light tar fraction and aromatic compound content. At 550 degrees C, the light tar fraction obtained with magnetite increased to 82.1%, compared with 70.7% for quartz sand, while the aromatic compound content increased to 50.7%, compared with 38.2% for quartz sand. Variation in HC/C caused no significant change in overall product distribution, but the phenol content increased from 18.9% to 28.1% as the ratio increased from 10/1-20/1. The attrition rate of magnetite is slightly higher than that of quartz sand that ranged from 2.5% to 4.5%. The dust yield decreased from 5.32 g/kgcoal without a solid heat carrier to 0.35 g/kgcoal with solid heat carrier, representing a dust removal efficiency of 93.4%. These results demonstrate that the DTBR provides an effective route for the integrated upgrading of coal tar and removal of pyrolysis dust.

Residual oil is prone to irreversible coking at high temperatures, which diminishes heat transfer efficiency and leads to pipeline blockage. Therefore, elucidating the coking mechanism is essential for extending industrial operation cycles. In this study, molecular structural models of saturates, aromatics, resins, and asphaltenes were constructed using component separation and an improved Brown-Ladner method. The coking process was investigated through reactive-force-field molecular dynamics (ReaxFF-MD) simulations combined with X-ray diffraction, Raman spectroscopy, Fourier-transform infrared spectroscopy and Elemental analyses. The results indicated that at the simulated temperature of 3250 K, the early stage of the reaction was dominated by side-chain cleavage and gas release, followed by synergistic chain scission and aromatic rearrangement, which promoted structural ordering. Notably, cross-linking of aromatic sheets induced rapid carbon-cluster growth: the largest cluster consisted of 2,080 carbon atoms, accounting for 83.74% of the total carbon in the system, while the H/C atomic ratio decreased from 1.27 to 0.39. In later stages, dehydrogenation and polycondensation, accompanied by structural stabilization, produced highly aromatized, densely packed coke with an H/C atomic ratio of 0.1. The change in the number of aromatic rings and the radial distribution function demonstrated a dynamic transition from disorder to order, which was also confirmed by experimental characterization. This study validates the reliability of ReaxFF-MD in elucidating the coking mechanisms of residual oil and supports the molecular design of coke inhibitors.

The integrated co-pyrolysis of biomass and coal with CO2 reforming of CH4 (CP-CRM) is regarded as an effective route to enhance tar yield, however, the effect of inherent minerals in coal and biomass on tar yield and quality remains unclear. In this work, a two-stepwise acid-leaching pretreatment was applied to demineralize NMH coal and cotton stalk, and their co-pyrolysis under N2 (CP-N2) and CP-CRM was investigated to elucidate the role of the inherent minerals in improving tar yield and compositions. Results showed that the minerals influenced the products distribution during co-pyrolysis. Demineralization pretreatment significantly enhanced the tar yield. With the stepwise removal by HCl and HCl/HF, the maximum tar yield at 450 degrees C in CP-N2 was improved from 18.88 wt% to 24.28 wt% and 27.21 wt%, respectively, indicating that AAEMs and transition metal salts in raw coal and biomass could catalyze the cracking of tar precursors and/or the condensation of volatiles. In CP-CRM, the maximum tar yield at 500 degrees C was increased by 18%, 6% and 6% in comparison with that in CP-N2 with the gradual demineralization by HCl and HCl/HF leaching, respectively, which was attributable to the stabilization of large free radicals and suppression of the condensed aromatic rings by the generated center dot H and center dot CHx radicals. Meanwhile, the inherent minerals also affected the quality and compositions of the resultant tar from CP-CRM. The light oil content gradually increased, while the content of anthracene oil and pitch decreased in the tar from CP-CRM, which was attributed to the suppression of polycondensation reactions by center dot H and center dot CHx. Additionally, the removal of AAEMs and Fe- species in raw materials decreased the contents of phenols and aliphatic compounds and boosted the content of aldehydes, ketones and benzenes. The naphthalenes content in resultant tar was higher than that in CP-N2, but gradually decreased with further removal of the minerals, different from the increase trend in CP-N2, which was attributed to the contribution of center dot H and center dot CHx from CRM. This work is helpful for efficient utilization of coal and biomass and improving the yield and quality of tar in co-pyrolysis.

Capacitive deionization (CDI) is a promising electrochemical desalination technology to address environmental pollution and freshwater scarcity. SnO2 features a high theoretical ion adsorption capacity and environmental compatibility, making it a prospective CDI electrode. Nevertheless, its application is limited by severe volume expansion and poor electrical conductivity, which impair charge transfer and structural stability. Herein, we developed a nanoconfinement strategy via ultrasonic spray pyrolysis to fabricate N, S co-doped hierarchical porous carbon spheres encapsulating SnO2 nanoparticles (SnO2/NSCS). Crucially, graphene quantum dots (GQDs) anchor to Sn4+ within microdroplet reactors, ensuring uniform dispersion and encapsulation of SnO2 while establishing localized conductive networks at heterointerfaces. This configuration enhances charge transfer through interfacial charge redistribution and improves ion accessibility via a hierarchical porous structure that shortens diffusion paths and exposes abundant active sites. Consequently, the SnO2/NSCS electrode delivers a stable desalination capacity of 39.23 mg g- 1 with a charge efficiency of 0.83 over 50 cycles in a 500 mg L- 1 NaCl solution. At a higher salinity (2000 mg L- 1 NaCl), the electrode achieved a maximum desalination capacity of 92.23 mg g- 1 with a rapid desalination rate of 15.38 mg g- 1 min-1. Moreover, it proved highly effective in removing heavy metal ions, achieving a superior Cu2+ adsorption capacity of 531.60 mg g- 1 and notable ion selectivity in a 400 mg L- 1 Cu2+ solution. This study introduces a confined encapsulation strategy for constructing high-performance CDI electrodes and provides valuable insights for designing wastewater remediation materials.

Oil-soluble catalyst is a promising alternative to non-oil-soluble catalyst due to excellent dispensability in coal-oil slurry and relatively high activity. To reveal evolution behavior of active phase of the oil-soluble Fe-based catalysts in direct liquefaction of Shangwan coal, three oil-soluble Fe-based catalysts (FeLA, FeOA, FeSA) were synthesized via saponification method with linoleic acid, oleic acid and stearic acid as organic ligands, and were compared with two traditional iron oxide catalysts (Fe2O3, FeOOH). The evolution of active compositions during different temperatures was studied by XRD, SEM, XPS and HRTEM. Results demonstrated superior stability and catalytic activity of oil-soluble catalyst during direct liquefaction. TG and FTIR analyses confirmed the decomposition at lower temperatures, and formed active phases more readily than Fe2O3 and FeOOH catalysts. The oil yields were significantly improved up to 62.82 wt%, 64.38 wt% and 66.36 wt% for FeLA, FeOA and FeSA, which were higher than those of Fe2O3 and FeOOH catalysts. FeOA and FeLA catalysts particularly excelled in promoting the formation of cycloalkanes, thereby improving oil quality. The characterizations by XRD and XPS analyses of the samples indicated that these oil-soluble catalysts rapidly form Fe0.875S at lower temperatures, avoiding intermediate oxide phases. Smaller crystallite sizes were produced for oil-soluble catalysts compared than Fe2O3 and FeOOH. Especially, substantial amounts of Fe0.875S were generated for FeSA during initial coal pyrolysis, which activated hydrogen to stabilize coal macromolecular radicals and enhanced coal conversion and yield. This work provides a guide for the development of highly efficient catalysts in direct coal liquefaction.

Elucidation of the hydrogen transfer mechanism between H-2, solvent, and coal is of great significance for improving the direct coal liquefaction (DCL) efficiency. To better understand the hydrogen transfer mechanism during the DCL, in this study, liquefaction of Shangwan coal was conducted under H-2 or D-2 and in the presence of Shenhua nanosized iron catalyst (SH-cat), NaFeS2 or molybdenum-based (Mo-cat) catalyst. Higher oil and lower preasphaltene and asphaltene (PAA) yields under H-2 than those under D-2 indicate a kinetic isotope effect in DCL, implying that hydrocracking of the intermediate PAA is part of the rate-determining step in DCL. Further, the deuterium content in the solvent after reaction was determined, and the deuterium balance among the DCL products, donor solvent, and gas phase hydrogen was established by using the mass cluster method developed in this study. The results showed that on average 30% of deuterium incorporated into the solvent and DCL products resulted from hydrogen transfer, and the remaining 70% was incorporated into the solvent and products by hydrogen exchange. In addition, the H-2 NMR results of the solvent after reaction with and without coal indicated that the hydrogen exchange exhibits high selectivity for alpha-aliphatic positions in tetralin, while the hydrogen transfer results in a more homogeneous deuterium distribution across both alpha- and beta-positions. Eventually, a reaction scheme of hydrogen transfer and exchange was proposed to determine the contribution of the hydrogen-shuttling role of the solvent to DCL. The ratio of H-2 transferred to coal through solvent under different catalysts was found to increase in the following order: Mo-cat < SH-cat < NaFeS2, which is contrary to the order of hydrogen activation capability of each catalyst. In other words, the catalyst with higher activity for hydrogen activation facilitates direct hydrogen transfer to coal, reducing reliance on the solvent as a transfer medium.

To investigate influence of mixing modes on integrated process of co-pyrolysis of coal and biomass with CO2 reforming of methane (CP-CRM), Naomaohu coal (NMH) and elm (ELM) were chosen and three mixing modes (NMH/ELM, ELM/NMH and Blends) were examined over Ni-based reforming catalysts prepared by ball milling, and compared with co-pyrolysis under N2 atmosphere (CP-N2). The results show that the products distribution was significantly affected by the mixing mode. Tar yield during CP-CRM under Blends model was higher than those of NMH/ELM and ELM/NMH, increasing by 35.29% compared with CP-N2. Meanwhile, light oil content in the tar was higher than those of NMH/ELM and ELM/NMH, but the pitch content was opposite. Phenols content in tar from Blends model was 19.52% higher than that of CP-N2, along with more free radicals in tar than that of CP-N2, which was mainly ascribed to the enhanced heat and mass transfer between raw material particles by mechanical mixing, making the co-pyrolysis process more complete. At the same time, the mechanical mixing was conducive to more efficient action of hydrogen-rich free radicals (such as ·H, ·CHx) on pyrolysis products, suppressing the secondary cracking and polymerization. The results provide a good guidance for regulating tar yield and compositions of the co-pyrolysis process.

Pyrolysis is a crucial way for clean and efficient utilization of low-rank coal, but the inherently low H/C ratio limits tar yield and quality. Hydropyrolysis has been proposed to regulate product formation by providing external H• free radicals. In this work, high-pressure thermogravimetric analysis and fixed-bed pyrolysis experiments were combined to clarify the comparative roles of total pressure and H2 partial pressure in product evolution during Hami tar-rich coal hydropyrolysis. TG/DTG results showed that an additional high-temperature DTG peak occurred under an H2 atmosphere, and the final weight loss increased from 44.92 wt% to 65.90 wt% as H2 pressure increased from 0.1 to 3.0 MPa, while it only showed a slight decrease under an inert atmosphere. Kinetic analysis indicated that the high-temperature stage under H2 was consistently described by the D3 (three-dimensional diffusion model) as pressure increased, with apparent activation energy increasing from 44.68 to 60.25 kJ/mol, suggesting an enhanced pressure effect on secondary reactions with hydrogen participation. The results of Hami coal pyrolysis in the fixed-bed reactor showed that high N2 pressure decreased tar yield due to restricted mass transfer and intensified secondary cracking of primary volatiles. In contrast, increasing H2 pressure and H2 concentration exhibited similar effects on increasing tar and gas yields while reducing char yield, with the maximum tar yield reaching 17.50 wt% at 3.0 MPa, 600 °C, and 100% H2, which was 49% higher than that under N2 (11.74 wt%) at the same condition. Besides, both increasing H2 pressure and H2 concentration promoted light tar yield to 12.69 wt% at 3.0 MPa 100% H2 through hydrogenation and stabilization of free radicals during coal pyrolysis, leading to decreased aliphatics and phenols contents and increased aromatics contents. Moreover, different effects of total pressure and H2 concentration on H2O/COx evolution and char pore structure were discussed. These findings help distinguish the effects of pressure-induced mass transfer limitation and hydrogen-radical-mediated reactions during Hami coal pyrolysis, providing fundamental insights into product evolution of coal pyrolysis under hydrogen-rich atmospheres and advancing efficient conversion technologies for tar-rich coal.

The co-pyrolysis of coal and waste plastics is a viable method for achieving efficient and clean utilization of coal and waste and enhancing light aromatic hydrocarbon production. In this study, the co-pyrolysis of Pingshuo coal and polystyrene (PS) was carried out via rapid infrared heating in a fixed bed reactor with varying mixing ratios to investigate the product distribution, tar composition, and char characteristics. The results revealed that the increase of PS mixing ratio increased the interaction of the co-pyrolysis volatiles, which raised the tar and light aromatic hydrocarbons yield. Especially for the mixing ratio of coal/PS being 7:3, the content of styrene and ethylbenzene in tar is 31.5 % and 15.2 % higher than the theoretically calculated value, respectively. Moreover, co-pyrolysis promoted the interaction between volatiles to produce biphenyls such as 1,3-diphenylpropane. Electron paramagnetic resonance results indicated that the co-pyrolysis char exhibited higher amounts of methoxy ether and 1-3 cyclic pi quinone free radicals, which was consistent with the decrease of phenols in the tar.

Pyrolysis is an effective approach to achieve clean and efficient utilization of massive waste tires. However, the differences of rubber compositions in different parts of tire result in significant variation on pyrolysis products distribution. Therefore, exploring pyrolysis characteristics of different parts in waste tire is crucial for efficient utilization. Herein, the effects of process parameters on products distribution and tar compositions from pyrolysis of tire tread, sidewall and bead were investigated. Meanwhile, pyrolysis char of tire bead was modified by acid leaching or activation by slight O2 and used as catalyst to upgrade tread pyrolysis volatiles to further enrich highvalue aromatics. Results indicate that the highest tar yield of 68.38 wt% is obtained from tread pyrolysis due to its high volatile content. Pyrolysis tar from tire sidewall is mainly cycloolefins with D-limonene content up to 35.40%, while aromatics dominate tread pyrolysis tar due to its higher content of styrene butadiene rubber, primarily enriching high-value D-limonene and aromatics. Besides, WTC-Acid catalyst effectively improves mesoporous structure and acidic sites, which is beneficial to the diffusion of pyrolysis volatiles, resulting in increase of aromatics content and yield in tar up to 82.34% and 46.75 wt%. Meanwhile, the yields of toluene, ethylbenzene and xylene are increased by 71.5%, 34.6% and 134.2%, respectively, over WTC-Acid than blank experiment and catalytic mechanism of tread pyrolysis volatiles was proposed. Tar yield remains stable within 54.97 wt% - 56.78 wt% after three loops of WTC-Acid. This study provides a guidance for optimizing clean and high-value pyrolysis of waste tire via individual pyrolysis of different parts and upgrading of pyrolysis volatiles over char from tire pyrolysis.