Investigating the physicochemical properties and embedding forms of residual carbon (RC) and slag particles (SPs) in coal gasification fine slag (FS) is the basis for achieving its separation and utilization. An in-depth understanding of their compositional characteristics allows for targeted treatment and utilization programs for different components. In this work, the physicochemical properties and embedding forms of RC and SPs in FS were systematically investigated. An innovative calculation method is proposed to determine the mass fraction of dispersed carbon particles, dispersed mineral-rich particles, and carbon–ash combined particles by using a high-temperature heating stage coupled with an optical microscope. The unburned RC with a rough, loose surface and a well-developed pore structure acted as a framework in which the smaller spherical SPs with a smooth surface were embedded. In addition, the sieving pretreatment process facilitated the enrichment of the RC. Moreover, the RC content showed significant dependencies according to the FS particle size. For FS with a particle size of 0.075–0.150 mm, the mass proportions of dispersed carbon, ash particles, and the carbon–ash combination were 15.19%, 38.72%, and 46.09%, respectively. These findings provide basic data and reliable technical support for the subsequent carbon and ash separation process and the comprehensive utilization of coal gasification slag.

The catalytic gasification of petroleum coke with different ratios of K₂CO₃ was investigated by a thermogravimetric analyzer (TGA) using the non-isothermal method. The initial, peak, and final gasification temperatures of the petroleum coke decreased greatly as the amount of K₂CO₃ increased, and the catalytic reaction became saturated at a concentration of K⁺ higher than 5 mmol/g; with the further increase in catalyst; the gasification rate varied slightly, but no inhibition effect was observed. The vaporization of the catalyst was confirmed during the gasification at high temperatures. The structural evolution of the residual coke with different carbon conversions was examined by X-ray diffraction (XRD), Raman spectroscopy, and N₂ adsorption analyses during gasification with and without the catalyst. The results showed that the carbon crystallite structure of the residual coke varied in the presence of the catalyst. As the carbon conversion increased, the structure of the residual coke without the catalyst became more ordered, and the number of aromatic rings decreased, while the graphitization degree of the residual coke in the presence of the catalyst decreased. Meanwhile, the surface area and pore volume of petroleum coke increased in the gasification process of the residual coke, irrespective of the presence of the catalyst. However, the reactivity of the residual coke did not change much with the variation in the carbon and pore structure during the reaction.

Understanding the catalytic pyrolysis mechanism of lignite is of great significance for obtaining a high yield of the target products or designing high-efficiency catalysts, which are generally derived by using simple model compounds, while the ordinary model compounds cannot represent the real atmosphere of lignite pyrolysis owing to the simple structures and single reactions. Based on the coal two-phase model, the extractable compounds are the important compositions of coal, which can reflect the partial characteristics of raw coal while obtaining a high extraction yield. Hence, a better understanding of the interaction between the coal structure and catalyst can be inferred by using a mobile phase in coal as model compounds instead of conventional simple compounds. In this work, tetrahydrofuran extracts of lignite were chosen as model compounds to study the catalytic pyrolysis mechanism with separate addition of Fe(NO₃)₃ and FeCl₃ by using a thermogravimetric combined with mass spectrometry. It was found that about 77.88% of the extracts were vaporized before 700 °C, and the residual yield was 22.12%. With the separate addition of 5 wt % of Fe(NO₃)₃ and FeCl₃, the conversion of the extracts increased to 84.38% and 89.66%. Meanwhile, the final temperature decreased to 650 and 550 °C, respectively. The addition of Fe(NO₃)₃ and FeCl₃ promoted the breakage of aliphatic chains at approximately 150 °C, leading to the generation of CH₄ and H₂ in the temperature range 100–200 °C, which were nearly invisible for that without catalyst. The addition of iron-based catalysts allowed more CO₂ formation at approximately 200 °C since they enabled efficient promotion of the cleavage of carboxyl functionals at lower temperatures. The enlarged peak of H₂O and CH₄ at approximately 500 °C means that iron-based catalysts are significant for the cleavage of methoxy groups in the catalytic respect. Aromatic side chains facilitated cracking at approximately 500 °C, leading to more light aliphatics and aromatics generation in this temperature range.

This study developed an analytical method based on comprehensive two-dimensional gas chromatography–mass spectrometry/flame ionization detection (GC×GC-MS/FID) for the simultaneous qualitative and quantitative analysis of phenolic compounds in coal-derived liquids. After sample injection, the analytes were first separated on a non-polar column in the first dimension and then transferred via a modulator to a medium-polar column for further orthogonal separation. The target phenolic compounds were simultaneously identified by MS and quantified by FID. By comparing the quantitative performance of the area normalization, external standard, and internal standard methods, the internal standard method was found to be more accurate and reliable. The limits of detection (LODs) for individual phenolic compounds ranged from 0.011 to 0.263 mg/L. Acceptable recoveries were obtained in spiked recovery tests using real coal tar samples, and the relative standard deviations (RSDs, n = 6) for repeatability tests met the acceptance criteria for quantitative analysis. These results demonstrate that the proposed GC×GC-MS/FID strategy enables efficient separation and reliable quantification of phenolic compounds, providing a valuable reference for the compositional analysis of complex mixtures in coal tar.