Rapid pyrolysis of several types of solid carbonaceous materials [lignite, bituminous coal, and petroleum coke (petcoke)] was conducted in a drop-tube furnace at 1300 °C under atmospheric pressure. Soot properties, including yield, particle size, microstructure, and reactivity, were studied, with focus on the key factors that influence soot gasification reactivity. Results show that the soot yield of bituminous coal is up to 15–20 wt %, which is nearly half of the volatile matter, while those of lignite and petcokes are merely several percentages of the raw material. The reactivity of soot is lower than that of coal char and higher than that of petcoke char. Among several soots, lignite soot is most active, while petcoke soot displays the lowest reactivity. The catalytic effect of the mineral content is excluded because no alkali metal and alkaline earth metal were detected in soot samples. The reactivity difference is independent of the particle size but closely related to the microstructure. The soot particles consist of primary spherical or nearly spherical nanometer particles with a recognizable central nucleus of about 5–15 nm. Concentrically arranged graphene layers form an onion-like structure. Soot formed from lignite has more bent graphene layers and a higher amorphous carbon content as a result of lattice defects, coincident with its high gasification reactivity.

A supercritical water reactor with throughput of 10  kg/h was set up, which was operated with continuous feeding of coal water slurry. The effects of reaction temperature (500–650 °C), pressure (20.0–30.0 MPa), Ca/C molar ratio (0–0.45) and O/C molar ratio (0–0.35) on the hydrogen generation characteristics were investigated. It is found that there is a notable increase in the hydrogen content and yield with the increase of reaction temperature. The hydrogen yield increases from 24.67 ml/g to 135.73 ml/g when the temperature increases from 500 °C to 650 °C. The contents of CO2 in gas product decrease, while that of hydrogen increases with the increase of Ca/C molar ratio. At Ca/C molar ratio of 0.45, nearly all CO2 is fixed. Correspondingly, the content of hydrogen in gas is 73.29%, and the yield of hydrogen is 348.30 ml/g compared to 135.42 ml/g in the absent of CaO. Moreover, both of CaO and KOH catalyze gasification and water-shift reaction. The formation of hydrogen and the carbon gasification efficiency are improved by the added H2O2 when O/C ratio is less than 0.3.

The effects of the addition of CaO, temperature, and residence time on the conversion and product yields of a high-ash peat in supercritical water was investigated. The experiments were carried out in an autoclave in the temperature range of 623–773 K at pressure up to 30 MPa. At a Ca/C molar ratio of 0.46, almost no CO2 remained in gas phase. It was found that CaO facilitates the extraction of volatile matter from peat and the decomposition of volatile matter to small molecular compounds. Moreover, CaO catalyses the steam reforming reaction of hydrocarbons and the water-shift reaction. The addition of KOH might favor the reforming reaction of oil product to hydrogen and carbon dioxide. Furthermore, the yield of oil reaches a maximum at the temperature approximately 723 K. A threefold increase in the yield of oil product was observed under 36.5 MPa compared with pyrolysis. However, the polar compounds decomposed with the prolongation of reaction time.