Sustainable hydrogen production from coal tar residue via supercritical water gasification

Hazardous wastes such as coal tar residue (CTR) pose a serious hazard to the environment and human health. In the context of ‘carbon peak and carbon neutrality’, the conversion of wasted resources into energy to replace fossil fuels is in line with the requirements of future social development. Supercritical water (SCW) offers a promising approach for converting hazardous waste CTR into energy. This article combines supercritical water gasification (SCWG) technology with the efficient utilization of CTR for the first time, providing a scientific solution for reducing environmental pollution and preparing hydrogen. In this article, we systematically investigated the effects of temperature (540–700 °C), residence time (5–60 min), material concentration (3 wt%-11 wt%), and six different catalysts on CTR SCWG. Experimental results indicate that higher temperature, longer reaction time, and lower CTR concentration are beneficial for gasification. When the temperature, retention time, material concentration, and catalyst are set at 700 °C, 60 min, 3 wt%, and K₂CO₃ respectively, most of the carbon in the CTR is converted into small molecular gases. The carbon gasification efficiency (CE) reaches 94.44 %, while the H₂ yield attains a value of 67.56 mol kg⁻¹. Finally, based on the analysis results of gas, liquid and solid products, the SCWG mechanism of CTR is summarized.