Hydrogen-rich syngas production by catalytic cracking of tar in wastewater under supercritical condition

This paper presents the results from experimental study of syngas production by catalytic cracking of tar in wastewater under supercritical condition. Ni/Al2O3 catalysts were prepared via the ultrasonic assisted incipient wetness impregnation on activated alumina, and calcined at 600 degrees C for 4 h. All catalysts showed mesoporous structure with specific surface area in a range of 146.6-215.3 m(2)/g. The effect of Ni loading (5-30 wt%), reaction temperature (400-500 degrees C), and tar concentration (0.5-7 wt%) were systematically investigated. The overall reaction efficiency and the gas yields, especially for H-2, were significantly enhanced with an addition of Ni/Al2O3 catalysts. With 20%Ni/Al2O3, the H-2 yield increased by 146% compared to the non-catalytic experiment. It is noteworthy that the reaction at 450 degrees C with the addition of 20%Ni/Al2O3 had a comparable efficiency to the reaction without catalyst at 500 degrees C. The maximum H-2 yield of 46.8 mol/kgtar was achieved with 20%Ni/Al2O3 at 500 degrees C and 0.5 wt% tar concentration. The catalytic performance of the catalysts gradually decreased as the reuse cycle increased, and could be recovered to 88% of the fresh catalyst after regeneration. 20%Ni/Al2O3 has a potential to improve H-2 production, as well as a good reusability. Thus, it is considered a promising catalyst for energy conversion of tar in wastewater. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.