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/Al 2 O 3 catalysts were prepared via the ultrasonic assisted incipient wetness impregnation on activated alumina , and calcined at 600 °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 °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/Al 2 O 3 catalysts. With 20%Ni/Al 2 O 3 , the H 2 yield increased by 146% compared to the non-catalytic experiment. It is noteworthy that the reaction at 450 °C with the addition of 20%Ni/Al 2 O 3 had a comparable efficiency to the reaction without catalyst at 500 °C. The maximum H 2 yield of 46.8 mol/kg tar was achieved with 20%Ni/Al 2 O 3 at 500 °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/Al 2 O 3 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.