Current global trends all point towards a carbon-free powered society. Such reduced dependency on fossil fuels has invigorated research on renewable energy sources. One proven renewable energy source is biomass- as it can be converted to gaseous fuels; case and point, as utilized in distributed power generation systems composed of biomass gasifiers and Solid Oxide Fuel Cells (SOFCs). However, such systems are not popular due to the formation of tar during the gasification process of the biomass as it contains lignin. Tar, the resultant aromatic hydrocarbon, induces coke formation of the electrodes of the gasifying system leading to decline in efficiency over time.
This has not gone unnoticed as various researchers have investigated tar removal by reforming using catalyst containing Nickel or various noble metals. Success has been achieved, unfortunately, a maintenance free catalyst in the reformer that can be used in rural setups is yet to be developed.
In a recent publication, Shimpei Yamaguchi (PhD candidate) and colleagues from the Osaka Research Institute of Industrial Science and Technology Izumi Center and the Graduate School of Engineering at Kyoto University developed a novel Ni based composite catalysts that could regenerate by Red-Ox cycles at lower temperature. Specifically, they focused on investigating the regenerative function of a composite catalyst containing NiAl2O4 at temperatures around 700-800°C. Their work is currently published in the research journal, International Journal of Hydrogen Energy.
In brief, the research approach entailed the in-depth evaluation of the regenerative function of the composite oxide catalyst containing NiAl2O4 spinel (NAO) and Ru added to NAO (RNAO) by Red-Ox cycles and their activity of auto thermal reforming of toluene. Additionally, the regenerative function of both NAO and RNAO were investigated by temperature programmed reduction (TPR) and oxidation at 850 0C repeatedly.
The authors reported that after the 7th Red-Ox cycle test at 850 °C, even though the regenerated amount of NiAl2O4 in NAO decreased to about 30% from the initial amount due to sintering promoted, that in RNAO remained fairly constant. Moreover, they also reported that as the Red-Ox cycles proceed, RuO2 in RNAO dispersed thus decreasing its size, by dissolving into the Ni crystalline structure that precipitated from NiAl2O4 when reduced.
To sum up, the study presented an in-depth evaluation of the regenerative characteristics of a composite catalyst containing NiAl2O4 spinel oxide (NAO) and Ru added NAO. The approach employed concentrated on Red-Ox cycles and activity of auto thermal reforming of toluene. Generally, the team was able to demonstrate that regeneration by Red-Ox cycles of NAO and RNAO were achieved repeatedly at 750-850 °C and they possessed higher activity of auto thermal reforming toluene than platinum catalysts. Altogether, it was concluded that the regenerative catalyst, NAO and RNAO would contribute to a maintenance free system for reforming tar of biomass gasification.
Shimpei Yamaguchi, Tomoatsu Ozaki, Takeshi Suyama, Hiroki Muroyama, Toshiaki Matsui, Koichi Eguchi. Evaluation of regenerative function and activity of reforming toluene by composite catalyst containing spinel oxide. International Journal of Hydrogen Energy Volume 44, Issue 18, 2019, Pages 9338-9347.Go To International Journal of Hydrogen Energy