In-situ removal of toluene as a biomass tar model compound using NiFe2O4 for application in chemical looping gasification oxygen carrier

Abstract

Efficient removal of tar is a major challenge for biomass gasification. A scheme based on chemical looping gasification (CLG) provides a promising alternative for converting biomass into syngas with low tar content. The current study investigates the reactivity of NiFe2O4 oxygen carrier for toluene (biomass tar model compound) removal. The NiFe2O4 oxygen carrier shows a dual-function of oxidation-catalysis for toluene cracking and significantly promotes toluene cracked into carbon and H2. A suitable temperature for toluene cracking is determined at 850 °C. As the weight hourly space velocity (WHSV) increases by approximately a factor of nine, the toluene removal decreases slightly by 2.78%. The toluene removal does not significantly decrease with the crystal phase transformation of the oxygen carrier. Addition of steam significantly eliminates the carbon deposition, which decreases to 4.97% at S/C (steam/toluene) ratio of 1.20. The catalytic activity of NiFe2O4 initially remained stable for a long time, and then started showing a slight decrease after transitory activation during the long-term experiment (82 h). These results fully demonstrate that the NiFe2O4 is a good oxygen carrier for tar removal in biomass CLG.