Chemical looping partial oxidation (CLPO) of toluene on LaFeO3 perovskites for tunable syngas production

Abstract

Tar is the by-product of coal and biomass gasification which decreases the purity of the primary syngas and causes blockages in the pipes. Chemical looping partial oxidation (CLPO) is a promising technology to convert tar to high-purity syngas in a sustainable way. Here, we synthesized LaFeO3 perovskites as oxygen carriers with five different wet chemistry synthesis methods and tested their performance for toluene CLPO in a fixed-bed reactor. The template synthesis method presents the highest purity, the most oxygen species adjacent to oxygen vacancy, the best resistance to the carbon deposition, and exhibits the best performance in CLPO, with up to ∼100 % toluene conversion efficiency, up to ∼100 % CO selectivity, and the best recyclability. The H2/CO ratio in the syngas products varies between 0.86 and 2.2 in different stages of the toluene CLPO process. By adjusting the reaction time of toluene catalytic cracking, the H2/CO ratio is tunable within this range. Based on these results, we designed a new in-situ CLPO process for tar-containing syngas purification that can achieve tunable H2/CO ratio for syngas. In the process, toluene cracking occurs in front of toluene partial oxidation by using reverse flow design to simultaneously achieve ∼100 % toluene conversion ratio and high conversion rate. This work shows that LaFeO3 is highly efficient in converting toluene to high-purity syngas, and it has the potential to convert tar-containing syngas in-situ to achieve energy- and cost-effective manufacture for high-value-added syngas products.