Chemical looping catalytic gasification of biomass over active LaNi Fe1-O3 perovskites as functional oxygen carriers

Abstract

• A citric acid–nitrate sol–gel method was used to prepare the LaNi x Fe 1-x O 3 perovskite. • Partial substitution of Fe by Ni in LaFeO 3 was beneficial to the BCLG process. • LaNi 0.5 Fe 0.5 O 3 was found to give desired results in the formation of syngas. Oxygen carriers (OCs) with perovskite structure are attracting increasing interests due to their redox tunability by introducing various dopants in the structure. In this study, LaNi x Fe 1- x O 3 ( x = 0, 0.1, 0.3, 0.5, 0.7, 1.0) perovskite OCs have been prepared by a citric acid–nitrate sol–gel method, characterized by means of X-ray diffraction (XRD) analysis and tested for algae chemical looping gasification in a fixed bed reactor. The effects of perovskite types, OC/biomass mass ratio (O/B), gasification temperature and water injection rate on the gasification performance were investigated. Lower Ni-doped (0 ≤ x ≤ 0.5) perovskites crystalized in the rhombohedra system which was isostructural with LaNiO 3 , while those with composition 0.5 ≤ x ≤ 1 crystalized in the orthorhombic system. Despite the high reactivity for LaNiO 3 , LaNi 0.5 Fe 0.5 O 3 (LN5F5) was found to be more stable at a high temperature and give almost as good results as LaNiO 3 in the formation of syngas. The relatively higher syngas yield of 0.833 m 3 ⋯kg −1 biomass was obtained under the O/B of 0.4, water injection rate of 0.3 ml⋯min −1 and gasification temperature at 850 °C. Continuous high yield of syngas was achieved during the first 5 redox cycles, while a slight decrease in the reactivity for LN5F5 after 5 cycles was observed due to the adhesion of small grains occurring on the surface of OCs. However, an obvious improvement in the gasification performance was attained for LN5F5 compared to raw biomass direct gasification, indicating that LN5F5 is a promising functional OC for chemical looping catalytic gasification of biomass.