Promoted calcium looping H ₂ production via catalytic reforming of polycyclic aromatic hydrocarbon using a synthesized CO ₂ absorbent prepared by impregnation

Abstract

Summary Promoting multicycle CO2 absorption ability and mechanical strength while enhancing heavy tar elimination performance of calcium‐based absorbents is a significant challenge for calcium looping gasification (CLG). A synthesized absorbent Fe/Ca‐Al was developed by an impregnation method consisting of two steps, during which an inert support and an iron catalytic component were integrated with calcium oxide (CaO). Fe/Ca‐Al was compared with three other candidate absorbents in terms of their basic properties and performances. Results indicated that the major components of the synthesized Fe/Ca‐Al were CaO, mayenite (Ca12Al14O33), and Ca2Fe2O5. The CO2 absorption ability of Fe/Ca‐Al gradually increased within 10 carbonation–calcination cycles and the mechanical strength was apparently promoted by the component Ca12Al14O33. Fe/Ca‐Al approached the largest conversion for the heavy tar model component 1‐methylnaphthalene (70.6%), the highest H2 yield (0.18 mol/[hr·g]), and the least coke deposition (8.18 mg/g) during reforming. The synergistic effects of Ca12Al14O33 and Ca2Fe2O5 on the performance of Fe/Ca‐Al were analyzed. The effects of the mass ratio Fe/CaO, temperature of reforming reaction, molar ratio of S/C in tar, and the absorbent particle size on the reforming performance of heavy tar were also explored. The results of this study should provide useful information and possible solutions for CLG to overcome development obstacles. Novelty Statement The present work simultaneously addresses the key challenges of CaO‐based absorbents, including not only cyclic carbonation reactivity and mechanical strength of the absorbents but also heavy tar reduction performance and the influence of different reaction conditions, which are rarely reported in the literature. A synthesized iron‐calcium absorbent is developed by a two‐step impregnation method, which is beneficial to enhance biomass heavy tar (such as PAH) reduction, cyclic CO2 capture, and mechanical strength of the absorbent for hydrogen production in calcium looping gasification.