Nanoparticle prepared mechanically stable hierarchically porous silica granulates and their application as oxygen carrier supports for chemical looping combustion

Abstract

Chemical looping combustion (CLC) represents a promising approach to capture CO₂ emissions in the fossil fuel powered energy generations. Oxygen carriers, composed of active metal oxides, play important roles in the CLC process by transferring oxygen between oxidation and reduction reactors. To avoid the agglomeration of metallic phase during the reduction process and ensure a long-term activity, a porous support granulate is highly required. In this work, we proposed a bottom-up strategy to fabricate mechanical stable hierarchical porous granulates from silica nanoparticles, via the integration of soft pore former Pluronic F127 and employment of cold isostatic pressing technique. According to this strategy, the developed silica granulates possess characteristics such as mesopore (ca. 33 nm) and macropore (ca. 175 nm) combined hierarchical porous structure, high pore volume (955 mm³ g⁻¹) and surface area (114 m² g⁻¹), as well as enhanced crushing force 1.94 N. Via the dry impregnation method, fully oxidized CuO was able to be loaded on the surface of porous granulates and a loading amount of 30 wt% was obtained after repeating the impregnation process only twice. Further simulated chemical looping tests revealed that, with the similar loading amount, CuO supported on developed silica granulate shows a higher oxygen transport capacity comparing with reference work.