Template-assisted synthesis of LaCoO3 from bio-silica: Catalytic insights into rice husk pyrolysis

Abstract

This study presents the synthesis of LaCoO₃ perovskites via a nanocasting approach using bio-silica extracted from residual rice husk (RH). The bio-silica was employed to prepare MCM-41 and SBA-15 hard templates, which served as scaffolds for perovskite formation. The resulting materials were thoroughly characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and nitrogen physisorption. The MCM-41 and SBA-15 templates exhibited high surface areas (1011 and 867 m² g⁻¹, respectively), comparable to commercial silica. After template removal, the LaCoO₃ perovskites retained significant surface areas of 55 m² g⁻¹ (MCM-41) and 80 m² g⁻¹ (SBA-15), with their texture and structure strongly influenced by the template type. The catalytic performance of nanocast LaCoO₃ perovskites and a sol–gel reference sample was evaluated in the fast pyrolysis of rice husk at 400 °C using 5 and 20 wt% catalyst loadings. Catalysts slightly increased the overall bio-oil yield (34–45 %), particularly at higher loading. Remarkably, while non-catalytic and 5 wt% catalytic pyrolysis produced bio-oils containing over 50 compounds, increasing the catalyst loading to 20 wt% reduced this number to 17–26 compounds, depending on the catalyst employed. The bio-oils were mainly composed of anhydrosugars; oxygenates (mainly furans and carbonyl-containing compounds); and aromatics, primarily phenolic derivatives. At higher loading, perovskite catalysts promoted selective pathways, enriching the pyrolysates in valuable products such as levoglucosan and 2,3-dihydrobenzofuran. These findings demonstrate the potential of LaCoO₃-based catalysts to modulate product selectivity in the fast pyrolysis of lignocellulosic biomass, offering promising opportunities for the valorization of agro-industrial residues.