Modificação estrutural e composicional de resíduos lignocelulósicos agroindustriais para produção de hidrocarvões microesféricos com aplicação catalítica

Abstract

The growing demand for sustainable practices has driven the development of processes aligned with the principles of green chemistry, which aim to reduce the environmental impacts associated with chemical processes. In addition, the sustainable chemical conversion of waste into versatile value-added platforms has emerged as a promising strategy in line with sustainable development practices. In this context, the present study aimed to use rice husk, an agro-industrial lignocellulosic residue, as a renewable feedstock for the production of functionalized hydrochars (HCs), in order to elucidate the role of the biopolymers constituting this biomass in the development of the surface and morphological characteristics of the HCs, targeting their application as heterogeneous acid catalysts. The production protocol was based on promoting structural and compositional modifications in the lignocellulosic biomass, followed by the hydrothermal carbonization of these precursors assisted by H₂SO₄. The structural modification step was carried out through hydrothermal treatment at 180 °C under different residence times, yielding precursors with distinct chemical and physicochemical characteristics. Subsequently, H₂SO₄-assisted hydrothermal carbonization (5 mol L⁻¹) was performed in a closed system under autogenous pressure for 4 h. The results demonstrated that short-duration hydrothermal treatment significantly contributed to the production of HCs with a high concentration of sulfur-containing functional groups, including sulfonic groups, providing potential application as heterogeneous catalysts in the acetalization reaction of glycerol with acetone for the selective production of solketal, a compound with considerable commercial relevance. Furthermore, the use of residual biomass combined with an efficient processing route highlights the contribution of this study to sustainable development in accordance with the principles of green chemistry.