Catalytic Performance of TiO2/SO₄²⁻ Prepared from TiO2 Precursors with Different Aggregation Scales in Transesterification

Abstract

The aggregation of TiO₂ precursors affects the structural evolution and catalytic performance of sulfated titania, highlighting a relationship between microscale and macroscale reactivity. In the present work, the sulfated titania (TiO₂/SO₄²⁻) solid acid catalysts were synthesized through the impregnation approach using two different precursors, pre-aggregated TiO₂ (microscale) and molecular-scale Ti(OH)₄. The catalysts were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller analysis, and ammonia temperature-programmed desorption (NH₃-TPD). Their catalytic activity was tested in the transesterification reaction of ethyl acetate with n-butanol. The TiO₂/SO₄²⁻ derived from Ti(OH)₄ precursor exhibited a single-phase anatase structure with (92%) higher specific surface area (63.85 m²g^− 1 vs. 33.38 m²g^− 1), smaller crystallite size (8.05 nm), and higher catalytic conversion (70%) as compared to the catalyst prepared from pre-aggregated TiO₂. These differences are attributed to variations in precursor aggregation, which influence crystallite growth, sulfate dispersion, and surface area acidity, thereby enhancing catalytic performance during transesterification. The present work establishes a link between TiO₂ precursor aggregation and the catalytic activity of TiO₂/SO₄²⁻. The results demonstrate that the aggregation state of the TiO₂ precursor inherently governs the physicochemical characteristics and catalytic behavior of sulfated titania, providing a rational basis for tailoring solid acid catalysts for esterification and transesterification reactions.