Morphology Tailoring of Sulfonic Acid Functionalized Organosilica Nanohybrids for the Synthesis of Biomass-Derived Alkyl Levulinates

Morphology evolution of sulfonic acid functionalized organosilica nanohybrids (Si(Et)Si-Pr/ArSO3H) with a 1D tubular structure (inner diameter of ca. 5nm), a 2D hexagonal mesostructure (pore diameter of ca. 5nm), and a 3D hollow spherical structure (shell thickness of 2-3nm and inner diameter of ca. 15nm) was successfully realized through P123-templated sol-gel cocondensation strategies and fine-tuning of the acidity followed by aging or a hydrothermal treatment. The Si(Et)Si-Pr/ArSO3H nanohybrids were applied in synthesis of alkyl levulinates from the esterification of levulinic acid and ethanolysis of furfural alcohol. Hollow spherical Si(Et)Si-Pr/ArSO3H and hexagonal mesoporous analogues exhibited the highest and lowest catalytic activity, respectively, among three types of nanohybrids; additionally, the activity was influenced by the SO3H loading. The activity differences are explained in terms of different BrOnsted acid and textural properties, reactant/product diffusion, and mass transfer rate, as well as accessibility of SO3H sites to the reactant molecules. The reusability of the nanohybrids was also evaluated.