Realizing Three-Dimensionally Ordered, Hydrothermally Stable Mesoporous Catalysts Via Assembly and Nanotemplating Strategies

Realization of high-selectivity catalytic conversions under the hydrothermal conditions of the biorefinery demands the development of next-generation, hydrothermally stable heterogeneous catalysts bearing three-dimensionally ordered mesoporous (3DOm) and hierarchical (i.e., macro-meso-microporous) pore structure that can accommodate bulky sugar molecules and their derivatives. The enhanced hydrothermal stability and reducible structure of titania establishes its promise as a robust substrate for liquid phase biofuel catalysis. Through a hierarchical nanotemplating strategy involving the infiltration of assembled, size-tunable silica nanoparticles with titanate solutions, we have successfully fabricated three-dimensionally ordered mesoporous titania structures with tunable pore size ranging from nanometers to tens of nanometers. The mesopore structure during high-temperature calcination, treatment intended for titania polymorph interconversion and enhanced crystallinity, is bolstered by the presence of the hard silica template.  The resulting nanoparticulate walls and ordered mesostructure lead to BET surface areas as high as 289 m²/g.  The confinement imparted by the sacrificial template enables fundamental insight into titania polymorphism as it relates to its sensitivity to the degree of confinement and surface chemistry imparted by the template.  We will employ glucose-fructose isomerization and dehydration as a probe reaction-diffusion system to elucidate structure-function relations linking pore topology, pore size, and systematic tuning of both organic and inorganic pore space functionalization (e.g., Pt, SO₃H) to catalytic activity and selectivity.