Abstract
In this paper, we present a versatile template-directed colloidal self-assembly method for the fabrication in aqueous phase of composition-tuned mesoporous RuO2@TiO2-SiO2 catalysts. Randomly methylated β-cyclodextrin/Pluronic F127 supramolecular assemblies were used as soft templates, TiO2 colloids as building blocks, and tetraethyl orthosilicate as a silica source. Catalysts were characterized at different stages of their synthesis using dynamic light scattering, N2-adsorption analysis, powder X-ray diffraction, temperature programmed reduction, high-resolution transmission electron microscopy, high-angle annular bright-field and dark-field scanning transmission electron microscopy, together with EDS elemental mapping. Results revealed that both the supramolecular template and the silica loading had a strong impact on the pore characteristics and crystalline structure of the mixed oxides, as well as on the morphology of the RuO2 nanocrystals. Their catalytic performance was then evaluated in the aqueous phase hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) under mild conditions (50 °C, 50 bar H2). Results showed that the cyclodextrin-derived catalyst displayed almost quantitative LA conversion and 99% GVL yield in less than one hour. Moreover, this catalyst could be reused at least five times without loss of activity. This work offers an effective approach to the utilization of cyclodextrins for engineering the surface morphology of Ru nanocrystals and pore characteristics of TiO2-based materials for catalytic applications in hydrogenation reactions.
Highlights
Introduction published maps and institutional affilWith the growing concerns of accelerated global warming that the world faces today, the production of alternative fuels and renewable chemicals from biomass is an utmost challenge for the global scientific community
A hybrid organic–inorganic material was obtained in aqueous phase by self-assembly of sol-gel synthesized TiO2 nanoparticles around the supramolecular assemblies formed between the randomly methylated β-CD
A versatile template-directed colloidal approach for the fabrication of composition-tuned TiO2 -SiO2 materials with controllable pore sizes and crystal phase compositions has been established by constructing a Randomly methylated β-CD (RaMeβCD)-Pluronic F127-titanium dioxide-silica mesophase before template removal
Summary
With the growing concerns of accelerated global warming that the world faces today, the production of alternative fuels and renewable chemicals from biomass is an utmost challenge for the global scientific community. In this regard, the search for efficient catalytic routes and sustainable chemical processes to convert biomass into high value chemicals in a cost-effective and environmentally friendly manner is an essential step in the development of biorefinery technologies [1,2,3]. Among biomass-derived compounds, levulinic acid (LA) has been identified as an important platform chemical that can be obtained from the dehydration of lignocellulosederived C6 sugars in the presence of mineral acids or ionic liquids. The hydrogenation and subsequent dehydration of LA produces γ-valerolactone (GVL) as its major product, which is considered as a sustainable fuel additive for the replacement of ethanol in ethanol/gasoline blends, in addition to its potential applications in pharmaceutical, iations.
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