Mesoporous RuO2/TiO2 composites prepared by cyclodextrin-assisted colloidal self-assembly: towards efficient catalysts for the hydrogenation of methyl oleate

Mesoporous RuO2/TiO2 composites were prepared using a template-directed colloidal self-assembly approach combined with a cyclodextrin (CD)-assisted aqueous impregnation method. The supramolecular assemblies formed between the randomly methylated beta-cyclodextrin (RaMeb-CD) and the block copolymer P123 acted as a template for the formation of a highly porous TiO2 network over which uniform dispersion of ruthenium nanoparticles was achieved. By combining dynamic light scattering, X-ray diffraction, N-2-adsorption, temperature-programmed reduction, field-emission scanning electron microscopy and high-resolution transmission electron microscopy, we show that CD-based assemblies provide a versatile and easily accessible toolbox with different functionalities for generating metal-supported catalysts with controlled pore architecture and uniform metal distribution. The performance of these supported catalysts was evaluated in the liquid phase hydrogenation of methyl oleate (MO, C18: 1) to methyl stearate (MS, C18: 0). Control of ruthenium dispersion into the large pores of RaMeb-CD-P123-templated TiO2 material enhanced catalyst activity and selectivity for the hydrogenation of the internal C=C bond and permitted catalyst separation and reuse without loss of activity. Our findings highlight the pivotal role played by the CD-based assemblies on the performance of supported ruthenium catalysts.