Synthesis and characterization Ru–C/SiO2 aerogel catalysts for sugar hydrogenation reactions

Synthesis of materials with combined chemistry and textural properties of carbon and silica aerogels was studied. The synthesized support was modified with ruthenium using evaporation impregnation and deposition–precipitation methods. The ruthenium modification methods were observed to influence the particle size, dispersion, surface area, pore volume and acidity of Ru–C–SiO₂ catalysts. Ruthenium particles of 1–2 nm were obtained with a simple impregnation–evaporation method, while deposition precipitations technique gave ruthenium particles ranging from 1 to 8 nm. Small Ru nanoparticles (1–2 nm) were stable even after being exposed at 700 °C or washed with ethanol for regeneration. Furthermore, the catalytic properties of Ru–C–SiO₂ catalysts in sugar hydrogenation were also observed to be influenced by the synthesis methods. The catalysts were tested in hydrogenation of sugars with different molecule sizes (i.e. glucose and cellobiose). d-Glucose was more reactive than d-cellobiose when they were studied separately. For the mixture of sugars higher reactivity of both sugars was observed in comparison with neat substrates for the catalyst made by evaporation-impregnation. On the contrary no significant differences between kinetics of the separated sugars and their mixture were observed for the catalyst prepared by deposition–precipitation. The results can be attributed to acidity and a combination of meso and microporosity of the catalysts. The support composite material could also be produced as a monolith, being a promising candidate for future industrial applications.