Mesoporous TiO ₂ Support Materials for Ru-Based CO ₂ Methanation Catalysts

Mesoporous TiO2 materials have been prepared by an aerosol process, which leverages on acetic acid mediated sol–gel chemistry and on the evaporation-induced self-assembly of surfactants to obtain materials with high specific surface area (SSA) and large mesoporous volume. The obtained spherical particles are calcined to release the porosity. It is shown that the mesoscopic order can be preserved when calcination is carried out at relatively low temperature (375 °C and below). Harsher calcination conditions provoke the progressive destruction of the mesostructure, concomitant with a progressive drop of the textural properties and with the crystallization of larger anatase domains. The mesoporous TiO2 material calcined at 350 °C (SSA = 260 m2·g–1; pore volume = 0.36 cm3·g–1; mean pore diameter = 5.4 nm) was selected as a promising support for preformed RuO2 nanoparticles. It is shown that the impregnation of RuO2 nanoparticles and subsequent annealing provoke intense modifications of the texture and crystallinity of the TiO2 materials. In addition to a drop in the textural parameters, RuO2-mediated crystallization of rutile TiO2 is highlighted at a temperature as low as 250 °C. After an in situ reduction in H2, the catalysts containing rutile TiO2 and maintaining relatively small RuO2 crystals showed the highest activity in the methanation of CO2 (up to 2.05 μmolCH4·gcat.–1·s–1) .