For comparison, the crystallite sizes of RuO2 are calculated via the Scherrer equation. As listed in Table , the higher the Ti loading up to 12%, the smaller the RuO2 crystallite size in calcined catalysts. H2 pulse chemisorption was also performed to quantitatively estimate the dispersion of Ru (Table ). The Ru dispersion on Ru/SiO2 is extremely poor, 0.1±0.04% (acknowledging the non-uniform distribution and agglomeration of Ru nanoparticles), but the Ru dispersion increases with the increase in Ti-content, reaching the highest at 12 mol% (2.5%, 3.7%, 7.4% and 5.3% for Ru/4%Ti-SiO2, Ru/8%Ti-SiO2, Ru/12%Ti-SiO2 and Ru/16%Ti-SiO2, respectively). All in all, the presence of Ti has a beneficial role in stabilizing Ru/RuO2 nanoparticles, thus impeding their growth and aggregation during the calcination and reduction. One may notice discrepancies between the sizes of Ru nanoparticles estimated from XRD and H2 pulse chemisorption. From XRD analysis, assuming that RuO2 particles shrink by around 24% during the reduction due to the difference in mass density between RuO2 and Ru , Ru crystallite sizes are expected to be 9.2 nm, 8.7 nm, 6.9 nm and 9.1 nm for Ru/4%Ti-SiO2, Ru/8%Ti-SiO2, Ru/12%Ti-SiO2 and Ru/16%Ti-SiO2, respectively. From H2 pulse chemisorption (details on the calculation found elsewhere ), Ru particle sizes are 37.3 nm, 25.4 nm, 12.8 nm and 17.9 nm for the same samples. The differences may arise, as XRD measures diffracting crystallites planes rather than entire particles .