Structural stability of ceria in catalysts used for reactions occurring at elevated temperatures is an important technological problem. In this work, we propose a simple method that should improve the thermal stability of Ru doped ceria nanoparticles supported on alumina. Nanosized (<= 5 nm), ruthenium doped ceria particles were synthesized by the reverse microemulsion method and then deposited on the functionalized gamma-Al2O3 support. Obtained catalysts were investigated using a wide range of characterization methods (e.g. XRD, HRTEM, STEM-HAADF, H-2-TPR, XPS) to determine the dispersion and stability of ceria in the oxidizing and reducing atmosphere. The catalytic activity of the samples was tested in the reaction of soot and propane combustion. It has been shown that covering of gamma-Al2O3 support with a monolayer of decanoic acid enabled uniform dispersion of RuxCe1-xO2-y nanoparticles and their very high resistance against sintering up to 800 degrees C in the oxidizing and especially in the reducing atmosphere. The ceria particles show also high reducibility at the low temperature range ((<)500 degrees C), what positively influences on their catalytic activity in the oxidation processes. Ru0.05Ce0.95O2-y deposited on the functionalized alumina is an active and stable catalyst for total oxidation of soot (T-50 = 487 degrees C) and propane (T-50 = 225 degrees C).