A process of reacting a metal chloride, especially chromium (III) chloride, with an alkali metal oleate at a temperature of from about 30.degree. to about 300.degree. C., and especially at about 70.+-.1.degree. C., in a solvent to form a metal oleate complex, especially a chromium-oleate complex, and reacting the complex with oleic acid at a reaction temperature of about 300.degree. C. or above in a solvent having a boiling point of higher than the reaction temperature, and precipitating and isolating metal oxide nanocrystals, especially chromium (III) oxide nanocrystals, which are useful as a catalyst in hydrofluorination reactions. Other metal oxide nanocrystals produced by this process include nanocrystals of vanadium oxide, molybedenum oxide, rhodium oxide, palladium oxide, ruthenium oxide, zirconium oxide, barium oxide, magnesium oxide, and calcium oxide are also synthesized by similar process scheme using their respective chloride precursors. The chromium (III) oxide nanocrystals produced are especially useful as a highly selective catalyst for hydrofluorination of chlorocarbons, hydrochlorocarbons, hydrofluorocarbons, hydrochlorofluorocarbons, chlorofluorocarbons and aliphatic hydrocarbons with HF to produce fluorinated or more highly fluorinated products.