An improved process for producing substantially non-polar doped or un-doped cerium oxide nanoparticle dispersions is disclosed. The cerium-containing oxide nanoparticles of an aqueous colloid are transferred to a substantially non-polar liquid comprising one or more amphiphilic materials, one or more low-polarity solvents, and one or more glycol ether promoter materials. The transfer is achieved by mixing the aqueous and substantially non-polar materials, forming an emulsion, followed by a phase separation into a remnant polar solution phase and a substantially non-polar organic colloid phase. The organic colloid phase is then collected. The promoter functions to speed the transfer of nanoparticles to the low-polarity phase. The promoter accelerates the phase separation, and also provides improved colloidal stability of the final substantially non-polar colloidal dispersion. Importantly, the glycol ether promoter reduces the temperature necessary to achieve the phase separation, while providing high extraction yield of nanoparticles into the low-polarity organic phase.