A storage vessel for emission control liquids such as aqueous solutions of urea is equipped with phase change materials that are calibrated to help maintain the liquid within a proper temperature range. Multiple phase change materials having phase transition temperatures of fifty to seventy degrees Celsius and seventy to one hundred degrees Celsius provide staged high-temperature stability for the urea solutions. Phase change materials can be included that also provide low temperature stability by changing from liquids to solids when freezing of the aqueous solution is threatened. Containers of phase change materials are applied to the interior or exterior surfaces of the storage vessel. Alternatively the storage vessel is included within and surrounded by a housing that forms an annular space with the storage vessel, and phase change materials are installed within the annular space. A method for using the storage vessel in an emissions control system also is presented.
