An apparatus and a method for controllably converting aluminum into alane. In the system of the invention, a reaction between aluminum and hydrogen to form alane is performed at temperatures below 100° C. using a supercritical fluid such as CO2 as a reaction medium, with the optional inclusion of a co-solvent, such as an ether, in the reaction vessel. Inert gas is used to exclude unwanted gases such as oxygen. The reaction of aluminum and hydrogen has been observed to proceed at approximately 60° C. using Me2O as an added solvent in CO2 at supercritical pressures.