Electrolytic reduction of pure alumina is not possible because

Electrolytic reduction of pure alumina [Al₂O₃] is not possible because, pure alumina melts at nearly ~2050⁰ C,it's very difficult to handle this much high temperature with respect to safety as well as economy concern, and pure Al₂O₃ conductivity is low.Therefore cryolite [ Na₃AlF₆] is added as impurity to pure Al₂O₃ .This results in lowering of melting point of alumina from 2050⁰ C to 950⁰ C and increases the electrical conductivity of electrolyte solution.