The present invention relates to a process for the conversion of an alcohol mixture (A) comprising about 20 w % to 100% isobutanol to make essentially propylene, comprising: a) introducing in a reactor (A) a stream comprising the mixture (A), optionally water, optionally an inert component, b) contacting said stream with a catalyst (A1) at a temperature above 450° C. in said reactor (A) at conditions effective to dehydrate at least a part of the isobutanol and other alcohols, if any, and make a cracking, c) recovering from said reactor (A) an effluent comprising: ethylene, propylene, water, optionally unconverted alcohols of the mixture (A), various hydrocarbons, and the optional inert component of step a), d) fractionating said effluent of step c) to produce at least an ethylene stream, a propylene stream, a fraction consisting essentially of hydrocarbons having 4 carbon atoms or more, water and the optional inert component of step a), optionally recycling ethylene in whole or in part at the inlet of the reactor (A), optionally recycling the fraction consisting essentially of hydrocarbons having 4 carbon atoms or more at the inlet of the reactor (A).