Process to prepare propylene from a mixture of hydrocarbons having an olefin content of between 5 and 50 wt.% and boiling for more than 90 vol.% between 35 and 280 °C or from a hydrocarbon feed comprising paraffins, naphthenics, aromatics and optionally up to 10 wt.% of olefins, wherein the process comprises the following steps: (a) feeding the mixture of hydrocarbons optionally in admixture with a recycle stream and having a temperature between 450 and 750 °C to a fixed bed reactor where the feed is contacted with a low acidic density cracking catalyst at a hydrocarbon partial pressure of below 3 bar and at a weight hourly space velocity of between 0.5 and 100 h - 1 , (b) isolating propylene and optionally other low boiling compounds from the effluent of step (a) wherein a first high boiling fractions remains, (c) feeding all or part of the first high boiling fraction optionally in admixture with a recycle stream and having a temperature between 400 and 750 °C to a fixed bed reactor where the first high boiling fraction is contacted with a high acidic density cracking catalyst at a hydrocarbon partial pressure of below 3 bar and at a weight hourly space velocity of between 0.5 and 100 h -1 and wherein the temperature of the mixture of hydrocarbons optionally in admixture with a recycle stream as fed to the reactor in step (a) is lower than the temperature of the first high boiling fraction optionally in admixture with a recycle stream as fed to the reactor in step (c), (d) isolating propylene and optionally other low boiling compounds from the effluent of step (c) wherein a second high boiling fractions remains, and (e) recycling all or part of the second high boiling fraction to step (a) and/or to step (c) as the optional recycle stream. (a) feeding the mixture of hydrocarbons optionally in admixture with a recycle stream and having a temperature between 450 and 750 °C to a fixed bed reactor where the feed is contacted with a low acidic density cracking catalyst at a hydrocarbon partial pressure of below 3 bar and at a weight hourly space velocity of between 0.5 and 100 h - 1 , (b) isolating propylene and optionally other low boiling compounds from the effluent of step (a) wherein a first high boiling fractions remains, (c) feeding all or part of the first high boiling fraction optionally in admixture with a recycle stream and having a temperature between 400 and 750 °C to a fixed bed reactor where the first high boiling fraction is contacted with a high acidic density cracking catalyst at a hydrocarbon partial pressure of below 3 bar and at a weight hourly space velocity of between 0.5 and 100 h -1 and wherein the temperature of the mixture of hydrocarbons optionally in admixture with a recycle stream as fed to the reactor in step (a) is lower than the temperature of the first high boiling fraction optionally in admixture with a recycle stream as fed to the reactor in step (c), (d) isolating propylene and optionally other low boiling compounds from the effluent of step (c) wherein a second high boiling fractions remains, and (e) recycling all or part of the second high boiling fraction to step (a) and/or to step (c) as the optional recycle stream. <EOS>