Process to prepare propylene

A process for preparing propylene from a hydrocarbon feedstock fraction comprising between 5 and 50 wt % olefin hydrocarbon compounds having 4 or more carbon atoms, the process comprising:

• isolating the hydrocarbon feedstock from an effluent of a fluid catalytic cracking process;
• contacting the hydrocarbon feedstock fraction with a mixture of a heterogeneous cracking catalyst and a heterogeneous dehydrogenation catalyst obtain propylene and other reaction products;
• wherein the heterogeneous cracking catalyst and the heterogeneous dehydrogenation catalyst are present as separate particles in one or more packed beds in an in-series configuration, each packed bed comprising the heterogeneous cracking catalyst and the heterogeneous dehydrogenation catalyst;
• wherein the hydrocarbon feedstock fraction, the propylene, and the other reaction products flow from an up-flow region to a down-flow region following a flow path;
• wherein in the direction of the flow path a concentration of the heterogeneous dehydrogenation catalyst in the one or more packed beds gradually or step-wise increases compared to the heterogeneous cracking catalyst;
• and
• wherein a content in the volume percent of the heterogeneous dehydrogenation catalyst particles relative to the total volume of catalyst particles varies from between 0% to 50% at a start of the flow path to between 20% and 100% at an end of the flow path.