What are the main industrial routes for propylene production?

Propylene production routes: Steam cracking of naphtha - co-product with ethylene, accounts for ~55% of supply. FCC - significant propylene from gasoline cracking, ~30% of supply; can be enhanced with ZSM-5 additive. Propane dehydrogenation (PDH) - catalytic (Cr/Al2O3 or Pt-Sn), growing rapidly due to shale gas propane availability. Metathesis - ethylene + butenes = propylene over W or Re catalyst. Methanol to propylene (MTP) - emerging route using coal-based methanol in China. Selection factors: feedstock availability and cost, integration with existing facilities, capital cost, and product purity requirements. PDH produces polymer-grade propylene directly; FCC propylene requires upgrading for polymer use. Global propylene demand growing faster than ethylene.