High Selectivity Production of Propylene from n-Butene: Thermodynamic and Experimental Study Using a Shape Selective Zeolite Catalyst

Propylene production by n-butene catalytic cracking was studied. Thermodynamic analysis and experimental results showed that a shape-selective catalyst, SAPO-34, with a small pore diameter and weak external acidic sites, can increase the propylene yield and selectivity to 48% and 66%, respectively, from the values of 31% and 36% over a ZSM-5 zeolite by inhibiting the formation of isobutene and other hydrocarbons whose dynamic diameters are larger than isobutene. The optimal temperature for the maximum equilibrium yield of propylene decreases from 600 to 550 °C. The effect of temperature, weight hourly space velocity and time-on-stream in the n-butene cracking process were also studied.