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Many petrochemical processes produce light olefin byproducts that can be used to produce propene. This study reports the kinetics of the reactions of ethene, propene and n-butene isomers over a SAPO-34 catalyst at 450 °C and different space velocities and discusses suitable modes of reaction to maximize propene yield. The shape selectivity of SAPO-34 prevented the formation of i-butene and high alkenes. When a single alkene (ethene, propene, or n-butene) was used as the reactant, the other alkenes were rapidly produced by dimerization and cracking such that the final compositions of the light alkenes were close to the equilibrium composition, with propene as the main species. Hydrogen transfer reactions to form an alkane from an alkene were slower than alkene inter-conversion. A kinetic model for alkene inter-conversion was deduced. Experimental and simulation results indicated that a lower partial pressure of the reactant gave increased propene yield when ethene was the feed.

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.

The dimethyl ether to olefins process is very important for converting coal to chemicals. A SAPO-34 molecular sieve with a particle size up to 50 μm has been synthesized with morpholine as the template. The cold model fluidization experiment indicates that the SAPO-34 catalyst with average size of 45–50 μm is of good fluidization properties. After high temperature steam treatment at 1073 K for 8 h, this large fluidizable catalyst showed good reactivity and selectivity for the dimethyl ether to olefins (DTO) reaction in a micro-reactor. X-ray diffraction characterization showed that the structure of the catalyst was maintained well. A fluidized reactor of 50 mm inner diameter was used to carry out the DTO reaction, which showed that the fluidizable SAPO-34 is a selective catalyst for light olefin production.