Reaction mechanism and kinetic modeling of olefin conversion over phosphorus modified ZSM-5 catalyst

摘要

Reaction pathways and kinetics of C-2-C-6 olefins cracking over ZSM-5 catalyst were investigated based on product distribution to develop a model. Experimental tests of the catalytic cracking of olefins were performed in the temperature range of 450-650 degrees C, space-time of 0.375-3.5 min, and partial pressure of 0.08-0.23 atm. For each feed, a possible reaction pathway was identified and used for the model. Based on the identified reactions a lumped kinetic model was developed using the power-law method. The developed model included direct olefin cracking, oligomerization, and re-cracking of oligomers. Thirteen reversible reactions were considered as major reactions to represent this complex system. For each forward and backward reaction step, apparent activation energy and pre-exponential factors were estimated. The model predicts the experimental product components with an R-2 value of 0.8735-0.9718. Comparison of experimental result with the developed model showed the developed model predicted the feed product distribution with accuracy. Sensitivity analysis was done to identify dominant reaction paths for each feed that affected the yield of ethylene and propylene, the main products that needed to be maximized during industrial catalytic cracking.