Light olefin production by catalytic co-cracking of Fischer–Tropsch distillate with methanol and the reaction kinetics investigation

Catalytic co-cracking of Fischer–Tropsch(FT) light distillate and methanol combines highly endothermic olefin cracking reaction with exothermic methanol conversion over ZSM-5 catalyst to produce light olefins through a nearly thermoneutral process. The kinetic behavior of co-cracking reactions was investigated by different feed conditions: methanol feed only, olefin feed only and co-feed of methanol with olefins or F–T distillate. The results showed that methanol converted to C_2–C_6 olefins in first-order parallel reaction at low space time, methylation and oligomerization–cracking prevailed for the co-feed of methanol and C_2–C_5 olefins, while for C_6–C_8 olefins,monomolecular cracking was the dominant reaction whether fed alone or co-fed with methanol. For FT distillate and methanol co-feed, alkanes were almost un-reactive, C_3–C_5 olefins were obtained as main products, accounting for 71 wt% for all products. A comprehensive co-cracking reaction scheme was proposed and the model parameters were estimated by the nonlinear least square method. It was verified by experimental data that the kinetic model was reliable to predict major product distribution for co-cracking of FT distillate with methanol and could be used for further reactor development and process design.

Light olefin production by catalytic co-cracking of Fischer-Tropsch distillate with methanol and the reaction kinetics investigation

Catalytic co-cracking of Fischer-Tropsch (FT) light distillate and methanol combines highly endothermic olefin cracking reaction with exothermic methanol conversion over ZSM-5 catalyst to produce light olefins through a nearly thermoneutral process. The kinetic behavior of co-cracking reactions was investigated by different feed conditions:methanol feed only, olefin feed only and co-feed of methanol with olefins or F-T distillate. The results showed that methanol converted to C₂-C₆ olefins in first-order parallel reaction at low space time, methylation and oligomerization-cracking prevailed for the co-feed of methanol and C₂-C₅ olefins, while for C₆-C₈ olefins, monomolecular cracking was the dominant reaction whether fed alone or co-fed with methanol. For FT distillate and methanol co-feed, alkanes were almost un-reactive, C₃-C₅ olefins were obtained as main products, accounting for 71 wt% for all products. A comprehensive co-cracking reaction scheme was proposed and the model parameters were estimated by the nonlinear least square method. It was verified by experimental data that the kinetic model was reliable to predict major product distribution for co-cracking of FT distillate with methanol and could be used for further reactor development and process design.