Abstract: The low conversion rate of paraffins, 52.58%—77.07%, limits the light olefins yield in straight-run naphtha catalytic cracking (SNCC). Reaction networks of n-octane, 2-methyl heptanes and 2,5-dimethyl hexane as models were established by DFT methods to investigate the initiative ways of ideal chain reaction and reaction direction. It is found that the existing naphthenic hydrocarbon with higher hydrogen donating ability in naphtha is the key reason for limited conversion of paraffins due to the hydride transfer reaction. The addition of IM-5 zeolite with specific microporous structure in catalyst can rationally strengthen the selective catalytic cracking reactions of paraffins in SNCC process.

Key words: straight-run naphtha, catalytic cracking, paraffins, reaction network, chain initiation, chain transfer, IM-5 zeolite