Radical induced cracking of naphtha model compound: Using bibenzyl as a novel radical initiator

Naphtha cracking for the production of olefins is extremely energy intensive, accounting for 40 % of the total energy consumption in the petrochemical industry. Since the main energy barrier of naphtha cracking is the radical initiation step, this work proposed an approach to induce the naphtha cracking by adding bibenzyl as a novel radical initiator. To verify the induction effect of bibenzyl on naphtha cracking, the conversion of naphtha model compound n-hexane with and without bibenzyl was investigated in 0.5-30 min at 400 degrees C and 440 degrees C and the products were analyzed in detail. It was found that the addition of bibenzyl increases the conversion of nhexane from 0.39 wt.% to 5.91 wt.% at 400 degrees C and from 3.41 wt.% to 31.45 wt.% at 440 degrees C for 30 min. The gaseous products consisting of C-1-C-4 alkanes and a-olefins showed an obviously increase after bibenzyl addition. The reaction pathways of benzyl radicals generated from the dissociation of C-al-C-al bonds of bibenzyl include abstracting H atoms from bibenzyl and n-hexane, and coupling with alkane radicals generated from n-hexane cracking. The incremental quantity of gaseous products is linear with the quantity of benzyl radicals. The slopes, reflecting the number of accelerated radical propagation reactions between molecules induced by per benzyl radical, increase with the decrease of bibenzyl. When the mass ratio of bibenzyl to n-hexane is 1:100, the average numbers of accelerated radical propagation reactions between molecules per benzyl radical are 185.74 and 186.38 at 400 degrees C and 440 degrees C, respectively.

Automated summary

This study investigated the induction effect of bibenzyl on naphtha cracking, showing a substantial increase in the conversion of n-hexane and the generation of gaseous products. The mechanism involves the generation of benzyl radicals from bibenzyl and their interactions with alkane radicals to accelerate radical propagation reactions, ultimately leading to enhanced naphtha cracking.