Synergistic effect of micro-meso-macroporous system and structural Al amount of ZSM-5 for intensification of light olefins production in n-hexane cracking

Abstract

Abstract The effect of Si/Al ratio on the structural and acidic properties of hierarchical ZSM-5 was studied. The zeolites were obtained under the fluoride medium and optimal synthesis conditions. The microchannel reactor improved the activity and stability of the catalysts in n-hexane cracking. The performance of the optimum catalyst in the increasing of olefins production was compared in the fixed bed and microchannel reactors. Investigation of the performance of the catalyst with Si/Al=200, as the optimum catalyst in the fixed bed reactor, showed that the microchannel reactor improved the yield of light olefins by improving the transmission phenomena (34.2 % vs 45.5 %). The hierarchical factor of this catalyst was equal to that of the optimum of the desilicated zeolites, which was obtained in the absence of extra templates and post-treatment operations. The synthesized zeolites showed a 55-64 % yield in the production of olefins in the microchannel reactor. Although the ZSM-5 with Si/Al=200 had a lower conversion, it was more selective to light olefins; especially propylene due to its optimum mesoporosity and acidity. Micro-meso-macroporous system seems to be a sustainable approach for the production of light olefins using microchannel reactors and hierarchical zeolites, which lead to the increasing of stability and activity of catalysts in the future technologies.