Effect of carbon number on the production of propylene and ethylene by catalytic cracking of straight-chain alkanes over phosphorus-modified ZSM-5

Abstract

Phosphorus-modified ZSM-5 (P-ZSM-5) shows catalytic activity for the cracking of alkanes to produce light olefins such as ethylene and propylene. Here, we investigated the effect of the carbon number (i.e., chain length) of straight-chain alkanes (n-pentane, n-hexane, n-heptane, and n-octane) on the production of ethylene and propylene by catalytic cracking over P-ZSM-5 at 923 K or 873 K. The percent of n-alkane converted and yields of light olefins increased with increasing carbon number of the reactant hydrocarbon. In the case of n-octane cracking at 923 K, 97.1% conversion of the alkane and 64.5% combined yield of ethylene and propylene were obtained. Up to a reaction time of 30 h, the P-ZSM-5 catalyst was stable and the n-octane conversion remained over 91.2%.