Production of C3/C4Olefins fromn-Hexane: Conceptual Design of a Catalytic Oxidative Cracking Process and Comparison to Steam Cracking

Abstract

A conceptual design of the catalytic oxidative cracking (COC) of hexane as a model compound of naphtha is reported. The design is based on experimental data which are elaborated through a structural design method to a process flow sheet. The potential of COC as an alternative to steam cracking (SC) is discussed through comparing the key differences between the two processes. The presence of Li/MgO catalyst in the COC process (i) induces hexane cracking at lower operation temperatures (575 °C) than in SC (800 °C) and (ii) controls the olefin distribution by increasing the ratio of (butylene + propylene)/ethylene. The product distribution, and thus the separation train of both processes, is different. Catalytic oxidative cracking is designed to maximize propylene and butylene production, while steam cracking is designed to maximize ethylene production. In comparison to SC, the COC process is more energy efficient and consumes 53% less total duty for a production capacity of 300 kton/year of light olefins. However, a preliminary economic evaluation illustrates that the loss of valuable feedstock as a result of combustion of part of the naphtha feed makes the COC process economically less attractive than SC.