Impact of Initial Surface Roughness and Aging on Coke Formation during Ethane Steam Cracking

Abstract

Alloys composition and morphology of the inner wall of steam cracking reactors are well-known key factors that affect their substantial coking tendency. The effect of surface roughness on the coking tendency remains uncharted so far and has been studied here for a 35/25 Ni/Cr wt % alloy in a quartz jet stirred reactor equipped with an electro-balance, under coil outlet industrially relevant ethane steam cracking conditions: Tgas phase = 1173 K, Ptot = 0.1 MPa and XC2H6 = 70 %. Up to 6 times higher initial coking rates have been observed during cyclic aging in an Rα surface roughness range of 0.15 - 7 μm and cyclic aging proved to have an effect mainly on the catalytic coking behavior. No effect was observed on the asymptotic coking rates. Scanning electron microscopy and energy diffractive X-ray surface analysis and cross-section elemental mappings suggest that the effect of surface roughness and aging on the catalytic coking rate derives mainly from changes in the metal surface composition. The amounts o...