Anticoking Performance of Electrodeposited Mn/MnO Surface Coating on Fe–Ni–Cr Alloy during Steam Cracking

Abstract

Manganese electrodeposition and anodization are performed on an Fe–Ni–Cr alloy (Incoloy 800H) to form an Mn/MnO surface coating after thermal pretreatment. The Mn/MnO-coated alloy is coked under simulated steam cracking conditions in ethylene-steam, and its anticoking performance is compared with pretreated, uncoated alloys. The mass of deposited coke during repeated coking cycles is measured by thermogravimetric analysis (TGA) and also determined from the measured CO/CO2 concentrations during decoking with air. Compared to the uncoated alloys that have Cr2O3-rich surfaces, the Mn/MnO-coated alloy shows 30–40% less deposited coke and a peak coke oxidation temperature reduced by about 100 °C. The Mn/MnO surface coating is hypothesized to reduce coke deposition by limiting the amount of Fe/Ni species on the surface and by catalyzing coke gasification/oxidation reactions via the formation of catalytically active Mn3+ species