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/CO 2 concentrations during decoking with air. Compared to the uncoated alloys that have Cr 2 O 3 -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 Mn 3+ species.

Preoxidation Film and Its Anticoking Behavior on an Optimized HP40Nb Alloy with Al, Zr, Y Addition

“…Al 2 O 3 oxide layer is formed by preoxidation in low oxygen pressure. The Al 2 O 3 oxide layer can prevent Fe and Ni elements from diffusing outward, colliding with C and H free radicals, and reducing surface catalytic coking. − The cracking depth and conversion rate of feedstock are reduced, the final reaction rate is reduced, and the amount of small molecule hydrocarbons and unsaturated hydrocarbons is reduced.…”