Abstract: In the process of producing ethylene through thermal cracking, it is difficult to avoid coking on the inner wall of furnace tube. Perovskite oxides have many advantages, such as rich chemical adsorption oxygen, flexible modification, high thermal stability and excellent oxidation/reduction performance, etc., it has been widely used in fields of environmental protection, thermochemical conversion, and synthesis of catalyst material and other fields. Inspired by the application of La_1-xSr_xMnO₃ perovskite material in the removal of hydrocarbons in the field of environmental protection, the plasma spraying method was used to prepare La_0.75Sr_0.25MnO₃ perovskite coating on stainless steel surface. The morphology, composition, and chemical structure of the perovskite coating and surface coke layer were investigated by means of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results showed that the coating was dense, with a thickness of about 30 μm. The anti-coking performance of the coating was evaluated by pyrolysis coking test of naphtha. The coking experiment results showed that the inhibition rate of coking reached 70.4% and 64.8% respectively when the cracking time was 1 h and 3 h. After 6 cycles of coking/cleaning, the coking inhibition rate of the coating still reached to 35.6%. Moreover, the coating could maintain good structural stability at high temperature of 900 ℃, which could meet the demand of inhibiting coking in hydrocarbon pyrolysis.

Key words: naphtha, pyrolysis, coking, perovskite coating, plasma spraying, suppressing coking