Study of anti-coking property of SiO2/S composite coatings deposited by atmospheric pressure chemical vapor deposition

To alleviate catalytic coking on the inner surfaces of radiant tubes for ethylene production in petrochemical plants, SiO2/S composite coatings were prepared on the surface of HP40 steel tube using dimethyldisulfide (DMDS) and tetraethylorthosilicate (TEOS) by atmospheric pressure chemical vapor deposition. A comparison of anti-coking property of the coated and uncoated HP40 steel tubes has been made under the same conditions. SiO2/S composite coatings are compact and have better anti-coking property. The coke on the coated HP40 steel tube is about 22% of that on the uncoated HP40 steel tube, and only small granular coke is deposited on the coated HP40 steel tube. However, the filamentous coke is formed on the uncoated HP40 steel tube. SiO2/S composite coatings have good thermal stability at cracking temperature by the comparison of Raman spectra before and after coking.