Inhibition effect of CeO2 promoted SiO2 coating on coke growth during steam cracking of ethane

The main goal of this research is to develop an effective coating to inhibit the direct contact of hydrocarbon with reactor metal wall along with the catalytic conversion of coke to carbon oxides. For this purpose, CeO2 promoted SiO2 coatings were deposited on the surface of an industrial HP 40 alloy. With the purpose of obtaining an effective passive coating with an appropriate morphology and low defects, different synthesis parameters such as the pretreatment of sublayer with sodium carbonate and sulfuric acid solutions and the roughness of HP 40 coupon is investigated. Afterwards, the SiO2 coating was improved with cerium oxide using different Ce/Si molar ratios (0, 0.25, 0.5, 0.75 and infinity) according to characterization and ethane cracking results. The amount of deposited coke is reduced with increasing the Ce/Si molar ratio up to 0.75. The coke is reduced from 1.6 mg for blank HP 40 to about 0.5 and 0.6 mg for 0.75CeO(2)/SiO2/HP40 and CeO2/SiO2/HP40 specimens, respectively. In addition, the characterization results of coked samples after ethane cracking revealed that the coating of different optimal layers successively inhibited the formation of filamentous carbon and metal migration. Thus, the deposited coke on the optimal coating coupons is mostly composed of amorphous soft carbon. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.