Investigation on Coking Performance with Sulfur / Phosphorous-Containing Additive and Anti-coking SiO2/S Coating during Thermal Cracking of Light Naphtha

Coke deposits during thermal cracking of light naphtha in the presence of the sulfur/phosphorous-containing additive and the anti-coking SiO2/S coating were investigated. The structure of the coke layer was studied. The results show that the coke is more amorphous with the additive mass concentration of 200 mu g.g(-1). The additive has altered the microstructure of the coke layer by effecting the dehydrogenation reaction during coke formation. Coke deposits on the SiO2/S coating prepared by atmosphere pressure chemical vapor deposition (APCVD) method are mainly composed of coke granules. The TGA results show that the coke deposits are mainly composed of a small amount of volatile coke and a large amount of hard coke. The results of the low H/C ratios show the highly condensed structure of the coke deposits. When additive is added, inorganic sulfur is mainly formed in the cokes based on the analysis of XPS spectra. Phosphorus in the cokes is in the form of PO43- and phosphide species. The analyses of Raman spectra indicate that the coke deposits formed during thermal cracking are mainly composed of amorphous carbon. Cokes deposited on the SiO2/S coating are more disordered, which may make the decoking operation facilitated. (C) 2017 The Authors. Published by Elsevier Ltd.