Influence of Metal Surface and Sulfur Addition on Coke Deposition in the Thermal Cracking of Hydrocarbons

Coke formation in the thermal cracking of hydrocarbons was studied in a pilot plant unit and in a micro-reactor with complete mixing of the gas phase, containing a hollow cylinder suspended at the arm of an electrobalance. The morphology of the coke was studied by SEM, while EDX was used to determine the concentration of metals in the coke layer. The influence of the metal surface composition, of its pretreatment and of the addition of various sulfur compounds on the coking rate and CO-production was investigated for conditions typical for those in the cracking coil. The CO-yield is not a measure of the coking rate. Sulfur compounds are very efficient in reducing the CO-yield, but promote coke formation. 48 refs.