High-temperature catalytic oxidative conversion of propane to propylene and ethylene involving coupling of exothermic and endothermic reactions

Abstract

Coupling of the exothermic catalytic oxidative conversion and endothermic thermal cracking (noncatalytic) reactions of propane to propylene and ethylene over the SrO/La₂O₃/SA5205 catalyst in the presence of steam and limited oxygen was investigated at different process conditions (temperature, 700-850°C; C₃H₈/O₂ ratio in feed, 2.0-8.0; H₂O/C₃H₈ ratio, 0.5-2.5; space velocity, 2000-15000 cm³ g^-1 h^-1). In the presence of steam and limited O₂, the endothermic thermal cracking and exothermic oxidative conversion reactions occur simultaneously and there is no coke formation on the catalyst. Because of the direct coupling of exothermic and endothermic reactions, this process occurs in a most energy efficient and safe manner. The propane conversion, selectivity for propylene, and net heat of reaction (ΔH_r) in the process are strongly influenced by the temperature and concentration of O₂ relative to the propane in the feed. The C₃H₆/C₂H₄ product ratio is also strongly influenced by the temperature, C₃H₈/O₂ feed ratio, and space velocity. The net heat of reaction can be controlled by manipulating the reaction temperature and C₃H₈/O₂ ratio in the feed; the process exothermicity is reduced drastically with increasing the temperature and/or C₃H₈/O₂ feed ratio.