Introducing K to Regulate the Electronic Structure of Perovskite-Type Oxide for the Efficient Reaction of Coke and Steam

In the decoking process of ethylene via steam cracking, the reaction between graphite carbon of coke and steam is difficult due to its stable structure and high reaction energy barrier. Graphite conversion is limited by the formation kinetics of ·OH radicals. Herein, electronic structures of double perovskite, single perovskite and R-P perovskite are regulated by accurately doping K/Sr amount at A-site metal via calcining metal organic framework (MOF) precursors. The results show that the oxygen vacancy of perovskite provides the adsorption site for H2O molecules and reduces the adsorption energy barrier. The high-valence Fe ions at B site are beneficial to charge transfer and promote the decomposition of water molecules to form adsorbed ·OH radicals and free ·OH radicals, which promotes graphic conversation. Under the conditions of reaction temperature 900°C, water flow rate 0.167 mL/min and reaction time 120 min, the conversion rate of graphite catalyzed by LaKSr0.17Fe1.5O6 double perovskite is 37.98%, which is 5.52 times of that without catalyst. Since the graphite carbon content of coke is less than 38%, the coke achieves 100% conversion. In addition, K is locked in the skeleton of double perovskite and has strong stability under high temperature conditions. This method provides an important strategy for the synthesis of heterogeneous catalysts.