Pulse pyrolysis of waste cooking oil over CaO: Exploration of catalyst deactivation pathway based on feedstock characteristics

Pulse pyrolysis was carried out to realize real-time monitoring of CaO catalyst deactivation and regeneration in the catalytic pyrolysis of waste cooking oil (WCO) and free fatty acids (FFAs) based on the pyrolysis characteristics of feed stocks. The high unsaturation of the feedstock decreases the initial decomposition temperature and reduces the content of oxygen-containing compounds. CaO catalyst was completely deactivated after several times of pulse pyrolysis. During the pyrolysis of WCO, the catalytic activity of CaO did not recover after the pause of pulse pyrolysis. However, the catalytic activity all recovered during the pyrolysis of FFAs, but the rate of deactivation was accelerated. A large amount of Ca(OH)2 and CaCO3 were detected in the deactivated catalyst, and soluble coke was not detected. The research suggested that the change of crystal phases and agglomeration were the vital cause that impact the CaO catalyst stability.