Zeolites Boost the Reactivity of Chemical Looping by Brønsted Acid Sites
Xuehui He, Yane Zheng, Kongzhai Li, Hua Wang, Lihong Jiang, Yuhao Wang
Abstract
Chemical looping reforming of CH 4 coupled with the reduction of CO 2 process can reduce fossil fuel consumption while effectively utilizing CO 2 to alleviate environmental stress. The crucial factor in the process is to design an efficient and reliable oxygen carrier. The introduction of silicalite-1 and ZSM-5 zeolites into the LaFe 0.8 Co 0.15 Cu 0.05 O 3 oxygen carrier is found to significantly improve the cycle stability. The addition of zeolites mitigates the agglomerative sintering of the oxygen carriers under high-temperature cycling. The NH 3 -TPD and pyridine-FTIR results confirm that silicalite-1 is almost acid-free and does not contain Brønsted acid, while ZSM-5 contains a larger amount of Brønsted acid, which plays an essential role in improving the reactivity and cycling stability of the oxygen carrier. The CO and H 2 yields of LaFe 0.8 Co 0.15 Cu 0.05 O 3 /10%ZSM-5(81) are as high as 3.26 and 6.28 mmol·g –1 with almost no carbon formation, and high CO and H 2 yields of 2.74 and 5.18 mmol·g –1 could still be achieved after 20 redox cycles. This work demonstrates that the stronger Brønsted acid of ZSM-5 facilitates the adsorption and activation of CH 4 and provides a basis for further exploring the influence of acidity or basicity in the chemical looping process.