Bioresource Technology 320 (2021) 124415 Available online 16 November 2020 0960-8524/© 2020 Elsevier Ltd. All rights reserved. Study on the mechanism of co-catalyzed pyrolysis of biomass by potassium and calcium Xiaojie Tian a , Yunpu Wang a, b, * , Zihong Zeng a , Leilei Dai a, b , Yujie Peng a , Lin Jiang a , Xiuhua Yang a , Linqing Yue a , Yuhuan Liu a, b , Roger Ruan b a State Key Laboratory of Food Science and Technology, Engineering Research Center for Biomass Conversion, Ministry of Education, Nanchang University, Nanchang 330047, China b Center for Biorefning and Department of Bioproducts and Biosystems Engineering University of Minnesota, 1390 Eckles Ave., St. Paul MN 55108, USA HIGHLIGHTS G R A P H I C A L ABSTRACT • The synergistic effect of K and Ca during pyrolysis was studied. • The addition of K 2 CO 3 promoted the decomposition and condensation of lignin. • The addition of Ca(OH) 2 and K 2 CO 3 promoted the uniform distribution of each other. • The inorganic components play an important role in evenly distributing the catalyst. A R T I C L E INFO Keywords: Microwave-assisted catalytic pyrolysis Biomass Potassium Calcium Mechanism ABSTRACT The effects of K and Ca on the pyrolysis of rice straw were studied. The results showed that impregnating a certain amount of Ca is benefcial to the uniform distribution of K, and mixing a certain amount of K is also benefcial to the uniform distribution of Ca. Ca and K would combine with the silicon-aluminum compound in the sample during the pyrolysis and become invalid. Ca can effectively reduce the invalid K, but cannot completely protect K from combining with the silicon-aluminum compound. The binary metal carbonates K 2 Ca(CO 3 ) 2 and K 2 Ca 2 (CO 3 ) 3 were produced during the pyrolysis of the samples, which have a limited effect for the uniform distribution of the catalysts. In addition, acid-leaching removed most of the inorganic components in rice straw, which made it diffcult for the catalyst to be evenly distributed, indicating that the inorganic components play an important role in evenly distributing the catalyst. 1. Introduction The increasing energy consumption and the environmental pollution have made it more and more urgent to fnd suitable renewable and environmentally friendly energy. As the fourth largest energy source after crude oil, coal and natural gas (Li et al., 2015; M¨ oller and Schr¨ oder, * Corresponding authors at: Engineering Research Center for Biomass Conversion, Ministry of Education, Nanchang University, Nanchang, Jiangxi 330047, China. E-mail address: wangyunpu@ncu.edu.cn (Y. Wang). Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech https://doi.org/10.1016/j.biortech.2020.124415 Received 12 October 2020; Received in revised form 9 November 2020; Accepted 11 November 2020