Catalytic behavior in CH4 decomposition of catalysts derived from red mud: Impact of residual Na2O

• Published in: International journal of hydrogen energy Vol. 47; no. 12; pp. 7836 - 7845
• Main Authors: Geng, Sulong, Zhang, Zhanguo, Li, Junjie, Qian, Jianguo, Liu, Jiao, Yu, Jian, Xu, Guangwen
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 08.02.2022
• Subjects: Catalyst; Fe2O3; Methane decomposition; Na2O; Nanocarbon; Red mud; Red mud; Na2O; Catalyst; Methane decomposition; Fe2O3; Nanocarbon
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2021.12.149

Catalyst samples for CH4 decomposition were prepared from red mud (RM) by an acid-leaching neutralization precipitation approach. Water-washing the resultant precipitates multiple times, followed by drying at 105 °C and calcination at 500 °C, resulted in a threshold of residual Na2O, equivalent to 96% Na2O removal. Drying the precipitate at a higher temperature of 200 °C, followed by repeated water washing, provided a deeper Na2O removal of 99% and made the resultant samples more active for the targeted reaction. Subsequently, four catalyst samples with a simulated red mud composition and NaOH contents from 0 to 0.3 wt% were prepared and the catalytic test results revealed that the Na2O remaining in the RM-derived catalysts did not only inhibit their activation in CH4 but also lower their maximal activities for CH4 decomposition. Finally, two catalysts with the same simulated red mud composition and their Na impregnated respectively on Fe2O3 and a mixture support of Al2O3-SiO2-TiO2 were prepared and tested to explore the effect of Na distribution on the activation behavior of RM-derived catalysts for CH4 decomposition. The activity testing results showed that it was the Na residual dispersed on iron oxides in the RM-derived samples to significantly inhibit the activation of CH4 decomposition. •Na2O in the RM-derived catalysts inhibited the activities for CH4 decomposition.•An approach was provided to realize the deeper Na2O removal of 99% in Red Mud.•The Na dispersed on Fe2O3 played an inhibiting role in the activation of catalysts.