Sequence of Ni/SiO2 and Cu/SiO2 in dual catalyst bed significantly impacts coke properties in glycerol steam reforming

• Published in: International journal of hydrogen energy Vol. 46; no. 52; pp. 26367 - 26380
• Main Authors: Gao, Zhiran, Li, Chao, Shao, Yuewen, Gao, Guoming, Xu, Qing, Tian, Hongli, Zhang, Shu, Hu, Xun
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 29.07.2021
• Subjects: Dual catalyst bed; Glycerol; Ni/SiO2 and Cu/SiO2; Properties of coke; Steam reforming; Glycerol; Dual catalyst bed; Ni/SiO2 and Cu/SiO2; Steam reforming; Properties of coke
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2021.05.140

Coke formation is a major challenge in steam reforming reactions. In addition to development of robust catalyst for tackling coking, in this study we explored the approach of using dual catalyst bed with the catalyst on top as the guard or sacrifice catalyst while with the bottom catalyst to catalyze the steam reforming. The rationale is that some oxygen-containing reactants are prone to polymerize on heating, and the polymeric coke could directly fall on surface of catalyst and leads to the rapid deactivation. Hence, glycerol was selected as the reactant for steam reforming in the catalyst bed with the Cu/SiO2 placed on the top of Ni/SiO2 catalyst. Our results demonstrate that first contact of glycerol to Cu/SiO2 on top changed abundance/type of small intermediates and the π-conjugated oligomers reached the Ni/SiO2 catalyst, rendering the Ni catalyst with a higher resistivity towards coking and deactivation. In addition, the carbon nanotube form of coke over Ni/SiO2 was thinner in wall thickness and larger in inner diameter of the cavity due to the impact of D-Cu/SiO2. Substantial polymeric coke with amorphous structure and low thermal stability formed over Cu/SiO2 via polymerisation of reaction intermediates. The characterization (in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS)) for the glycerol steam reforming indicated that the Cu/SiO2 and Ni/SiO2 catalyst induced the formation of the very different functionalities of the reaction intermediates. [Display omitted] •Cu/SiO2 is used as a guard catalyst on top of Ni/SiO2 for glycerol steam reforming.•Cu/SiO2 on top made Ni/SiO2 more resistant to deactivation.•Cu/SiO2 impacted intermediates and π-conjugated oligomers reaching Ni/SiO2.•Cu/SiO2 affected wall thickness and inner diameter of carbon nanotube over Ni/SiO2.•Coke over Cu/SiO2 is polymeric, amorphous and thermally unstable.