Ca2Fe2O5: A promising oxygen carrier for CO/CH4 conversion and almost-pure H2 production with inherent CO2 capture over a two-step chemical looping hydrogen generation process

Zhao Sun, Shiyi Chen, Jun Hu, Aimin Chen, Asif Hasan Rony, Christopher K. Russell, Wenguo Xiang, Maohong Fan, M. Darby Dyar and Elizabeth C. Dklute

Applied Energy, 2018, vol. 211, issue C, 442 pages

Abstract: Chemical looping hydrogen generation (CLHG) is a promising technology for high-purity hydrogen production with inherent CO2 separation. The selection of a high-performance oxygen carrier capable of being reduced and oxidized over multiple redox cycles against deactivation is a key issue for CLHG technology. In this work, a two-step chemical looping hydrogen generation (TCLHG) process is proposed by using a novel calcium ferrite, Ca2Fe2O5, as an oxygen carrier which is synthesized with applied a citric acid assisted sol–gel method. The experimental results indicate that the reduced oxygen carrier achieves one-step oxidation from Fe0 to Fe3+ by using steam as an oxidizing agent. Thus, higher yields of hydrogen could be generated compared with Fe2O3. The fresh and reacted Ca-Fe based oxygen carriers were characterized using different methods such as XRD, SEM/EDS, TEM, N2 adsorption, H2-TPR, XPS, and Mossbauer spectroscopy test etc. The oxygen release and storage capacity, cyclic stability, and carbon deposition characteristics of the Ca-Fe based oxygen carriers were investigated using TGA and a fixed bed reactor with multicycles of CO/CH4 reduction and H2O/O2 oxidation. Ca2Fe2O5 is proved to be a more stable formation of the calcium ferrite compounds and a promising oxygen carrier for TCLHG process which shows perfect reducibility, oxidation activity, and cyclic stability. The existence of Ca appears to perform a significant effect on the Fe3+ reduction and Fe0 oxidation and the reduction from Fe3+ to Fe0 was concluded to be a simple one-step reaction.

Keywords: Chemical looping; Hydrogen generation; TCLHG; CO2capture; Ca2Fe2O5; Oxygen carrier (search for similar items in EconPapers)
Date: 2018
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (17)

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DOI: 10.1016/j.apenergy.2017.11.005

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