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. (1st February 2018)

• Record Type: Journal Article
• Authors: Sun, Zhao; Chen, Shiyi; Hu, Jun; Chen, Aimin; Rony, Asif Hasan; Russell, Christopher K.; Xiang, Wenguo; Fan, Maohong; Darby Dyar, M.; Dklute, Elizabeth C.
• Is Part Of: Applied energy. Volume 211(2018)
• Page Start: 431
• Page End: 442
• Publication Date: 2018-02-01
• Subjects: Chemical looping -- Hydrogen generation -- TCLHG -- CO2capture -- Ca2Fe2O5 -- Oxygen carrier; Power (Mechanics) -- Periodicals; Energy conservation -- Periodicals; Energy conversion -- Periodicals; 621.042
• DOI: 10.1016/j.apenergy.2017.11.005
• Languages: English
• ISSNs: 0306-2619

Abstract

Graphical abstract: Highlights: A modified sol–gel method was used for the preparation of oxygen carriers. A two-step chemical looping hydrogen generation process is proposed. The existence of Ca shows significant effect on the Fe 3+ reduction and Fe 0 oxidation. The hydrogen yields could be increased by using Ca2 Fe2 O5 as oxygen carrier. 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, Ca2 Fe2 O5, 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 Fe 0 to Fe 3+ by using steam as an oxidizing agent. Thus, higher yields of hydrogen could be generated compared with Fe2 O3 . 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 H2 O/O2 oxidation. Ca2 Fe2 O5 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 Fe 3+ reduction and Fe 0 oxidation and the reduction from Fe 3+ to Fe 0 was concluded to be a simple one-step reaction.