(66c) Multiple Thermochemical Water-Splitting Cycles for H2 Generation Using Sol-Gel Derived Ferrites In A Packed Bed Reactor

Multiple Thermochemical Water-Splitting Cycles for H₂
Generation Using Sol-Gel Derived Ferrites In A Packed Bed Reactor.

Rahul R. Bhosale,
Rajesh V. Shende, Jan A. Puszynski

Department of Chemical & Biological Engineering,

South Dakota School of Mines & Technology, Rapid City,
SD 57701

Two-step
thermochemical water-splitting process which utilizes mixed valence metal oxide
i.e. ferrite based redox reactions is one of the green ways of producing H₂.
In this process, the first step belongs to endothermic reduction of ferrite at
elevated temperatures by releasing O₂. Whereas,
the second step corresponds to the oxidation of the reduced ferrite by taking O₂
from water and producing H₂ via water-splitting reaction at lower
temperatures. As the current research trends in H₂ generation via
thermochemical water-splitting process are focused towards higher levels of H₂
production at lower operating temperatures, it is believed that ferrite nanoparticles
synthesized by using sol-gel technique will significantly improve the H₂
yield¹. Sol-gel derived ferrite nanoparticles with higher specific
surface area are believed to be potential candidates to overcome the
hydrodynamic limitations associated with this process and might provide higher
number of active sites for water-splitting reactions resulting into higher
yields of H₂. In this investigation, phase pure ferrites that
include Ni-/Zn-/Sn-/Mn-/Co-ferrite and doped ferrites such as Ni-Zn-/Ni-Mn-/Ni-Co-/Co-Zn-/Co-Mn-ferrite
were synthesized using sol-gel technique. As-synthesized
gels were aged for 24 h and heated rapidly in a muffle furnace at 600^oC
in air environment and quenched. The calcined powder thus obtained was
characterized using powder X-ray diffraction, BET surface area analyzer, scanning
electron microscopy (SEM) and transmission electron microscopy (TEM). The
ferrite powder was placed in a packed bed reactor and water-splitting reaction was
performed at different temperatures. After water-splitting reaction, the
material was regenerated in the temperature range of 900^oC ? 1100^oC
and reused for multiple thermochemical cycles. An attempt was made to perform tens
of thermochemical cycles at lower water-splitting and regeneration temperatures
of 800 ? 1100^oC. Synthesis and characterization of ferrites and transient
H₂ profiles obtained using online H₂ sensor during
multiple thermochemical cycles at various experimental conditions will be
presented. Furthermore, efforts are underway to investigate the water-splitting
reaction kinetics and transport modeling of the thermochemical water-splitting in
a packed bed reactor.

1.     
Rahul R. Bhosale, Rajesh V. Shende, Jan A. Puszynski, Thermochemical
water-splitting for H₂ generation using sol-gel derived Mn-ferrite
in a packed bed reactor, International Journal of Hydrogen Energy, 2011
(In press).