C. D. Bohn

A high performance oxygen storage material for chemical looping processes with CO2 capture

Chemical looping combustion (CLC) is a novel combustion technology that involves cyclic reduction and oxidation of oxygen storage materials to provide oxygen for the combustion of fuels to CO2 and H2O, whilst giving a pure stream of CO2 suitable for sequestration or utilisation. Here, we report a method for preparing of oxygen storage materials from layered double hydroxides (LDHs) precursors and demonstrate their applications in the CLC process. The LDHs precursor enables homogeneous mixing of elements at the molecular level, giving a high degree of dispersion and high-loading of active metal oxide in the support after calcination. Using a Cu–Al LDH precursor as a prototype, we demonstrate that rational design of oxygen storage materials by material chemistry significantly improved the reactivity and stability in the high temperature redox cycles. We discovered that the presence of sodium-containing species were effective in inhibiting the formation of copper aluminates (CuAl2O4 or CuAlO2) and stabilising the copper phase in an amorphous support over multiple redox cycles. A representative nanostructured Cu-based oxygen storage material derived from the LDH precursor showed stable gaseous O2 release capacity (∼5 wt%), stable oxygen storage capacity (∼12 wt%), and stable reaction rates during reversible phase changes between CuO–Cu2O–Cu at high temperatures (800–1000 °C). We anticipate that the strategy can be extended to manufacture a variety of metal oxide composites for applications in novel high temperature looping cycles for clean energy production and CO2 capture.

Experimental Investigation of Two Modified Chemicallooping Compustion Cycles Using Syngas from Cylindersand the Gasification of Solid Fuels

Two modified Chemical Looping Combustion (CLC) schemes were investigated: (a) CLC with in situ gasification of a solid carbonaceous fuel in the fuel reactor, and (b) CLC for the production of high purity hydrogen from low grade syngas. A comparison between the performance of the two modified cycles using (i) syngas from cylinders and (ii) syngas derived from the gasification of various solid fuels was made. Preliminary results indicate that both processes can be operated with sufficient conversions using low and high-rank coals. However, agglomeration of the oxygen carrier was observed if wood was used in process (a), probably owing to the formation of low-melting eutectics between the oxygen carrier and metals from the wood ash.