Oxygen Uncoupling Property and Kinetics of a Copper Manganese Composite Oxygen Carrier in a Packed-Bed Reactor

Abstract

Decreasing the reduction temperature of an oxygen carrier is the key to reduce energy consumption further and avoid the operational difficulties of chemical looping air separation (CLAS). The copper manganese composite oxygen carrier with zirconia as an inert binder, which has a relatively low temperature of oxygen uncoupling, was developed. In the packed-bed reactor, effects of several important operating parameters, viz., the feed gas rate, temperature, and inlet oxygen concentration, on the separation reactivity were discussed. At higher reaction temperatures, the reduction reactivity increases but the oxidation reactivity decreases. In comparison to a copper oxygen carrier, the equilibrium oxygen concentration of the copper manganese oxygen carrier is greatly enhanced. High gas flow rates can accelerate the separation reaction. In the reduction step, a lower oxygen concentration leads to a higher reduction reactivity. In the oxidation step, the higher oxidation reactivity requires higher oxygen concentrations. The oxygen uncoupling kinetics was determined by the lnln kinetic method. The separation activation energy was determined at 162.95 kJ mol–1, and the most likely mechanism function is the unreacted shrinking core model (R 2). The main compositions in fresh and oxidized composite oxygen carriers are Cu x Mn3–x O4 and ZrO2. After reduction, the active phase compositions are transformed into Cu x Mn2–x O2. The inert phase of ZrO2 is stable during the redox reaction. The repeated separation capability of the composite oxygen carrier over 20 consecutive redox cycles is high.

Virtual Special Issue of Recent Research Advances in China: Chemical Looping

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Orthogonal Preparation of SrFeO3-δ Nanocomposites as Effective Oxygen Transfer Agents for Chemical-Looping Steam Methane Reforming

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