Geopolimer composites for chemical looping combustion

Chemical looping combustion enables the inherent separation of CO2 in presence of a solid oxygen carrier. The combination of iron oxide and a geopolymer matrix has been recently reported as a promising alternative to traditional oxygen carriers, thanks to its low cost and the green and easy production process. In this work, a novel manganese oxide/geopolymer composite has been developed, characterized and compared to an iron oxide-based material. Additionally, a mixed iron/manganese geopolymer has been produced to explore the synergic effect of the two oxides. The materials demonstrated suitable characteristics for the process, as a high reproducibility, proper porosity, and a good stability to the operating conditions. Laboratory experiments have been carried out in a double reactor plant for gasification and CLC. The tests conducted at 900 °C revealed the better performance of the Mn-based oxygen carrier, which also exhibited the ability to release O2 in inert conditions. In short cycles, efficiencies in CO conversion up to 99% were achieved and some synergies between Fe and Mn oxides were evidenced by the laboratory plant and XRD analyses.