Metal Salts On The Chemical Chain Reaction Modified The Role Of Reactive Oxygen Oxygen Carrier

Chemical-looping oxidation (CLO) is a new technology for fuel utilization, which is characterized by low energy consumption and high efficiency. Chemical-looping combustion (CLC) and chemical-looping partial oxidation (CLPO) are two forms of this technology. CLC is a new generation combustion technology with high efficiency and low cost for CO2capture, which is performed using a successive cycle between the fuel and the air via suitable solid oxides as oxygen donors (named oxygen carrier). Chemical-looping partial oxidation is a novel method for syngas (a mixture of H2and CO, which is an important chemical intermediate in gas to liquid technology) generation from fuel. Fuel (such as CH4) is first oxidized by oxygen carriers to syngas2), and then the reduced oxygen carrier can be reoxidized by air. This technology not only avoids the risk of the explosion due to the separation of fuel and oxygen but also reduces the cost of syngas production because of the instead of pure oxygen by air. Complete oxidation or partial oxidation of fuel depends on the activity and selectivity of oxygen in the oxygen carriers.In this thesis, modification of CeO2and Fe2O3based oxygen carriers for chemical-looping partial oxidation of methane and chemical-looping complete oxidation of methane, respectively, with various potassium salts was investigated. Much attraction was focused on the feasibility of controlling the activities and contents of oxygen species on such oxygen carriers with the abilities of partial oxidation or complete oxidation. The prepared oxygen carriers were characterized by XRD, BET and H2-TPR techniques and the performance for the methane oxidation were investigated through temperature-programmed and isothermal reactions.The results showed that addition of K2CO3into CeO2could not only improve the anti-carbon property of oxygen carriers, but also increase the amount of surface oxygen species, therefore increasing the CH4conversion and CO percentage molar concentration in the offgas. On the other hand, the increased surface oxygen also resulted in the furthrer oxidation of H2, which was harmful for the production of synthesis gas with the H2/CO at2.0. CeO2as a promoter could improve the concentration of the surface oxygen of Fe2O3by the interaction between the CeO2and Fe2O3. Moreover, the interaction between the CeO2and Fe2O3could also cause the lattice distrotion and increase the oxygen vacancy in oxygen carriers, improving the release of lattice oxygen. Al2O3as a support increased the specific surface area of the oxygen carrier and made sufficient contact between the fuel and oxygen carrier, which result in the improvement of the oxygen activity and reactivity of oxygen carriers. The modification of KNO3could increase the concentrations of surface oxygen vacancy and adsorption oxygen, and this improved the redox property of Ce-Fe/Al2O3materials, increasing the reaction rate bewteen the oxygen carriers and CH4. In addtion, KNO3could also improve the anti-carbon property Ce-Fe/Al2O3oxygen carrier. The10%KNO3/Ce-Fe/Al2O3oxygen carrier showed the best activity and stability for chemical-looping combustion of methane in the present work.